= Gerrit Code Review - Plugin Development The Gerrit server functionality can be extended by installing plugins. This page describes how plugins for Gerrit can be developed. For PolyGerrit-specific plugin development, consult with link:pg-plugin-dev.html[PolyGerrit Plugin Development] guide. Depending on how tightly the extension code is coupled with the Gerrit server code, there is a distinction between `plugins` and `extensions`. [[plugin]] A `plugin` in Gerrit is tightly coupled code that runs in the same JVM as Gerrit. It has full access to all server internals. Plugins are tightly coupled to a specific major.minor server version and may require source code changes to compile against a different server version. Plugins may require a specific major.minor.patch server version and may need rebuild and revalidation across different patch levels. A different patch level may only add new API interfaces and never change or extend existing ones. [[extension]] An `extension` in Gerrit runs inside of the same JVM as Gerrit in the same way as a plugin, but has limited visibility to the server's internals. The limited visibility reduces the extension's dependencies, enabling it to be compatible across a wider range of server versions. Most of this documentation refers to either type as a plugin. [[getting-started]] == Getting started To get started with the development of a plugin clone the sample plugin: ---- $ git clone https://gerrit.googlesource.com/plugins/cookbook-plugin ---- This is a project that demonstrates the various features of the plugin API. It can be taken as an example to develop an own plugin. When starting from this example one should take care to adapt the `Gerrit-ApiVersion` in the `BUILD` to the version of Gerrit for which the plugin is developed. [[API]] == API There are two different API formats offered against which plugins can be developed: gerrit-extension-api.jar:: A stable but thin interface. Suitable for extensions that need to be notified of events, but do not require tight coupling to the internals of Gerrit. Extensions built against this API can expect to be binary compatible across a wide range of server versions. gerrit-plugin-api.jar:: The complete internals of the Gerrit server, permitting a plugin to tightly couple itself and provide additional functionality that is not possible as an extension. Plugins built against this API are expected to break at the source code level between every major.minor Gerrit release. A plugin that compiles against 2.5 will probably need source code level changes to work with 2.6, 2.7, and so on. == Manifest Plugins may provide optional description information with standard manifest fields: ---- Implementation-Title: Example plugin showing examples Implementation-Version: 1.0 Implementation-Vendor: Example, Inc. ---- === ApiType Plugins using the tightly coupled `gerrit-plugin-api.jar` must declare this API dependency in the manifest to gain access to server internals. If no `Gerrit-ApiType` is specified the stable `extension` API will be assumed. This may cause ClassNotFoundExceptions when loading a plugin that needs the plugin API. ---- Gerrit-ApiType: plugin ---- === Explicit Registration Plugins that use explicit Guice registration must name the Guice modules in the manifest. Up to three modules can be named in the manifest. `Gerrit-Module` supplies bindings to the core server; `Gerrit-SshModule` supplies SSH commands to the SSH server (if enabled); `Gerrit-HttpModule` supplies servlets and filters to the HTTP server (if enabled). If no modules are named automatic registration will be performed by scanning all classes in the plugin JAR for `@Listen` and `@Export("")` annotations. ---- Gerrit-Module: tld.example.project.CoreModuleClassName Gerrit-SshModule: tld.example.project.SshModuleClassName Gerrit-HttpModule: tld.example.project.HttpModuleClassName ---- === Batch runtime Gerrit can be run as a server, serving HTTP or SSH requests, or as an offline program. Plugins can contribute Guice modules to this batch runtime by binding `Gerrit-BatchModule` to one of their classes. The Guice injector is bound to less classes, and some Gerrit features will be absent - on purpose. This feature was originally introduced to support plugins during an offline reindexing task. ---- Gerrit-BatchModule: tld.example.project.CoreModuleClassName ---- In this runtime, only the module designated by `Gerrit-BatchModule` is enabled, not `Gerrit-SysModule`. [[plugin_name]] === Plugin Name A plugin can optionally provide its own plugin name. ---- Gerrit-PluginName: replication ---- This is useful for plugins that contribute plugin-owned capabilities that are stored in the `project.config` file. Another use case is to be able to put project specific plugin configuration section in `project.config`. In this case it is advantageous to reserve the plugin name to access the configuration section in the `project.config` file. If `Gerrit-PluginName` is omitted, then the plugin's name is determined from the plugin file name. If a plugin provides its own name, then that plugin cannot be deployed multiple times under different file names on one Gerrit site. For Maven driven plugins, the following line must be included in the pom.xml file: [source,xml] ---- name ---- For Bazel driven plugins, the following line must be included in the BUILD configuration file: [source,python] ---- manifest_entries = [ 'Gerrit-PluginName: name', ] ---- A plugin can get its own name injected at runtime: [source,java] ---- public class MyClass { private final String pluginName; @Inject public MyClass(@PluginName String pluginName) { this.pluginName = pluginName; } [...] } ---- A plugin can get its canonical web URL injected at runtime: [source,java] ---- public class MyClass { private final String url; @Inject public MyClass(@PluginCanonicalWebUrl String url) { this.url = url; } [...] } ---- The URL is composed of the server's canonical web URL and the plugin's name, i.e. `http://review.example.com:8080/plugin-name`. The canonical web URL may be injected into any .jar plugin regardless of whether or not the plugin provides an HTTP servlet. [[reload_method]] === Reload Method If a plugin holds an exclusive resource that must be released before loading the plugin again (for example listening on a network port or acquiring a file lock) the manifest must declare `Gerrit-ReloadMode` to be `restart`. Otherwise the preferred method of `reload` will be used, as it enables the server to hot-patch an updated plugin with no down time. ---- Gerrit-ReloadMode: restart ---- In either mode ('restart' or 'reload') any plugin or extension can be updated without restarting the Gerrit server. The difference is how Gerrit handles the upgrade: restart:: The old plugin is completely stopped. All registrations of SSH commands and HTTP servlets are removed. All registrations of any extension points are removed. All registered LifecycleListeners have their `stop()` method invoked in reverse order. The new plugin is started, and registrations are made from the new plugin. There is a brief window where neither the old nor the new plugin is connected to the server. This means SSH commands and HTTP servlets will return not found errors, and the plugin will not be notified of events that occurred during the restart. reload:: The new plugin is started. Its LifecycleListeners are permitted to perform their `start()` methods. All SSH and HTTP registrations are atomically swapped out from the old plugin to the new plugin, ensuring the server never returns a not found error. All extension point listeners are atomically swapped out from the old plugin to the new plugin, ensuring no events are missed (however some events may still route to the old plugin if the swap wasn't complete yet). The old plugin is stopped. To reload/restart a plugin the link:cmd-plugin-reload.html[plugin reload] command can be used. [[init_step]] === Init step Plugins can contribute their own "init step" during the Gerrit init wizard. This is useful for guiding the Gerrit administrator through the settings needed by the plugin to work properly. For instance plugins to integrate Jira issues to Gerrit changes may contribute their own "init step" to allow configuring the Jira URL, credentials and possibly verify connectivity to validate them. ---- Gerrit-InitStep: tld.example.project.MyInitStep ---- MyInitStep needs to follow the standard Gerrit InitStep syntax and behavior: writing to the console using the injected ConsoleUI and accessing / changing configuration settings using Section.Factory. In addition to the standard Gerrit init injections, plugins receive the @PluginName String injection containing their own plugin name. During their initialization plugins may get access to the `project.config` file of the `All-Projects` project and they are able to store configuration parameters in it. For this a plugin `InitStep` can get `com.google.gerrit.pgm.init.api.AllProjectsConfig` injected: [source,java] ---- public class MyInitStep implements InitStep { private final String pluginName; private final ConsoleUI ui; private final AllProjectsConfig allProjectsConfig; @Inject public MyInitStep(@PluginName String pluginName, ConsoleUI ui, AllProjectsConfig allProjectsConfig) { this.pluginName = pluginName; this.ui = ui; this.allProjectsConfig = allProjectsConfig; } @Override public void run() throws Exception { } @Override public void postRun() throws Exception { ui.message("\n"); ui.header(pluginName + " Integration"); boolean enabled = ui.yesno(true, "By default enabled for all projects"); Config cfg = allProjectsConfig.load().getConfig(); if (enabled) { cfg.setBoolean("plugin", pluginName, "enabled", enabled); } else { cfg.unset("plugin", pluginName, "enabled"); } allProjectsConfig.save(pluginName, "Initialize " + pluginName + " Integration"); } } ---- Bear in mind that the Plugin's InitStep class will be loaded but the standard Gerrit runtime environment is not available and the plugin's own Guice modules were not initialized. This means the InitStep for a plugin is not executed in the same way that the plugin executes within the server, and may mean a plugin author cannot trivially reuse runtime code during init. For instance a plugin that wants to verify connectivity may need to statically call the constructor of their connection class, passing in values obtained from the Section.Factory rather than from an injected Config object. Plugins' InitSteps are executed during the "Gerrit Plugin init" phase, after the extraction of the plugins embedded in the distribution .war file into `$GERRIT_SITE/plugins` and before the DB Schema initialization or upgrade. A plugin's InitStep cannot refer to Gerrit's DB Schema or any other Gerrit runtime objects injected at startup. [source,java] ---- public class MyInitStep implements InitStep { private final ConsoleUI ui; private final Section.Factory sections; private final String pluginName; @Inject public GitBlitInitStep(final ConsoleUI ui, Section.Factory sections, @PluginName String pluginName) { this.ui = ui; this.sections = sections; this.pluginName = pluginName; } @Override public void run() throws Exception { ui.header("\nMy plugin"); Section mySection = getSection("myplugin", null); mySection.string("Link name", "linkname", "MyLink"); } @Override public void postRun() throws Exception { } } ---- [[classpath]] == Classpath Each plugin is loaded into its own ClassLoader, isolating plugins from each other. A plugin or extension inherits the Java runtime and the Gerrit API chosen by `Gerrit-ApiType` (extension or plugin) from the hosting server. Plugins are loaded from a single JAR file. If a plugin needs additional libraries, it must include those dependencies within its own JAR. Plugins built using Maven may be able to use the link:http://maven.apache.org/plugins/maven-shade-plugin/[shade plugin] to package additional dependencies. Relocating (or renaming) classes should not be necessary due to the ClassLoader isolation. [[events]] == Listening to Events Certain operations in Gerrit trigger events. Plugins may receive notifications of these events by implementing the corresponding listeners. * `com.google.gerrit.common.EventListener`: + Allows to listen to events without user visibility restrictions. These are the same link:cmd-stream-events.html#events[events] that are also streamed by the link:cmd-stream-events.html[gerrit stream-events] command. * `com.google.gerrit.common.UserScopedEventListener`: + Allows to listen to events visible to the specified user. These are the same link:cmd-stream-events.html#events[events] that are also streamed by the link:cmd-stream-events.html[gerrit stream-events] command. * `com.google.gerrit.extensions.events.LifecycleListener`: + Plugin start and stop * `com.google.gerrit.extensions.events.NewProjectCreatedListener`: + Project creation * `com.google.gerrit.extensions.events.ProjectDeletedListener`: + Project deletion * `com.google.gerrit.extensions.events.HeadUpdatedListener`: + Update of HEAD on a project * `com.google.gerrit.extensions.events.UsageDataPublishedListener`: + Publication of usage data * `com.google.gerrit.extensions.events.GarbageCollectorListener`: + Garbage collection ran on a project * `com.google.gerrit.server.extensions.events.ChangeIndexedListener`: + Update of the change secondary index * `com.google.gerrit.server.extensions.events.AccountIndexedListener`: + Update of the account secondary index * `com.google.gerrit.server.extensions.events.GroupIndexedListener`: + Update of the group secondary index * `com.google.gerrit.server.extensions.events.ProjectIndexedListener`: + Update of the project secondary index * `com.google.gerrit.httpd.WebLoginListener`: + User login or logout interactively on the Web user interface. The event listener is under the Gerrit http package to automatically inherit the javax.servlet.http dependencies and allowing to influence the login or logout flow with additional redirections. [[stream-events]] == Sending Events to the Events Stream Plugins may send events to the events stream where consumers of Gerrit's `stream-events` ssh command will receive them. To send an event, the plugin must invoke one of the `postEvent` methods in the `EventDispatcher` interface, passing an instance of its own custom event class derived from `com.google.gerrit.server.events.Event`. [source,java] ---- import com.google.gerrit.common.EventDispatcher; import com.google.gerrit.extensions.registration.DynamicItem; import com.google.gwtorm.server.OrmException; import com.google.inject.Inject; class MyPlugin { private final DynamicItem eventDispatcher; @Inject myPlugin(DynamicItem eventDispatcher) { this.eventDispatcher = eventDispatcher; } private void postEvent(MyPluginEvent event) { try { eventDispatcher.get().postEvent(event); } catch (OrmException e) { // error handling } } } ---- Plugins which define new Events should register them via the `com.google.gerrit.server.events.EventTypes.registerClass()` method. This will make the EventType known to the system. Deserializing events with the `com.google.gerrit.server.events.EventDeserializer` class requires that the event be registered in EventTypes. == Modifying the Stream Event Flow It is possible to modify the stream event flow from plugins by registering an `com.google.gerrit.server.events.EventDispatcher`. A plugin may register a Dispatcher class to replace the internal Dispatcher. EventDispatcher is a DynamicItem, so Gerrit may only have one copy. [[validation]] == Validation Listeners Certain operations in Gerrit can be validated by plugins by implementing the corresponding link:config-validation.html[listeners]. [[change-message-modifier]] == Change Message Modifier `com.google.gerrit.server.git.ChangeMessageModifier`: plugins implementing this can modify commit message of the change being submitted by Rebase Always and Cherry Pick submit strategies as well as change being queried with COMMIT_FOOTERS option. [[merge-super-set-computation]] == Merge Super Set Computation The algorithm to compute the merge super set to detect changes that should be submitted together can be customized by implementing `com.google.gerrit.server.git.MergeSuperSetComputation`. MergeSuperSetComputation is a DynamicItem, so Gerrit may only have one implementation. [[receive-pack]] == Receive Pack Initializers Plugins may provide ReceivePackInitializer instances, which will be invoked by Gerrit just before a ReceivePack instance will be used. Usually, plugins will make use of the setXXX methods on the ReceivePack to set additional properties on it. The interactions with the core Gerrit ReceivePack initialization and between ReceivePackInitializers can be complex. Please read the ReceivePack Javadoc and Gerrit AsyncReceiveCommits implementation carefully. [[post-receive-hook]] == Post Receive-Pack Hooks Plugins may register PostReceiveHook instances in order to get notified when JGit successfully receives a pack. This may be useful for those plugins which would like to monitor changes in Git repositories. [[upload-pack]] == Upload Pack Initializers Plugins may provide UploadPackInitializer instances, which will be invoked by Gerrit just before a UploadPack instance will be used. Usually, plugins will make use of the setXXX methods on the UploadPack to set additional properties on it. The interactions with the core Gerrit UploadPack initialization and between UploadPackInitializers can be complex. Please read the UploadPack Javadoc and Gerrit Upload/UploadFactory implementations carefully. [[pre-upload-hook]] == Pre Upload-Pack Hooks Plugins may register PreUploadHook instances in order to get notified when JGit is about to upload a pack. This may be useful for those plugins which would like to monitor usage in Git repositories. [[post-upload-hook]] == Post Upload-Pack Hooks Plugins may register PostUploadHook instances in order to get notified after JGit is done uploading a pack. [[ssh]] == SSH Commands Plugins may provide commands that can be accessed through the SSH interface (extensions do not have this option). Command implementations must extend the base class SshCommand: [source,java] ---- import com.google.gerrit.sshd.SshCommand; import com.google.gerrit.sshd.CommandMetaData; @CommandMetaData(name="print", description="Print hello command") class PrintHello extends SshCommand { @Override protected void run() { stdout.print("Hello\n"); } } ---- If no Guice modules are declared in the manifest, SSH commands may use auto-registration by providing an `@Export` annotation: [source,java] ---- import com.google.gerrit.extensions.annotations.Export; import com.google.gerrit.sshd.SshCommand; @Export("print") class PrintHello extends SshCommand { @Override protected void run() { stdout.print("Hello\n"); } } ---- If explicit registration is being used, a Guice module must be supplied to register the SSH command and declared in the manifest with the `Gerrit-SshModule` attribute: [source,java] ---- import com.google.gerrit.sshd.PluginCommandModule; class MyCommands extends PluginCommandModule { @Override protected void configureCommands() { command(PrintHello.class); } } ---- For a plugin installed as name `helloworld`, the command implemented by PrintHello class will be available to users as: ---- $ ssh -p 29418 review.example.com helloworld print ---- [[multiple-commands]] === Multiple Commands bound to one implementation Multiple SSH commands can be bound to the same implementation class. For example a Gerrit Shell plugin can bind different shell commands to the same implementation class: [source,java] ---- public class SshShellModule extends PluginCommandModule { @Override protected void configureCommands() { command("ls").to(ShellCommand.class); command("ps").to(ShellCommand.class); [...] } } ---- With the possible implementation: [source,java] ---- public class ShellCommand extends SshCommand { @Override protected void run() throws UnloggedFailure { String cmd = getName().substring(getPluginName().length() + 1); ProcessBuilder proc = new ProcessBuilder(cmd); Process cmd = proc.start(); [...] } } ---- And the call: ---- $ ssh -p 29418 review.example.com shell ls $ ssh -p 29418 review.example.com shell ps ---- [[root-level-commands]] === Root Level Commands Single command plugins are also supported. In this scenario plugin binds SSH command to its own name. `SshModule` must inherit from `SingleCommandPluginModule` class: [source,java] ---- public class SshModule extends SingleCommandPluginModule { @Override protected void configure(LinkedBindingBuilder b) { b.to(ShellCommand.class); } } ---- If the plugin above is deployed under sh.jar file in `$site/plugins` directory, generic commands can be called without specifying the actual SSH command. Note in the example below, that the called commands `ls` and `ps` was not explicitly bound: ---- $ ssh -p 29418 review.example.com sh ls $ ssh -p 29418 review.example.com sh ps ---- [[search_operators]] == Search Operators Plugins can define new search operators to extend change searching by implementing the `ChangeQueryBuilder.ChangeOperatorFactory` interface and registering it to an operator name in the plugin module's `configure()` method. The search operator name is defined during registration via the DynamicMap annotation mechanism. The plugin name will get appended to the annotated name, with an underscore in between, leading to the final operator name. An example registration looks like this: bind(ChangeOperatorFactory.class) .annotatedWith(Exports.named("sample")) .to(SampleOperator.class); If this is registered in the `myplugin` plugin, then the resulting operator will be named `sample_myplugin`. The search operator itself is implemented by ensuring that the `create()` method of the class implementing the `ChangeQueryBuilder.ChangeOperatorFactory` interface returns a `Predicate`. Here is a sample operator factory definition which creates a `MyPredicate`: [source,java] ---- @Singleton public class SampleOperator implements ChangeQueryBuilder.ChangeOperatorFactory { public static class MyPredicate extends OperatorChangePredicate { ... } @Override public Predicate create(ChangeQueryBuilder builder, String value) throws QueryParseException { return new MyPredicate(value); } } ---- [[search_operands]] === Search Operands === Plugins can define new search operands to extend change searching. Plugin methods implementing search operands (returning a `Predicate`), must be defined on a class implementing one of the `ChangeQueryBuilder.ChangeOperandsFactory` interfaces (.e.g., ChangeQueryBuilder.ChangeHasOperandFactory). The specific `ChangeOperandFactory` class must also be bound to the `DynamicSet` from a module's `configure()` method in the plugin. The new operand, when used in a search would appear as: operatorName:operandName_pluginName A sample `ChangeHasOperandFactory` class implementing, and registering, a new `has:sample_pluginName` operand is shown below: ==== @Singleton public class SampleHasOperand implements ChangeHasOperandFactory { public static class Module extends AbstractModule { @Override protected void configure() { bind(ChangeHasOperandFactory.class) .annotatedWith(Exports.named("sample") .to(SampleHasOperand.class); } } @Override public Predicate create(ChangeQueryBuilder builder) throws QueryParseException { return new HasSamplePredicate(); } ==== [[command_options]] === Command Options === Plugins can provide additional options for each of the gerrit ssh and the REST API commands by implementing the DynamicBean interface and registering it to a command class name in the plugin module's `configure()` method. The plugin's name will be prepended to the name of each @Option annotation found on the DynamicBean object provided by the plugin. The example below shows a plugin that adds an option to log a value from the gerrit 'ban-commits' ssh command. [source, java] ---- public class SshModule extends AbstractModule { private static final FluentLogger logger = FluentLogger.forEnclosingClass(); @Override protected void configure() { bind(DynamicOptions.DynamicBean.class) .annotatedWith(Exports.named( com.google.gerrit.sshd.commands.BanCommitCommand.class)) .to(BanOptions.class); } public static class BanOptions implements DynamicOptions.DynamicBean { @Option(name = "--log", aliases = { "-l" }, usage = "Say Hello in the Log") private void parse(String arg) { logger.atSevere().log("Say Hello in the Log %s", arg); } } ---- [[query_attributes]] === Query Attributes === Plugins can provide additional attributes to be returned in Gerrit queries by implementing the ChangeAttributeFactory interface and registering it to the ChangeQueryProcessor.ChangeAttributeFactory class in the plugin module's 'configure()' method. The new attribute(s) will be output under a "plugin" attribute in the change query output. This can be further controlled with an option registered in the Http and Ssh modules' 'configure*()' methods. The example below shows a plugin that adds two attributes ('exampleName' and 'changeValue'), to the change query output, when the query command is provided the --myplugin-name--all option. [source, java] ---- public class Module extends AbstractModule { @Override protected void configure() { bind(ChangeAttributeFactory.class) .annotatedWith(Exports.named("example")) .to(AttributeFactory.class); } } public class MyQueryOptions implements DynamicBean { @Option(name = "--all", usage = "Include plugin output") public boolean all = false; } public static class HttpModule extends HttpPluginModule { @Override protected void configureServlets() { bind(DynamicBean.class) .annotatedWith(Exports.named(QueryChanges.class)) .to(MyQueryOptions.class); } } public static class SshModule extends PluginCommandModule { @Override protected void configureCommands() { bind(DynamicBean.class) .annotatedWith(Exports.named(Query.class)) .to(MyQueryOptions.class); } } public class AttributeFactory implements ChangeAttributeFactory { protected MyQueryOptions options; public class PluginAttribute extends PluginDefinedInfo { public String exampleName; public String changeValue; public PluginAttribute(ChangeData c) { this.exampleName = "Attribute Example"; this.changeValue = Integer.toString(c.getId().get()); } } @Override public PluginDefinedInfo create(ChangeData c, ChangeQueryProcessor qp, String plugin) { if (options == null) { options = (MyQueryOptions) qp.getDynamicBean(plugin); } if (options.all) { return new PluginAttribute(c); } return null; } } ---- Example ---- ssh -p 29418 localhost gerrit query --myplugin-name--all "change:1" --format json Output: { "url" : "http://localhost:8080/1", "plugins" : [ { "name" : "myplugin-name", "exampleName" : "Attribute Example", "changeValue" : "1" } ], ... } ---- [[simple-configuration]] == Simple Configuration in `gerrit.config` In Gerrit, global configuration is stored in the `gerrit.config` file. If a plugin needs global configuration, this configuration should be stored in a `plugin` subsection in the `gerrit.config` file. This approach of storing the plugin configuration is only suitable for plugins that have a simple configuration that only consists of key-value pairs. With this approach it is not possible to have subsections in the plugin configuration. Plugins that require a complex configuration need to store their configuration in their link:#configuration[own configuration file] where they can make use of subsections. On the other hand storing the plugin configuration in a 'plugin' subsection in the `gerrit.config` file has the advantage that administrators have all configuration parameters in one file, instead of having one configuration file per plugin. To avoid conflicts with other plugins, it is recommended that plugins only use the `plugin` subsection with their own name. For example the `helloworld` plugin should store its configuration in the `plugin.helloworld` subsection: ---- [plugin "helloworld"] language = Latin ---- Via the `com.google.gerrit.server.config.PluginConfigFactory` class a plugin can easily access its configuration and there is no need for a plugin to parse the `gerrit.config` file on its own: [source,java] ---- @Inject private com.google.gerrit.server.config.PluginConfigFactory cfg; [...] String language = cfg.getFromGerritConfig("helloworld") .getString("language", "English"); ---- [[configuration]] == Configuration in own config file Plugins can store their configuration in an own configuration file. This makes sense if the plugin configuration is rather complex and requires the usage of subsections. Plugins that have a simple key-value pair configuration can store their configuration in a link:#simple-configuration[`plugin` subsection of the `gerrit.config` file]. The plugin configuration file must be named after the plugin and must be located in the `etc` folder of the review site. For example a configuration file for a `default-reviewer` plugin could look like this: .$site_path/etc/default-reviewer.config ---- [branch "refs/heads/master"] reviewer = Project Owners reviewer = john.doe@example.com [match "file:^.*\.txt"] reviewer = My Info Developers ---- Plugins that have sensitive configuration settings can store those settings in an own secure configuration file. The plugin's secure configuration file must be named after the plugin and must be located in the `etc` folder of the review site. For example a secure configuration file for a `default-reviewer` plugin could look like this: .$site_path/etc/default-reviewer.secure.config ---- [auth] password = secret ---- Via the `com.google.gerrit.server.config.PluginConfigFactory` class a plugin can easily access its configuration: [source,java] ---- @Inject private com.google.gerrit.server.config.PluginConfigFactory cfg; [...] String[] reviewers = cfg.getGlobalPluginConfig("default-reviewer") .getStringList("branch", "refs/heads/master", "reviewer"); String password = cfg.getGlobalPluginConfig("default-reviewer") .getString("auth", null, "password"); ---- [[simple-project-specific-configuration]] == Simple Project Specific Configuration in `project.config` In Gerrit, project specific configuration is stored in the project's `project.config` file on the `refs/meta/config` branch. If a plugin needs configuration on project level (e.g. to enable its functionality only for certain projects), this configuration should be stored in a `plugin` subsection in the project's `project.config` file. This approach of storing the plugin configuration is only suitable for plugins that have a simple configuration that only consists of key-value pairs. With this approach it is not possible to have subsections in the plugin configuration. Plugins that require a complex configuration need to store their configuration in their link:#project-specific-configuration[own configuration file] where they can make use of subsections. On the other hand storing the plugin configuration in a 'plugin' subsection in the `project.config` file has the advantage that project owners have all configuration parameters in one file, instead of having one configuration file per plugin. To avoid conflicts with other plugins, it is recommended that plugins only use the `plugin` subsection with their own name. For example the `helloworld` plugin should store its configuration in the `plugin.helloworld` subsection: ---- [plugin "helloworld"] enabled = true ---- Via the `com.google.gerrit.server.config.PluginConfigFactory` class a plugin can easily access its project specific configuration and there is no need for a plugin to parse the `project.config` file on its own: [source,java] ---- @Inject private com.google.gerrit.server.config.PluginConfigFactory cfg; [...] boolean enabled = cfg.getFromProjectConfig(project, "helloworld") .getBoolean("enabled", false); ---- It is also possible to get missing configuration parameters inherited from the parent projects: [source,java] ---- @Inject private com.google.gerrit.server.config.PluginConfigFactory cfg; [...] boolean enabled = cfg.getFromProjectConfigWithInheritance(project, "helloworld") .getBoolean("enabled", false); ---- Project owners can edit the project configuration by fetching the `refs/meta/config` branch, editing the `project.config` file and pushing the commit back. Plugin configuration values that are stored in the `project.config` file can be exposed in the ProjectInfoScreen to allow project owners to see and edit them from the UI. For this an instance of `ProjectConfigEntry` needs to be bound for each parameter. The export name must be a valid Git variable name. The variable name is case-insensitive, allows only alphanumeric characters and '-', and must start with an alphabetic character. The example below shows how the parameters `plugin.helloworld.enabled` and `plugin.helloworld.language` are bound to be editable from the Web UI. For the parameter `plugin.helloworld.enabled` "Enable Greeting" is provided as display name and the default value is set to `true`. For the parameter `plugin.helloworld.language` "Preferred Language" is provided as display name and "en" is set as default value. [source,java] ---- class Module extends AbstractModule { @Override protected void configure() { bind(ProjectConfigEntry.class) .annotatedWith(Exports.named("enabled")) .toInstance(new ProjectConfigEntry("Enable Greeting", true)); bind(ProjectConfigEntry.class) .annotatedWith(Exports.named("language")) .toInstance(new ProjectConfigEntry("Preferred Language", "en")); } } ---- By overwriting the `onUpdate` method of `ProjectConfigEntry` plugins can be notified when this configuration parameter is updated on a project. [[configuring-groups]] === Referencing groups in `project.config` Plugins can refer to groups so that when they are renamed, the project config will also be updated in this section. The proper format to use is the same as for any other group reference in the `project.config`, as shown below. ---- group group_name ---- The file `groups` must also contains the mapping of the group name and its UUID, refer to link:config-project-config.html#file-groups[file groups] [[project-specific-configuration]] == Project Specific Configuration in own config file Plugins can store their project specific configuration in an own configuration file in the projects `refs/meta/config` branch. This makes sense if the plugins project specific configuration is rather complex and requires the usage of subsections. Plugins that have a simple key-value pair configuration can store their project specific configuration in a link:#simple-project-specific-configuration[ `plugin` subsection of the `project.config` file]. The plugin configuration file in the `refs/meta/config` branch must be named after the plugin. For example a configuration file for a `default-reviewer` plugin could look like this: .default-reviewer.config ---- [branch "refs/heads/master"] reviewer = Project Owners reviewer = john.doe@example.com [match "file:^.*\.txt"] reviewer = My Info Developers ---- Via the `com.google.gerrit.server.config.PluginConfigFactory` class a plugin can easily access its project specific configuration: [source,java] ---- @Inject private com.google.gerrit.server.config.PluginConfigFactory cfg; [...] String[] reviewers = cfg.getProjectPluginConfig(project, "default-reviewer") .getStringList("branch", "refs/heads/master", "reviewer"); ---- It is also possible to get missing configuration parameters inherited from the parent projects: [source,java] ---- @Inject private com.google.gerrit.server.config.PluginConfigFactory cfg; [...] String[] reviewers = cfg.getProjectPluginConfigWithInheritance(project, "default-reviewer") .getStringList("branch", "refs/heads/master", "reviewer"); ---- Project owners can edit the project configuration by fetching the `refs/meta/config` branch, editing the `.config` file and pushing the commit back. == React on changes in project configuration If a plugin wants to react on changes in the project configuration, it can implement a `GitReferenceUpdatedListener` and filter on events for the `refs/meta/config` branch: [source,java] ---- public class MyListener implements GitReferenceUpdatedListener { private final MetaDataUpdate.Server metaDataUpdateFactory; @Inject MyListener(MetaDataUpdate.Server metaDataUpdateFactory) { this.metaDataUpdateFactory = metaDataUpdateFactory; } @Override public void onGitReferenceUpdated(Event event) { if (event.getRefName().equals(RefNames.REFS_CONFIG)) { Project.NameKey p = new Project.NameKey(event.getProjectName()); try { ProjectConfig oldCfg = parseConfig(p, event.getOldObjectId()); ProjectConfig newCfg = parseConfig(p, event.getNewObjectId()); if (oldCfg != null && newCfg != null && !oldCfg.getProject().getSubmitType().equals(newCfg.getProject().getSubmitType())) { // submit type has changed ... } } catch (IOException | ConfigInvalidException e) { ... } } } private ProjectConfig parseConfig(Project.NameKey p, String idStr) throws IOException, ConfigInvalidException, RepositoryNotFoundException { ObjectId id = ObjectId.fromString(idStr); if (ObjectId.zeroId().equals(id)) { return null; } return ProjectConfig.read(metaDataUpdateFactory.create(p), id); } } ---- [[capabilities]] == Plugin Owned Capabilities Plugins may provide their own capabilities and restrict usage of SSH commands or `UiAction` to the users who are granted those capabilities. Plugins define the capabilities by overriding the `CapabilityDefinition` abstract class: [source,java] ---- public class PrintHelloCapability extends CapabilityDefinition { @Override public String getDescription() { return "Print Hello"; } } ---- If no Guice modules are declared in the manifest, capability may use auto-registration by providing an `@Export` annotation: [source,java] ---- @Export("printHello") public class PrintHelloCapability extends CapabilityDefinition { [...] } ---- Otherwise the capability must be bound in a plugin module: [source,java] ---- public class HelloWorldModule extends AbstractModule { @Override protected void configure() { bind(CapabilityDefinition.class) .annotatedWith(Exports.named("printHello")) .to(PrintHelloCapability.class); } } ---- With a plugin-owned capability defined in this way, it is possible to restrict usage of an SSH command or `UiAction` to members of the group that were granted this capability in the usual way, using the `RequiresCapability` annotation: [source,java] ---- @RequiresCapability("printHello") @CommandMetaData(name="print", description="Print greeting in different languages") public final class PrintHelloWorldCommand extends SshCommand { [...] } ---- Or with `UiAction`: [source,java] ---- @RequiresCapability("printHello") public class SayHelloAction extends UiAction implements RestModifyView { [...] } ---- Capability scope was introduced to differentiate between plugin-owned capabilities and core capabilities. Per default the scope of the `@RequiresCapability` annotation is `CapabilityScope.CONTEXT`, that means: * when `@RequiresCapability` is used within a plugin the scope of the capability is assumed to be that plugin. * If `@RequiresCapability` is used within the core Gerrit Code Review server (and thus is outside of a plugin) the scope is the core server and will use the `GlobalCapability` known to Gerrit Code Review server. If a plugin needs to use a core capability name (e.g. "administrateServer") this can be specified by setting `scope = CapabilityScope.CORE`: [source,java] ---- @RequiresCapability(value = "administrateServer", scope = CapabilityScope.CORE) [...] ---- [[ui_extension]] == UI Extension [[panels]] === Panels UI plugins can contribute panels to Gerrit screens. Gerrit screens define extension points where plugins can add GWT panels with custom controls: * Change Screen: ** `GerritUiExtensionPoint.CHANGE_SCREEN_HEADER`: + Panel will be shown in the header bar to the right of the change status. ** `GerritUiExtensionPoint.CHANGE_SCREEN_HEADER_RIGHT_OF_BUTTONS`: + Panel will be shown in the header bar on the right side of the buttons. ** `GerritUiExtensionPoint.CHANGE_SCREEN_HEADER_RIGHT_OF_POP_DOWNS`: + Panel will be shown in the header bar on the right side of the pop down buttons. ** `GerritUiExtensionPoint.CHANGE_SCREEN_BELOW_COMMIT_INFO_BLOCK`: + Panel will be shown below the commit info block. ** `GerritUiExtensionPoint.CHANGE_SCREEN_BELOW_CHANGE_INFO_BLOCK`: + Panel will be shown below the change info block. ** `GerritUiExtensionPoint.CHANGE_SCREEN_BELOW_RELATED_INFO_BLOCK`: + Panel will be shown below the related info block. ** `GerritUiExtensionPoint.CHANGE_SCREEN_HISTORY_RIGHT_OF_BUTTONS`: + Panel will be shown in the history bar on the right side of the buttons. ** The following parameters are provided: *** `GerritUiExtensionPoint.Key.CHANGE_INFO`: + The link:rest-api-changes.html#change-info[ChangeInfo] entity for the current change. + The link:rest-api-changes.html#revision-info[RevisionInfo] entity for the current patch set. * Project Info Screen: ** `GerritUiExtensionPoint.PROJECT_INFO_SCREEN_TOP`: + Panel will be shown at the top of the screen. ** `GerritUiExtensionPoint.PROJECT_INFO_SCREEN_BOTTOM`: + Panel will be shown at the bottom of the screen. ** The following parameters are provided: *** `GerritUiExtensionPoint.Key.PROJECT_NAME`: + The name of the project. * User Password Screen: ** `GerritUiExtensionPoint.PASSWORD_SCREEN_BOTTOM`: + Panel will be shown at the bottom of the screen. ** The following parameters are provided: *** `GerritUiExtensionPoint.Key.ACCOUNT_INFO`: + The link:rest-api-accounts.html#account-info[AccountInfo] entity for the current user. * User Preferences Screen: ** `GerritUiExtensionPoint.PREFERENCES_SCREEN_BOTTOM`: + Panel will be shown at the bottom of the screen. ** The following parameters are provided: *** `GerritUiExtensionPoint.Key.ACCOUNT_INFO`: + The link:rest-api-accounts.html#account-info[AccountInfo] entity for the current user. * User Profile Screen: ** `GerritUiExtensionPoint.PROFILE_SCREEN_BOTTOM`: + Panel will be shown at the bottom of the screen below the grid with the profile data. ** The following parameters are provided: *** `GerritUiExtensionPoint.Key.ACCOUNT_INFO`: + The link:rest-api-accounts.html#account-info[AccountInfo] entity for the current user. Example panel: [source,java] ---- public class MyPlugin extends PluginEntryPoint { @Override public void onPluginLoad() { Plugin.get().panel(GerritUiExtensionPoint.CHANGE_SCREEN_BELOW_CHANGE_INFO_BLOCK, "my_panel_name", new Panel.EntryPoint() { @Override public void onLoad(Panel panel) { panel.setWidget(new InlineLabel("My Panel for change " + panel.getInt(GerritUiExtensionPoint.Key.CHANGE_ID, -1)); } }); } } ---- Change Screen panel ordering may be specified in the project config. Values may be either "plugin name" or "plugin name"."panel name". Panels not specified in the config will be added to the end in load order. Panels specified in the config that are not found will be ignored. Example config: ---- [extension-panels "CHANGE_SCREEN_BELOW_CHANGE_INFO_BLOCK"] panel = helloworld.change_id panel = myotherplugin panel = myplugin.my_panel_name ---- [[actions]] === Actions Plugins can contribute UI actions on core Gerrit pages. This is useful for workflow customization or exposing plugin functionality through the UI in addition to SSH commands and the REST API. For instance a plugin to integrate Jira with Gerrit changes may contribute a "File bug" button to allow filing a bug from the change page or plugins to integrate continuous integration systems may contribute a "Schedule" button to allow a CI build to be scheduled manually from the patch set panel. Two different places on core Gerrit pages are supported: * Change screen * Project info screen Plugins contribute UI actions by implementing the `UiAction` interface: [source,java] ---- @RequiresCapability("printHello") class HelloWorldAction implements UiAction, RestModifyView { static class Input { boolean french; String message; } private Provider user; @Inject HelloWorldAction(Provider user) { this.user = user; } @Override public String apply(RevisionResource rev, Input input) { final String greeting = input.french ? "Bonjour" : "Hello"; return String.format("%s %s from change %s, patch set %d!", greeting, Strings.isNullOrEmpty(input.message) ? Objects.firstNonNull(user.get().getUserName(), "world") : input.message, rev.getChange().getId().toString(), rev.getPatchSet().getPatchSetId()); } @Override public Description getDescription( RevisionResource resource) { return new Description() .setLabel("Say hello") .setTitle("Say hello in different languages"); } } ---- Sometimes plugins may want to be able to change the state of a patch set or change in the `UiAction.apply()` method and reflect these changes on the core UI. For example a buildbot plugin which exposes a 'Schedule' button on the patch set panel may want to disable that button after the build was scheduled and update the tooltip of that button. But because of Gerrit's caching strategy the following must be taken into consideration. The browser is allowed to cache the `UiAction` information until something on the change is modified. More accurately the change row needs to be modified in the database to have a more recent `lastUpdatedOn` or a new `rowVersion`, or the +refs/meta/config+ of the project or any parents needs to change to a new SHA-1. The ETag SHA-1 computation code can be found in the `ChangeResource.getETag()` method. The easiest way to accomplish this is to update `lastUpdatedOn` of the change: [source,java] ---- @Override public Object apply(RevisionResource rcrs, Input in) { // schedule a build [...] // update change ReviewDb db = dbProvider.get(); try (BatchUpdate bu = batchUpdateFactory.create( db, project.getNameKey(), user, TimeUtil.nowTs())) { bu.addOp(change.getId(), new BatchUpdate.Op() { @Override public boolean updateChange(ChangeContext ctx) { return true; } }); bu.execute(); } [...] } ---- `UiAction` must be bound in a plugin module: [source,java] ---- public class Module extends AbstractModule { @Override protected void configure() { install(new RestApiModule() { @Override protected void configure() { post(REVISION_KIND, "say-hello") .to(HelloWorldAction.class); } }); } } ---- The module above must be declared in the `pom.xml` for Maven driven plugins: [source,xml] ---- com.googlesource.gerrit.plugins.cookbook.Module ---- or in the `BUILD` configuration file for Bazel driven plugins: [source,python] ---- manifest_entries = [ 'Gerrit-Module: com.googlesource.gerrit.plugins.cookbook.Module', ] ---- In some use cases more user input must be gathered, for that `UiAction` can be combined with the JavaScript API. This would display a small popup near the activation button to gather additional input from the user. The JS file is typically put in the `static` folder within the plugin's directory: [source,javascript] ---- Gerrit.install(function(self) { function onSayHello(c) { var f = c.textfield(); var t = c.checkbox(); var b = c.button('Say hello', {onclick: function(){ c.call( {message: f.value, french: t.checked}, function(r) { c.hide(); window.alert(r); c.refresh(); }); }}); c.popup(c.div( c.prependLabel('Greeting message', f), c.br(), c.label(t, 'french'), c.br(), b)); f.focus(); } self.onAction('revision', 'say-hello', onSayHello); }); ---- The JS module must be exposed as a `WebUiPlugin` and bound as an HTTP Module: [source,java] ---- public class HttpModule extends HttpPluginModule { @Override protected void configureServlets() { DynamicSet.bind(binder(), WebUiPlugin.class) .toInstance(new JavaScriptPlugin("hello.js")); } } ---- The HTTP module above must be declared in the `pom.xml` for Maven driven plugins: [source,xml] ---- com.googlesource.gerrit.plugins.cookbook.HttpModule ---- or in the `BUILD` configuration file for Bazel driven plugins [source,python] ---- manifest_entries = [ 'Gerrit-HttpModule: com.googlesource.gerrit.plugins.cookbook.HttpModule', ] ---- If `UiAction` is annotated with the `@RequiresCapability` annotation, then the capability check is done during the `UiAction` gathering, so the plugin author doesn't have to set `UiAction.Description.setVisible()` explicitly in this case. The following prerequisites must be met, to satisfy the capability check: * user is authenticated * user is a member of a group which has the `Administrate Server` capability, or * user is a member of a group which has the required capability The `apply` method is called when the button is clicked. If `UiAction` is combined with JavaScript API (its own JavaScript function is provided), then a popup dialog is normally opened to gather additional user input. A new button is placed on the popup dialog to actually send the request. Every `UiAction` exposes a REST API endpoint. The endpoint from the example above can be accessed from any REST client, i. e.: ---- curl -X POST -H "Content-Type: application/json" \ -d '{message: "François", french: true}' \ --user joe:secret \ http://host:port/a/changes/1/revisions/1/cookbook~say-hello "Bonjour François from change 1, patch set 1!" ---- A special case is to bind an endpoint without a view name. This is particularly useful for `DELETE` requests: [source,java] ---- public class Module extends AbstractModule { @Override protected void configure() { install(new RestApiModule() { @Override protected void configure() { delete(PROJECT_KIND) .to(DeleteProject.class); } }); } } ---- For a `UiAction` bound this way, a JS API function can be provided. Currently only one restriction exists: per plugin only one `UiAction` can be bound per resource without view name. To define a JS function for the `UiAction`, "/" must be used as the name: [source,javascript] ---- Gerrit.install(function(self) { function onDeleteProject(c) { [...] } self.onAction('project', '/', onDeleteProject); }); ---- [[action-visitor]] === Action Visitors In addition to providing new actions, plugins can have fine-grained control over the link:rest-api-changes.html#action-info[ActionInfo] map, modifying or removing existing actions, including those contributed by core. Visitors are provided the link:rest-api-changes.html#action-info[ActionInfo], which is mutable, along with copies of the link:rest-api-changes.html#change-info[ChangeInfo] and link:rest-api-changes.html#revision-info[RevisionInfo]. They can modify the action, or return `false` to exclude it from the resulting map. These operations only affect the action buttons that are displayed in the UI; the underlying REST API endpoints are not affected. Multiple plugins may implement the visitor interface, but the order in which they are run is undefined. For example, to exclude "Cherry-Pick" only from certain projects, and rename "Abandon": [source,java] ---- public class MyActionVisitor implements ActionVisitor { @Override public boolean visit(String name, ActionInfo actionInfo, ChangeInfo changeInfo) { if (name.equals("abandon")) { actionInfo.label = "Drop"; } return true; } @Override public boolean visit(String name, ActionInfo actionInfo, ChangeInfo changeInfo, RevisionInfo revisionInfo) { if (project.startsWith("some-team/") && name.equals("cherrypick")) { return false; } return true; } } ---- [[top-menu-extensions]] == Top Menu Extensions Plugins can contribute items to Gerrit's top menu. A single top menu extension can have multiple elements and will be put as the last element in Gerrit's top menu. Plugins define the top menu entries by implementing `TopMenu` interface: [source,java] ---- public class MyTopMenuExtension implements TopMenu { @Override public List getEntries() { return Lists.newArrayList( new MenuEntry("Top Menu Entry", Lists.newArrayList( new MenuItem("Gerrit", "http://gerrit.googlecode.com/")))); } } ---- Plugins can also add additional menu items to Gerrit's top menu entries by defining a `MenuEntry` that has the same name as a Gerrit top menu entry: [source,java] ---- public class MyTopMenuExtension implements TopMenu { @Override public List getEntries() { return Lists.newArrayList( new MenuEntry(GerritTopMenu.PROJECTS, Lists.newArrayList( new MenuItem("Browse Repositories", "https://gerrit.googlesource.com/")))); } } ---- `MenuItems` that are bound for the `MenuEntry` with the name `GerritTopMenu.PROJECTS` can contain a `${projectName}` placeholder which is automatically replaced by the actual project name. E.g. plugins may register an link:#http[HTTP Servlet] to handle project specific requests and add an menu item for this: [source,java] --- new MenuItem("My Screen", "/plugins/myplugin/project/${projectName}"); --- This also enables plugins to provide menu items for project aware screens: [source,java] --- new MenuItem("My Screen", "/x/my-screen/for/${projectName}"); --- If no Guice modules are declared in the manifest, the top menu extension may use auto-registration by providing an `@Listen` annotation: [source,java] ---- @Listen public class MyTopMenuExtension implements TopMenu { [...] } ---- Otherwise the top menu extension must be bound in the plugin module used for the Gerrit system injector (Gerrit-Module entry in MANIFEST.MF): [source,java] ---- package com.googlesource.gerrit.plugins.helloworld; public class HelloWorldModule extends AbstractModule { @Override protected void configure() { DynamicSet.bind(binder(), TopMenu.class).to(MyTopMenuExtension.class); } } ---- [source,manifest] ---- Gerrit-ApiType: plugin Gerrit-Module: com.googlesource.gerrit.plugins.helloworld.HelloWorldModule ---- It is also possible to show some menu entries only if the user has a certain capability: [source,java] ---- public class MyTopMenuExtension implements TopMenu { private final String pluginName; private final Provider userProvider; private final List menuEntries; @Inject public MyTopMenuExtension(@PluginName String pluginName, Provider userProvider) { this.pluginName = pluginName; this.userProvider = userProvider; menuEntries = new ArrayList(); // add menu entry that is only visible to users with a certain capability if (canSeeMenuEntry()) { menuEntries.add(new MenuEntry("Top Menu Entry", Collections .singletonList(new MenuItem("Gerrit", "http://gerrit.googlecode.com/")))); } // add menu entry that is visible to all users (even anonymous users) menuEntries.add(new MenuEntry("Top Menu Entry", Collections .singletonList(new MenuItem("Documentation", "/plugins/myplugin/")))); } private boolean canSeeMenuEntry() { if (userProvider.get().isIdentifiedUser()) { CapabilityControl ctl = userProvider.get().getCapabilities(); return ctl.canPerform(pluginName + "-" + MyCapability.ID) || ctl.canAdministrateServer(); } else { return false; } } @Override public List getEntries() { return menuEntries; } } ---- [[settings-screen]] == Plugin Settings Screen If a plugin implements a screen for administrating its settings that is available under "#/x//settings" it is automatically linked from the plugin list screen. [[http]] == HTTP Servlets Plugins or extensions may register additional HTTP servlets, and wrap them with HTTP filters. Servlets may use auto-registration to declare the URL they handle: [source,java] ---- import com.google.gerrit.extensions.annotations.Export; import com.google.inject.Singleton; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; @Export("/print") @Singleton class HelloServlet extends HttpServlet { protected void doGet(HttpServletRequest req, HttpServletResponse res) throws IOException { res.setContentType("text/plain"); res.setCharacterEncoding("UTF-8"); res.getWriter().write("Hello"); } } ---- The auto registration only works for standard servlet mappings like `/foo` or `+/foo/*+`. Regex style bindings must use a Guice ServletModule to register the HTTP servlets and declare it explicitly in the manifest with the `Gerrit-HttpModule` attribute: [source,java] ---- import com.google.inject.servlet.ServletModule; class MyWebUrls extends ServletModule { protected void configureServlets() { serve("/print").with(HelloServlet.class); } } ---- For a plugin installed as name `helloworld`, the servlet implemented by HelloServlet class will be available to users as: ---- $ curl http://review.example.com/plugins/helloworld/print ---- [[data-directory]] == Data Directory Plugins can request a data directory with a `@PluginData` Path (or File, deprecated) dependency. A data directory will be created automatically by the server in `$site_path/data/$plugin_name` and passed to the plugin. Plugins can use this to store any data they want. [source,java] ---- @Inject MyType(@PluginData java.nio.file.Path myDir) { this.in = Files.newInputStream(myDir.resolve("my.config")); } ---- [[secure-store]] == SecureStore SecureStore allows to change the way Gerrit stores sensitive data like passwords. In order to replace the default SecureStore (no-op) implementation, a class that extends `com.google.gerrit.server.securestore.SecureStore` needs to be provided (with dependencies) in a separate jar file. Then link:pgm-SwitchSecureStore.html[SwitchSecureStore] must be run to switch implementations. The SecureStore implementation is instantiated using a Guice injector which binds the `File` annotated with the `@SitePath` annotation. This means that a SecureStore implementation class can get access to the `site_path` like in the following example: [source,java] ---- @Inject MySecureStore(@SitePath java.io.File sitePath) { // your code } ---- No Guice bindings or modules are required. Gerrit will automatically discover and bind the implementation. [[accountcreation]] == Account Creation Plugins can hook into the link:rest-api-accounts.html#create-account[account creation] REST API and inject additional external identifiers for an account that represents a user in some external user store. For that, an implementation of the extension point `com.google.gerrit.server.account.AccountExternalIdCreator` must be registered. [source,java] ---- class MyExternalIdCreator implements AccountExternalIdCreator { @Override public List create(Account.Id id, String username, String email) { // your code } } bind(AccountExternalIdCreator.class) .annotatedWith(UniqueAnnotations.create()) .to(MyExternalIdCreator.class); } ---- [[download-commands]] == Download Commands Gerrit offers commands for downloading changes and cloning projects using different download schemes (e.g. for downloading via different network protocols). Plugins can contribute download schemes, download commands and clone commands by implementing `com.google.gerrit.extensions.config.DownloadScheme`, `com.google.gerrit.extensions.config.DownloadCommand` and `com.google.gerrit.extensions.config.CloneCommand`. The download schemes, download commands and clone commands which are used most often are provided by the Gerrit core plugin `download-commands`. [[included-in]] == Included In For merged changes the link:user-review-ui.html#included-in[Included In] drop-down panel shows the branches and tags in which the change is included. Plugins can add additional systems in which the change can be included by implementing `com.google.gerrit.extensions.config.ExternalIncludedIn`, e.g. a plugin can provide a list of servers on which the change was deployed. [[change-report-formatting]] == Change Report Formatting When a change is pushed for review from the command line, Gerrit reports the change(s) received with their URL and subject. By implementing the `com.google.gerrit.server.git.ChangeReportFormatter` interface, a plugin may change the formatting of the report. [[links-to-external-tools]] == Links To External Tools Gerrit has extension points that enables development of a light-weight plugin that links commits to external tools (GitBlit, CGit, company specific resources etc). PatchSetWebLinks will appear to the right of the commit-SHA1 in the UI. [source, java] ---- import com.google.gerrit.extensions.annotations.Listen; import com.google.gerrit.extensions.webui.PatchSetWebLink;; import com.google.gerrit.extensions.webui.WebLinkTarget; @Listen public class MyWeblinkPlugin implements PatchSetWebLink { private String name = "MyLink"; private String placeHolderUrlProjectCommit = "http://my.tool.com/project=%s/commit=%s"; private String imageUrl = "http://placehold.it/16x16.gif"; @Override public WebLinkInfo getPatchSetWebLink(String projectName, String commit) { return new WebLinkInfo(name, imageUrl, String.format(placeHolderUrlProjectCommit, project, commit), WebLinkTarget.BLANK); } } ---- ParentWebLinks will appear to the right of the SHA1 of the parent revisions in the UI. The implementation should in most use cases direct to the same external service as PatchSetWebLink; it is provided as a separate interface because not all users want to have links for the parent revisions. FileWebLinks will appear in the side-by-side diff screen on the right side of the patch selection on each side. DiffWebLinks will appear in the side-by-side and unified diff screen in the header next to the navigation icons. ProjectWebLinks will appear in the project list in the `Repository Browser` column. BranchWebLinks will appear in the branch list in the last column. FileHistoryWebLinks will appear on the access rights screen. TagWebLinks will appear in the tag list in the last column. If a `get*WebLink` implementation returns `null`, the link will be omitted. This allows the plugin to selectively "enable" itself on a per-project/branch/file basis. [[lfs-extension]] == LFS Storage Plugins Gerrit provides an extension point that enables development of link:https://github.com/github/git-lfs/blob/master/docs/api/v1/http-v1-batch.md[ LFS (Large File Storage)] storage plugins. Gerrit core exposes the default LFS protocol endpoint `/info/lfs/objects/batch` and forwards the requests to the configured link:config-gerrit.html#lfs[lfs.plugin] plugin which implements the LFS protocol. By exposing the default LFS endpoint, the git-lfs client can be used without any configuration. [source, java] ---- /** Provide an LFS protocol implementation */ import org.eclipse.jgit.lfs.server.LargeFileRepository; import org.eclipse.jgit.lfs.server.LfsProtocolServlet; @Singleton public class LfsApiServlet extends LfsProtocolServlet { private static final long serialVersionUID = 1L; private final S3LargeFileRepository repository; @Inject LfsApiServlet(S3LargeFileRepository repository) { this.repository = repository; } @Override protected LargeFileRepository getLargeFileRepository() { return repository; } } /** Register the LfsApiServlet to listen on the default LFS protocol endpoint */ import static com.google.gerrit.httpd.plugins.LfsPluginServlet.URL_REGEX; import com.google.gerrit.httpd.plugins.HttpPluginModule; public class HttpModule extends HttpPluginModule { @Override protected void configureServlets() { serveRegex(URL_REGEX).with(LfsApiServlet.class); } } /** Provide an implementation of the LargeFileRepository */ import org.eclipse.jgit.lfs.server.s3.S3Repository; public class S3LargeFileRepository extends S3Repository { ... } ---- [[metrics]] == Metrics === Metrics Reporting To send Gerrit's metrics data to an external reporting backend, a plugin can get a `MetricRegistry` injected and register an instance of a class that implements the `Reporter` interface from link:http://metrics.dropwizard.io/[ DropWizard Metrics]. Metric reporting plugin implementations are provided for link:https://gerrit.googlesource.com/plugins/metrics-reporter-jmx/[JMX], link:https://gerrit.googlesource.com/plugins/metrics-reporter-elasticsearch/[Elastic Search], and link:https://gerrit.googlesource.com/plugins/metrics-reporter-graphite/[Graphite]. There is also a working example of reporting metrics to the console in the link:https://gerrit.googlesource.com/plugins/cookbook-plugin/+/master/src/main/java/com/googlesource/gerrit/plugins/cookbook/ConsoleMetricReporter.java[ cookbook plugin]. === Providing own metrics Plugins may provide metrics to be dispatched to external reporting services by getting a `MetricMaker` injected and creating instances of specific types of metric: * Counter + Metric whose value increments during the life of the process. * Timer + Metric recording time spent on an operation. * Histogram + Metric recording statistical distribution (rate) of values. Note that metrics cannot be recorded from plugin init steps that are run during site initialization. By default, plugin metrics are recorded under `plugins/${plugin-name}/${metric-name}`. This can be changed by setting `plugins.${plugin-name}.metricsPrefix` in the `gerrit.config` file. For example: ---- [plugin "my-plugin"] metricsPrefix = my-metrics ---- will cause the metrics to be recorded under `my-metrics/${metric-name}`. See the replication metrics in the link:https://gerrit.googlesource.com/plugins/replication/+/master/src/main/java/com/googlesource/gerrit/plugins/replication/ReplicationMetrics.java[ replication plugin] for an example of usage. [[account-patch-review-store]] == AccountPatchReviewStore The AccountPatchReviewStore is used to store reviewed flags on changes. A reviewed flag is a tuple of (patch set ID, file, account ID) and records whether the user has reviewed a file in a patch set. Each user can easily have thousands of reviewed flags and the number of reviewed flags is growing without bound. The store must be able handle this data volume efficiently. Gerrit implements this extension point, but plugins may bind another implementation, e.g. one that supports multi-master. ---- DynamicItem.bind(binder(), AccountPatchReviewStore.class) .to(MultiMasterAccountPatchReviewStore.class); ... public class MultiMasterAccountPatchReviewStore implements AccountPatchReviewStore { ... } ---- [[documentation]] == Documentation If a plugin does not register a filter or servlet to handle URLs `+/Documentation/*+` or `+/static/*+`, the core Gerrit server will automatically export these resources over HTTP from the plugin JAR. Static resources under the `static/` directory in the JAR will be available as `/plugins/helloworld/static/resource`. This prefix is configurable by setting the `Gerrit-HttpStaticPrefix` attribute. Documentation files under the `Documentation/` directory in the JAR will be available as `/plugins/helloworld/Documentation/resource`. This prefix is configurable by setting the `Gerrit-HttpDocumentationPrefix` attribute. Documentation may be written in the Markdown flavor link:https://github.com/vsch/flexmark-java[flexmark-java] if the file name ends with `.md`. Gerrit will automatically convert Markdown to HTML if accessed with extension `.html`. [[macros]] Within the Markdown documentation files macros can be used that allow to write documentation with reasonably accurate examples that adjust automatically based on the installation. The following macros are supported: [width="40%",options="header"] |=================================================== |Macro | Replacement |@PLUGIN@ | name of the plugin |@URL@ | Gerrit Web URL |@SSH_HOST@ | SSH Host |@SSH_PORT@ | SSH Port |=================================================== The macros will be replaced when the documentation files are rendered from Markdown to HTML. Macros that start with `\` such as `\@KEEP@` will render as `@KEEP@` even if there is an expansion for `KEEP` in the future. [[auto-index]] === Automatic Index If a plugin does not handle its `/` URL itself, Gerrit will redirect clients to the plugin's `/Documentation/index.html`. Requests for `/Documentation/` (bare directory) will also redirect to `/Documentation/index.html`. If neither resource `Documentation/index.html` or `Documentation/index.md` exists in the plugin JAR, Gerrit will automatically generate an index page for the plugin's documentation tree by scanning every `*.md` and `*.html` file in the Documentation/ directory. For any discovered Markdown (`*.md`) file, Gerrit will parse the header of the file and extract the first level one title. This title text will be used as display text for a link to the HTML version of the page. For any discovered HTML (`*.html`) file, Gerrit will use the name of the file, minus the `*.html` extension, as the link text. Any hyphens in the file name will be replaced with spaces. If a discovered file is named `about.md` or `about.html`, its content will be inserted in an 'About' section at the top of the auto-generated index page. If both `about.md` and `about.html` exist, only the first discovered file will be used. If a discovered file name beings with `cmd-` it will be clustered into a 'Commands' section of the generated index page. If a discovered file name beings with `servlet-` it will be clustered into a 'Servlets' section of the generated index page. If a discovered file name beings with `rest-api-` it will be clustered into a 'REST APIs' section of the generated index page. All other files are clustered under a 'Documentation' section. Some optional information from the manifest is extracted and displayed as part of the index page, if present in the manifest: [width="40%",options="header"] |=================================================== |Field | Source Attribute |Name | Implementation-Title |Vendor | Implementation-Vendor |Version | Implementation-Version |URL | Implementation-URL |API Version | Gerrit-ApiVersion |=================================================== [[deployment]] == Deployment Compiled plugins and extensions can be deployed to a running Gerrit server using the link:cmd-plugin-install.html[plugin install] command. Web UI plugins distributed as a single `.js` file (or `.html` file for Polygerrit) can be deployed without the overhead of JAR packaging. For more information refer to link:cmd-plugin-install.html[plugin install] command. Plugins can also be copied directly into the server's directory at `$site_path/plugins/$name.(jar|js|html)`. For Web UI plugins, the name of the file, minus the `.js` or `.html` extension, will be used as the plugin name. For JAR plugins, the value of the `Gerrit-PluginName` manifest attribute will be used, if provided, otherwise the name of the file, minus the `.jar` extension, will be used. For Web UI plugins, the plugin version is derived from the filename. If the filename contains one or more hyphens, the version is taken from the portion following the last hyphen. For example if the plugin filename is `my-plugin-1.0.js` the version will be `1.0`. For JAR plugins, the version is taken from the `Version` attribute in the manifest. Unless disabled, servers periodically scan the `$site_path/plugins` directory for updated plugins. The time can be adjusted by link:config-gerrit.html#plugins.checkFrequency[plugins.checkFrequency]. For disabling plugins the link:cmd-plugin-remove.html[plugin remove] command can be used. Disabled plugins can be re-enabled using the link:cmd-plugin-enable.html[plugin enable] command. == Known issues and bugs === Error handling in UI when using the REST API When a plugin invokes a REST endpoint in the UI, it provides an `AsyncCallback` to handle the result. At the moment the `onFailure(Throwable)` of the callback is never invoked, even if there is an error. Errors are always handled by the Gerrit core UI which shows the error dialog. This means currently plugins cannot do any error handling and e.g. ignore expected errors. In the following example the REST endpoint would return '404 Not Found' if the user has no username and the Gerrit core UI would display an error dialog for this. However having no username is not an error and the plugin may like to handle this case. [source,java] ---- new RestApi("accounts").id("self").view("username") .get(new AsyncCallback() { @Override public void onSuccess(NativeString username) { // TODO } @Override public void onFailure(Throwable caught) { // never invoked } }); ---- [[reviewer-suggestion]] == Reviewer Suggestion Plugins Gerrit provides an extension point that enables Plugins to rank the list of reviewer suggestion a user receives upon clicking "Add Reviewer" on the change screen. Gerrit supports both a default suggestion that appears when the user has not yet typed anything and a filtered suggestion that is shown as the user starts typing. Plugins receive a candidate list and can return a `Set` of suggested reviewers containing the `Account.Id` and a score for each reviewer. The candidate list is non-binding and plugins can choose to return reviewers not initially contained in the candidate list. Server administrators can configure the overall weight of each plugin by setting the `addreviewer.pluginName-exportName.weight` value in `gerrit.config`. [source, java] ---- import com.google.gerrit.common.Nullable; import com.google.gerrit.extensions.annotations.ExtensionPoint; import com.google.gerrit.reviewdb.client.Account; import com.google.gerrit.reviewdb.client.Change; import com.google.gerrit.reviewdb.client.Project; import java.util.Set; public class MyPlugin implements ReviewerSuggestion { public Set suggestReviewers(Project.NameKey project, @Nullable Change.Id changeId, @Nullable String query, Set candidates) { Set suggestions = new HashSet<>(); // Implement your ranking logic here return suggestions; } } ---- [[mail-filter]] == Mail Filter Plugins Gerrit provides an extension point that enables Plugins to discard incoming messages and prevent further processing by Gerrit. This can be used to implement spam checks, signature validations or organization specific checks like IP filters. [source, java] ---- import com.google.gerrit.extensions.annotations.ExtensionPoint; import com.google.gerrit.mail.MailMessage; public class MyPlugin implements MailFilter { public boolean shouldProcessMessage(MailMessage message) { // Implement your filter logic here return true; } } ---- [[ssh-command-interception]] == SSH Command Interception Gerrit provides an extension point that allows a plugin to intercept creation of SSH commands and override the functionality with its own implementation. [source, java] ---- import com.google.gerrit.sshd.SshCreateCommandInterceptor; class MyCommandInterceptor implements SshCreateCommandInterceptor { @Override public String intercept(String in) { return pluginName + " mycommand"; ---- [[pre-submit-evaluator]] == Pre-submit Validation Plugins Gerrit provides an extension point that enables plugins to prevent a change from being submitted. [IMPORTANT] This extension point **must NOT** be used for long or slow operations, like calling external programs or content, running unit tests... Slow operations will hurt the whole Gerrit instance. This can be used to implement custom rules that changes have to match to become submittable. A more concrete example: the Prolog rules engine can be implemented using this. Gerrit calls the plugins once per change and caches the results. Although it is possible to predict when this interface will be triggered, this should not be considered as a feature. Plugins should only rely on the internal state of the ChangeData, not on external values like date and time, remote content or randomness. Plugins are expected to support rules inheritance themselves, providing ways to configure it and handling the logic behind it. Please note that no inheritance is sometimes better than badly handled inheritance: mis-communication and strange behaviors caused by inheritance may and will confuse the users. Each plugins is responsible for handling the project hierarchy and taking wise actions. Gerrit does not enforce it. Once Gerrit has gathered every plugins' SubmitRecords, it stores them. Plugins accept or reject a given change using `SubmitRecord.Status`. If a change is ready to be submitted, `OK`. If it is not ready and requires modifications, `NOT_READY`. Other statuses are available for particular cases. A change can be submitted if all the plugins accept the change. Plugins may also decide not to vote on a given change by returning an empty Collection (ie: the plugin is not enabled for this repository), or to vote several times (ie: one SubmitRecord per project in the hierarchy). The results are handled as if multiple plugins voted for the change. If a plugin decides not to vote, it's name will not be displayed in the UI and it will not be recoded in the database. .Gerrit's Pre-submit handling with three plugins [width="50%",cols="^m,^m,^m,^m",frame="topbot",options="header"] |======================================================= | Plugin A | Plugin B | Plugin C | Final decision | OK | OK | OK | OK | OK | OK | / | OK | OK | OK | RULE_ERROR | NOT_READY | OK | NOT_READY | OK | NOT_READY | NOT_READY | OK | OK | NOT_READY |======================================================= This makes composing plugins really easy. - If a plugin places a veto on a change, it can't be submitted. - If a plugin isn't enabled for a project (or isn't needed for this change), it returns an empty collection. - If all the plugins answer `OK`, the change can be submitted. A more rare case, but worth documenting: if there are no installed plugins, the labels will be compared to the rules defined in the project's config, and the permission system will be used to allow or deny a submit request. Some rules are defined internally to provide a common base ground (and sanity): changes that are marked as WIP or that are closed (abandoned, merged) can't be merged. [source, java] ---- import java.util.Collection; import com.google.gerrit.common.data.SubmitRecord; import com.google.gerrit.common.data.SubmitRecord.Status; import com.google.gerrit.server.query.change.ChangeData; import com.google.gerrit.server.rules.SubmitRule; public class MyPluginRules implements SubmitRule { public Collection evaluate(ChangeData changeData) { // Implement your submitability logic here // Assuming we want to prevent this change from being submitted: SubmitRecord record; record.status = Status.NOT_READY; return record; } } ---- Don't forget to register your class! [source, java] ---- import com.google.gerrit.extensions.annotations.Exports; import com.google.inject.AbstractModule; public class MyPluginModule extends AbstractModule { @Override protected void configure() { bind(SubmitRule.class).annotatedWith(Exports.named("myPlugin")).to(MyPluginRules.class); } } ---- Plugin authors should also consider binding their SubmitRule using a `Gerrit-BatchModule`. See link:dev-plugins.html[Batch runtime] for more informations. The SubmitRule extension point allows you to write complex rules, but writing small self-contained rules should be preferred: doing so allows end users to compose several rules to form more complex submit checks. The `SubmitRequirement` class allows rules to communicate what the user needs to change in order to be compliant. These requirements should be kept once they are met, but marked as `OK`. If the requirements were not displayed, reviewers would need to use their precious time to manually check that they were met. == SEE ALSO * link:js-api.html[JavaScript API] * link:dev-rest-api.html[REST API Developers' Notes] GERRIT ------ Part of link:index.html[Gerrit Code Review] SEARCHBOX ---------