REST endpoint to reload gerrit.config

Change-Id: I8e2739a23c6bb0ed6981e05eafeddd8571ad67b6

Documentation/rest-api-config.txt

@@ -194,6 +194,51 @@ is returned that contains detected consistency problems.
 ----
 
 
+[[reload-config]]
+=== Reload Config
+--
+'POST /config/server/reload'
+--
+
+Reloads the gerrit.config configuration.
+
+Not all configuration value can be picked up by this command. Which config
+sections and values that are supported is documented here:
+link:config-gerrit.html[Configuration]
+
+_The output shows only modified config values that are picked up by Gerrit
+and applied._
+
+If a config entry is added or removed from gerrit.config, but still brings
+no effect due to a matching default value, no output for this entry is shown.
+
+.Request
+----
+  POST /config/server/reload HTTP/1.0
+----
+
+As result a link:#config-update-info[ConfigUpdateInfo] entity is returned that
+contains information about how the updated config entries were handled.
+
+.Response
+----
+  HTTP/1.1 200 OK
+  Content-Type: application/json; charset=UTF-8
+
+  )]}'
+  {
+    "rejected": [],
+    "applied": [
+      {
+        "config_key": "addreviewer.maxAllowed",
+        "old_value": "20",
+        "new_value": "15"
+      }
+    ]
+  }
+----
+
+
 [[confirm-email]]
 === Confirm Email
 --
@@ -1609,6 +1654,39 @@ Possible values are `ERROR` and `WARNING`.
 |`message` |Message describing the consistency problem.
 |======================
 
+[[config-update-info]]
+=== ConfigUpdateInfo
+The entity describes the result of a reload of gerrit.config.
+
+If a changed config value is missing from the `applied` and the `rejected`
+lists there are no guarantees to whether they have or have not taken effect.
+
+[options="header",cols="1,6"]
+|======================
+|Field Name|Description
+|`applied` |A list of link:#config-update-entry-info[ConfigUpdateEntryInfos]
+describing the applied configuration changes. +
+Every config value change representation present in this list is guaranteed to
+have taken effect.
+|`rejected` |A list of link:#config-update-entry-info[ConfigUpdateEntryInfos]
+describing the rejected configuration changes.  +
+Every config value change representation present in this list is guaranteed not
+to have taken effect.
+|======================
+
+[[config-update-entry-info]]
+=== ConfigUpdateEntryInfo
+The entity describes an updated config value.
+
+[options="header",cols="1,6"]
+|======================
+|Field Name|Description
+|`config_key` |The config key that contains the value.
+|`old_value`  |The old config value. +
+Missing if value was not previously configured.
+|`new_value`  |The new config value, picked up after reload.
+|======================
+
 [[download-info]]
 === DownloadInfo
 The `DownloadInfo` entity contains information about supported download

java/com/google/gerrit/extensions/api/config/ConfigUpdateEntryInfo.java

@@ -0,0 +1,21 @@
+// Copyright (C) 2018 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.extensions.api.config;
+
+public class ConfigUpdateEntryInfo {
+  public String configKey;
+  public String oldValue;
+  public String newValue;
+}

java/com/google/gerrit/server/restapi/config/ConfigRestModule.java

@@ -37,6 +37,7 @@ public class ConfigRestModule extends RestApiModule {
     get(CONFIG_KIND, "version").to(GetVersion.class);
     get(CONFIG_KIND, "info").to(GetServerInfo.class);
     post(CONFIG_KIND, "check.consistency").to(CheckConsistency.class);
+    post(CONFIG_KIND, "reload").to(ReloadConfig.class);
     get(CONFIG_KIND, "preferences").to(GetPreferences.class);
     put(CONFIG_KIND, "preferences").to(SetPreferences.class);
     get(CONFIG_KIND, "preferences.diff").to(GetDiffPreferences.class);

java/com/google/gerrit/server/restapi/config/ReloadConfig.java

@@ -0,0 +1,83 @@
+// Copyright (C) 2018 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.restapi.config;
+
+import static com.google.common.collect.ImmutableList.toImmutableList;
+
+import com.google.gerrit.extensions.api.config.ConfigUpdateEntryInfo;
+import com.google.gerrit.extensions.common.Input;
+import com.google.gerrit.extensions.restapi.RestApiException;
+import com.google.gerrit.extensions.restapi.RestModifyView;
+import com.google.gerrit.server.config.ConfigResource;
+import com.google.gerrit.server.config.ConfigUpdatedEvent;
+import com.google.gerrit.server.config.ConfigUpdatedEvent.ConfigUpdateEntry;
+import com.google.gerrit.server.config.ConfigUpdatedEvent.UpdateResult;
+import com.google.gerrit.server.config.GerritServerConfigReloader;
+import com.google.gerrit.server.permissions.GlobalPermission;
+import com.google.gerrit.server.permissions.PermissionBackend;
+import com.google.gerrit.server.permissions.PermissionBackendException;
+import com.google.inject.Inject;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class ReloadConfig implements RestModifyView<ConfigResource, Input> {
+
+  private GerritServerConfigReloader config;
+  private PermissionBackend permissions;
+
+  @Inject
+  ReloadConfig(GerritServerConfigReloader config, PermissionBackend permissions) {
+    this.config = config;
+    this.permissions = permissions;
+  }
+
+  @Override
+  public Map<String, List<ConfigUpdateEntryInfo>> apply(ConfigResource resource, Input input)
+      throws RestApiException, PermissionBackendException {
+    permissions.currentUser().check(GlobalPermission.ADMINISTRATE_SERVER);
+
+    List<ConfigUpdatedEvent.Update> updates = config.reloadConfig();
+
+    Map<String, List<ConfigUpdateEntryInfo>> reply = new HashMap<>();
+    for (UpdateResult result : UpdateResult.values()) {
+      reply.put(result.name().toLowerCase(), new ArrayList<>());
+    }
+    if (updates.isEmpty()) {
+      return reply;
+    }
+    updates
+        .stream()
+        .forEach(u -> reply.get(u.getResult().name().toLowerCase()).addAll(toEntryInfos(u)));
+    return reply;
+  }
+
+  private static List<ConfigUpdateEntryInfo> toEntryInfos(ConfigUpdatedEvent.Update update) {
+    return update
+        .getConfigUpdates()
+        .stream()
+        .map(e -> toConfigUpdateEntryInfo(e))
+        .collect(toImmutableList());
+  }
+
+  private static ConfigUpdateEntryInfo toConfigUpdateEntryInfo(ConfigUpdateEntry e) {
+    ConfigUpdateEntryInfo uei = new ConfigUpdateEntryInfo();
+    uei.configKey = e.key.toString();
+    uei.oldValue = e.oldVal;
+    uei.newValue = e.newVal;
+    return uei;
+  }
+}