Add ssh command to show current sequence value

Change-Id: Ifcbff0943bbdacfd792a4c2454492522dec8609a

Documentation/cmd-index.txt

@@ -178,6 +178,9 @@ link:cmd-reload-config.html[gerrit reload-config]::
 link:cmd-set-account.html[gerrit set-account]::
 	Change an account's settings.
 
+link:cmd-sequence-show.html[gerrit sequence show]::
+        Display current sequence value.
+
 link:cmd-set-members.html[gerrit set-members]::
 	Set group members.
 

Documentation/cmd-sequence-show.txt

@@ -0,0 +1,48 @@
+= gerrit sequence show
+
+== NAME
+gerrit sequence show - Display current sequence value.
+
+== SYNOPSIS
+[verse]
+--
+_ssh_ -p <port> <host> _gerrit sequence show_ <NAME>
+--
+
+== DESCRIPTION
+Gerrit maintains the generation of the next available sequence numbers for
+account, group and change entities. The sequences are stored as UTF-8 text in
+a blob pointed to by the `refs/sequences/accounts`, `refs/sequences/groups`
+and `refs/sequences/changes` refs. Those refs are stored in `All-Users` and
+`All-Projects` git repositories correspondingly.
+
+This command allows to display the current sequence value for those sequences.
+
+== ACCESS
+Caller must be a member of the privileged 'Administrators' group.
+
+== SCRIPTING
+This command is intended to be used in scripts.
+
+== OPTIONS
+<NAME>::
+  Sequence name to show the current value for.
+  Currently supported values:
+    * accounts
+    * groups
+    * changes
+
+== EXAMPLES
+Display the current value for the 'changes' sequence:
+
+----
+$ ssh -p 29418 review.example.com gerrit sequence show changes
+42
+----
+
+GERRIT
+------
+Part of link:index.html[Gerrit Code Review]
+
+SEARCHBOX
+---------

java/com/google/gerrit/httpd/init/WebAppInitializer.java

@@ -99,6 +99,7 @@ import com.google.gerrit.sshd.SshKeyCacheImpl;
 import com.google.gerrit.sshd.SshModule;
 import com.google.gerrit.sshd.commands.DefaultCommandModule;
 import com.google.gerrit.sshd.commands.IndexCommandsModule;
+import com.google.gerrit.sshd.commands.SequenceCommandsModule;
 import com.google.gerrit.sshd.plugin.LfsPluginAuthCommand;
 import com.google.inject.AbstractModule;
 import com.google.inject.CreationException;
@@ -372,6 +373,7 @@ public class WebAppInitializer extends GuiceServletContextListener implements Fi
             sysInjector.getInstance(DownloadConfig.class),
             sysInjector.getInstance(LfsPluginAuthCommand.Module.class)));
     modules.add(new IndexCommandsModule(sysInjector));
+    modules.add(new SequenceCommandsModule());
     return sysInjector.createChildInjector(modules);
   }
 

java/com/google/gerrit/pgm/Daemon.java

@@ -109,6 +109,7 @@ import com.google.gerrit.sshd.SshKeyCacheImpl;
 import com.google.gerrit.sshd.SshModule;
 import com.google.gerrit.sshd.commands.DefaultCommandModule;
 import com.google.gerrit.sshd.commands.IndexCommandsModule;
+import com.google.gerrit.sshd.commands.SequenceCommandsModule;
 import com.google.gerrit.sshd.plugin.LfsPluginAuthCommand;
 import com.google.inject.AbstractModule;
 import com.google.inject.Guice;
@@ -517,6 +518,7 @@ public class Daemon extends SiteProgram {
             sysInjector.getInstance(LfsPluginAuthCommand.Module.class)));
     if (!replica) {
       modules.add(new IndexCommandsModule(sysInjector));
+      modules.add(new SequenceCommandsModule());
     }
     return sysInjector.createChildInjector(modules);
   }

java/com/google/gerrit/server/notedb/RepoSequence.java

@@ -291,4 +291,23 @@ public class RepoSequence {
     ObjectId newId = ins.insert(OBJ_BLOB, Integer.toString(val).getBytes(UTF_8));
     return new ReceiveCommand(ObjectId.zeroId(), newId, RefNames.REFS_SEQUENCES + name);
   }
+
+  public int current() {
+    counterLock.lock();
+    try (Repository repo = repoManager.openRepository(projectName);
+        RevWalk rw = new RevWalk(repo)) {
+      Optional<IntBlob> blob = IntBlob.parse(repo, refName, rw);
+      int current;
+      if (!blob.isPresent()) {
+        current = seed.get();
+      } else {
+        current = blob.get().value();
+      }
+      return current;
+    } catch (IOException e) {
+      throw new StorageException(e);
+    } finally {
+      counterLock.unlock();
+    }
+  }
 }

java/com/google/gerrit/server/notedb/Sequences.java

@@ -128,4 +128,16 @@ public class Sequences {
       return groupSeq.next();
     }
   }
+
+  public int currentChangeId() {
+    return changeSeq.current();
+  }
+
+  public int currentAccountId() {
+    return accountSeq.current();
+  }
+
+  public int currentGroupId() {
+    return groupSeq.current();
+  }
 }

java/com/google/gerrit/sshd/commands/SequenceCommandsModule.java

@@ -0,0 +1,31 @@
+// Copyright (C) 2019 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.sshd.commands;
+
+import com.google.gerrit.sshd.CommandModule;
+import com.google.gerrit.sshd.CommandName;
+import com.google.gerrit.sshd.Commands;
+import com.google.gerrit.sshd.DispatchCommandProvider;
+
+public class SequenceCommandsModule extends CommandModule {
+
+  @Override
+  protected void configure() {
+    CommandName gerrit = Commands.named("gerrit");
+    CommandName sequence = Commands.named(gerrit, "sequence");
+    command(sequence).toProvider(new DispatchCommandProvider(sequence));
+    command(sequence, SequenceShowCommand.class);
+  }
+}

java/com/google/gerrit/sshd/commands/SequenceShowCommand.java

@@ -0,0 +1,54 @@
+// Copyright (C) 2019 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.sshd.commands;
+
+import com.google.gerrit.common.data.GlobalCapability;
+import com.google.gerrit.extensions.annotations.RequiresCapability;
+import com.google.gerrit.server.notedb.Sequences;
+import com.google.gerrit.sshd.CommandMetaData;
+import com.google.gerrit.sshd.SshCommand;
+import com.google.inject.Inject;
+import org.kohsuke.args4j.Argument;
+
+/** Display sequence value. */
+@RequiresCapability(GlobalCapability.ADMINISTRATE_SERVER)
+@CommandMetaData(name = "show", description = "Display the sequence value")
+final class SequenceShowCommand extends SshCommand {
+  @Argument(index = 0, metaVar = "NAME", required = true, usage = "sequence name")
+  private String name;
+
+  @Inject Sequences sequences;
+
+  @Override
+  public void run() throws Exception {
+    int current;
+    switch (name) {
+      case "changes":
+        current = sequences.currentChangeId();
+        break;
+      case "accounts":
+        current = sequences.currentAccountId();
+        break;
+      case "groups":
+        current = sequences.currentGroupId();
+        break;
+      default:
+        throw die("Unknown sequence name: " + name);
+    }
+    stdout.print(current);
+    stdout.print('\n');
+    stdout.flush();
+  }
+}

javatests/com/google/gerrit/acceptance/ssh/SshCommandsIT.java

@@ -67,6 +67,7 @@ public class SshCommandsIT extends AbstractDaemonTest {
           "receive-pack",
           "rename-group",
           "review",
+          "sequence",
           "set-account",
           "set-head",
           "set-members",
@@ -96,6 +97,7 @@ public class SshCommandsIT extends AbstractDaemonTest {
               "gerrit plugin",
               ImmutableList.of("add", "enable", "install", "ls", "reload", "remove", "rm"))
           .put("gerrit test-submit", ImmutableList.of("rule", "type"))
+          .put("gerrit sequence", ImmutableList.of("show"))
           .build();
 
   private static final ImmutableMap<String, List<String>> SLAVE_COMMANDS =