Use BatchRefUpdate to execute reference changes

Some storage backends for JGit are able to update multiple references
in a single pass efficiently. Take advantage of this by pushing
any normal reference updates (such as direct push or branch create)
into a single BatchRefUpdate object.

Change-Id: Iadd7c5a3271f5ab8eaf31881392c85dd5b0a709d

gerrit-server/src/main/java/com/google/gerrit/server/git/MultiProgressMonitor.java

@@ -17,6 +17,7 @@ package com.google.gerrit.server.git;
 import static java.util.concurrent.TimeUnit.NANOSECONDS;
 
 import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.lib.ProgressMonitor;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -58,7 +59,7 @@ public class MultiProgressMonitor {
   private static final char NO_SPINNER = ' ';
 
   /** Handle for a sub-task. */
-  public class Task {
+  public class Task implements ProgressMonitor {
     private final String name;
     private final int total;
     private volatile int count;
@@ -76,6 +77,7 @@ public class MultiProgressMonitor {
      *
      * @param completed number of work units completed.
      */
+    @Override
     public void update(final int completed) {
       count += completed;
       if (total != UNKNOWN) {
@@ -97,6 +99,23 @@ public class MultiProgressMonitor {
         wakeUp();
       }
     }
+
+    @Override
+    public void start(int totalTasks) {
+    }
+
+    @Override
+    public void beginTask(String title, int totalWork) {
+    }
+
+    @Override
+    public void endTask() {
+    }
+
+    @Override
+    public boolean isCancelled() {
+      return false;
+    }
   }
 
   private final OutputStream out;

gerrit-server/src/main/java/com/google/gerrit/server/git/ReceiveCommits.java

@@ -68,6 +68,7 @@ import com.google.inject.assistedinject.Assisted;
 import org.eclipse.jgit.errors.IncorrectObjectTypeException;
 import org.eclipse.jgit.errors.MissingObjectException;
 import org.eclipse.jgit.lib.AbbreviatedObjectId;
+import org.eclipse.jgit.lib.BatchRefUpdate;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectReader;
@@ -253,6 +254,7 @@ public class ReceiveCommits {
   private Task closeProgress;
   private Task commandProgress;
   private MessageSender messageSender;
+  private BatchRefUpdate batch;
 
   @Inject
   ReceiveCommits(final ReviewDb db,
@@ -460,6 +462,10 @@ public class ReceiveCommits {
     closeProgress = progress.beginSubTask("closed", UNKNOWN);
     commandProgress = progress.beginSubTask("refs", UNKNOWN);
 
+    batch = repo.getRefDatabase().newBatchUpdate();
+    batch.setRefLogIdent(rp.getRefLogIdent());
+    batch.setRefLogMessage("push", true);
+
     parseCommands(commands);
     if (newChange != null && newChange.getResult() == NOT_ATTEMPTED) {
       createNewChanges();
@@ -469,6 +475,22 @@ public class ReceiveCommits {
     doReplaces();
     replaceProgress.end();
 
+    if (!batch.getCommands().isEmpty()) {
+      try {
+        batch.execute(rp.getRevWalk(), commandProgress);
+      } catch (IOException err) {
+        int cnt = 0;
+        for (ReceiveCommand cmd : batch.getCommands()) {
+          if (cmd.getResult() == NOT_ATTEMPTED) {
+            cmd.setResult(REJECTED_OTHER_REASON, "internal server error");
+            cnt++;
+          }
+        }
+        log.error(String.format(
+            "Failed to store %d refs in %s", cnt, project.getName()), err);
+      }
+    }
+
     if (!errors.isEmpty()) {
       for (Error error : errors.keySet()) {
         rp.sendMessage(buildError(error, errors.get(error)));
@@ -691,9 +713,7 @@ public class ReceiveCommits {
     RefControl ctl = projectControl.controlForRef(cmd.getRefName());
     if (ctl.canCreate(rp.getRevWalk(), obj)) {
       validateNewCommits(ctl, cmd);
-      if (cmd.getResult() == NOT_ATTEMPTED) {
+      batch.addCommand(cmd);
-        cmd.execute(rp);
-      }
     } else {
       errors.put(Error.CREATE, ctl.getRefName());
       reject(cmd, "can not create new references");
@@ -708,9 +728,7 @@ public class ReceiveCommits {
       }
 
       validateNewCommits(ctl, cmd);
-      if (cmd.getResult() == NOT_ATTEMPTED) {
+      batch.addCommand(cmd);
-        cmd.execute(rp);
-      }
     } else {
       if (GitRepositoryManager.REF_CONFIG.equals(ctl.getRefName())) {
         errors.put(Error.CONFIG_UPDATE, GitRepositoryManager.REF_CONFIG);
@@ -743,9 +761,7 @@ public class ReceiveCommits {
   private void parseDelete(final ReceiveCommand cmd) {
     RefControl ctl = projectControl.controlForRef(cmd.getRefName());
     if (ctl.canDelete()) {
-      if (cmd.getResult() == NOT_ATTEMPTED) {
+      batch.addCommand(cmd);
-        cmd.execute(rp);
-      }
     } else {
       if (GitRepositoryManager.REF_CONFIG.equals(ctl.getRefName())) {
         reject(cmd, "cannot delete project configuration");
@@ -778,9 +794,7 @@ public class ReceiveCommits {
     }
 
     if (ctl.canForceUpdate()) {
-      if (cmd.getResult() == NOT_ATTEMPTED) {
+      batch.setAllowNonFastForwards(true).addCommand(cmd);
-        cmd.execute(rp);
-      }
     } else {
       cmd.setResult(REJECTED_NONFASTFORWARD, " need '"
           + PermissionRule.FORCE_PUSH + "' privilege.");