1 files changed, 197 insertions, 0 deletions
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/git/ChangeMergeQueue.java b/gerrit-server/src/main/java/com/google/gerrit/server/git/ChangeMergeQueue.java
new file mode 100644
index 0000000000..d6c8f4ab3b
--- /dev/null
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/git/ChangeMergeQueue.java
@@ -0,0 +1,197 @@
+// Copyright (C) 2009 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.git;
+
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+import static java.util.concurrent.TimeUnit.SECONDS;
+
+import com.google.gerrit.reviewdb.Branch;
+import com.google.gerrit.reviewdb.Project;
+import com.google.inject.Inject;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.TimeUnit;
+
+public class ChangeMergeQueue implements MergeQueue {
+  private static final Logger log =
+      LoggerFactory.getLogger(ChangeMergeQueue.class);
+
+  private final Map<Branch.NameKey, MergeEntry> active =
+      new HashMap<Branch.NameKey, MergeEntry>();
+  private final Map<Branch.NameKey, RecheckJob> recheck =
+      new HashMap<Branch.NameKey, RecheckJob>();
+
+  private final WorkQueue workQueue;
+  private final MergeOp.Factory opFactory;
+
+  @Inject
+  ChangeMergeQueue(final WorkQueue wq, final MergeOp.Factory of) {
+    workQueue = wq;
+    opFactory = of;
+  }
+
+  @Override
+  public void merge(final Branch.NameKey branch) {
+    if (start(branch)) {
+      mergeImpl(branch);
+    }
+  }
+
+  private synchronized boolean start(final Branch.NameKey branch) {
+    final MergeEntry e = active.get(branch);
+    if (e == null) {
+      // Let the caller attempt this merge, its the only one interested
+      // in processing this branch right now.
+      //
+      active.put(branch, new MergeEntry(branch));
+      return true;
+    } else {
+      // Request that the job queue handle this merge later.
+      //
+      e.needMerge = true;
+      return false;
+    }
+  }
+
+  @Override
+  public synchronized void schedule(final Branch.NameKey branch) {
+    MergeEntry e = active.get(branch);
+    if (e == null) {
+      e = new MergeEntry(branch);
+      active.put(branch, e);
+    }
+    e.needMerge = true;
+    scheduleJob(e);
+  }
+
+  @Override
+  public synchronized void recheckAfter(final Branch.NameKey branch,
+      final long delay, final TimeUnit delayUnit) {
+    final long now = System.currentTimeMillis();
+    final long at = now + MILLISECONDS.convert(delay, delayUnit);
+    RecheckJob e = recheck.get(branch);
+    if (e == null) {
+      e = new RecheckJob(branch);
+      workQueue.getDefaultQueue().schedule(e, now - at, MILLISECONDS);
+      recheck.put(branch, e);
+    }
+    e.recheckAt = Math.max(at, e.recheckAt);
+  }
+
+  private synchronized void finish(final Branch.NameKey branch) {
+    final MergeEntry e = active.get(branch);
+    if (e == null) {
+      // Not registered? Shouldn't happen but ignore it.
+      //
+      return;
+    }
+
+    if (!e.needMerge) {
+      // No additional merges are in progress, we can delete it.
+      //
+      active.remove(branch);
+      return;
+    }
+
+    scheduleJob(e);
+  }
+
+  private void scheduleJob(final MergeEntry e) {
+    if (!e.jobScheduled) {
+      // No job has been scheduled to execute this branch, but it needs
+      // to run a merge again.
+      //
+      e.jobScheduled = true;
+      workQueue.getDefaultQueue().schedule(e, 0, TimeUnit.SECONDS);
+    }
+  }
+
+  private synchronized void unschedule(final MergeEntry e) {
+    e.jobScheduled = false;
+    e.needMerge = false;
+  }
+
+  private void mergeImpl(final Branch.NameKey branch) {
+    try {
+      opFactory.create(branch).merge();
+    } catch (Throwable e) {
+      log.error("Merge attempt for " + branch + " failed", e);
+    } finally {
+      finish(branch);
+    }
+  }
+
+  private synchronized void recheck(final RecheckJob e) {
+    final long remainingDelay = e.recheckAt - System.currentTimeMillis();
+    if (MILLISECONDS.convert(10, SECONDS) < remainingDelay) {
+      // Woke up too early, the job deadline was pushed back.
+      // Reschedule for the new deadline. We allow for a small
+      // amount of fuzz due to multiple reschedule attempts in
+      // a short period of time being caused by MergeOp.
+      //
+      workQueue.getDefaultQueue().schedule(e, remainingDelay, MILLISECONDS);
+    } else {
+      // Schedule a merge attempt on this branch to see if we can
+      // actually complete it this time.
+      //
+      schedule(e.dest);
+    }
+  }
+
+  private class MergeEntry implements Runnable {
+    final Branch.NameKey dest;
+    boolean needMerge;
+    boolean jobScheduled;
+
+    MergeEntry(final Branch.NameKey d) {
+      dest = d;
+    }
+
+    public void run() {
+      unschedule(this);
+      mergeImpl(dest);
+    }
+
+    @Override
+    public String toString() {
+      final Project.NameKey project = dest.getParentKey();
+      return "submit " + project.get() + " " + dest.getShortName();
+    }
+  }
+
+  private class RecheckJob implements Runnable {
+    final Branch.NameKey dest;
+    long recheckAt;
+
+    RecheckJob(final Branch.NameKey d) {
+      dest = d;
+    }
+
+    @Override
+    public void run() {
+      recheck(this);
+    }
+
+    @Override
+    public String toString() {
+      final Project.NameKey project = dest.getParentKey();
+      return "recheck " + project.get() + " " + dest.getShortName();
+    }
+  }
+}