Add stream-events command
The stream-events command outputs patchset added, comment added, change merged, and change abandoned events in JSON format over SSH. Streaming ends when the client disconnects or aborts the command. Change-Id: Iba3ff56c23ab91cf3b855d5dde6c40d9735b643f
This commit is contained in:
Kenny Root
committed by
Shawn O. Pearce
Shawn O. Pearce
parent
f458bf6337
commit
15ac1b83f5
228
gerrit-sshd/src/main/java/com/google/gerrit/sshd/commands/StreamEvents.java
Executable file
228
gerrit-sshd/src/main/java/com/google/gerrit/sshd/commands/StreamEvents.java
Executable file
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// Copyright (C) 2010 The Android Open Source Project
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package com.google.gerrit.sshd.commands;
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import com.google.gerrit.common.ChangeHookRunner;
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import com.google.gerrit.common.ChangeListener;
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import com.google.gerrit.common.ChangeHookRunner.ChangeEvent;
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import com.google.gerrit.server.IdentifiedUser;
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import com.google.gerrit.server.git.WorkQueue;
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import com.google.gerrit.server.git.WorkQueue.CancelableRunnable;
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import com.google.gerrit.sshd.BaseCommand;
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import com.google.gerrit.sshd.StreamCommandExecutor;
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import com.google.gson.Gson;
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import com.google.inject.Inject;
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import org.apache.sshd.server.Environment;
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import java.io.IOException;
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import java.io.PrintWriter;
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import java.util.concurrent.Future;
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import java.util.concurrent.LinkedBlockingQueue;
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final class StreamEvents extends BaseCommand {
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/** Maximum number of events that may be queued up for each connection. */
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private static final int MAX_EVENTS = 128;
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/** Number of events to write before yielding off the thread. */
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private static final int BATCH_SIZE = 32;
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@Inject
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private IdentifiedUser currentUser;
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@Inject
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private ChangeHookRunner hooks;
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@Inject
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@StreamCommandExecutor
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private WorkQueue.Executor pool;
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/** Queue of events to stream to the connected user. */
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private final LinkedBlockingQueue<ChangeEvent> queue =
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new LinkedBlockingQueue<ChangeEvent>(MAX_EVENTS);
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private final Gson gson = new Gson();
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/** Special event to notify clients they missed other events. */
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private final Object droppedOutputEvent = new Object() {
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@SuppressWarnings("unused")
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final String type = "dropped-output";
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};
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private final ChangeListener listener = new ChangeListener() {
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@Override
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public void onChangeEvent(final ChangeEvent event) {
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offer(event);
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}
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};
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private final CancelableRunnable writer = new CancelableRunnable() {
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@Override
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public void run() {
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writeEvents();
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}
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@Override
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public void cancel() {
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onExit(0);
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}
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};
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/** True if {@link #droppedOutputEvent} needs to be sent. */
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private volatile boolean dropped;
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/** Lock to protect {@link #queue}, {@link #task}, {@link #done}. */
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private final Object taskLock = new Object();
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/** True if no more messages should be sent to the output. */
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private boolean done;
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/**
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* Currently scheduled task to spin out {@link #queue}.
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* <p>
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* This field is usually {@code null}, unless there is at least one object
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* present inside of {@link #queue} ready for delivery. Tasks are only started
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* when there are events to be sent.
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*/
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private Future<?> task;
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private PrintWriter stdout;
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@Override
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public void start(final Environment env) throws IOException {
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try {
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parseCommandLine();
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} catch (UnloggedFailure e) {
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String msg = e.getMessage();
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if (!msg.endsWith("\n")) {
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msg += "\n";
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}
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err.write(msg.getBytes("UTF-8"));
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err.flush();
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onExit(1);
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return;
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}
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stdout = toPrintWriter(out);
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hooks.addChangeListener(listener, currentUser);
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}
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@Override
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protected void onExit(final int rc) {
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hooks.removeChangeListener(listener);
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synchronized (taskLock) {
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done = true;
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}
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super.onExit(rc);
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}
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@Override
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public void destroy() {
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hooks.removeChangeListener(listener);
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final boolean exit;
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synchronized (taskLock) {
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if (task != null) {
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task.cancel(true);
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exit = false; // onExit will be invoked by the task cancellation.
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} else {
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exit = !done;
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}
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done = true;
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}
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if (exit) {
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onExit(0);
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}
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}
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private void offer(final ChangeEvent event) {
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synchronized (taskLock) {
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if (!queue.offer(event)) {
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dropped = true;
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}
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if (task == null && !done) {
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task = pool.submit(writer);
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}
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}
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}
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private ChangeEvent poll() {
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synchronized (taskLock) {
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ChangeEvent event = queue.poll();
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if (event == null) {
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task = null;
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}
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return event;
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}
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}
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private void writeEvents() {
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int processed = 0;
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while (processed < BATCH_SIZE) {
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if (Thread.interrupted() || stdout.checkError()) {
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// The other side either requested a shutdown by calling our
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// destroy() above, or it closed the stream and is no longer
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// accepting output. Either way terminate this instance.
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//
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hooks.removeChangeListener(listener);
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flush();
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onExit(0);
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return;
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}
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if (dropped) {
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write(droppedOutputEvent);
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dropped = false;
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}
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final ChangeEvent event = poll();
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if (event == null) {
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break;
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}
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write(event);
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processed++;
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}
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flush();
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if (BATCH_SIZE <= processed) {
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// We processed the limit, but more might remain in the queue.
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// Schedule the write task again so we will come back here and
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// can process more events.
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//
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synchronized (taskLock) {
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task = pool.submit(writer);
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}
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}
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}
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private void write(final Object message) {
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final String msg = gson.toJson(message) + "\n";
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synchronized (stdout) {
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stdout.print(msg);
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}
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}
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private void flush() {
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synchronized (stdout) {
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stdout.flush();
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}
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}
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}
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