com.google.gerrit.sshd.commands.StreamEvents Maven / Gradle / Ivy
// Copyright (C) 2010 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 static java.nio.charset.StandardCharsets.UTF_8;
import com.google.common.flogger.FluentLogger;
import com.google.gerrit.common.data.GlobalCapability;
import com.google.gerrit.extensions.annotations.RequiresCapability;
import com.google.gerrit.extensions.registration.DynamicSet;
import com.google.gerrit.extensions.registration.RegistrationHandle;
import com.google.gerrit.server.CurrentUser;
import com.google.gerrit.server.DynamicOptions;
import com.google.gerrit.server.IdentifiedUser;
import com.google.gerrit.server.events.Event;
import com.google.gerrit.server.events.EventGson;
import com.google.gerrit.server.events.EventTypes;
import com.google.gerrit.server.events.UserScopedEventListener;
import com.google.gerrit.server.git.WorkQueue.CancelableRunnable;
import com.google.gerrit.sshd.BaseCommand;
import com.google.gerrit.sshd.CommandMetaData;
import com.google.gerrit.sshd.StreamCommandExecutor;
import com.google.gson.Gson;
import com.google.inject.Inject;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Future;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import org.apache.sshd.server.Environment;
import org.apache.sshd.server.channel.ChannelSession;
import org.kohsuke.args4j.Option;
@RequiresCapability(GlobalCapability.STREAM_EVENTS)
@CommandMetaData(name = "stream-events", description = "Monitor events occurring in real time")
public final class StreamEvents extends BaseCommand {
private static final FluentLogger logger = FluentLogger.forEnclosingClass();
/** Maximum number of events that may be queued up for each connection. */
private static final int MAX_EVENTS = 128;
/** Number of events to write before yielding off the thread. */
private static final int BATCH_SIZE = 32;
@Option(
name = "--subscribe",
aliases = {"-s"},
metaVar = "SUBSCRIBE",
usage = "subscribe to specific stream-events")
private List subscribedToEvents = new ArrayList<>();
@Inject private IdentifiedUser currentUser;
@Inject private DynamicSet eventListeners;
@Inject @StreamCommandExecutor private ScheduledThreadPoolExecutor pool;
@Inject @EventGson private Gson gson;
/** Queue of events to stream to the connected user. */
private final LinkedBlockingQueue queue = new LinkedBlockingQueue<>(MAX_EVENTS);
private RegistrationHandle eventListenerRegistration;
/** Special event to notify clients they missed other events. */
private static final class DroppedOutputEvent extends Event {
private static final String TYPE = "dropped-output";
DroppedOutputEvent() {
super(TYPE);
}
}
static {
EventTypes.register(DroppedOutputEvent.TYPE, DroppedOutputEvent.class);
}
/** True if {@link DroppedOutputEvent} needs to be sent. */
private volatile boolean dropped;
/** Lock to protect {@link #queue}, {@link #task}, {@link #done}. */
private final Object taskLock = new Object();
/** True if no more messages should be sent to the output. */
private boolean done;
/**
* Currently scheduled task to spin out {@link #queue}.
*
* This field is usually {@code null}, unless there is at least one object present inside of
* {@link #queue} ready for delivery. Tasks are only started when there are events to be sent.
*/
private Future task;
@Override
public void start(ChannelSession channel, Environment env) throws IOException {
try (DynamicOptions pluginOptions = new DynamicOptions(injector, dynamicBeans)) {
try {
parseCommandLine(pluginOptions);
} catch (UnloggedFailure e) {
String msg = e.getMessage();
if (!msg.endsWith("\n")) {
msg += "\n";
}
err.write(msg.getBytes(UTF_8));
err.flush();
onExit(1);
return;
}
PrintWriter stdout = toPrintWriter(out);
CancelableRunnable writer =
new CancelableRunnable() {
@Override
public void run() {
writeEvents(this, stdout);
}
@Override
public void cancel() {
onExit(0);
}
@Override
public String toString() {
StringBuilder b = new StringBuilder();
b.append("Stream Events");
if (currentUser.getUserName().isPresent()) {
b.append(" (").append(currentUser.getUserName().get()).append(")");
}
return b.toString();
}
};
eventListenerRegistration =
eventListeners.add(
"gerrit",
new UserScopedEventListener() {
@Override
public void onEvent(Event event) {
if (subscribedToEvents.isEmpty()
|| subscribedToEvents.contains(event.getType())) {
offer(writer, event);
}
}
@Override
public CurrentUser getUser() {
return currentUser;
}
});
}
}
private void removeEventListenerRegistration() {
if (eventListenerRegistration != null) {
eventListenerRegistration.remove();
}
}
@Override
protected void onExit(int rc) {
removeEventListenerRegistration();
synchronized (taskLock) {
done = true;
}
super.onExit(rc);
}
@Override
public void destroy(ChannelSession channel) {
removeEventListenerRegistration();
final boolean exit;
synchronized (taskLock) {
if (task != null) {
task.cancel(true);
exit = false; // onExit will be invoked by the task cancellation.
} else {
exit = !done;
}
done = true;
}
if (exit) {
onExit(0);
}
}
private void offer(CancelableRunnable writer, Event event) {
synchronized (taskLock) {
if (!queue.offer(event)) {
dropped = true;
}
if (task == null && !done) {
task = pool.submit(writer);
}
}
}
private Event poll() {
synchronized (taskLock) {
Event event = queue.poll();
if (event == null) {
task = null;
}
return event;
}
}
private void writeEvents(CancelableRunnable writer, PrintWriter stdout) {
int processed = 0;
while (processed < BATCH_SIZE) {
if (Thread.interrupted() || stdout.checkError()) {
// The other side either requested a shutdown by calling our
// destroy() above, or it closed the stream and is no longer
// accepting output. Either way terminate this instance.
//
removeEventListenerRegistration();
flush(stdout);
onExit(0);
return;
}
if (dropped) {
write(stdout, new DroppedOutputEvent());
dropped = false;
}
final Event event = poll();
if (event == null) {
break;
}
write(stdout, event);
processed++;
}
flush(stdout);
if (BATCH_SIZE <= processed) {
// We processed the limit, but more might remain in the queue.
// Schedule the write task again so we will come back here and
// can process more events.
//
synchronized (taskLock) {
task = pool.submit(writer);
}
}
}
private void write(PrintWriter stdout, Object message) {
String msg = null;
try {
msg = gson.toJson(message) + "\n";
} catch (Exception e) {
logger.atWarning().withCause(e).log("Could not deserialize the msg");
}
if (msg != null) {
synchronized (stdout) {
stdout.print(msg);
}
}
}
private void flush(PrintWriter stdout) {
synchronized (stdout) {
stdout.flush();
}
}
}