vy commented on a change in pull request #452: URL: https://github.com/apache/logging-log4j2/pull/452#discussion_r554000037
########## File path: log4j-core/src/main/java/org/apache/logging/log4j/core/appender/AsyncAppenderEventForwarder.java ########## @@ -0,0 +1,147 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You 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 org.apache.logging.log4j.core.appender; + +import org.apache.logging.log4j.Logger; +import org.apache.logging.log4j.core.LogEvent; +import org.apache.logging.log4j.core.config.AppenderControl; +import org.apache.logging.log4j.core.util.Log4jThread; +import org.apache.logging.log4j.status.StatusLogger; + +import java.util.List; +import java.util.concurrent.BlockingQueue; +import java.util.concurrent.atomic.AtomicLong; + +class AsyncAppenderEventForwarder extends Log4jThread { + + private static final AtomicLong THREAD_COUNTER = new AtomicLong(0); + + private static final Logger LOGGER = StatusLogger.getLogger(); + + private final AppenderControl errorAppender; + + private final List<AppenderControl> appenders; + + private final BlockingQueue<LogEvent> queue; + + private volatile boolean stopped; + + AsyncAppenderEventForwarder( + final String name, + final AppenderControl errorAppender, + final List<AppenderControl> appenders, + final BlockingQueue<LogEvent> queue) { + super("AsyncAppenderEventForwarder-" + THREAD_COUNTER.incrementAndGet() + "-" + name); + this.errorAppender = errorAppender; + this.appenders = appenders; + this.queue = queue; + this.stopped = false; + } + + @Override + public void run() { + LOGGER.trace("{} has started.", getName()); + forwardAll(); + forwardRemaining(); + } + + private void forwardAll() { + while (!stopped) { + LogEvent event; + try { + event = queue.take(); + } catch (final InterruptedException ignored) { + // Restore the interrupted flag cleared when the exception is caught. + interrupt(); + break; + } + event.setEndOfBatch(queue.isEmpty()); + forwardOne(event); + } + LOGGER.trace("{} has stopped.", getName()); + } + + private void forwardRemaining() { + int eventCount = 0; + while (true) { + // Note the non-blocking Queue#poll() method! + final LogEvent event = queue.poll(); + if (event == null) { + break; + } + event.setEndOfBatch(queue.isEmpty()); + forwardOne(event); + eventCount++; + } + LOGGER.trace( + "{} has processed the last {} remaining event(s).", + getName(), eventCount); + } + + void forwardOne(final LogEvent event) { + + // Forward the event to all registered appenders. + boolean succeeded = false; + // noinspection ForLoopReplaceableByForEach (avoid iterator instantion) + for (int appenderIndex = 0; appenderIndex < appenders.size(); appenderIndex++) { + final AppenderControl control = appenders.get(appenderIndex); + try { + control.callAppender(event); + succeeded = true; + } catch (final Throwable ignored) { + // If no appender is successful, the error appender will get it. + } + } + + // Fallback to the error appender if none has succeeded so far. + if (!succeeded && errorAppender != null) { + try { + errorAppender.callAppender(event); + } catch (final Throwable ignored) { + // If the error appender also fails, there is nothing further + // we can do about it. + } + } + + } + + void stop(final long timeoutMillis) throws InterruptedException { + + // Mark the completion, if necessary. + synchronized (this) { + if (!stopped) { + stopped = true; + LOGGER.trace("{} is signaled to stop.", getName()); + } + } + + // There is a slight chance that the thread is not started yet, wait for + // it to run. Otherwise, interrupt+join might block. + // noinspection StatementWithEmptyBody + while (Thread.State.NEW.equals(getState())); Review comment: @carterkozak, I guess we are sort of done, right? This `while` block discussion is the only one left there. I don't have a strong opinion here. How shall we proceed? ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
