graylog OutputBufferProcessor 简单说明

OutputBufferProcessor 对于输出处理比较重要，包含了路由（比如不同stream 写到外部put，写到不同的外部MessageOutput 中
OutputBufferProcessor 也是Disruptor 的一个handler

参考处理

public void onEvent(MessageEvent event) throws Exception {
        incomingMessages.mark();
 
        final Message msg = event.getMessage();
        if (msg == null) {
            LOG.debug("Skipping null message.");
            return;
        }
        LOG.debug("Processing message <{}> from OutputBuffer.", msg.getId());
       // 消息的路由
        final Set<MessageOutput> messageOutputs = outputRouter.getStreamOutputsForMessage(msg);
        msg.recordCounter(serverStatus, "matched-outputs", messageOutputs.size());
       // 处理消息
        final Future<?> defaultOutputCompletion = processMessage(msg, defaultMessageOutput);
 
        final CountDownLatch streamOutputsDoneSignal = new CountDownLatch(messageOutputs.size());
        for (final MessageOutput output : messageOutputs) {
            processMessage(msg, output, streamOutputsDoneSignal);
        }
 
        // Wait until all writer threads for stream outputs have finished or timeout is reached.
        if (!streamOutputsDoneSignal.await(configuration.getOutputModuleTimeout(), TimeUnit.MILLISECONDS)) {
            LOG.warn("Timeout reached. Not waiting any longer for stream output writer threads to complete.");
        }
 
        // now block until the default output has finished. most batching outputs will already been done because their
        // fast path is really fast (usually an insert into a queue), but the slow flush path might block for a long time
        // this exerts the back pressure to the system
        if (defaultOutputCompletion != null) {
            Uninterruptibles.getUninterruptibly(defaultOutputCompletion);
        } else {
            LOG.error("The default output future was null, this is a bug!");
        }
 
        if (msg.hasRecordings()) {
            LOG.debug("Message event trace: {}", msg.recordingsAsString());
        }
 
        outputThroughput.inc();
 
        LOG.debug("Wrote message <{}> to all outputs. Finished handling.", msg.getId());
 
        event.clearMessages();
    }

incomingMessages.mark();

processMessage 处理,核心是写到MessageOutput中

private Future<?> processMessage(final Message msg, final MessageOutput output, final CountDownLatch doneSignal) {
        if (output == null) {
            LOG.error("Output was null!");
            doneSignal.countDown();
            return Futures.immediateCancelledFuture();
        }
        if (!output.isRunning()) {
            LOG.debug("Skipping stopped output {}", output.getClass().getName());
            doneSignal.countDown();
            return Futures.immediateCancelledFuture();
        }
 
        Future<?> future = null;
        try {
            LOG.debug("Writing message to [{}].", output.getClass());
            if (LOG.isTraceEnabled()) {
                LOG.trace("Message id for [{}]: <{}>", output.getClass(), msg.getId());
            }
            future = executor.submit(new Runnable() {
                @Override
                public void run() {
                    try (Timer.Context ignored = processTime.time()) {
                        output.write(msg);
                    } catch (Exception e) {
                        LOG.error("Error in output [" + output.getClass() + "].", e);
                    } finally {
                        doneSignal.countDown();
                    }
                }
            });
        } catch (Exception e) {
            LOG.error("Could not write message batch to output [" + output.getClass() + "].", e);
            doneSignal.countDown();
        }
        return future;
    }

if (output == null) {

参考资料

​​https://github.com/Graylog2/graylog2-server/blob/626be1f0d80506705b5ba41fbea33c2ec0164bc0/graylog2-server/src/main/java/org/graylog2/buffers/processors/OutputBufferProcessor.java​​​
​​​https://github.com/Graylog2/graylog2-server/blob/626be1f0d80506705b5ba41fbea33c2ec0164bc0/graylog2-server/src/main/java/org/graylog2/plugin/outputs/MessageOutput.java​​