GelfAppender

@Override    public void append(LogEvent event) {        final Layout
     layout = getLayout();        final String formattedMessage;        if (layout == null) {            formattedMessage = event.getMessage().getFormattedMessage();        } else {            formattedMessage = new String(layout.toByteArray(event), StandardCharsets.UTF_8);        }        final GelfMessageBuilder builder = new GelfMessageBuilder(formattedMessage, hostName)                .timestamp(event.getTimeMillis() / 1000d)                .level(GelfMessageLevel.fromNumericLevel(Severity.getSeverity(event.getLevel()).getCode()))                .additionalField("loggerName", event.getLoggerName())                .additionalField("threadName", event.getThreadName());        final Marker marker = event.getMarker();        if (marker != null) {            builder.additionalField("marker", marker.getName());        }        if (includeThreadContext) {            for (Map.Entry
    
      entry : event.getContextMap().entrySet()) {                builder.additionalField(entry.getKey(), entry.getValue());            }            // Guard against https://issues.apache.org/jira/browse/LOG4J2-1530            final ThreadContext.ContextStack contextStack = event.getContextStack();            if (contextStack != null) {                final List
     
       contextStackItems = contextStack.asList();                if (contextStackItems != null && !contextStackItems.isEmpty()) {                    builder.additionalField("contextStack", contextStackItems.toString());                }            }        }        if (includeSource) {            final StackTraceElement source = event.getSource();            if (source != null) {                builder.additionalField("sourceFileName", source.getFileName());                builder.additionalField("sourceMethodName", source.getMethodName());                builder.additionalField("sourceClassName", source.getClassName());                builder.additionalField("sourceLineNumber", source.getLineNumber());            }        }        @SuppressWarnings("all")        final Throwable thrown = event.getThrown();        if (includeStackTrace && thrown != null) {            String stackTrace;            if (includeExceptionCause) {                final StringWriter stringWriter = new StringWriter();                final PrintWriter printWriter = new PrintWriter(stringWriter);                thrown.printStackTrace(printWriter);                stackTrace = stringWriter.toString();            } else {                stackTrace = getSimpleStacktraceAsString(thrown);            }            builder.additionalField("exceptionClass", thrown.getClass().getCanonicalName());            builder.additionalField("exceptionMessage", thrown.getMessage());            builder.additionalField("exceptionStackTrace", stackTrace);            builder.fullMessage(formattedMessage);        }        if (!additionalFields.isEmpty()) {            builder.additionalFields(additionalFields);        }        final GelfMessage gelfMessage = builder.build();        try {            final boolean sent = client.trySend(gelfMessage);            if (!sent) {                LOG.debug("Couldn't send message: {}", gelfMessage);            }        } catch (Exception e) {            throw new AppenderLoggingException("failed to write log event to GELF server: " + e.getMessage(), e);        }    }
     
    

gelfclient

基于netty来实现

public class GelfTcpTransport extends AbstractGelfTransport {    private static final Logger LOG = LoggerFactory.getLogger(GelfTcpTransport.class);    /**     * Creates a new TCP GELF transport.     *     * @param config the GELF client configuration     */    public GelfTcpTransport(GelfConfiguration config) {        super(config);    }    @Override    protected void createBootstrap(final EventLoopGroup workerGroup) {        final Bootstrap bootstrap = new Bootstrap();        final GelfSenderThread senderThread = new GelfSenderThread(queue, config.getMaxInflightSends());        bootstrap.group(workerGroup)                .channel(NioSocketChannel.class)                .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, config.getConnectTimeout())                .option(ChannelOption.TCP_NODELAY, config.isTcpNoDelay())                .option(ChannelOption.SO_KEEPALIVE, config.isTcpKeepAlive())                .remoteAddress(config.getRemoteAddress())                .handler(new ChannelInitializer
    
     () {                    @Override                    protected void initChannel(SocketChannel ch) throws Exception {                        if (config.isTlsEnabled()) {                            LOG.debug("TLS enabled.");                            final SslContext sslContext;                            if (!config.isTlsCertVerificationEnabled()) {                                // If the cert should not be verified just use an insecure trust manager.                                LOG.debug("TLS certificate verification disabled!");                                sslContext = SslContext.newClientContext(InsecureTrustManagerFactory.INSTANCE);                            } else if (config.getTlsTrustCertChainFile() != null) {                                // If a cert chain file is set, use it.                                LOG.debug("TLS certificate chain file: {}", config.getTlsTrustCertChainFile());                                sslContext = SslContext.newClientContext(config.getTlsTrustCertChainFile());                            } else {                                // Otherwise use the JVM default cert chain.                                sslContext = SslContext.newClientContext();                            }                            ch.pipeline().addLast(sslContext.newHandler(ch.alloc()));                        }                        // The graylog2-server uses '\0'-bytes as delimiter for TCP frames.                        ch.pipeline().addLast(new GelfTcpFrameDelimiterEncoder());                        // We cannot use GZIP encoding for TCP because the headers contain '\0'-bytes then.                        ch.pipeline().addLast(new GelfMessageJsonEncoder());                        ch.pipeline().addLast(new SimpleChannelInboundHandler
     
      () {                            @Override                            protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {                                // We do not receive data.                            }                            @Override                            public void channelActive(ChannelHandlerContext ctx) throws Exception {                                senderThread.start(ctx.channel());                            }                            @Override                            public void channelInactive(ChannelHandlerContext ctx) throws Exception {                                LOG.info("Channel disconnected!");                                senderThread.stop();                                scheduleReconnect(ctx.channel().eventLoop());                            }                            @Override                            public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {                                LOG.error("Exception caught", cause);                            }                        });                    }                });        if (config.getSendBufferSize() != -1) {            bootstrap.option(ChannelOption.SO_SNDBUF, config.getSendBufferSize());        }        bootstrap.connect().addListener(new ChannelFutureListener() {            @Override            public void operationComplete(ChannelFuture future) throws Exception {                if (future.isSuccess()) {                    LOG.debug("Connected!");                } else {                    LOG.error("Connection failed: {}", future.cause().getMessage());                    scheduleReconnect(future.channel().eventLoop());                }            }        });    }}
     
    

docs