记 Spring Cloud Gateway 内存溢出查询过程环境配置： org.springframework.boot ： 2.1.4.RELEASE org.springframework.cloud ：Greenwich.SR1事故记录：
由于网关存在 RequestBody 丢失的情况，顾采用了网上的通用解决方案，使用如下方式解决：
@Beanpublic RouteLocator tpauditRoutes(RouteLocatorBuilder builder) { return builder.routes().route("gateway-post", r -> r.order(1) .method(HttpMethod.POST) .and() .readBody(String.class, requestBody -> {return true;}) # 重点在这 .and() .path("/gateway/**") .filters(f -> {f.stripPrefix(1);return f;}) .uri("lb://APP-API")).build();}
测试环境，Spring Cloud Gateway 网关功能编写完成。开始进行测试环境压测。
正常采用梯度压测方式，最高用户峰值设置为400并发。经历两轮时长10分钟左右压测，没有异常情况出现。
中午吃饭时间，设置了1个小时的时间进行测试。
回来的时候系统报出如下异常
2019-08-12 15:06:07,296 1092208 [reactor-http-server-epoll-12] WARN io.netty.channel.AbstractChannelHandlerContext.warn:146 - An exception '{}' [enable DEBUG level for full stacktrace] was thrown by a user handler's exceptionCaught() method while handling the following exception:io.netty.util.internal.OutOfDirectMemoryError: failed to allocate 16777216 byte(s) of direct memory (used: 503316487, max: 504889344) at io.netty.util.internal.PlatformDependent.incrementMemoryCounter(PlatformDependent.java:640) at io.netty.util.internal.PlatformDependent.allocateDirectNoCleaner(PlatformDependent.java:594) at io.netty.buffer.PoolArena$DirectArena.allocateDirect(PoolArena.java:764) at io.netty.buffer.PoolArena$DirectArena.newChunk(PoolArena.java:740) at io.netty.buffer.PoolArena.allocateNormal(PoolArena.java:244) at io.netty.buffer.PoolArena.allocate(PoolArena.java:214) at io.netty.buffer.PoolArena.allocate(PoolArena.java:146) at io.netty.buffer.PooledByteBufAllocator.newDirectBuffer(PooledByteBufAllocator.java:324) at io.netty.buffer.AbstractByteBufAllocator.directBuffer(AbstractByteBufAllocator.java:185) at io.netty.buffer.AbstractByteBufAllocator.directBuffer(AbstractByteBufAllocator.java:176) at io.netty.buffer.AbstractByteBufAllocator.ioBuffer(AbstractByteBufAllocator.java:137) at io.netty.channel.DefaultMaxMessagesRecvByteBufAllocator$MaxMessageHandle.allocate(DefaultMaxMessagesRecvByteBufAllocator.java:114) at io.netty.channel.epoll.EpollRecvByteAllocatorHandle.allocate(EpollRecvByteAllocatorHandle.java:72) at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:793) at io.netty.channel.epoll.AbstractEpollChannel$AbstractEpollUnsafe$1.run(AbstractEpollChannel.java:382) at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:163) at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:404) at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:315) at io.
当时一脸懵逼，马上开始监控 Jvm 堆栈，减少jvm的内存空间，提升并发数以后，重启项目重新压测，
项目启动参数如下：
java -jar -Xmx1024M /opt/deploy/gateway-appapi/cloud-employ-gateway-0.0.5-SNAPSHOT.jar↓↓↓↓修改为↓↓↓↓java -jar -Xmx512M /opt/deploy/gateway-appapi/cloud-employ-gateway-0.0.5-SNAPSHOT.jar
缩减了一半内存启动，等待问题复现。等待3分钟问题再次复现，但是同时Jvm却的进行了Full GC。
EC EU OC OU MC MU CCSC CCSU YGC YGCT FGC FGCT 275456.0 100103.0 484864.0 50280.2 67672.0 64001.3 9088.0 8463.2 501 11.945 3 0.262 275968.0 25072.3 484864.0 47329.3 67672.0 63959.4 9088.0 8448.8 502 11.970 4 0.429
没错，在出现问题的时候，系统出现了Full Gc，但是OU并没有达到触发的原因。
结合日志中的 direct memory，想到了Jvm 中的堆外内存。
使用 -XX:MaxDirectMemorySize 可以进行设置 Jvm 堆外内存大小，当 Direct ByteBuffer 分配的堆外内存到达指定大小后，即触发Full GC。
该值是有上限的，默认是64M，最大为 sun.misc.VM.maxDirectMemory()。
结合所有情况，表明堆外内存使用存在内存溢出的情况。
报错内容为Netty框架，新增以下配置，开启Netty错误日志打印：
-Dio.netty.leakDetection.targetRecords=40 #设置Records 上限-Dio.netty.leakDetection.level=advanced #设置日志级别
项目启动，没任何问题，开启压测后服务报出如下异常：
2019-08-13 14:59:01,656 18047 [reactor-http-nio-7] ERROR io.netty.util.ResourceLeakDetector.reportTracedLeak:317 - LEAK: ByteBuf.release() was not called before it's garbage-collected. See http://netty.io/wiki/reference-counted-objects.html for more information.Recent access records: 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Source)
在 #3 中，我发现了一个眼熟的类，ReadBodyPredicateFactory.java ，还记得最开始的时候使用 readbody 配置么？
这里就是进行 cachedRequestBodyObject 的写入类，
追踪一下Readbody源码
/** * This predicate is BETA and may be subject to change in a future release. A * predicate that checks the contents of the request body * @param inClass the class to parse the body to * @param predicate a predicate to check the contents of the body * @param <T> the type the body is parsed to * @return a {@link BooleanSpec} to be used to add logical operators */ public <T> BooleanSpec readBody(Class<T> inClass, Predicate<T> predicate) { return asyncPredicate(getBean(ReadBodyPredicateFactory.class) .applyAsync(c -> c.setPredicate(inClass, predicate))); }
异步调用的 ReadBodyPredicateFactory.applyAsync() 和 错误日志中的
org.springframework.cloud.gateway.handler.predicate.ReadBodyPredicateFactory.lambda$null$0(ReadBodyPredicateFactory.java:102)
指向方法一致。查看源码102行：
Flux<DataBuffer> cachedFlux = Flux.defer(() -> Flux.just(dataBuffer.slice(0, dataBuffer.readableByteCount())));
此处 Spring Cloud Gateway 通过 dataBuffer.slice 切割出了新的 dataBuffer，但是通过 Netty 的内存检测工具判断，此处的 dataBuffer 并没有被回收。
错误如下，日志很多容易被忽视。
ERROR io.netty.util.ResourceLeakDetector.reportTracedLeak:317 – LEAK: ByteBuf.release() was not called before it’s garbage-collected. See http://netty.io/wiki/reference-counted-objects.html for more information.
找到问题那就要解决才行，尝试修改源码
@Override@SuppressWarnings("unchecked")public AsyncPredicate<ServerWebExchange> applyAsync(Config config) { return exchange -> { Class inClass = config.getInClass(); Object cachedBody = exchange.getAttribute(CACHE_REQUEST_BODY_OBJECT_KEY); Mono<?> modifiedBody; // We can only read the body from the request once, once that // happens if we // try to read the body again an exception will be thrown. The below // if/else // caches the body object as a request attribute in the // ServerWebExchange // so if this filter is run more than once (due to more than one // route // using it) we do not try to read the request body multiple times if (cachedBody != null) { try { boolean test = config.predicate.test(cachedBody); exchange.getAttributes().put(TEST_ATTRIBUTE, test); return Mono.just(test); } catch (ClassCastException e) { if (LOGGER.isDebugEnabled()) { LOGGER.debug("Predicate test failed because class in predicate " + "does not match the cached body object", e); } } return Mono.just(false); } else { // Join all the DataBuffers so we have a single DataBuffer for // the body return DataBufferUtils.join(exchange.getRequest().getBody()).flatMap(dataBuffer -> { // Update the retain counts so we can read the body twice, // once to parse into an object // that we can test the predicate against and a second time // when the HTTP client sends // the request downstream // Note: if we end up reading the body twice we will run // into // a problem, but as of right // now there is no good use case for doing this DataBufferUtils.retain(dataBuffer); // Make a slice for each read so each read has its own // read/write indexes Flux<DataBuffer> cachedFlux = Flux .defer(() -> Flux.just(dataBuffer.slice(0, dataBuffer.readableByteCount()))); ServerHttpRequest mutatedRequest = new ServerHttpRequestDecorator(exchange.getRequest()) { @Override public Flux<DataBuffer> getBody() { return cachedFlux; } }; # 新增如下代码 DataBufferUtils.release(dataBuffer); return ServerRequest.create(exchange.mutate().request(mutatedRequest).build(), messageReaders) .bodyToMono(inClass).doOnNext(objectValue -> { exchange.getAttributes().put(CACHE_REQUEST_BODY_OBJECT_KEY, objectValue); exchange.getAttributes().put(CACHED_REQUEST_BODY_KEY, cachedFlux); }).map(objectValue -> config.predicate.test(objectValue)); }); } };}
Spring Cloud Gateway 在配置的架构中，版本为2.1.1，修改以上代码后，启动项目测试，问题没有复现，正常运行。
同样这个问题，也可以选择升级 Spring Cloud Gateway 版本，在官方2.1.2版本中，此处代码已被重构，升级后测试也完全正常。
以上为个人经验，希望能给大家一个参考，也希望大家多多支持。
游手好闲会使人心智生锈
