Spring Cloud Gateway 内存溢出解决过程

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：

@Bean
public 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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	reactor.netty.http.server.HttpTrafficHandler.channelRead(HttpTrafficHandler.java:191)
	io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:359)
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	io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:438)
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	io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:359)
	io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:345)
	io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:337)
	io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1408)
	io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:359)
	io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:345)
	io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:930)
	io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:163)
	io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:677)
	io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:612)
	io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:529)
	io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:491)
	io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:905)
	java.lang.Thread.run(Unknown Source)
#2:
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	org.springframework.core.io.buffer.NettyDataBuffer.asByteBuffer(NettyDataBuffer.java:266)
	org.springframework.core.codec.StringDecoder.decodeDataBuffer(StringDecoder.java:207)
	org.springframework.core.codec.StringDecoder.decodeDataBuffer(StringDecoder.java:59)
	org.springframework.core.codec.AbstractDataBufferDecoder.lambda$decodeToMono$1(AbstractDataBufferDecoder.java:68)
	reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:107)
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	io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:359)
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	io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:337)
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	io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:345)
	io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:337)
	io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1408)
	io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:359)
	io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:345)
	io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:930)
	io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:163)
	io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:677)
	io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:612)
	io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:529)
	io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:491)
	io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:905)
	java.lang.Thread.run(Unknown Source)
#3:
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	org.springframework.core.io.buffer.NettyDataBuffer.slice(NettyDataBuffer.java:260)
	org.springframework.core.io.buffer.NettyDataBuffer.slice(NettyDataBuffer.java:42)
	org.springframework.cloud.gateway.handler.predicate.ReadBodyPredicateFactory.lambda$null$0(ReadBodyPredicateFactory.java:102)
	reactor.core.publisher.FluxDefer.subscribe(FluxDefer.java:46)
	reactor.core.publisher.MonoCollectList.subscribe(MonoCollectList.java:59)
	reactor.core.publisher.MonoFilterFuseable.subscribe(MonoFilterFuseable.java:44)
	reactor.core.publisher.MonoMapFuseable.subscribe(MonoMapFuseable.java:56)
	reactor.core.publisher.MonoSubscriberContext.subscribe(MonoSubscriberContext.java:47)
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	reactor.core.publisher.MonoPeek.subscribe(MonoPeek.java:71)
	reactor.core.publisher.MonoMap.subscribe(MonoMap.java:55)
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	reactor.core.publisher.FluxMapFuseable$MapFuseableConditionalSubscriber.onNext(FluxMapFuseable.java:287)
	reactor.core.publisher.FluxFilterFuseable$FilterFuseableConditionalSubscriber.onNext(FluxFilterFuseable.java:331)
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	io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:359)
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	io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:337)
	reactor.netty.http.server.HttpTrafficHandler.channelRead(HttpTrafficHandler.java:191)
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	io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:345)
	io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:337)
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	io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:297)
	io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:253)
	io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:359)
	io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:345)
	io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:337)
	io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1408)
	io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:359)
	io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:345)
	io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:930)
	io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:163)
	io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:677)
	io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:612)
	io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:529)
	io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:491)
	io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:905)
	java.lang.Thread.run(Unknown 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  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。