问题背景
线上环境spring cloud gateway偶尔遇到如下异常：
DataBufferLimitException: Exceeded limit on max bytes to buffer : 262144
问题的产生原因很容易查到，REST API接口请求数据超过256K，被网关拦截。正常我们加大缓冲区的配置即可，-1表示不限制。但是并没有解决问题，下面介绍我的分析过程和解决办法。
spring:
codec:
max-in-memory-size: 1048576
环境信息：
Spring Boot 2.2.1.RELEASE
异常信息：
2021-02-04 15:39:33.014 [reactor-http-epoll-2] ERROR org.springframework.boot.autoconfigure.web.reactive.error.AbstractErrorWebExceptionHandler - [1513c08e-1] 500 Server Error for HTTP POST "/x-service/path"
org.springframework.core.io.buffer.DataBufferLimitException: Exceeded limit on max bytes to buffer : 262144
at org.springframework.core.io.buffer.LimitedDataBufferList.raiseLimitException(LimitedDataBufferList.java:101)
Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException:
Error has been observed at the following site(s):
|_ checkpoint ⇢ org.springframework.cloud.gateway.filter.WeightCalculatorWebFilter [DefaultWebFilterChain]
|_ checkpoint ⇢ org.springframework.boot.actuate.metrics.web.reactive.server.MetricsWebFilter [DefaultWebFilterChain]
|_ checkpoint ⇢ HTTP POST "/x-service/path" [ExceptionHandlingWebHandler]
Stack trace:
at org.springframework.core.io.buffer.LimitedDataBufferList.raiseLimitException(LimitedDataBufferList.java:101)
at org.springframework.core.io.buffer.LimitedDataBufferList.updateCount(LimitedDataBufferList.java:94)
at org.springframework.core.io.buffer.LimitedDataBufferList.add(LimitedDataBufferList.java:59)
at reactor.core.publisher.MonoCollect$CollectSubscriber.onNext(MonoCollect.java:124)
at reactor.core.publisher.FluxMap$MapSubscriber.onNext(FluxMap.java:114)
at reactor.core.publisher.FluxPeek$PeekSubscriber.onNext(FluxPeek.java:192)
at reactor.core.publisher.FluxMap$MapSubscriber.onNext(FluxMap.java:114)
at reactor.netty.channel.FluxReceive.onInboundNext(FluxReceive.java:331)
at reactor.netty.channel.ChannelOperations.onInboundNext(ChannelOperations.java:352)
at reactor.netty.http.server.HttpServerOperations.onInboundNext(HttpServerOperations.java:484)
...
分析过程
-
定位异常触发点
org.springframework.core.io.buffer.LimitedDataBufferList.java
image.png
-
查找maxByteCount的设置代码
org.springframework.http.codec.support.BaseDefaultCodecs.java
image.png
- 经过调试发现，启动时初始化是正常的，配置此参数有效spring.codec.max-in-memory-size
- 但业务调用的时候此参数接受值为null，配置并未生效
- 继续查找调用源头发现，我们的自定义拦截器获取body信息，代码如下
ServerRequest serverRequest = ServerRequest.create(exchange, HandlerStrategies.withDefaults().messageReaders());
- 因为HandlerStrategies.withDefaults()是重新创建的对象，并未使用Spring注入的对象，造成配置不生效
-
查看gateway的ModifyRequestBodyGatewayFilterFactory，使用注入的messageReaders即可
org.springframework.cloud.gateway.filter.factory.rewrite.ModifyRequestBodyGatewayFilterFactory.java
image.png
解决办法
参考ModifyRequestBodyGatewayFilterFactory调整自定义拦截器，使用注入的配置类。
代码如下：
@Component
@Slf4j
public class XXXFilter implements GlobalFilter, Ordered {
@Autowired
ServerCodecConfigurer codecConfigurer;
@Override
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
ServerHttpRequest request = exchange.getRequest();
try {
if (request.getHeaders().getContentLength() > 0) {
ServerRequest serverRequest = ServerRequest.create(exchange, codecConfigurer.getReaders());
Mono<String> bodyToMono = serverRequest.bodyToMono(String.class);
return bodyToMono.flatMap(reqBody -> {
if (isJson(reqBody)) {
String perms = JSONObject.parseObject(reqBody).getString("perms");
if (StringUtils.isNotEmpty(perms)) {
exchange.getAttributes().put(Constants.XXX_REQUEST_PERMS_ATTR, perms);
}
}
ServerHttpRequestDecorator requestDecorator = new ServerHttpRequestDecorator(exchange.getRequest()) {
@Override
public Flux<DataBuffer> getBody() {
NettyDataBufferFactory nettyDataBufferFactory = new NettyDataBufferFactory(ByteBufAllocator.DEFAULT);
DataBuffer bodyDataBuffer = nettyDataBufferFactory.wrap(reqBody.getBytes());
return Flux.just(bodyDataBuffer);
}
};
return chain.filter(exchange.mutate().request(requestDecorator).build());
});
}
return chain.filter(exchange);
} catch (Exception e) {
log.error("Exception[XXXFilter]:", e);
return chain.filter(exchange);
}
}
