聊聊nginx与tomcat的5xx

2019年9月27日 126次阅读来源: codecraft

序

本文主要讲述一下nginx与tomcat的502、504、503错误及其常见的产生原因。

502

定义

502 Bad Gateway : 作为网关或者代理工作的服务器尝试执行请求时，从上游服务器接收到无效的响应。

常见原因

后端服务挂了的情况,直接502
后端服务在重启

实例

将后端服务关掉，然后向nginx发送请求后端接口，日志如下：

access.log

127.0.0.1 - - [22/Dec/2017:20:44:38 +0800] "GET /timeout/long-write HTTP/1.1" 502 537 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.108 Safari/537.36"

error.log

2017/12/22 20:45:12 [error] 1481#0: *3 kevent() reported that connect() failed (61: Connection refused) while connecting to upstream, client: 127.0.0.1, server: localhost, request: "GET /timeout/long-write HTTP/1.1", upstream: "http://[::1]:8080/timeout//long-write", host: "localhost:8888"

504

定义

504 Gateway Timeout : 作为网关或者代理工作的服务器尝试执行请求时，未能及时从上游服务器（URI标识出的服务器，例如HTTP、FTP、LDAP）或者辅助服务器（例如DNS）收到响应。注意：某些代理服务器在DNS查询超时时会返回400或者500错误

常见原因

该接口太耗时，后端服务接收到请求，开始执行，未能在设定时间返回数据给nginx
后端服务器整体负载太高，接受到请求之后，由于线程繁忙，未能安排给请求的接口，导致未能在设定时间返回数据给nginx

实例

前端返回

<html>
<head><title>504 Gateway Time-out</title></head>
<body bgcolor="white">
<center><h1>504 Gateway Time-out</h1></center>
<hr><center>openresty/1.9.15.1</center>
</body>
</html>
<!-- a padding to disable MSIE and Chrome friendly error page -->
<!-- a padding to disable MSIE and Chrome friendly error page -->
<!-- a padding to disable MSIE and Chrome friendly error page -->
<!-- a padding to disable MSIE and Chrome friendly error page -->
<!-- a padding to disable MSIE and Chrome friendly error page -->
<!-- a padding to disable MSIE and Chrome friendly error page -->

access.log

192.168.99.1 - - [22/Dec/2017:21:58:20 +0800] "GET /timeout/long-resp HTTP/1.1" 504 591 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.108 Safari/537.36" "-" "-"

error.log

2017/12/22 21:58:20 [error] 5#5: *7 upstream timed out (110: Connection timed out) while reading response header from upstream, client: 192.168.99.1, server: , request: "GET /timeout/long-resp HTTP/1.1", upstream: "http://192.168.99.100:8080/timeout//long-resp", host: "192.168.99.100:8686"

nginx.conf

        location /timeout/long-resp {
            proxy_connect_timeout    30;
            proxy_read_timeout       100;
            proxy_send_timeout       10;
            proxy_pass http://192.168.99.100:8080/timeout/long-resp ;
        }

java代码

    @GetMapping("/timeout/long-resp")
    public String longResp() throws InterruptedException {
        TimeUnit.SECONDS.sleep(120);
        return "finish";
    }

服务器接受请求一直没有返回,nginx在等待100秒后报Connection timed out,返回504；但是后端继续执行，在第120秒才执行完。

503(`相对少见`)

定义

503 Service Unavailable : 表示服务器当前处于暂时不可用状态，无论是有意还是无意，当服务器端处于无法应答的状态时，就会返回该状态码。其中，服务端因维护需要而停止服务属于有意的情况。而当服务器自身负载过高，处于无法响应的状态时，则属于无意的情况。另外，负载均衡器或者web服务器的前置机等这些地方的服务器也有可能返回503.

常见原因

nginx进行限流，超过限速则返回503
后端服务进行常规维护，比如pause tomcat

nginx限流返回503实例

config

http{
    ## test 503
    limit_conn_zone $binary_remote_addr zone=addr:10m;
    server {
        listen 8686;
        location /timeout {
            limit_conn addr 1;
            proxy_connect_timeout    30;
            proxy_read_timeout       100;
            proxy_send_timeout       2;
            proxy_pass http://192.168.99.100:8080/timeout/ ;
        }
    }
}

error.log

2017/12/24 20:58:29 [error] 5#5: *1473 limiting connections by zone "addr", client: 192.168.99.1, server: , request: "GET /timeout/busy HTTP/1.1", host: "192.168.99.100:8686"

access.log

192.168.99.1 - - [24/Dec/2017:20:58:39 +0800] "GET /timeout/busy HTTP/1.1" 503 219 "-" "-" "-" "-"

client

wrk -t12 -c200 -d100s -T60s  --latency http://192.168.99.100:8686/timeout/busy
➜  ~ curl -i http://192.168.99.100:8686/timeout/busy
HTTP/1.1 503 Service Temporarily Unavailable
Server: openresty/1.9.15.1
Date: Sun, 24 Dec 2017 12:58:26 GMT
Content-Type: text/html
Content-Length: 219
Connection: keep-alive
<html>
<head><title>503 Service Temporarily Unavailable</title></head>
<body bgcolor="white">
<center><h1>503 Service Temporarily Unavailable</h1></center>
<hr><center>openresty/1.9.15.1</center>
</body>
</html>

tomcat返回503实例

Http11Processor

tomcat-embed-core-8.5.23-sources.jar!/org/apache/coyote/http11/Http11Processor.java

    @Override
    public SocketState service(SocketWrapperBase<?> socketWrapper)
        throws IOException {
        RequestInfo rp = request.getRequestProcessor();
        rp.setStage(org.apache.coyote.Constants.STAGE_PARSE);

        // Setting up the I/O
        setSocketWrapper(socketWrapper);
        inputBuffer.init(socketWrapper);
        outputBuffer.init(socketWrapper);

        // Flags
        keepAlive = true;
        openSocket = false;
        readComplete = true;
        boolean keptAlive = false;
        SendfileState sendfileState = SendfileState.DONE;

        while (!getErrorState().isError() && keepAlive && !isAsync() && upgradeToken == null &&
                sendfileState == SendfileState.DONE && !endpoint.isPaused()) {
                //......

                if (endpoint.isPaused()) {
                    // 503 - Service unavailable
                    response.setStatus(503);
                    setErrorState(ErrorState.CLOSE_CLEAN, null);
                } else {
                    keptAlive = true;
                    // Set this every time in case limit has been changed via JMX
                    request.getMimeHeaders().setLimit(endpoint.getMaxHeaderCount());
                    if (!inputBuffer.parseHeaders()) {
                        // We've read part of the request, don't recycle it
                        // instead associate it with the socket
                        openSocket = true;
                        readComplete = false;
                        break;
                    }
                    if (!disableUploadTimeout) {
                        socketWrapper.setReadTimeout(connectionUploadTimeout);
                    }
                }

        }    
    }

只要endpoint的状态是paused，则返回503

AbstractEndpoint

tomcat-embed-core-8.5.23-sources.jar!/org/apache/tomcat/util/net/AbstractEndpoint.java

    /**
     * Pause the endpoint, which will stop it accepting new connections.
     */
    public void pause() {
        if (running && !paused) {
            paused = true;
            unlockAccept();
            getHandler().pause();
        }
    }

    /**
     * Resume the endpoint, which will make it start accepting new connections
     * again.
     */
    public void resume() {
        if (running) {
            paused = false;
        }
    }

这里是endpoint的pause以及resume方法

请求

当请求进入Http11Processor的service方法到执行endpoint.isPaused()方法期间，tomcat被pause了，这个时候，就会返回503，如下：

➜  ~ curl -i http://localhost:8080/demo/test
HTTP/1.1 503
Transfer-Encoding: chunked
Date: Sun, 24 Dec 2017 14:10:16 GMT
Connection: close

小结

通常是后端服务挂了或在重启

通常是请求的接口执行耗时，亦或是后端服务负载高，执行耗时

通常是nginx限流或后端服务pause进行维护

doc

    原文作者：codecraft
    原文地址: https://segmentfault.com/a/1190000012595322
    本文转自网络文章，转载此文章仅为分享知识，如有侵权，请联系博主进行删除。

序

502

定义

常见原因

实例

504

定义

常见原因

实例

503(相对少见)

定义

常见原因

nginx限流返回503实例

tomcat返回503实例

小结

doc

503(`相对少见`)