java http长链接(keep-alive)导致的问题
两种由http长链接(keep-alive)导致的问题,当然这两种问题都有多种原因导致,这里只分析针对keep-alive相关而产生的异常。
1 SocketException: Connection reset
报错堆栈日志:
Caused by: java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(SocketInputStream.java:209)
at java.net.SocketInputStream.read(SocketInputStream.java:141)
at org.apache.http.impl.io.SessionInputBufferImpl.streamRead(SessionInputBufferImpl.java:137)
at org.apache.http.impl.io.SessionInputBufferImpl.fillBuffer(SessionInputBufferImpl.java:153)
at org.apache.http.impl.io.SessionInputBufferImpl.readLine(SessionInputBufferImpl.java:282)
at org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:138)
at org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:56)
at org.apache.http.impl.io.AbstractMessageParser.parse(AbstractMessageParser.java:259)
at org.apache.http.impl.DefaultBHttpClientConnection.receiveResponseHeader(DefaultBHttpClientConnection.java:163)
at org.apache.http.impl.conn.CPoolProxy.receiveResponseHeader(CPoolProxy.java:165)
at org.apache.http.protocol.HttpRequestExecutor.doReceiveResponse(HttpRequestExecutor.java:273)
at org.apache.http.protocol.HttpRequestExecutor.execute(HttpRequestExecutor.java:125)
at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:272)
at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:185)
at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:89)
at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:111)
at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:72)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:221)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:165)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:140)
复制代码
关于SocketException在官方文档有描述: docs.oracle.com/javase/8/do…
本质原因是 服务器通过TCP协议给客户端返回了RST消息,表示已经完成了发送和接收,如果客户端此时从流中读取数据时会发生Connection reset,往流中写数据时就会发生Connection reset Connection reset by peer。注意Socket.close()语义和TCP FIN消息之间略有不匹配。 而至于为什么服务端会返回 RST消息,那就是http keep-alive 导致的问题了。 如果是springboot的服务器,那么默认的keep-alive timeout是60s,如果客户端使用的是apache httpclient,默认的keep-alive是在 org.apache.http.impl.client.DefaultConnectionKeepAliveStrategy类设置的,代码如下:
public long getKeepAliveDuration(final HttpResponse response, final HttpContext context) {
Args.notNull(response, "HTTP response");
final HeaderElementIterator it = new BasicHeaderElementIterator(
response.headerIterator(HTTP.CONN_KEEP_ALIVE));
while (it.hasNext()) {
final HeaderElement he = it.nextElement();
final String param = he.getName();
final String value = he.getValue();
if (value != null && param.equalsIgnoreCase("timeout")) {
try {
return Long.parseLong(value) * 1000;
} catch(final NumberFormatException ignore) {
}
}
}
return -1;
}
复制代码
可见,如果response header如果没有返回Keep-Alive,那么就会是-1,也就是无限的, hc.apache.org/httpcompone… "If the Keep-Alive header is not present in the response, HttpClient assumes the connection can be kept alive indefinitely"
所以问题就比较明白了,springboot服务端没有返回Keep-Alive的header,客户端如果使用了apache httpclient,且没有设置Keep-Alive的话,就会导致服务端的超时是60s,客户端就认为是无限的,在某些情况下,服务端关闭了链接,客户端还会获取这个连接,就会导致上面的问题。
既然找到原因了那么就需要解决,httpclient文档中也给了说要设置默认的超时时间,即给一个自定义的实现。
2 NoHttpResponseException: xxx.xxx.xxx.xxx failed to respond
Caused by: org.apache.http.NoHttpResponseException: xxx.xxx.xxx.xxx failed to respond
at org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:141)
at org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:56)
at org.apache.http.impl.io.AbstractMessageParser.parse(AbstractMessageParser.java:259)
at org.apache.http.impl.DefaultBHttpClientConnection.receiveResponseHeader(DefaultBHttpClientConnection.java:163)
at org.apache.http.impl.conn.CPoolProxy.receiveResponseHeader(CPoolProxy.java:165)
at org.apache.http.protocol.HttpRequestExecutor.doReceiveResponse(HttpRequestExecutor.java:273)
at org.apache.http.protocol.HttpRequestExecutor.execute(HttpRequestExecutor.java:125)
at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:272)
at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:185)
at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:89)
at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:111)
at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:72)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:221)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:165)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:140)
复制代码
补充知识点:
1 'Connection: Keep-Alive' header头只用来在HTTP 1.0中, 而在HTTP 1.1中默认都是Keep-Alive的,所以不需要再添加'Connection: Keep-Alive'的头。所以在springboot1.5以上版本中,即使你在请求的header中加了'Connection: Keep-Alive'的头,在返回的header中是没有Connection的。相关链接: github.com/spring-proj…
2 curl 命令可以使用--http1.0 来强制走http1.0协议。
3 springboot中 tomcat 默认的keepalive timeout是60s, github.com/spring-proj…