[英]HttpClient can't get response from server
This problem has blocked our whole team half a day! 这个问题已经使我们的整个团队半天无法工作了!
We use apache httpclient 4.3.x to post and get data from an storage server which provides http api. 我们使用apache httpclient 4.3.x来发布并从提供http api的存储服务器中获取数据。 In order to improve performance, we used
PoolingHttpClientConnectionManager
: 为了提高性能,我们使用了
PoolingHttpClientConnectionManager
:
public HttpClient createHttpClient() {
Registry registry = RegistryBuilder.create()....build();
PoolingHttpClientConnectionManager connectionManager = new PoolingHttpClientConnectionManager(registry);
connectionManager.setMaxTotal(50);
connectionManager.setDefaultMaxPerRoute(50);
CloseableHttpClient httpClient = HttpClients.custom()
.setConnectionManager(connectionManager)
.build();
return httpClient;
}
Then we hold an instance of the httpClient in our program, reuse it with every http request: 然后,在程序中保存一个httpClient实例,将其与每个http请求一起重用:
Global httpClient: 全局httpClient:
HttpClient httpClient = createHttpClient();
Post some data: 发布一些数据:
HttpPost httpPut = new HttpPost("...");
HttpResponse response = httpClient.execute(httpPut);
// Notice we get the response content here!
String content = EntityUtils.toString(response.getEntity());
System.out.println(content);
httpPut.releaseConnection();
response.close();
Then get: 然后得到:
HttpGet httpGet = new HttpGet("...");
// Blocked at this line !!!!
HttpResponse response = httpClient.execute(httpGet);
String content = EntityUtils.toString(response.getEntity());
System.out.println(content);
httpPut.releaseConnection();
response.close();
Please notice the line: // Blocked at this line !!!!
请注意以下行:
// Blocked at this line !!!!
The program has blocked at that line and never go to next line. 程序已在该行被阻止,并且从不进入下一行。 In debugging mode, I can see it has been blocked at:
在调试模式下,我可以看到它已在以下位置被阻止:
SocketInputStream.socketRead0()
I've searched for a lot of questions and documents, but no lucky. 我搜索了很多问题和文档,但并不幸运。
My colleage just fix it by setting NoConnectionReuseStrategy.INSTANCE
: 我的
NoConnectionReuseStrategy.INSTANCE
只是通过设置NoConnectionReuseStrategy.INSTANCE
解决它:
HttpClients.custom()
.setConnectionManager(connectionManager)
// Following line fixed the problem, but why?
.setConnectionReuseStrategy(NoConnectionReuseStrategy.INSTANCE)
.build();
Now it doens't blocked, but why? 现在它没有被阻止,但是为什么呢?
What does "reuse connection" mean? “重用连接”是什么意思? And is there performance issue by using
NoConnectionReuseStrategy
? 使用
NoConnectionReuseStrategy
是否存在性能问题?
Thank you, guys~ 谢谢大家〜
I tried to reproduce the blocking http-get (also as an exercise for myself) but even without closing responses I could not get it to block. 我试图重现阻止的http-get(也是我自己的一种练习),但是即使没有关闭响应,我也无法阻止它。 The ONLY time I managed to make the http-get block is by doing a
response.getEntity().getContent()
without reading from the returned InputStream
and without closing the returned InputStream
. 我设法制作http-get块的唯一时间是通过执行
response.getEntity().getContent()
而不读取返回的InputStream
且不关闭返回的InputStream
。 For my tests I used Tomcat 7.0.47 with two very simple servlets (one responding "OK" to a get, the other echoing a post) as a server. 在我的测试中,我将Tomcat 7.0.47与两个非常简单的servlet(作为响应get响应“ OK”,另一个响应POST)用作服务器。 The client started 50 threads with each thread performing 30 alternating http-get and http-post request (total of 1500 requests).
客户端启动了50个线程,每个线程执行30个交替的http-get和http-post请求(总共1500个请求)。 The client did not use the
RegistryBuilder
, instead the default one is used (created by the PoolingHttpClientConnectionManager
itself). 客户端未使用
RegistryBuilder
,而是使用默认值(由PoolingHttpClientConnectionManager
本身创建)。
About the NoConnectionReuseStrategy
: by default (HttpClient created with HttpClients.createDefault()
, I used org.apache.httpcomponents:httpclient:4.3.1
) a connection pool is used with a maximum of 2 connections to 1 server. 关于
NoConnectionReuseStrategy
:默认情况下(使用HttpClients.createDefault()
创建的HttpClients.createDefault()
,我使用的是org.apache.httpcomponents:httpclient:4.3.1
),连接池最多使用1个服务器的2个连接。 Eg even if 5 threads are doing all kinds of requests at the same time to 1 server, the connection pool opens only 2 connections, re-uses them for all requests and ensures that 1 connection is used by 1 thread at any given time. 例如,即使5个线程同时对1个服务器执行各种请求,连接池也仅打开2个连接,将它们重新用于所有请求,并确保在任何给定时间1个线程使用1个连接。 This can have a very positive impact on client performance and significantly reduces load on the server.
这会对客户端性能产生非常积极的影响,并显着减少服务器上的负载。 The only thing you must make sure is to call
response.close()
in a finally-block (this ensures the connection is returned to the connection pool). 您唯一必须确保的是在finally块中调用
response.close()
(这可确保将连接返回到连接池)。 By using the NoConnectionReuseStrategy
you basically disable the connection pool: for each request a new connection will be created. 通过使用
NoConnectionReuseStrategy
您基本上可以禁用连接池:对于每个请求,将创建一个新的连接。 I recommend you enable debug-logging for category org.apache.http.impl.conn.PoolingHttpClientConnectionManager
, it is very informative. 我建议您为
org.apache.http.impl.conn.PoolingHttpClientConnectionManager
类别启用调试日志记录,这非常有用。
A note about httpPut.releaseConnection()
: this does not actually release a connection, it only ensures that you can re-use the "httpPut" object in a next request (see the apidocs , follow the shown link). 关于
httpPut.releaseConnection()
注释:实际上并不会释放连接,它只是确保您可以在下一个请求中重用“ httpPut”对象(请参阅apidocs , 单击显示的链接)。 Also note that in your code for the "httpGet", you call releaseConnection()
on "httpPut" instead of "httpGet". 另请注意,在“ httpGet”的代码中,您在“ httpPut”而不是“ httpGet”上调用
releaseConnection()
。
Ran into this problem just a while back. 不久前就遇到了这个问题。 In case someone else comes across this problem, this post might be useful.
如果其他人遇到此问题,这篇文章可能会有用。
I am using a Java Servlet to service my requests. 我正在使用Java Servlet来处理我的请求。 When I wrote to the response stream using the PrintWriter instance my client blocked.
当我使用PrintWriter实例写入响应流时,客户端被阻止。 Tried writing to the OutputStream directly
response.getOutputStream.write("myresponse")
and it worked. 尝试直接写入到OutputStream的
response.getOutputStream.write("myresponse")
并成功。
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