Gaojie Liu created HTTPCORE-750:
-----------------------------------
Summary: H2ConnPool creates too many conns under high load at
initialization time
Key: HTTPCORE-750
URL: https://issues.apache.org/jira/browse/HTTPCORE-750
Project: HttpComponents HttpCore
Issue Type: Bug
Components: HttpCore
Affects Versions: 5.1.1
Environment: Linux / Ubuntu / openjdk version "1.8.0_292"
Reporter: Gaojie Liu
Fix For: 5.1.2, 5.2-alpha1
There is an implementation problem in
*AbstractIOSessionPool.getSessionInternal()*
Wrong pattern (starting line 190 in httpcore5-5.1.1) :
if (poolEntry.sessionFuture == null) {
*poolEntry.sessionFuture =* connectSession(
namedEndpoint,
connectTimeout,
new FutureCallback<IOSession>() {
...
@Override
public void failed(final Exception ex) {
synchronized (poolEntry) {
poolEntry.session = null;
*poolEntry.sessionFuture = null;*
...
}
}
...
});
In case of a synchronous failure during connectSession (for example :
UnknownHostException), the sessionFuture cleanup in the failed() callback (line
216) is executed +before+ poolEntry.sessionFuture is assigned with the return
value of connectSession (line 191)
Thus, after the failure, a cancelled future is assigned to
poolEntry.sessionFuture and never cleaned up !
This result in a stalled entry in the pool because the _if
(poolEntry.sessionFuture == null)_ condition will no longer return true.
*Quick Reproducer*
H2AsyncClientBuilder httpClientBuilder = HttpAsyncClients.customHttp2()
.setDefaultRequestConfig(RequestConfig.custom()
.setConnectTimeout(5000,
TimeUnit.MILLISECONDS)
.setResponseTimeout(5000,
TimeUnit.MILLISECONDS)
.build())
.setH2Config(H2Config.custom()
.setPushEnabled(false)
.build());
CloseableHttpAsyncClient client = httpClientBuilder.build();
client.start();
for(int n=1;n<=2;n++)
{
System.out.println("Try #"+n);
HttpHost targetHost = new HttpHost(URIScheme.HTTPS.getId(),
"invalidhost-gfhsgfxyzd.com", 443);
SimpleHttpRequest request = new SimpleHttpRequest("GET",
targetHost, "/");
Future<SimpleHttpResponse> responseFuture =
client.execute(request, null);
try
{
responseFuture.get(); // {color:#FF0000}*HANGS FOREVER at Try
#2*{color}
}
catch (ExecutionException e)
{
e.printStackTrace();
}
}
*Quick Fix*
Cleaning the sessionFuture immediately after connectSession() returns in case
its already done fixes the issue :
(Line 234)
+ if (poolEntry.sessionFuture != null && poolEntry.sessionFuture.isDone())
+ poolEntry.sessionFuture = null;
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