GitHub user hirthwork opened a pull request:
https://github.com/apache/httpcore/pull/21
Fix race condition in
org.apache.http.nio.protocol.HttpAsyncRequestExecutor.endOfInput and
org.apache.http.impl.nio.client.AbstractClientExchangeHandler.connectionAllocated(conn)
Got pretty bad race condition when sending async requests.
Symptoms & Environment: We have target host which sometimes closes
connections after requests processing but no `Connection: close` header was
set. Some requests hangs, i.e. `BasicFuture` methods `.cancelled`, `.completed`
or `.failed` methods are never called.
Analysis:
Let there be two threads:
- T1 is the async client reactor thread.
- T2 is the thread that initiates HTTP request.
T1: completes HTTP request and calls `connmgr.releaseConnection`
T2: initiates HTTP requests asks connmgr for connection and immediately
gets connection that was just released by T1
T1: receives EOF on released connection and falls into
`HttpAsyncRequestExecutor.endOfInput`. Connection has valid
`HTTP_EXCHANGE_STATE`, but `HTTP_HANDLER` is null
T2: sets `HTTP_HANDLER`, requests output and checks `.isState`. Everything
is OK here.
T1: goes to the end of `.endOfInput` and closes connection. `HTTP_HANDLER`
is not null anymore, but is won't be notified about connection close, soon
connection will be garbage collected and it will never be released and
`HTTP_HANDLER.basicFuture` will never be notified.
Suggested fix (not sure if it is optimal, but it changed behaviour to be
more redundant):
At the start of `.endOfInput` try to notify `HTTP_HANDLER`. If there is no
one, set variable `handlerNotified` to false.
After connection close check `handlerNotified` and if it wasn't, then check
if somebody has set `HTTP_HANDLER` externally.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/hirthwork/httpcore 4.4.x
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/httpcore/pull/21.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #21
----
commit aa680cafe67e92dfe7bdb96e03c67bb9f1905b87
Author: Dmitry Potapov <[email protected]>
Date: 2016-02-05T18:44:15Z
HttpAsyncRequestExecutor.getState(conn) and
HttpAsyncRequestExecutor.getHandler(conn) made static
commit 363df092bfbabe8b32e2223615af0671f9846bcb
Author: Dmitry Potapov <[email protected]>
Date: 2016-02-05T18:47:28Z
Double check for HttpAsyncClientExchangeHandler presence in
HttpAsyncRequestExecutor.endOfInput
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