MultiThreadedHttpConnectionManager does not properly respond to thread
interrupts
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Key: HTTPCLIENT-633
URL: https://issues.apache.org/jira/browse/HTTPCLIENT-633
Project: HttpComponents HttpClient
Issue Type: Bug
Components: HttpConn
Affects Versions: 3.1 Beta 1
Reporter: John Goodwin
MultiThreadedHttpConnectionManager uses interrupts to notify waiting threads
when a connection is ready for them. Issues arise if the threads are
interrupted by someone else while they are still waiting on a thread, because
doGetConnection does not remove the threads from the queue of waiting threads
when they are interrupted:
connectionPool.wait(timeToWait);
// we have not been interrupted so we need to remove
ourselves from the
// wait queue
hostPool.waitingThreads.remove(waitingThread);
connectionPool.waitingThreads.remove(waitingThread);
} catch (InterruptedException e) {
// do nothing } finally {
if (useTimeout) {
endWait = System.currentTimeMillis();
timeToWait -= (endWait - startWait);
} }
Under ordinary circumstances, the queue maintenance is done by the
notifyWaitingThread method. However, if the thread is interrupted by any other
part of the system, it will (1) not actually be released, since the loop in
doGetConnection will force it back to the wait, and (2) will be added the
waiting thread to the queue repeatedly, which basically means that the thread
will eventually receive the interrupt from notifyWaitingThread at some later
point, when it is no longer actually waiting for a connection.
This code could probably be re-architected to make it less error-prone, but the
fundamental issue seems to be the use of interrupts to signal waiting threads,
as opposed to something like a notify.
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