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http: speed up shutdown

This continues/fixes #6719.

`event_base_loopbreak` was not doing what I expected it to, at least in
libevent 2.0.21.
What I expected was that it sets a timeout, given that no other pending
events it would exit in N seconds. However, what it does was delay the
event loop exit with 10 seconds, even if nothing is pending.

Solve it in a different way: give the event loop thread time to exit
out of itself, and if it doesn't, send loopbreak.

This speeds up the RPC tests a lot, each exit incurred a 10 second
overhead, with this change there should be no shutdown overhead in the
common case and up to two seconds if the event loop is blocking.

As a bonus this breaks dependency on boost::thread_group, as the HTTP
server minds its own offspring.
0.13
Wladimir J. van der Laan 9 years ago
parent
commit
a264c32e33
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  1. 30
      src/httpserver.cpp
  2. 2
      src/httpserver.h
  3. 2
      src/init.cpp

30
src/httpserver.cpp

@ -438,15 +438,17 @@ bool InitHTTPServer() @@ -438,15 +438,17 @@ bool InitHTTPServer()
return true;
}
bool StartHTTPServer(boost::thread_group& threadGroup)
boost::thread threadHTTP;
bool StartHTTPServer()
{
LogPrint("http", "Starting HTTP server\n");
int rpcThreads = std::max((long)GetArg("-rpcthreads", DEFAULT_HTTP_THREADS), 1L);
LogPrintf("HTTP: starting %d worker threads\n", rpcThreads);
threadGroup.create_thread(boost::bind(&ThreadHTTP, eventBase, eventHTTP));
threadHTTP = boost::thread(boost::bind(&ThreadHTTP, eventBase, eventHTTP));
for (int i = 0; i < rpcThreads; i++)
threadGroup.create_thread(boost::bind(&HTTPWorkQueueRun, workQueue));
boost::thread(boost::bind(&HTTPWorkQueueRun, workQueue));
return true;
}
@ -461,13 +463,6 @@ void InterruptHTTPServer() @@ -461,13 +463,6 @@ void InterruptHTTPServer()
// Reject requests on current connections
evhttp_set_gencb(eventHTTP, http_reject_request_cb, NULL);
}
if (eventBase) {
// Force-exit event loop after predefined time
struct timeval tv;
tv.tv_sec = 10;
tv.tv_usec = 0;
event_base_loopexit(eventBase, &tv);
}
if (workQueue)
workQueue->Interrupt();
}
@ -480,6 +475,20 @@ void StopHTTPServer() @@ -480,6 +475,20 @@ void StopHTTPServer()
workQueue->WaitExit();
delete workQueue;
}
if (eventBase) {
LogPrint("http", "Waiting for HTTP event thread to exit\n");
// Give event loop a few seconds to exit (to send back last RPC responses), then break it
// Before this was solved with event_base_loopexit, but that didn't work as expected in
// at least libevent 2.0.21 and always introduced a delay. In libevent
// master that appears to be solved, so in the future that solution
// could be used again (if desirable).
// (see discussion in https://github.com/bitcoin/bitcoin/pull/6990)
if (!threadHTTP.try_join_for(boost::chrono::milliseconds(2000))) {
LogPrintf("HTTP event loop did not exit within allotted time, sending loopbreak\n");
event_base_loopbreak(eventBase);
threadHTTP.join();
}
}
if (eventHTTP) {
evhttp_free(eventHTTP);
eventHTTP = 0;
@ -488,6 +497,7 @@ void StopHTTPServer() @@ -488,6 +497,7 @@ void StopHTTPServer()
event_base_free(eventBase);
eventBase = 0;
}
LogPrint("http", "Stopped HTTP server\n");
}
struct event_base* EventBase()

2
src/httpserver.h

@ -28,7 +28,7 @@ bool InitHTTPServer(); @@ -28,7 +28,7 @@ bool InitHTTPServer();
* This is separate from InitHTTPServer to give users race-condition-free time
* to register their handlers between InitHTTPServer and StartHTTPServer.
*/
bool StartHTTPServer(boost::thread_group& threadGroup);
bool StartHTTPServer();
/** Interrupt HTTP server threads */
void InterruptHTTPServer();
/** Stop HTTP server */

2
src/init.cpp

@ -661,7 +661,7 @@ bool AppInitServers(boost::thread_group& threadGroup) @@ -661,7 +661,7 @@ bool AppInitServers(boost::thread_group& threadGroup)
return false;
if (GetBoolArg("-rest", false) && !StartREST())
return false;
if (!StartHTTPServer(threadGroup))
if (!StartHTTPServer())
return false;
return true;
}

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