rsyslog/runtime/wtp.c

/* wtp.c
 *
 * This file implements the worker thread pool (wtp) class.
 * 
 * File begun on 2008-01-20 by RGerhards
 *
 * There is some in-depth documentation available in doc/dev_queue.html
 * (and in the web doc set on http://www.rsyslog.com/doc). Be sure to read it
 * if you are getting aquainted to the object.
 *
 * Copyright 2008 Rainer Gerhards and Adiscon GmbH.
 *
 * This file is part of the rsyslog runtime library.
 *
 * The rsyslog runtime library is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * The rsyslog runtime library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with the rsyslog runtime library.  If not, see <http://www.gnu.org/licenses/>.
 *
 * A copy of the GPL can be found in the file "COPYING" in this distribution.
 * A copy of the LGPL can be found in the file "COPYING.LESSER" in this distribution.
 */
#include "config.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <signal.h>
#include <pthread.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>

#ifdef OS_SOLARIS
#	include <sched.h>
#	define pthread_yield() sched_yield()
#endif

#include "rsyslog.h"
#include "stringbuf.h"
#include "srUtils.h"
#include "wtp.h"
#include "wti.h"
#include "obj.h"
#include "glbl.h"

/* static data */
DEFobjStaticHelpers
DEFobjCurrIf(glbl)

/* forward-definitions */

/* methods */

/* get the header for debug messages
 * The caller must NOT free or otherwise modify the returned string!
 */
static inline uchar *
wtpGetDbgHdr(wtp_t *pThis)
{
	ISOBJ_TYPE_assert(pThis, wtp);

	if(pThis->pszDbgHdr == NULL)
		return (uchar*) "wtp"; /* should not normally happen */
	else
		return pThis->pszDbgHdr;
}



/* Not implemented dummy function for constructor */
static rsRetVal NotImplementedDummy() { return RS_RET_OK; }
/* Standard-Constructor for the wtp object
 */
BEGINobjConstruct(wtp) /* be sure to specify the object type also in END macro! */
	pThis->bOptimizeUniProc = glbl.GetOptimizeUniProc();
	pthread_mutex_init(&pThis->mut, NULL);
	pthread_mutex_init(&pThis->mutThrdShutdwn, NULL);
	pthread_cond_init(&pThis->condThrdTrm, NULL);
	/* set all function pointers to "not implemented" dummy so that we can safely call them */
	pThis->pfChkStopWrkr = NotImplementedDummy;
	pThis->pfIsIdle = NotImplementedDummy;
	pThis->pfDoWork = NotImplementedDummy;
	pThis->pfOnIdle = NotImplementedDummy;
	pThis->pfOnWorkerCancel = NotImplementedDummy;
	pThis->pfOnWorkerStartup = NotImplementedDummy;
	pThis->pfOnWorkerShutdown = NotImplementedDummy;
ENDobjConstruct(wtp)


/* Construction finalizer
 * rgerhards, 2008-01-17
 */
rsRetVal
wtpConstructFinalize(wtp_t *pThis)
{
	DEFiRet;
	int i;
	uchar pszBuf[64];
	size_t lenBuf;
	wti_t *pWti;

	ISOBJ_TYPE_assert(pThis, wtp);

	dbgprintf("%s: finalizing construction of worker thread pool\n", wtpGetDbgHdr(pThis));
	/* alloc and construct workers - this can only be done in finalizer as we previously do
	 * not know the max number of workers
	 */
	if((pThis->pWrkr = malloc(sizeof(wti_t*) * pThis->iNumWorkerThreads)) == NULL)
		ABORT_FINALIZE(RS_RET_OUT_OF_MEMORY);

	for(i = 0 ; i < pThis->iNumWorkerThreads ; ++i) {
		CHKiRet(wtiConstruct(&pThis->pWrkr[i]));
		pWti = pThis->pWrkr[i];
		lenBuf = snprintf((char*)pszBuf, sizeof(pszBuf), "%s/w%d", wtpGetDbgHdr(pThis), i);
		CHKiRet(wtiSetDbgHdr(pWti, pszBuf, lenBuf));
		CHKiRet(wtiSetpWtp(pWti, pThis));
		CHKiRet(wtiConstructFinalize(pWti));
	}
		

finalize_it:
	RETiRet;
}


/* Destructor */
BEGINobjDestruct(wtp) /* be sure to specify the object type also in END and CODESTART macros! */
	int i;
CODESTARTobjDestruct(wtp)
	wtpProcessThrdChanges(pThis); /* process thread changes one last time */

	/* destruct workers */
	for(i = 0 ; i < pThis->iNumWorkerThreads ; ++i)
		wtiDestruct(&pThis->pWrkr[i]);

	free(pThis->pWrkr);
	pThis->pWrkr = NULL;

	/* actual destruction */
	pthread_cond_destroy(&pThis->condThrdTrm);
	pthread_mutex_destroy(&pThis->mut);
	pthread_mutex_destroy(&pThis->mutThrdShutdwn);

	if(pThis->pszDbgHdr != NULL)
		free(pThis->pszDbgHdr);
ENDobjDestruct(wtp)


/* wake up at least one worker thread.
 * rgerhards, 2008-01-20
 */
rsRetVal
wtpWakeupWrkr(wtp_t *pThis)
{
	DEFiRet;

	/* TODO; mutex? I think not needed, as we do not need predictable exec order -- rgerhards, 2008-01-28 */
	ISOBJ_TYPE_assert(pThis, wtp);
	pthread_cond_signal(pThis->pcondBusy);
	RETiRet;
}

/* wake up all worker threads.
 * rgerhards, 2008-01-16
 */
rsRetVal
wtpWakeupAllWrkr(wtp_t *pThis)
{
	DEFiRet;

	ISOBJ_TYPE_assert(pThis, wtp);
	d_pthread_mutex_lock(pThis->pmutUsr);
	pthread_cond_broadcast(pThis->pcondBusy);
	d_pthread_mutex_unlock(pThis->pmutUsr);
	RETiRet;
}


/* check if we had any worker thread changes and, if so, act
 * on them. At a minimum, terminated threads are harvested (joined).
 * This function MUST NEVER block on the queue mutex!
 */
rsRetVal
wtpProcessThrdChanges(wtp_t *pThis)
{
	DEFiRet;
	int i;

	ISOBJ_TYPE_assert(pThis, wtp);

	if(pThis->bThrdStateChanged == 0)
		FINALIZE;

	if(d_pthread_mutex_trylock(&(pThis->mutThrdShutdwn)) != 0) {
		/* another thread is already in the loop */
		FINALIZE;
	}

	/* Note: there is a left-over potential race condition below:
	 * pThis->bThrdStateChanged may be re-set by another thread while
	 * we work on it and thus the loop may terminate too early. However,
	 * there are no really bad effects from that so I perfer - for this
	 * version - to live with the problem as is. Not a good idea to 
	 * introduce that large change into the stable branch without very
	 * good reason. -- rgerhards, 2009-04-02
	 */
	do {
		/* reset the change marker */
		pThis->bThrdStateChanged = 0;
		/* go through all threads */
		for(i = 0 ; i < pThis->iNumWorkerThreads ; ++i) {
			wtiProcessThrdChanges(pThis->pWrkr[i], LOCK_MUTEX);
		}
	/* restart if another change occured while we were processing the changes */
	} while(pThis->bThrdStateChanged != 0);

	d_pthread_mutex_unlock(&(pThis->mutThrdShutdwn));

finalize_it:
	RETiRet;
}


/* Sent a specific state for the worker thread pool.
 * rgerhards, 2008-01-21
 */
rsRetVal
wtpSetState(wtp_t *pThis, wtpState_t iNewState)
{
	DEFiRet;

	ISOBJ_TYPE_assert(pThis, wtp);
	pThis->wtpState = iNewState;
	/* TODO: must wakeup workers? seen to be not needed -- rgerhards, 2008-01-28 */

	RETiRet;
}


/* check if the worker shall shutdown (1 = yes, 0 = no)
 * TODO: check if we can use atomic operations to enhance performance
 * Note: there may be two mutexes locked, the bLockUsrMutex is the one in our "user"
 * (e.g. the queue clas)
 * rgerhards, 2008-01-21
 */
rsRetVal
wtpChkStopWrkr(wtp_t *pThis, int bLockMutex, int bLockUsrMutex)
{
	DEFiRet;
	DEFVARS_mutexProtection;

	ISOBJ_TYPE_assert(pThis, wtp);

	BEGIN_MTX_PROTECTED_OPERATIONS(&pThis->mut, bLockMutex);
	if(   (pThis->wtpState == wtpState_SHUTDOWN_IMMEDIATE)
	   || ((pThis->wtpState == wtpState_SHUTDOWN) && pThis->pfIsIdle(pThis->pUsr, bLockUsrMutex)))
		iRet = RS_RET_TERMINATE_NOW;
	END_MTX_PROTECTED_OPERATIONS(&pThis->mut);

	/* try customer handler if one was set and we do not yet have a definite result */
	if(iRet == RS_RET_OK && pThis->pfChkStopWrkr != NULL) {
		iRet = pThis->pfChkStopWrkr(pThis->pUsr, bLockUsrMutex);
	}

	RETiRet;
}


#pragma GCC diagnostic ignored "-Wempty-body"
/* Send a shutdown command to all workers and see if they terminate.
 * A timeout may be specified.
 * rgerhards, 2008-01-14
 */
rsRetVal
wtpShutdownAll(wtp_t *pThis, wtpState_t tShutdownCmd, struct timespec *ptTimeout)
{
	DEFiRet;
	int bTimedOut;
	int iCancelStateSave;

	ISOBJ_TYPE_assert(pThis, wtp);

	wtpSetState(pThis, tShutdownCmd);
	wtpWakeupAllWrkr(pThis);

	/* see if we need to harvest (join) any terminated threads (even in timeout case,
	 * some may have terminated...
	 */
	wtpProcessThrdChanges(pThis);
		
	/* and wait for their termination */
	pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &iCancelStateSave);
	d_pthread_mutex_lock(&pThis->mut);
	pthread_cleanup_push(mutexCancelCleanup, &pThis->mut);
	pthread_setcancelstate(iCancelStateSave, NULL);
	bTimedOut = 0;
	while(pThis->iCurNumWrkThrd > 0 && !bTimedOut) {
		dbgprintf("%s: waiting %ldms on worker thread termination, %d still running\n",
			   wtpGetDbgHdr(pThis), timeoutVal(ptTimeout), pThis->iCurNumWrkThrd);

		if(d_pthread_cond_timedwait(&pThis->condThrdTrm, &pThis->mut, ptTimeout) != 0) {
			dbgprintf("%s: timeout waiting on worker thread termination\n", wtpGetDbgHdr(pThis));
			bTimedOut = 1;	/* we exit the loop on timeout */
		}
	}
	pthread_cleanup_pop(1);

	if(bTimedOut)
		iRet = RS_RET_TIMED_OUT;
	
	/* see if we need to harvest (join) any terminated threads (even in timeout case,
	 * some may have terminated...
	 */
	wtpProcessThrdChanges(pThis);

	RETiRet;
}
#pragma GCC diagnostic warning "-Wempty-body"


/* indicate that a thread has terminated and awake anyone waiting on it
 * rgerhards, 2008-01-23
 */
rsRetVal wtpSignalWrkrTermination(wtp_t *pThis)
{
	DEFiRet;
	/* I leave the mutex code here out as it gives us deadlocks. I think it is not really
	 * needed and we are on the safe side. I leave this comment in if practice proves us
	 * wrong. The whole thing should be removed after half a year or year if we see there
	 * actually is no issue (or revisit it from a theoretical POV).
	 * rgerhards, 2008-01-28
	 * revisited 2008-09-30, still a bit unclear, leave in
	 */
	/*TODO: mutex or not mutex, that's the question ;)DEFVARS_mutexProtection;*/

	ISOBJ_TYPE_assert(pThis, wtp);

	/*BEGIN_MTX_PROTECTED_OPERATIONS(&pThis->mut, LOCK_MUTEX);*/
	pthread_cond_signal(&pThis->condThrdTrm); /* activate anyone waiting on thread shutdown */
	/*END_MTX_PROTECTED_OPERATIONS(&pThis->mut);*/
	RETiRet;
}


/* Unconditionally cancel all running worker threads.
 * rgerhards, 2008-01-14
 */
rsRetVal
wtpCancelAll(wtp_t *pThis)
{
	DEFiRet;
	int i;

	ISOBJ_TYPE_assert(pThis, wtp);

	/* process any pending thread requests so that we know who actually is still running */
	wtpProcessThrdChanges(pThis);

	/* go through all workers and cancel those that are active */
	for(i = 0 ; i < pThis->iNumWorkerThreads ; ++i) {
		dbgprintf("%s: try canceling worker thread %d\n", wtpGetDbgHdr(pThis), i);
		wtiCancelThrd(pThis->pWrkr[i]);
	}

	RETiRet;
}



/* Set the Inactivity Guard
 * rgerhards, 2008-01-21
 */
rsRetVal
wtpSetInactivityGuard(wtp_t *pThis, int bNewState, int bLockMutex)
{
	DEFiRet;
	DEFVARS_mutexProtection;

	BEGIN_MTX_PROTECTED_OPERATIONS(&pThis->mut, bLockMutex);
	pThis->bInactivityGuard = bNewState;
	END_MTX_PROTECTED_OPERATIONS(&pThis->mut);

	RETiRet;
}


/* cancellation cleanup handler for executing worker
 * decrements the worker counter
 * rgerhards, 2008-01-20
 */
void
wtpWrkrExecCancelCleanup(void *arg)
{
	wtp_t *pThis = (wtp_t*) arg;

	BEGINfunc
	ISOBJ_TYPE_assert(pThis, wtp);
	pThis->iCurNumWrkThrd--;
	wtpSignalWrkrTermination(pThis);

	dbgprintf("%s: thread CANCELED with %d workers running.\n", wtpGetDbgHdr(pThis), pThis->iCurNumWrkThrd);
	ENDfunc
}


/* wtp worker shell. This is started and calls into the actual
 * wti worker.
 * rgerhards, 2008-01-21
 */
#pragma GCC diagnostic ignored "-Wempty-body"
static void *
wtpWorker(void *arg) /* the arg is actually a wti object, even though we are in wtp! */
{
	DEFiRet;
	DEFVARS_mutexProtection;
	wti_t *pWti = (wti_t*) arg;
	wtp_t *pThis;
	sigset_t sigSet;

	ISOBJ_TYPE_assert(pWti, wti);
	pThis = pWti->pWtp;
	ISOBJ_TYPE_assert(pThis, wtp);

	sigfillset(&sigSet);
	pthread_sigmask(SIG_BLOCK, &sigSet, NULL);

	BEGIN_MTX_PROTECTED_OPERATIONS(&pThis->mut, LOCK_MUTEX);

	/* do some late initialization */

	pthread_cleanup_push(wtpWrkrExecCancelCleanup, pThis);

	/* finally change to RUNNING state. We need to check if we actually should still run,
	 * because someone may have requested us to shut down even before we got a chance to do
	 * our init. That would be a bad race... -- rgerhards, 2008-01-16
	 */
	wtiSetState(pWti, eWRKTHRD_RUNNING, 0, MUTEX_ALREADY_LOCKED); /* we are running now! */

	do {
		END_MTX_PROTECTED_OPERATIONS(&pThis->mut);

		iRet = wtiWorker(pWti); /* just to make sure: this is NOT protected by the mutex! */

		BEGIN_MTX_PROTECTED_OPERATIONS(&pThis->mut, LOCK_MUTEX);
	} while(pThis->iCurNumWrkThrd == 1 && pThis->bInactivityGuard == 1);
	/* inactivity guard prevents shutdown of all workers while one should be running due to race
	 * condition. It can lead to one more worker running than desired, but that is acceptable. After
	 * all, that worker will shutdown itself due to inactivity timeout. If, however, none were running
	 * when one was required, processing could come to a halt. -- rgerhards, 2008-01-21
	 */

	pthread_cleanup_pop(0);
	pThis->iCurNumWrkThrd--;
	wtpSignalWrkrTermination(pThis);

	dbgprintf("%s: Worker thread %lx, terminated, num workers now %d\n",
		  wtpGetDbgHdr(pThis), (unsigned long) pWti, pThis->iCurNumWrkThrd);

	END_MTX_PROTECTED_OPERATIONS(&pThis->mut);

	ENDfunc
	pthread_exit(0);
}
#pragma GCC diagnostic warning "-Wempty-body"


/* start a new worker */
static rsRetVal
wtpStartWrkr(wtp_t *pThis, int bLockMutex)
{
	DEFiRet;
	DEFVARS_mutexProtection;
	wti_t *pWti;
	int i;
	int iState;

	ISOBJ_TYPE_assert(pThis, wtp);

	wtpProcessThrdChanges(pThis);	// TODO: Performance: this causes a lot of FUTEX calls

	BEGIN_MTX_PROTECTED_OPERATIONS(&pThis->mut, bLockMutex);

	pThis->iCurNumWrkThrd++;

	/* find free spot in thread table. If we find at least one worker that is in initialization,
	 * we do NOT start a new one. Let's give the other one a chance, first.
	 */
	for(i = 0 ; i < pThis->iNumWorkerThreads ; ++i) {
		if(wtiGetState(pThis->pWrkr[i], LOCK_MUTEX) == eWRKTHRD_STOPPED) {
			break;
		}
	}

	if(i == pThis->iNumWorkerThreads)
		ABORT_FINALIZE(RS_RET_NO_MORE_THREADS);

	pWti = pThis->pWrkr[i];
	wtiSetState(pWti, eWRKTHRD_RUN_CREATED, 0, LOCK_MUTEX);
	iState = pthread_create(&(pWti->thrdID), NULL, wtpWorker, (void*) pWti);
	dbgprintf("%s: started with state %d, num workers now %d\n",
		  wtpGetDbgHdr(pThis), iState, pThis->iCurNumWrkThrd);

	/* we try to give the starting worker a little boost. It won't help much as we still
 	 * hold the queue's mutex, but at least it has a chance to start on a single-CPU system.
 	 */
#	if !defined(__hpux) /* pthread_yield is missing there! */
	if(pThis->bOptimizeUniProc)
		pthread_yield();
#	endif

	/* indicate we just started a worker and would like to see it running */
	wtpSetInactivityGuard(pThis, 1, MUTEX_ALREADY_LOCKED);

finalize_it:
	END_MTX_PROTECTED_OPERATIONS(&pThis->mut);
	RETiRet;
}


/* set the number of worker threads that should be running. If less than currently running,
 * a new worker may be started. Please note that there is no guarantee the number of workers
 * said will be running after we exit this function. It is just a hint. If the number is
 * higher than one, and no worker is started, the "busy" condition is signaled to awake a worker.
 * So the caller can assume that there is at least one worker re-checking if there is "work to do"
 * after this function call.
 * rgerhards, 2008-01-21
 */
rsRetVal
wtpAdviseMaxWorkers(wtp_t *pThis, int nMaxWrkr)
{
	DEFiRet;
	DEFVARS_mutexProtection;
	int nMissing; /* number workers missing to run */
	int i;

	ISOBJ_TYPE_assert(pThis, wtp);

	if(nMaxWrkr == 0)
		FINALIZE;

	BEGIN_MTX_PROTECTED_OPERATIONS(&pThis->mut, LOCK_MUTEX);

	if(nMaxWrkr > pThis->iNumWorkerThreads) /* limit to configured maximum */
		nMaxWrkr = pThis->iNumWorkerThreads;

	nMissing = nMaxWrkr - pThis->iCurNumWrkThrd;

	if(nMissing > 0) {
		dbgprintf("%s: high activity - starting %d additional worker thread(s).\n", wtpGetDbgHdr(pThis), nMissing);
		/* start the rqtd nbr of workers */
		for(i = 0 ; i < nMissing ; ++i) {
			CHKiRet(wtpStartWrkr(pThis, MUTEX_ALREADY_LOCKED));
		}
	} else  {
		if(nMaxWrkr > 0) {
	dbgprintf("wtpAdviseMaxWorkers signals busy\n");
			wtpWakeupWrkr(pThis);
		}
	}

	
finalize_it:
	END_MTX_PROTECTED_OPERATIONS(&pThis->mut);
	RETiRet;
}


/* some simple object access methods */
DEFpropSetMeth(wtp, toWrkShutdown, long)
DEFpropSetMeth(wtp, wtpState, wtpState_t)
DEFpropSetMeth(wtp, iNumWorkerThreads, int)
DEFpropSetMeth(wtp, pUsr, void*)
DEFpropSetMethPTR(wtp, pmutUsr, pthread_mutex_t)
DEFpropSetMethPTR(wtp, pcondBusy, pthread_cond_t)
DEFpropSetMethFP(wtp, pfChkStopWrkr, rsRetVal(*pVal)(void*, int))
DEFpropSetMethFP(wtp, pfRateLimiter, rsRetVal(*pVal)(void*))
DEFpropSetMethFP(wtp, pfIsIdle, rsRetVal(*pVal)(void*, int))
DEFpropSetMethFP(wtp, pfDoWork, rsRetVal(*pVal)(void*, void*, int))
DEFpropSetMethFP(wtp, pfOnIdle, rsRetVal(*pVal)(void*, int))
DEFpropSetMethFP(wtp, pfOnWorkerCancel, rsRetVal(*pVal)(void*, void*))
DEFpropSetMethFP(wtp, pfOnWorkerStartup, rsRetVal(*pVal)(void*))
DEFpropSetMethFP(wtp, pfOnWorkerShutdown, rsRetVal(*pVal)(void*))


/* return the current number of worker threads.
 * TODO: atomic operation would bring a nice performance
 * enhancemcent
 * rgerhards, 2008-01-27
 */
int
wtpGetCurNumWrkr(wtp_t *pThis, int bLockMutex)
{
	DEFVARS_mutexProtection;
	int iNumWrkr;

	BEGINfunc
	ISOBJ_TYPE_assert(pThis, wtp);

	BEGIN_MTX_PROTECTED_OPERATIONS(&pThis->mut, bLockMutex);
	iNumWrkr = pThis->iCurNumWrkThrd;
	END_MTX_PROTECTED_OPERATIONS(&pThis->mut);

	ENDfunc
	return iNumWrkr;
}


/* set the debug header message
 * The passed-in string is duplicated. So if the caller does not need
 * it any longer, it must free it. Must be called only before object is finalized.
 * rgerhards, 2008-01-09
 */
rsRetVal
wtpSetDbgHdr(wtp_t *pThis, uchar *pszMsg, size_t lenMsg)
{
	DEFiRet;

	ISOBJ_TYPE_assert(pThis, wtp);
	assert(pszMsg != NULL);
	
	if(lenMsg < 1)
		ABORT_FINALIZE(RS_RET_PARAM_ERROR);

	if(pThis->pszDbgHdr != NULL) {
		free(pThis->pszDbgHdr);
		pThis->pszDbgHdr = NULL;
	}

	if((pThis->pszDbgHdr = malloc(sizeof(uchar) * lenMsg + 1)) == NULL)
		ABORT_FINALIZE(RS_RET_OUT_OF_MEMORY);

	memcpy(pThis->pszDbgHdr, pszMsg, lenMsg + 1); /* always think about the \0! */

finalize_it:
	RETiRet;
}

/* dummy */
rsRetVal wtpQueryInterface(void) { return RS_RET_NOT_IMPLEMENTED; }

/* exit our class
 */
BEGINObjClassExit(wtp, OBJ_IS_CORE_MODULE) /* CHANGE class also in END MACRO! */
CODESTARTObjClassExit(nsdsel_gtls)
	/* release objects we no longer need */
	objRelease(glbl, CORE_COMPONENT);
ENDObjClassExit(wtp)


/* Initialize the stream class. Must be called as the very first method
 * before anything else is called inside this class.
 * rgerhards, 2008-01-09
 */
BEGINObjClassInit(wtp, 1, OBJ_IS_CORE_MODULE)
	/* request objects we use */
	CHKiRet(objUse(glbl, CORE_COMPONENT));
ENDObjClassInit(wtp)

/*
 * vi:set ai:
 */