From 9b48c4a481c64503605f25e1d0648d24f43437f1 Mon Sep 17 00:00:00 2001
From: Rainer Gerhards <rgerhards@adiscon.com>
Date: Wed, 2 Apr 2008 16:53:29 +0000
Subject: begun working on time-window based dequeueing (and rate limiting in  
   general)

---
 queue.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)

(limited to 'queue.c')

diff --git a/queue.c b/queue.c
index ed720c55..bfdac204 100644
--- a/queue.c
+++ b/queue.c
@@ -55,6 +55,7 @@ DEFobjStaticHelpers
 /* forward-definitions */
 rsRetVal queueChkPersist(queue_t *pThis);
 static rsRetVal queueSetEnqOnly(queue_t *pThis, int bEnqOnly, int bLockMutex);
+static rsRetVal queueRateLimiter(queue_t *pThis);
 static int queueChkStopWrkrDA(queue_t *pThis);
 static int queueIsIdleDA(queue_t *pThis);
 static rsRetVal queueConsumerDA(queue_t *pThis, wti_t *pWti, int iCancelStateSave);
@@ -341,6 +342,7 @@ queueInitDA(queue_t *pThis, int bEnqOnly, int bLockMutex)
 		lenBuf = snprintf((char*)pszBuf, sizeof(pszBuf), "%s:DA", obj.GetName((obj_t*) pThis));
 		CHKiRet(wtpConstruct		(&pThis->pWtpDA));
 		CHKiRet(wtpSetDbgHdr		(pThis->pWtpDA, pszBuf, lenBuf));
+		CHKiRet(wtpSetpfRateLimiter	(pThis->pWtpDA, (rsRetVal (*)(void *pUsr)) queueRateLimiter));
 		CHKiRet(wtpSetpfChkStopWrkr	(pThis->pWtpDA, (rsRetVal (*)(void *pUsr, int)) queueChkStopWrkrDA));
 		CHKiRet(wtpSetpfIsIdle		(pThis->pWtpDA, (rsRetVal (*)(void *pUsr, int)) queueIsIdleDA));
 		CHKiRet(wtpSetpfDoWork		(pThis->pWtpDA, (rsRetVal (*)(void *pUsr, void *pWti, int)) queueConsumerDA));
@@ -1450,6 +1452,60 @@ finalize_it:
 }
 
 
+/* The rate limiter - we only need one - do we? 
+ *
+* Here we may wait if a dequeue time window is defined or if we are
+ * rate-limited. TODO: If we do so, we should also look into the
+ * way new worker threads are spawned. Obviously, it doesn't make much
+ * sense to spawn additional worker threads when none of them can do any
+ * processing. However, it is deemed acceptable to allow this for an initial
+ * implementation of the timeframe/rate limiting feature.
+ * Please also note that these feature could also be implemented at the action
+ * level. However, that would limit them to be used together with actions. We have
+ * taken the broader approach, moving it right into the queue. This is even
+ * necessary if we want to prevent spawning of multiple unnecessary worker
+ * threads as described above. -- rgerhards, 2008-04-02
+ *
+ *
+ * time window: tCurr is current time; tFrom is start time, tTo is end time (in mil 24h format).
+ * We may have tFrom = 4, tTo = 10 --> run from 4 to 10 hrs. nice and happy
+ * we may also have tFrom= 22, tTo = 4 -> run from 10pm to 4am, which is actually two
+ *     windows: 0-4; 22-23:59
+ * so when to run? Let's assume we have 3am
+ *
+ * if(tTo < tFrom) {
+ * 	if(tCurr < tTo [3 < 4] || tCurr > tFrom [3 > 22])
+ * 		do work
+ * 	else
+ * 		sleep for tFrom - tCurr "hours" [22 - 5 --> 17]
+ * } else {
+ * 	if(tCurr >= tFrom [3 >= 4] && tCurr < tTo [3 < 10])
+ * 		do work
+ * 	else
+ * 		sleep for tTo - tCurr "hours" [4 - 3 --> 1]
+ * }
+ *
+ * Bottom line: we need to check which type of window we have and need to adjust our
+ * logic accordingly. Of course, sleep calculations need to be done up to the minute,
+ * but you get the idea from the code above.
+ */
+static rsRetVal
+queueRateLimiter(queue_t *pThis)
+{
+	DEFiRet;
+
+	ISOBJ_TYPE_assert(pThis, queue);
+
+	dbgoprint((obj_t*) pThis, "entering rate limiter\n");
+	srSleep(2, 0);
+
+finalize_it:
+	dbgoprint((obj_t*) pThis, "rate limiter returns with iRet %d\n", iRet);
+	RETiRet;
+}
+
+
+
 /* This is the queue consumer in the regular (non-DA) case. It is 
  * protected by the queue mutex, but MUST release it as soon as possible.
  * rgerhards, 2008-01-21
@@ -1690,6 +1746,7 @@ rsRetVal queueStart(queue_t *pThis) /* this is the ConstructionFinalizer */
 	lenBuf = snprintf((char*)pszBuf, sizeof(pszBuf), "%s:Reg", obj.GetName((obj_t*) pThis));
 	CHKiRet(wtpConstruct		(&pThis->pWtpReg));
 	CHKiRet(wtpSetDbgHdr		(pThis->pWtpReg, pszBuf, lenBuf));
+	CHKiRet(wtpSetpfRateLimiter	(pThis->pWtpReg, (rsRetVal (*)(void *pUsr)) queueRateLimiter));
 	CHKiRet(wtpSetpfChkStopWrkr	(pThis->pWtpReg, (rsRetVal (*)(void *pUsr, int)) queueChkStopWrkrReg));
 	CHKiRet(wtpSetpfIsIdle		(pThis->pWtpReg, (rsRetVal (*)(void *pUsr, int)) queueIsIdleReg));
 	CHKiRet(wtpSetpfDoWork		(pThis->pWtpReg, (rsRetVal (*)(void *pUsr, void *pWti, int)) queueConsumerReg));
-- 
cgit