From: Simon Schubert <2@0x2c.org>
Date: Mon, 28 Jun 2010 21:06:19 +0000 (+0200)
Subject: randomize delivery backoff times
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=0de88752bf18606a67dac982a82c726ade31bfb3;p=people%2Fms%2Fdma.git

randomize delivery backoff times

Submitted-by:  Peter Pentchev (earlier version)
Bug:  #599542
---

diff --git a/dma.c b/dma.c
index e6192a1..4685e09 100644
--- a/dma.c
+++ b/dma.c
@@ -268,11 +268,16 @@ static void
 deliver(struct qitem *it)
 {
 	int error;
-	unsigned int backoff = MIN_RETRY;
+	unsigned int backoff;
 	const char *errmsg = "unknown bounce reason";
 	struct timeval now;
 	struct stat st;
 
+	if (it->remote)
+		backoff = MIN_RETRY;
+	else
+		backoff = 1;	/* one second for local deliveries */
+
 retry:
 	syslog(LOG_INFO, "trying delivery");
 
@@ -299,10 +304,12 @@ retry:
 				 MAX_TIMEOUT);
 			goto bounce;
 		}
-		if (sleep(backoff) == 0)
-			backoff *= 2;
-		if (backoff > MAX_RETRY)
-			backoff = MAX_RETRY;
+		if (sleep(backoff) == 0) {
+			/* pick the next backoff between [1.5, 2.5) times backoff */
+			backoff = backoff + backoff / 2 + random() % backoff;
+			if (backoff > MAX_RETRY)
+				backoff = MAX_RETRY;
+		}
 		goto retry;
 
 	case -1: