From: antirez <antirez@gmail.com>
Date: Thu, 30 Aug 2012 15:57:02 +0000 (+0200)
Subject: Sentinel: do not crash against slaves not publishing the runid.
X-Git-Url: https://git.saurik.com/redis.git/commitdiff_plain/6276434ad22ded9f5bf9997137c311e447154908

Sentinel: do not crash against slaves not publishing the runid.

Older versions of Redis (before 2.4.17) don't publish the runid field in
INFO. This commit makes Sentinel able to handle that without crashing.
---

diff --git a/src/sentinel.c b/src/sentinel.c
index 11df7335..659820f6 100644
--- a/src/sentinel.c
+++ b/src/sentinel.c
@@ -2521,9 +2521,21 @@ void sentinelStartFailoverIfNeeded(sentinelRedisInstance *master) {
 int compareSlavesForPromotion(const void *a, const void *b) {
     sentinelRedisInstance **sa = (sentinelRedisInstance **)a,
                           **sb = (sentinelRedisInstance **)b;
+    char *sa_runid, *sb_runid;
+
     if ((*sa)->slave_priority != (*sb)->slave_priority)
         return (*sa)->slave_priority - (*sb)->slave_priority;
-    return strcasecmp((*sa)->runid,(*sb)->runid);
+
+    /* If priority is the same, select the slave with that has the
+     * lexicographically smaller runid. Note that we try to handle runid
+     * == NULL as there are old Redis versions that don't publish runid in
+     * INFO. A NULL runid is considered bigger than any other runid. */
+    sa_runid = (*sa)->runid;
+    sb_runid = (*sb)->runid;
+    if (sa_runid == NULL && sb_runid == NULL) return 0;
+    else if (sa_runid == NULL) return 1;  /* a > b */
+    else if (sb_runid == NULL) return -1; /* a < b */
+    return strcasecmp(sa_runid, sb_runid);
 }
 
 sentinelRedisInstance *sentinelSelectSlave(sentinelRedisInstance *master) {