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Cluster: added progressive election delay according to slave rank.

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Note that when we compute the initial delay, there are probably still
more up to date information to receive from slaves with new offsets, so
the delay is recomputed when new data is available.
This commit is contained in:
antirez
2014-01-29 16:51:11 +01:00
parent 6f54032080
commit 940531e9b7
2 changed files with 28 additions and 3 deletions
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30
src/cluster.c
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@ -301,6 +301,7 @@ void clusterInit(void) {
dictCreate(&clusterNodesBlackListDictType,NULL);
server.cluster->failover_auth_time = 0;
server.cluster->failover_auth_count = 0;
server.cluster->failover_auth_rank = 0;
server.cluster->failover_auth_epoch = 0;
server.cluster->last_vote_epoch = 0;
server.cluster->stats_bus_messages_sent = 0;
@ -2000,13 +2001,36 @@ void clusterHandleSlaveFailover(void) {
{
server.cluster->failover_auth_time = mstime() +
500 + /* Fixed delay of 500 milliseconds, let FAIL msg propagate. */
data_age / 10 + /* Add 100 milliseconds for every second of age. */
random() % 500; /* Random delay between 0 and 500 milliseconds. */
server.cluster->failover_auth_count = 0;
server.cluster->failover_auth_sent = 0;
server.cluster->failover_auth_rank = clusterGetSlaveRank();
/* We add another delay that is proportional to the slave rank.
* Specifically 1 second * rank. This way slaves that have a probably
* less updated replication offset, are penalized. */
server.cluster->failover_auth_time +=
server.cluster->failover_auth_rank * 1000;
redisLog(REDIS_WARNING,
"Start of election delayed for %lld milliseconds.",
server.cluster->failover_auth_time - mstime());
"Start of election delayed for %lld milliseconds (rank is #%d).",
server.cluster->failover_auth_time - mstime(),
server.cluster->failover_auth_rank);
return;
}
/* It is possible that we received more updated offsets from other
* slaves for the same master since we computed our election delay.
* Update the delay if our rank changed. */
if (server.cluster->failover_auth_sent == 0) {
int newrank = clusterGetSlaveRank();
if (newrank > server.cluster->failover_auth_rank) {
long long added_delay =
(newrank - server.cluster->failover_auth_rank) * 1000;
server.cluster->failover_auth_time += added_delay;
server.cluster->failover_auth_rank = newrank;
redisLog(REDIS_WARNING,
"Slave rank updated to #%d, added %lld milliseconds of delay.",
newrank, added_delay);
}
return;
}