From a445aa30a0fb72bc54da083998b3458fad92820f Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Thu, 26 Sep 2013 13:00:41 +0200
Subject: [PATCH] Cluster: master node now uses new protocol to vote.
---
src/cluster.c | 69 +++++++++++++++++++++++++--------------------------
src/redis.h | 3 +++
2 files changed, 37 insertions(+), 35 deletions(-)
diff --git a/src/cluster.c b/src/cluster.c
index 9ce2905e..24d3efe3 100644
--- a/src/cluster.c
+++ b/src/cluster.c
@@ -258,6 +258,7 @@ void clusterInit(void) {
server.cluster->failover_auth_time = 0;
server.cluster->failover_auth_count = 0;
server.cluster->failover_auth_epoch = 0;
+ server.cluster->last_vote_epoch = 0;
memset(server.cluster->migrating_slots_to,0,
sizeof(server.cluster->migrating_slots_to));
memset(server.cluster->importing_slots_from,0,
@@ -396,6 +397,7 @@ clusterNode *createClusterNode(char *nodename, int flags) {
memset(node->ip,0,sizeof(node->ip));
node->port = 0;
node->fail_reports = listCreate();
+ node->voted_time = 0;
listSetFreeMethod(node->fail_reports,zfree);
return node;
}
@@ -1178,15 +1180,18 @@ int clusterProcessPacket(clusterLink *link) {
}
} else if (type == CLUSTERMSG_TYPE_FAILOVER_AUTH_REQUEST) {
if (!sender) return 1; /* We don't know that node. */
- /* If we are not a master, ignore that message at all. */
- if (!(server.cluster->myself->flags & REDIS_NODE_MASTER)) return 0;
clusterSendFailoverAuthIfNeeded(sender,hdr);
} else if (type == CLUSTERMSG_TYPE_FAILOVER_AUTH_ACK) {
if (!sender) return 1; /* We don't know that node. */
- /* If this is a master, increment the number of acknowledges
- * we received so far. */
- if (sender->flags & REDIS_NODE_MASTER)
+ /* We consider this vote only if the sender if a master serving
+ * a non zero number of slots, with the currentEpoch that is equal
+ * to our currentEpoch. */
+ if (sender->flags & REDIS_NODE_MASTER &&
+ sender->numslots > 0 &&
+ senderCurrentEpoch == server.cluster->currentEpoch)
+ {
server.cluster->failover_auth_count++;
+ }
} else {
redisLog(REDIS_WARNING,"Received unknown packet type: %d", type);
}
@@ -1538,43 +1543,38 @@ void clusterSendFailoverAuth(clusterNode *node, uint64_t reqtime) {
clusterSendMessage(node->link,buf,totlen);
}
-/* If we believe 'node' is the "first slave" of it's master, reply with
- * a FAILOVER_AUTH_GRANTED packet.
- * The 'request' field points to the authorization request packet header, we
- * need it in order to copy back the 'time' field in our reply.
- *
- * To be a first slave the sender must:
- * 1) Be a slave.
- * 2) Its master should be in FAIL state.
- * 3) Ordering all the slaves IDs for its master by run-id, it should be the
- * first (the smallest) among the ones not in FAIL / PFAIL state.
- */
+/* Vote for the node asking for our vote if there are the conditions. */
void clusterSendFailoverAuthIfNeeded(clusterNode *node, clusterMsg *request) {
- char first[REDIS_CLUSTER_NAMELEN];
clusterNode *master = node->slaveof;
- int j;
+ uint64_t requestEpoch = ntohu64(request->currentEpoch);
- /* Node is a slave? Its master is down? */
+ /* IF we are not a master serving at least 1 slot, we don't have the
+ * right to vote, as the cluster size in Redis Cluster is the number
+ * of masters serving at least one slot, and quorum is the cluster size + 1 */
+ if (!(server.cluster->myself->flags & REDIS_NODE_MASTER)) return;
+ if (server.cluster->myself->numslots == 0) return;
+
+ /* Request epoch must be >= our currentEpoch. */
+ if (requestEpoch < server.cluster->currentEpoch) return;
+
+ /* I already voted for this epoch? Return ASAP. */
+ if (server.cluster->last_vote_epoch == server.cluster->currentEpoch) return;
+
+ /* Node must be a slave and its master down. */
if (!(node->flags & REDIS_NODE_SLAVE) ||
master == NULL ||
!(master->flags & REDIS_NODE_FAIL)) return;
- /* Iterate all the master slaves to check what's the first one. */
- memset(first,0xff,sizeof(first));
- for (j = 0; j < master->numslaves; j++) {
- clusterNode *slave = master->slaves[j];
+ /* We did not voted for a slave about this master for two
+ * times the node timeout. This is not strictly needed for correctness
+ * of the algorithm but makes the base case more linear. */
+ if (server.unixtime - node->slaveof->voted_time <
+ server.cluster_node_timeout * 2) return;
- if (slave->flags & (REDIS_NODE_FAIL|REDIS_NODE_PFAIL)) continue;
- if (memcmp(slave->name,first,sizeof(first)) < 0) {
- memcpy(first,slave->name,sizeof(first));
- }
- }
-
- /* Is 'node' the first slave? */
- if (memcmp(node->name,first,sizeof(first)) != 0) return;
-
- /* We can send the packet. */
+ /* We can vote for this slave. */
clusterSendFailoverAuth(node,request->time);
+ server.cluster->last_vote_epoch = server.cluster->currentEpoch;
+ node->slaveof->voted_time = server.unixtime;
}
/* This function is called if we are a slave node and our master serving
@@ -1583,8 +1583,7 @@ void clusterSendFailoverAuthIfNeeded(clusterNode *node, clusterMsg *request) {
* The gaol of this function is:
* 1) To check if we are able to perform a failover, is our data updated?
* 2) Try to get elected by masters.
- * 3) Check if there is the majority of masters agreeing we should failover.
- * 4) Perform the failover informing all the other nodes.
+ * 3) Perform the failover informing all the other nodes.
*/
void clusterHandleSlaveFailover(void) {
time_t data_age = server.unixtime - server.repl_down_since;
diff --git a/src/redis.h b/src/redis.h
index 2b7ca7a0..66c751a1 100644
--- a/src/redis.h
+++ b/src/redis.h
@@ -628,6 +628,7 @@ struct clusterNode {
time_t ping_sent; /* Unix time we sent latest ping */
time_t pong_received; /* Unix time we received the pong */
time_t fail_time; /* Unix time when FAIL flag was set */
+ time_t voted_time; /* Last time we voted for a slave of this master */
char ip[REDIS_IP_STR_LEN]; /* Latest known IP address of this node */
int port; /* Latest known port of this node */
clusterLink *link; /* TCP/IP link with this node */
@@ -650,6 +651,8 @@ typedef struct {
int failover_auth_count; /* Number of votes received so far. */
int failover_auth_sent; /* True if we already asked for votes. */
uint64_t failover_auth_epoch; /* Epoch of the current election. */
+ /* The followign fields are uesd by masters to take state on elections. */
+ uint64_t last_vote_epoch; /* Epoch of the last vote granted. */
} clusterState;
/* Redis cluster messages header */