Cluster: new state information, cluster size.

The definition of cluster size is: the number of known nodes in the
cluster that are masters and serving at least an hash slot.

src/cluster.c

@@ -217,6 +217,7 @@ void clusterInit(void) {
     server.cluster = zmalloc(sizeof(clusterState));
     server.cluster->myself = NULL;
     server.cluster->state = REDIS_CLUSTER_FAIL;
+    server.cluster->size = 1;
     server.cluster->nodes = dictCreate(&clusterNodesDictType,NULL);
     server.cluster->node_timeout = 15;
     memset(server.cluster->migrating_slots_to,0,
@@ -1254,6 +1255,24 @@ void clusterUpdateState(void) {
     } else {
         server.cluster->state = REDIS_CLUSTER_FAIL;
     }
+
+    /* Compute the cluster size, that is the number of master nodes
+     * serving at least a single slot. */
+    {
+        dictIterator *di;
+        dictEntry *de;
+
+        server.cluster->size = 0;
+        di = dictGetIterator(server.cluster->nodes);
+        while((de = dictNext(di)) != NULL) {
+            clusterNode *node = dictGetVal(de);
+
+            if (node->flags & REDIS_NODE_MASTER &&
+                popcount(node->slots,sizeof(node->slots)))
+                server.cluster->size++;
+        }
+        dictReleaseIterator(di);
+    }
 }
 
 /* -----------------------------------------------------------------------------

src/redis.h

@@ -570,6 +570,7 @@ typedef struct clusterNode clusterNode;
 typedef struct {
     clusterNode *myself;  /* This node */
     int state;            /* REDIS_CLUSTER_OK, REDIS_CLUSTER_FAIL, ... */
+    int size;             /* Num of master nodes with at least one slot */
     int node_timeout;
     dict *nodes;          /* Hash table of name -> clusterNode structures */
     clusterNode *migrating_slots_to[REDIS_CLUSTER_SLOTS];
@@ -960,6 +961,7 @@ long long mstime(void);
 void getRandomHexChars(char *p, unsigned int len);
 uint64_t crc64(uint64_t crc, const unsigned char *s, uint64_t l);
 void exitFromChild(int retcode);
+long popcount(void *s, long count);
 
 /* networking.c -- Networking and Client related operations */
 redisClient *createClient(int fd);