INFO: show num of slave-expires keys tracked.

src/expire.c

@@ -334,6 +334,12 @@ void rememberSlaveKeyWithExpire(redisDb *db, robj *key) {
     dictSetUnsignedIntegerVal(de,dbids);
 }
 
+/* Return the number of keys we are tracking. */
+size_t getSlaveKeyWithExpireCount(void) {
+    if (slaveKeysWithExpire == NULL) return 0;
+    return dictSize(slaveKeysWithExpire);
+}
+
 /* Remove the keys in the hash table. We need to do that when data is
  * flushed from the server. We may receive new keys from the master with
  * the same name/db and it is no longer a good idea to expire them.

src/server.c

@@ -3008,7 +3008,8 @@ sds genRedisInfoString(char *section) {
             "pubsub_channels:%ld\r\n"
             "pubsub_patterns:%lu\r\n"
             "latest_fork_usec:%lld\r\n"
-            "migrate_cached_sockets:%ld\r\n",
+            "migrate_cached_sockets:%ld\r\n"
+            "slave_expires_tracked_keys:%zu\r\n",
             server.stat_numconnections,
             server.stat_numcommands,
             getInstantaneousMetric(STATS_METRIC_COMMAND),
@@ -3027,7 +3028,8 @@ sds genRedisInfoString(char *section) {
             dictSize(server.pubsub_channels),
             listLength(server.pubsub_patterns),
             server.stat_fork_time,
-            dictSize(server.migrate_cached_sockets));
+            dictSize(server.migrate_cached_sockets),
+            getSlaveKeyWithExpireCount());
     }
 
     /* Replication */

src/server.h

@@ -1734,6 +1734,7 @@ void activeExpireCycle(int type);
 void expireSlaveKeys(void);
 void rememberSlaveKeyWithExpire(redisDb *db, robj *key);
 void flushSlaveKeysWithExpireList(void);
+size_t getSlaveKeyWithExpireCount(void);
 
 /* evict.c -- maxmemory handling and LRU eviction. */
 void evictionPoolAlloc(void);