The most important general-purpose monitoring command is sh.status(). You need to run this command from a shell connected to a mongos instance, as a database user with sufficient cluster administration rights. A screenshot of the output for our sharded cluster model is shown in the Enabling sharding on the database sub-section of Chapter 15, Deploying a Sharded Cluster.
Look carefully for the following information, summarized here:
| Information key | What to look for |
| shards | Should show a list of shards, with a list of tags exactly as you specified. |
| active mongoses | How many mongos instances are connected and their version numbers. |
| replica set | Whether or not autosplit (chunks are automatically split) is enabled on this sharded cluster. |
| balancer | Failed balancer rounds in last 5 attempts should be 0. Migration Results for the last 24 hours: You should see a number followed by Success... |
