MongoDB Shard distribution issue

Question

I am facing an issue in the shard distribution.

MongoDB Version: 3.0.15

I have a collection that is sharded. I have two shards.

Output of db.getCollection('event').stats()

{
 "sharded" : true,
 "capped" : false,
 "ns" : "coll.event",
 "count" : 386631514,
  size" : NumberLong(4178195857267),
 "storageSize" : 293516279808.0,
 "totalIndexSize" : 391203631104.0,
 "shards" : {
    **"shard0000" :** {
    "ns" : "coll.event",
    "count" : 182463940,
    "size" : NumberLong(2187685928765),
    "avgObjSize" : 11989,
    "storageSize" : 148825059328.0,
    "capped" : false,            
    },
**"shard0001"** : {
    "ns" : "coll.event",
    "count" : 204167574,
    "size" : NumberLong(1990509928502),
    "avgObjSize" : 9749,
    "storageSize" : 144691220480.0,
    "capped" : false,
    }
},
"ok" : 1.0
}

Output of Shard Distribution

db.getCollection('event').getShardDistribution()

Shard shard0000 at localhost:27010

Even though there are two shards, the shard distribution shows only one. Now only one of the sharded folder is getting full.

Why is it so? What do I have to do to make the shard distribution common?

Answer 1

As per MongoDB documentation here which prints the data distribution statistics for a sharded collection. You must call the getShardDistribution() method on a sharded collection, as in the following example:

db.myShardedCollection.getShardDistribution()

In the following example, the collection has two shards. The output displays both the individual shard distribution information as well the total shard distribution:

Shard <shard-a> at <host-a>
 data : <size-a> docs : <count-a> chunks : <number of chunks-a>
 estimated data per chunk : <size-a>/<number of chunks-a>
 estimated docs per chunk : <count-a>/<number of chunks-a>

Shard <shard-b> at <host-b>
 data : <size-b> docs : <count-b> chunks : <number of chunks-b>
 estimated data per chunk : <size-b>/<number of chunks-b>
 estimated docs per chunk : <count-b>/<number of chunks-b>

Totals
 data : <stats.size> docs : <stats.count> chunks : <calc total chunks>
 Shard <shard-a> contains  <estDataPercent-a>% data, <estDocPercent-a>% docs in cluster, avg obj size on shard : stats.shards[ <shard-a> ].avgObjSize
 Shard <shard-b> contains  <estDataPercent-b>% data, <estDocPercent-b>% docs in cluster, avg obj size on shard : stats.shards[ <shard-b> ].avgObjSize

For your further ref here, here