top¶

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Definition
Syntax
Event Fields
Example
Learn More

top¶: top is an administrative command that returns usage statistics for each collection. You can use top metrics to compare the relative performance of your collections against each other.

Important

The top command must be run against a mongod instance. Running top against a mongos instance returns an error.

Definition¶

For every collection, top returns the amount of time, in microseconds, that each event takes to execute and a count of how many times each event has executed. The time and count metrics reset only after you restart your mongod instance.

Syntax¶

Issue the top command against the admin database:

copy

db.runCommand(
   {
     top: 1
   }
)

Event Fields¶

The top command returns usage statistics for the following event fields:

Field	Description
`total`	The combination of all `readLock` and `writeLock` operations.
`readLock`	Usage statistics for operations that use read locks. These operations include but are not limited to queries and aggregations.
`writeLock`	Usage statistics for operations that use write locks. These operations include but are not limited to inserting, updating, and removing documents.
`queries`	Usage statistics for query operations such as `find`. The `queries.time` and `queries.count` fields also update `readLock.time` and increment `readLock.count`.
`getmore`	Usage statistics for `getMore` operations. The `getmore.time` and `getmore.count` fields also update `readLock.time` and increment `readLock.count`.
`insert`	Usage statistics for `insert` operations. The `insert.time` and `insert.count` fields also update `readLock.time` and increment `readLock.count`.
`update`	Usage statistics for `update` operations. The `update.time` and `update.count` fields also update `readLock.time` and increment `readLock.count`.
`remove`	Usage statistics for `delete` operations. The `remove.time` and `remove.count` fields also update `readLock.time` and increment `readLock.count`.
`commands`	Usage statistics for operations such as aggregations, index creation, and index removal. Depending on the type of command, the `commands.time` and `commands.count` fields update the `writeLock` fields or the `readLock` fields. For example, aggregation operations increment `readLock.time` and `readLock.count`. Index creation increments `writeLock.time` and `writeLock.count`.

Example¶

The output of the top command resembles the following output:

copy

{
  "totals" : {
     note: "all times in microseconds",
     "records.users" : {
                  "total" : {
                          "time" : 305277,
                          "count" : 2825
                  },
                  "readLock" : {
                          "time" : 305264,
                          "count" : 2824
                  },
                  "writeLock" : {
                          "time" : 13,
                          "count" : 1
                  },
                  "queries" : {
                          "time" : 305264,
                          "count" : 2824
                  },
                  "getmore" : {
                          "time" : 0,
                          "count" : 0
                  },
                  "insert" : {
                          "time" : 0,
                          "count" : 0
                  },
                  "update" : {
                          "time" : 0,
                          "count" : 0
                  },
                  "remove" : {
                          "time" : 0,
                          "count" : 0
                  },
                  "commands" : {
                          "time" : 0,
                          "count" : 0
                  }
          }
}

Learn More¶

What type of locking does MongoDB use?

← shardConnPoolStats validate →