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mongostat Examples

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This page shows examples for mongostat.

Run mongostat from the system command line, not the mongo shell.

Specify mongostat Collection Period and Frequency

In the first example, mongostat will return data every second for 20 seconds. mongostat collects data from the mongod instance running on the localhost interface on port 27017. All of the following invocations produce identical behavior:

mongostat --rowcount=20 1
mongostat --rowcount=20
mongostat -n=20 1
mongostat -n=20

In the next example, mongostat returns data every 5 minutes (or 300 seconds) for as long as the program runs. mongostat collects data from the mongod instance running on the localhost interface on port 27017. The following invocations produce identical behavior:

mongostat --rowcount=0 300
mongostat -n=0 300
mongostat 300

In the following example, mongostat returns data every 5 minutes for an hour (12 times.) mongostat collects data from the mongod instance running on the localhost interface on port 27017. The following invocations produce identical behavior:

mongostat --rowcount=12 300
mongostat -n=12 300

Add Fields to mongostat Output

-O allows you to specify fields from the serverStatus output to add to the default mongostat output. If you include a space in your custom filed name, do not put additional quotes around the field name.

The following example adds fields to the default mongostat output:

mongostat -O='host,version,network.numRequests=network requests'

The mongostat output resembles:

insert query update delete getmore command dirty used flushes vsize   res qrw arw net_in net_out conn                time            host version network requests
    *0    *0     *0     *0       0     2|0  0.0% 0.0%       0 2.51G 19.0M 0|0 0|0   158b   39.4k    2 Oct 11 12:14:45.878 localhost:37017  3.3.14               91
    *0    *0     *0     *0       0     1|0  0.0% 0.0%       0 2.51G 19.0M 0|0 0|0   157b   39.3k    2 Oct 11 12:14:46.879 localhost:37017  3.3.14               95
    *0    *0     *0     *0       0     1|0  0.0% 0.0%       0 2.51G 19.0M 0|0 0|0   157b   39.2k    2 Oct 11 12:14:47.884 localhost:37017  3.3.14               99

The following fields are added to the default output:

The network.numRequests field has a custom field name, "network requests".

Specify mongostat Output Fields

-o specifies the columns mongostat includes in its output. You can specify any serverStatus field as a mongostat output column.

The following example uses custom fields for mongostat:

mongostat --port 27500 -o='host,opcounters.insert.rate()=Insert Rate,opcounters.query.rate()=Query Rate,opcounters.command.rate()=Command Rate,wiredTiger.cache.pages requested from the cache=Pages Req,metrics.document.inserted=inserted rate'

The mongostat output resembles:

           host Insert Rate Query Rate Command Rate Pages Req Inserted Rate
localhost:27500         180          1            8   2999446          9638
localhost:27500          40          3           12   2999601          9678
localhost:27500         181          2            9   3000207          9859
localhost:27500          39          2           12   3000362          9899
localhost:27500         181          2           11   3000969         10080
localhost:27500          39          2           10   3001124         10120

The counters and corresponding custom field names are:

Counter
Custom Field Name
opcounters.insert.rate
Insert Rate
opcounters.query.rate
Query Rate
opcounters.command.rate
Command Rate
wiredTiger.cache.pages requested from the cache
Pages Req
metrics.document.inserted
Inserted Rate

View Rate of Change for a Field with .rate()

.rate() enables you to view the rate per second at which a numerical field has changed from one mongostat call to the next. For example, you can view the rate at which documents have been inserted during an insert operation. .rate() can therefore help you view the performance of your mongod instance.

The following example reports on the rate of change of the metrics.document.inserted serverStatus field. The invocation uses -o's ability to specify the name of an column to label metrics.document.inserted.rate() as "inserted rate" and metrics.document.inserted as "inserted":

mongostat -o='host,mem,bits,metrics.document.inserted.rate()=inserted rate,metrics.document.inserted=inserted' --rowcount=5

The output would then resemble:

           host mem.bits inserted rate inserted
localhost:37017       64           501     3455
localhost:37017       64           967    13128
localhost:37017       64           972    22851
localhost:37017       64           214    25000
localhost:37017       64             0    25000

View Field Changes with .diff()

.diff() returns the difference between the current serverStatus field value and the value from the previous mongostat call. The following example returns statistics on the number of documents being inserted into a collection: inserted diff is the difference in the metrics.document.inserted field between subsequent calls, while inserted is the value of metrics.document.inserted:

mongostat -o='host,mem.bits,metrics.document.inserted.diff()=inserted diff,metrics.document.inserted=inserted' --rowcount=5

The output would then resemble:

           host mem.bits inserted diff inserted
localhost:27017       64             0    25359
localhost:27017       64            94    25453
localhost:27017       64           938    26391
localhost:27017       64           964    27355
localhost:27017       64           978    28333

View Statistics for a Replica Set or Sharded Cluster

In many cases, using the --discover option will help provide a more complete snapshot of the state of an entire group of machines. If a mongos process connected to a sharded cluster is running on port 27017 of the local machine, you can use the following form to return statistics from all members of the cluster:

mongostat --discover

View Statistics in an Interactive Interface

Use the --interactive option to view statistics in a non-scrolling ncurses -style interactive output. The --interactive option lets you highlight specific hosts, columns, or fields to view. When combined with --discover, --interactive displays statistics for all members of a replica set or sharded cluster, as in the following example:

mongostat --discover --interactive

The output for a sharded cluster would then resemble:

                  host insert query update delete getmore command dirty used flushes mapped vsize   res faults qrw arw net_in net_out conn set repl                time
hostname.local:27018     *0    *0     *0     *0       0     1|0  0.0% 0.0%       0        3.25G 25.0M    n/a 0|0 1|0   157b   43.9k   19 tic  PRI Nov  2 11:44:46.439
hostname.local:27019     *0    *0     *0     *0       0     2|0  0.0% 0.0%       0        3.18G 26.0M    n/a 0|0 1|0   322b   44.4k   12 tic  SEC Nov  2 11:44:46.439
hostname.local:27020     *0    *0     *0     *0       0     2|0  0.0% 0.0%       0        3.18G 26.0M    n/a 0|0 1|0   322b   44.4k   12 tic  SEC Nov  2 11:44:46.439
hostname.local:27021   2017    *0     *0     *0     826  1029|0  0.0% 0.0%       0        3.25G 31.0M    n/a 0|0 1|0  1.74m   1.60m   20 tac  PRI Nov  2 11:44:46.439
hostname.local:27022  *2021    *0     *0     *0       0     2|0  0.0% 0.0%       0        3.19G 32.0M    n/a 0|0 1|0   322b   44.6k   12 tac  SEC Nov  2 11:44:46.438
hostname.local:27023  *2022    *0     *0     *0       0     3|0  0.0% 0.0%       0        3.19G 33.0M    n/a 0|0 1|0   323b   44.7k   12 tac  SEC Nov  2 11:44:46.438
     localhost:27017   2071    *0     *0     *0       0  2073|0                  0     0B 2.43G 9.00M      0 0|0 0|0   249k    130k    4      RTR Nov  2 11:44:47.429
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Connect to a MongoDB Atlas Cluster using AWS IAM Credentials

New in version 100.1.0.

To connect to a MongoDB Atlas cluster which has been configured to support authentication via AWS IAM credentials, provide a connection string to mongostat similar to the following:

mongostat 'mongodb+srv://<aws access key id>:<aws secret access key>@cluster0.example.com/testdb?authSource=$external&authMechanism=MONGODB-AWS' <other options>

Connecting to Atlas using AWS IAM credentials in this manner uses the MONGODB-AWS authentication mechanism and the $external authSource, as shown in this example.

If using an AWS session token, as well, provide it with the AWS_SESSION_TOKEN authMechanismProperties value, as follows:

mongostat 'mongodb+srv://<aws access key id>:<aws secret access key>@cluster0.example.com/testdb?authSource=$external&authMechanism=MONGODB-AWS&authMechanismProperties=AWS_SESSION_TOKEN:<aws session token>' <other options>

Note

If the AWS access key ID, secret access key, or session token include the following characters:

: / ? # [ ] @

those characters must be converted using percent encoding.

Alternatively, the AWS access key ID, secret access key, and optionally session token can each be provided outside of the connection string using the --username, --password, and --awsSessionToken options instead, like so:

mongostat 'mongodb+srv://cluster0.example.com/testdb?authSource=$external&authMechanism=MONGODB-AWS' --username <aws access key id> --password <aws secret access key> --awsSessionToken <aws session token> <other options>

When provided as command line parameters, these three options do not require percent encoding.

You may also set these credentials on your platform using standard AWS IAM environment variables. mongostat checks for the following environment variables when you use the MONGODB-AWS authentication mechanism:

  • AWS_ACCESS_KEY_ID

  • AWS_SECRET_ACCESS_KEY

  • AWS_SESSION_TOKEN

If set, these credentials do not need to be specified in the connection string or via their explicit options.

Note

If you chose to use the AWS environment variables to specify these values, you cannot mix and match with the corresponding explicit or connection string options for these credentials. Either use the environment variables for access key ID and secret access key (and session token if used), or specify each of these using the explicit or connection string options instead.

The following example sets these environment variables in the bash shell:

export AWS_ACCESS_KEY_ID='<aws access key id>'
export AWS_SECRET_ACCESS_KEY='<aws secret access key>'
export AWS_SESSION_TOKEN='<aws session token>'

Syntax for setting environment variables in other shells will be different. Consult the documentation for your platform for more information.

You can verify that these environment variables have been set with the following command:

env | grep AWS

Once set, the following example connects to a MongoDB Atlas cluster using these environment variables:

mongostat 'mongodb+srv://cluster0.example.com/testdb?authSource=$external&authMechanism=MONGODB-AWS'  <other options>

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