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mongostat

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This documentation is for version 100.10.0 of mongostat.

Synopsis

mongostat is a command-line tool that provides a quick overview of the status of a currently running mongod or mongos instance. Use mongostat to help identify system bottlenecks.

mongostat is functionally similar to the UNIX/Linux file system utility vmstat, but provides data regarding mongod and mongos instances.

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

Syntax

mongostat syntax:

mongostat <options> <connection-string> <polling interval in seconds>

Options

--help

Returns information on the options and use of mongostat.

--verbose, -v

Increases the amount of internal reporting returned on standard output or in log files. Increase the verbosity with the -v form by including the option multiple times, (e.g. -vvvvv.)

--version

Returns the mongostat release number.

--config=<filename>

New in version 100.3.0.

Specifies the full path to a YAML configuration file containing sensitive values for the following options to mongostat:

This is the recommended way to specify a password to mongostat, aside from specifying it through a password prompt.

The configuration file takes the following form:

password: <password>
uri: mongodb://mongodb0.example.com:27017
sslPEMKeyPassword: <password>

Specifying a password to the password: field and providing a connection string in the uri: field which contains a conflicting password will result in an error.

Be sure to secure this file with appropriate filesystem permissions.

Note

If you specify a configuration file with --config and also use the --password, --uri or --sslPEMKeyPassword option to mongostat, each command line option overrides its corresponding option in the configuration file.

--uri=<connectionString>

Specifies the resolvable URI connection string of the MongoDB deployment, enclosed in quotes:

--uri="mongodb://[username:password@]host1[:port1][,host2[:port2],...[,hostN[:portN]]][/[database][?options]]"

Starting with version 100.0 of mongostat, the connection string may alternatively be provided as a positional parameter, without using the --uri option:

mongostat mongodb://[username:password@]host1[:port1][,host2[:port2],...[,hostN[:portN]]][/[database][?options]]

As a positional parameter, the connection string may be specified at any point on the command line, as long as it begins with either mongodb:// or mongodb+srv://. For example:

mongostat --username joe --password secret1 mongodb://mongodb0.example.com:27017 --ssl

Only one connection string can be provided. Attempting to include more than one, whether using the --uri option or as a positional argument, will result in an error.

For information on the components of the connection string, see the Connection String URI Format documentation.

Note

Some components in the connection string may alternatively be specified using their own explicit command-line options, such as --username and --password. Providing a connection string while also using an explicit option and specifying conflicting information will result in an error.

Note

If using mongostat on Ubuntu 18.04, you may experience a cannot unmarshal DNS error message when using SRV connection strings (in the form mongodb+srv://) with the --uri option. If so, use one of the following options instead:

Warning

On some systems, a password provided in a connection string with the --uri option may be visible to system status programs such as ps that may be invoked by other users. Consider instead:

  • omitting the password in the connection string to receive an interactive password prompt, or

  • using the --config option to specify a configuration file containing the password.

--host=<hostname><:port>, -h=<hostname><:port>

Default: localhost:27017

Specifies the resolvable hostname of the MongoDB deployment. By default, mongostat attempts to connect to a MongoDB instance running on the localhost on port number 27017.

To connect to a replica set, you can specify the set member or members to report on, as in the following (see also the --discover flag):

--host=<hostname1><:port>,<hostname2><:port>,<...>

If you use IPv6 and use the <address>:<port> format, you must enclose the portion of an address and port combination in brackets (e.g. [<address>]).

Alternatively, you can also specify the hostname directly in the URI connection string. Providing a connection string while also using --host and specifying conflicting information will result in an error.

--port=<port>

Default: 27017

Specifies the TCP port on which the MongoDB instance listens for client connections.

Alternatively, you can also specify the port directly in the URI connection string. Providing a connection string while also using --port and specifying conflicting information will result in an error.

--ssl

Enables connection to a mongod or mongos that has TLS/SSL support enabled.

Alternatively, you can also configure TLS/SSL support directly in the URI connection string. Providing a connection string while also using --ssl and specifying conflicting information will result in an error.

For more information about TLS/SSL and MongoDB, see Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients.

--sslCAFile=<filename>

Specifies the .pem file that contains the root certificate chain from the Certificate Authority. Specify the file name of the .pem file using relative or absolute paths.

Alternatively, you can also specify the .pem file directly in the URI connection string. Providing a connection string while also using --sslCAFile and specifying conflicting information will result in an error.

For more information about TLS/SSL and MongoDB, see Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients.

--sslPEMKeyFile=<filename>

Specifies the .pem file that contains both the TLS/SSL certificate and key. Specify the file name of the .pem file using relative or absolute paths.

This option is required when using the --ssl option to connect to a mongod or mongos that has CAFile enabled without allowConnectionsWithoutCertificates.

Alternatively, you can also specify the .pem file directly in the URI connection string. Providing a connection string while also using --sslPEMKeyFile and specifying conflicting information will result in an error.

For more information about TLS/SSL and MongoDB, see Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients.

--sslPEMKeyPassword=<value>

Specifies the password to de-crypt the certificate-key file (i.e. --sslPEMKeyFile). Use the --sslPEMKeyPassword option only if the certificate-key file is encrypted. In all cases, the mongostat will redact the password from all logging and reporting output.

If the private key in the PEM file is encrypted and you do not specify the --sslPEMKeyPassword option, the mongostat will prompt for a passphrase. See TLS/SSL Certificate Passphrase.

Alternatively, you can also specify the password directly in the URI connection string. Providing a connection string while also using --sslPEMKeyPassword and specifying conflicting information will result in an error.

For more information about TLS/SSL and MongoDB, see Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients.

Warning

On some systems, a password provided directly using the --sslPEMKeyPassword option may be visible to system status programs such as ps that may be invoked by other users. Consider using the --config option to specify a configuration file containing the password instead.

--sslCRLFile=<filename>

Specifies the .pem file that contains the Certificate Revocation List. Specify the file name of the .pem file using relative or absolute paths.

For more information about TLS/SSL and MongoDB, see Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients.

--sslAllowInvalidCertificates

Bypasses the validation checks for server certificates and allows the use of invalid certificates. When using the allowInvalidCertificates setting, MongoDB logs as a warning the use of the invalid certificate.

Warning

Although available, avoid using the --sslAllowInvalidCertificates option if possible. If the use of --sslAllowInvalidCertificates is necessary, only use the option on systems where intrusion is not possible.

Connecting to a mongod or mongos instance without validating server certificates is a potential security risk. If you only need to disable the validation of the hostname in the TLS/SSL certificates, see --sslAllowInvalidHostnames.

Alternatively, you can also disable certificate validation directly in the URI connection string. Providing a connection string while also using --sslAllowInvalidCertificates and specifying conflicting information will result in an error.

For more information about TLS/SSL and MongoDB, see Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients.

--sslAllowInvalidHostnames

Disables the validation of the hostnames in TLS/SSL certificates. Allows mongostat to connect to MongoDB instances even if the hostname in their certificates do not match the specified hostname.

Alternatively, you can also disable hostname validation directly in the URI connection string. Providing a connection string while also using --sslAllowInvalidHostnames and specifying conflicting information will result in an error.

For more information about TLS/SSL and MongoDB, see Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients.

--username=<username>, -u=<username>

Specifies a username with which to authenticate to a MongoDB database that uses authentication. Use in conjunction with the --password and --authenticationDatabase options.

Alternatively, you can also specify the username directly in the URI connection string. Providing a connection string while also using --username and specifying conflicting information will result in an error.

If connecting to a MongoDB Atlas cluster using the MONGODB-AWS authentication mechanism, you can specify your AWS access key ID in:

See Connect to a MongoDB Atlas Cluster using AWS IAM Credentials for an example of each.

--password=<password>, -p=<password>

Specifies a password with which to authenticate to a MongoDB database that uses authentication. Use in conjunction with the --username and --authenticationDatabase options.

To prompt the user for the password, pass the --username option without --password or specify an empty string as the --password value, as in --password="" .

Alternatively, you can also specify the password directly in the URI connection string. Providing a connection string while also using --password and specifying conflicting information will result in an error.

If connecting to a MongoDB Atlas cluster using the MONGODB-AWS authentication mechanism, you can specify your AWS secret access key in:

See Connect to a MongoDB Atlas Cluster using AWS IAM Credentials for an example of each.

Warning

On some systems, a password provided directly using the --password option may be visible to system status programs such as ps that may be invoked by other users. Consider instead:

  • omitting the --password option to receive an interactive password prompt, or

  • using the --config option to specify a configuration file containing the password.

--awsSessionToken=<AWS Session Token>

If connecting to a MongoDB Atlas cluster using the MONGODB-AWS authentication mechanism, and using session tokens in addition to your AWS access key ID and secret access key, you can specify your AWS session token in:

See Connect to a MongoDB Atlas Cluster using AWS IAM Credentials for an example of each.

Only valid when using the MONGODB-AWS authentication mechanism.

--authenticationDatabase=<dbname>

Specifies the authentication database where the specified --username has been created. See Authentication Database.

--authenticationDatabase is required for mongod and mongos instances that use Authentication on Self-Managed Deployments.

If using the GSSAPI (Kerberos), PLAIN (LDAP SASL), or MONGODB-AWS authentication mechanisms, you must set --authenticationDatabase to $external.

Alternatively, you can also specify the authentication database directly in the URI connection string. Providing a connection string while also using --authenticationDatabase and specifying conflicting information will result in an error.

--authenticationMechanism=<name>

Default: SCRAM-SHA-1

Specifies the authentication mechanism the mongostat instance uses to authenticate to the mongod or mongos.

Changed in version 100.1.0: Starting in version 100.1.0, mongostat adds support for the MONGODB-AWS authentication mechanism when connecting to a MongoDB Atlas cluster.

Value
Description

RFC 7677 standard Salted Challenge Response Authentication Mechanism using the SHA-256 hash function.

Requires featureCompatibilityVersion set to 4.0.

MongoDB TLS/SSL certificate authentication.
MONGODB-AWS

External authentication using AWS IAM credentials for use in connecting to a MongoDB Atlas cluster. See Connect to a MongoDB Atlas Cluster using AWS IAM Credentials.

New in version 100.1.0.

GSSAPI (Kerberos)
External authentication using Kerberos. This mechanism is available only in MongoDB Enterprise.
PLAIN (LDAP SASL)
External authentication using LDAP. You can also use PLAIN for authenticating in-database users. PLAIN transmits passwords in plain text. This mechanism is available only in MongoDB Enterprise.

Alternatively, you can also specify the authentication mechanism directly in the URI connection string. Providing a connection string while also using --authenticationMechanism and specifying conflicting information will result in an error.

--gssapiServiceName=<string>

Specify the name of the service using GSSAPI/Kerberos. Only required if the service does not use the default name of mongodb.

This option is available only in MongoDB Enterprise.

--gssapiHostName=<string>

Specify the hostname of a service using GSSAPI/Kerberos. Only required if the hostname of a machine does not match the hostname resolved by DNS.

This option is available only in MongoDB Enterprise.

--humanReadable=<boolean>

Default: true

When true, mongostat formats dates and quantity values for easier reading, as in the following sample output:

insert query update delete getmore command dirty used flushes vsize  res qrw arw net_in net_out conn                time
   991    *0     *0     *0       0     2|0  3.4% 4.5%       0 2.90G 297M 0|0 0|0  12.9m   84.2k    2 Oct  6 09:45:37.478
   989    *0     *0     *0       0     2|0  3.6% 4.7%       0 2.91G 310M 0|0 0|0  12.9m   84.1k    2 Oct  6 09:45:38.476
   988    *0     *0     *0       0     1|0  3.7% 4.8%       0 2.92G 323M 0|0 0|0  12.8m   83.8k    2 Oct  6 09:45:39.481
   976    *0     *0     *0       0     2|0  3.9% 5.0%       0 2.94G 335M 0|0 0|0  12.7m   83.7k    2 Oct  6 09:45:40.476

When false, mongostat returns the raw data, as in the following sample output:

insert query update delete getmore command dirty used flushes      vsize       res qrw arw   net_in net_out conn                      time
   992    *0     *0     *0       0     2|0   1.3  2.4       0 2941255680 149946368 0|0 0|0 12913607   84271    2 2016-10-06T09:45:25-04:00
   989    *0     *0     *0       0     1|0   1.5  2.6       0 2974810112 163577856 0|0 0|0 12873225   84087    2 2016-10-06T09:45:26-04:00
   996    *0     *0     *0       0     1|0   1.6  2.8       0 2972712960 177209344 0|0 0|0 12955423   84345    2 2016-10-06T09:45:27-04:00
   987    *0     *0     *0       0     1|0   1.8  2.9       0 2989490176 190840832 0|0 0|0 12861852   84008    2 2016-10-06T09:45:28-04:00
-o=<field list>

When output fields are specified with -o, only the specified fields are included in the mongostat output.

Use dot notation to specify serverStatus fields, as in metrics.document.inserted.

A custom field name can include spaces. If you include a space, do not put additional quotes around the field name. To specify a custom name for a field, use <field>=<customName>, as in:

mongostat -o='host=H,time=T,version=MongoDB Version'

-o supports the following methods to modify the information returned for a given serverStatus field:

.rate()

Use .rate() to view the rate per second at which a serverStatus field is changing from mongostat call to call.

View Rate of Change for a Field with .rate() illustrates how to use mongostat with -o and the .rate() method.

.diff()

Use .diff() to view how much a serverStatus field has changed since the previous mongostat call. The interval between calls is specified by <sleeptime>.

View Field Changes with .diff() illustrates how to use mongostat with -o and the .diff() method.

mongostat supports specifying either -o or -O: you cannot include both options.

See Specify mongostat Output Fields for an example of -o.

-O=<field list>

When specified, mongostat includes the specified serverStatus fields after the default mongostat output.

Use dot notation to specify serverStatus fields, as in metrics.document.inserted.

A custom field name can include spaces. If you include a space, do not put additional quotes around the field name. To specify a custom name for a field, use <field>=<customName>, as in:

mongostat -O=host=H,time=T

mongostat supports specifying either -O or -o: you cannot include both options.

See Add Fields to mongostat Output for an example of -O.

--noheaders

Disables the output of column or field names.

--rowcount=<number>, -n=<number>

Controls the number of rows to output. Use in conjunction with the sleeptime argument to control the duration of a mongostat operation.

Unless --rowcount is specified, mongostat will return an infinite number of rows (e.g. value of 0.)

--discover

Discovers and reports on statistics from all members of a replica set or sharded cluster. When connected to any member of a replica set, --discover all non-hidden members of the replica set. When connected to a mongos, mongostat will return data from all shards in the cluster. If a replica set provides a shard in the sharded cluster, mongostat will report on non-hidden members of that replica set.

The mongostat --host option is not required but potentially useful in this case.

When running with --discover, mongostat respects --rowcount.

--all

Configures mongostat to return all optional fields.

--json

Returns output for mongostat in JSON format.

--interactive

Display mongostat output in an interactive non-scrolling interface rather than the default scrolling output.

--interactive is not available with the --json option.

See: View Statistics in an Interactive Interface for an example of --interactive.

<sleeptime>

Default: 1

The final mongostat argument is the length of time, in seconds, that mongostat waits in between calls. By default mongostat returns one call every second.

mongostat returns values that reflect the operations over a 1 second period. For values of <sleeptime> greater than 1, mongostat averages data to reflect average operations per second.

Fields

mongostat returns values that reflect the operations over a 1 second period. When mongostat <sleeptime> has a value greater than 1, mongostat averages the statistics to reflect average operations per second.

mongostat outputs the following fields:

inserts

The number of objects inserted into the database per second. If followed by an asterisk (e.g. *), the datum refers to a replicated operation.

query

The number of query operations per second.

update

The number of update operations per second.

delete

The number of delete operations per second.

getmore

The number of get more (i.e. cursor batch) operations per second.

command

The number of commands per second. On secondary systems, mongostat presents two values separated by a pipe character (e.g. |), in the form of local|replicated commands.

flushes

For the WiredTiger Storage Engine, flushes refers to the number of WiredTiger checkpoints triggered between each polling interval.

dirty

Only for WiredTiger Storage Engine. The percentage of the WiredTiger cache with dirty bytes, calculated by wiredTiger.cache.tracked dirty bytes in the cache / wiredTiger.cache.maximum bytes configured.

used

Only for WiredTiger Storage Engine. The percentage of the WiredTiger cache that is in use, calculated by wiredTiger.cache.bytes currently in the cache / wiredTiger.cache.maximum bytes configured.

vsize

The amount of virtual memory in megabytes used by the process at the time of the last mongostat call.

res

The amount of resident memory in megabytes used by the process at the time of the last mongostat call.

locked

The percent of time in a global write lock. Only appears when mongostat runs against pre-3.0 versions of MongoDB instances.

qr

The length of the queue of clients waiting to read data from the MongoDB instance.

qw

The length of the queue of clients waiting to write data from the MongoDB instance.

ar

The number of active clients performing read operations.

aw

The number of active clients performing write operations.

netIn

The amount of network traffic, in bytes, received by the MongoDB instance.

This includes traffic from mongostat itself.

netOut

The amount of network traffic, in bytes, sent by the MongoDB instance.

This includes traffic from mongostat itself.

conn

The total number of open connections.

set

The name, if applicable, of the replica set.

repl

The replication status of the member.

Value
Replication Type
PRI
SEC
REC
recovering
UNK
unknown
RTR
mongos process ("router")
ARB

Additional Information

For more information about monitoring MongoDB, see Monitoring for MongoDB.

For more background on other MongoDB status outputs see:

For an additional utility that provides MongoDB metrics see mongotop.

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