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Percona Documentation

MongoDB

How to set up PMM to monitor a MongoDB or Percona Server for MongoDB database instance.

Before you start

Check that:

Create PMM account and set permissions

We recommend using a dedicated account to connect PMM Client to the monitored database instance.

Run the example codes below in a mongo session to:

  • create custom roles with the privileges required for creating/restoring backups and working with Query Analytics (QAN)
  • create/update a database user with these roles above, plus the built-in clusterMonitor role

Values for username (user) and password (pwd) are examples. Replace them before using these code snippets.

Create roles with privileges for backups and QAN

 db.getSiblingDB("admin").createRole({
    role: "explainRole",
    privileges: [{
        resource: {
            db: "",
            collection: ""
        },
        actions: [
            "listIndexes",
            "listCollections",
            "dbStats",
            "dbHash",
            "collStats",
            "find"
        ]
    }],
    roles: []
})

 db.getSiblingDB("admin").createRole({
    "role": "pbmAnyAction",
    "privileges": [{
        "resource": {
            "anyResource": true
        },
        "actions": [
            "anyAction"
        ]
    }],
    "roles": []
});

Create/update user and assign created roles

 db.getSiblingDB("admin").createUser({
    user: "pmm",
    pwd: "pmm",
    roles: [
        { role: "explainRole", db: "admin" },
        { role: "clusterMonitor", db: "admin" },
        { role: "read", db: "local" },
        { "db" : "admin", "role" : "readWrite", "collection": "" },
        { "db" : "admin", "role" : "backup" },
        { "db" : "admin", "role" : "clusterMonitor" },
        { "db" : "admin", "role" : "restore" },
        { "db" : "admin", "role" : "pbmAnyAction" }
    ]
})
 db.getSiblingDB("admin").updateUser("pmm", {
    roles: [
        { role: "explainRole", db: "admin" },
        { role: "clusterMonitor", db: "admin" },
        { role: "read", db: "local" },
        { "db" : "admin", "role" : "readWrite", "collection": "" },
        { "db" : "admin", "role" : "backup" },
        { "db" : "admin", "role" : "clusterMonitor" },
        { "db" : "admin", "role" : "restore" },
        { "db" : "admin", "role" : "pbmAnyAction" }
    ]
})

Permissions for advanced metrics

To fetch advanced metrics, use the following to provide additional privileges to an existing PMM user:

{
resource : {
    db : "",
    collection : "system.profile"
    },
actions : [
    "collStats",
    "dbStats",
    "indexStats"
   ]
}

If the role explainRole already exists, then you can use the following command to provide additional privileges:

 db.runCommand({
    grantPrivilegesToRole: "explainRole",
    privileges: [{
        "resource": {
            "db": "",
            "collection": "system.profile"
        },
        "actions": [
            "indexStats",
            "dbStats",
            "collStats"
        ]
    }]
})

Profiling

To use PMM Query Analytics, you must turn on MongoDB’s profiling feature.

You can set profiling:

  • permanently, by editing the MongoDB configuration file and restarting the database instance (recommended);
  • when starting MongoDB, by passing arguments to mongod on the command line;
  • until the next database instance restart, by running a command in a mongo session.

Profiling is turned off by default as it can adversely affect the performance of the database server.

Set profiling in the configuration file

  1. Edit the configuration file (usually /etc/mongod.conf).

  2. Create or add this to the operationProfiling section. (Read more.)

    operationProfiling:
  mode: all
  slowOpThresholdMs: 200
  rateLimit: 100 # (Only available with Percona Server for MongoDB.)

    Important

    This is a YAML file. Indentation matters.

  3. Restart the mongod service. (Example for systemd.)

    systemctl restart mongod

Set profiling on the command Line

mongod --dbpath=DATABASEDIR --profile 2 --slowms 200 --rateLimit 100
  • --dbpath: The path to database files (usually /var/lib/mongo).
  • --profile: The MongoDB profiling level. A value of 2 tells the server to collect profiling data for all operations. To lower the load on the server, use a value of 1 to only record slow operations.
  • --slowms: An operation is classified as slow if it runs for longer than this number of milliseconds.

  • --rateLimit: (Only available with Percona Server for MongoDB.) The sample rate of profiled queries. A value of 100 means sample every 100th fast query. (Read more.)

    Caution

    Smaller values improve accuracy but can adversly affect the performance of your server.

Set profiling in a mongo session

In a mongo session, the profiler should be enabled per database. For example, to enable the profiler in the testdb, run this:

> use testdb
> db.setProfilingLevel(2, {slowms: 0})

If you have already added a service, you should remove it and re-add it after changing the profiling level.

Add service

When you have configured your database server, you can add a MongoDB service with the user interface or on the command line.

Important

To monitor MongoDB sharded clusters, PMM requires access to all cluster components. Make sure to add all config servers, shards, and mongos. Otherwise, PMM will not be able to correctly collect metrics and populate dashboards.

With the user interface

  1. Select {{icon.configuration}} Configuration → {{icon.inventory}} Inventory.

  2. Select MongoDB – Add a remote instance.

  3. Enter or select values for the fields.

  4. Click Add service.

On the command line

Use pmm-admin to add the database server as a service using one of these example commands.

When successful, PMM Client will print MongoDB Service added with the service’s ID and name. Use the --environment and -custom-labels options to set tags for the service to help identify them.

Tips

  • When adding nodes of a sharded cluster, add each node separately using the --cluster mycluster option for the MongoDB Cluster Summary dashboard to populate correctly. Also use the --replication-set option to specify a replication set. Example: --replication-set config for your config servers; --replication-set rs1 for your servers in the first replica set, --replication-set rs2 for your servers in the second replica set, and so on.
  • Atlas doesn’t support direct connections. When connecting to an Atlas instance, use the pmm-admin option --direct-connection=false. (Doing so will prevent replicaset status from working and the MongoDB Overview dashboard widget will show invalid values.)

Examples

pmm-admin add mongodb \
--username=pmm_mongodb --password=password \
--query-source=profiler --cluster=mycluster

pmm-admin add mongodb \
--username=pmm_mongodb --password=password \
mongo 127.0.0.1:27017

pmm-admin add mongodb \
--username=pmm_mongodb --password=password \
--service-name=mymongosvc --host=127.0.0.1 --port=27017

Connect via UNIX socket

pmm-admin add mongodb --socket=/tmp/mongodb-27017.sock

Connecting via SSL/TLS

pmm-admin add mongodb --tls \
--tls-certificate-key-file=PATHTOCER \
--tls-certificate-key-file-password=IFPASSWORDTOCERTISSET \
--tls-ca-file=PATHTOCACERT
--authentication-mechanism=AUTHENTICATION-MECHANISM
--authentication-database=AUTHENTICATION-DATABASE

where:

  • PATHTOCERT: Path to TLS certificate file.
  • IFPASSWORDTOCERTISSET: Password for TLS certificate file.
  • PATHTOCACERT: Path to certificate authority file.
  • AUTHENTICATION-MECHANISM: Authentication mechanism. Default is empty. Use MONGODB-X509 for SSL certificates.
  • AUTHENTICATION-DATABASE: Authentication database. Default is empty. Use $external for SSL certificates.

Check the service

With the user interface

  1. Select {{icon.configuration}} Configuration → {{icon.inventory}} Inventory.
  2. In the Services tab, verify the Service name, Addresses, and any other relevant values used when adding the service.
  3. In the Options column, expand the Details section and check that the Agents are using the desired data source.
  4. If your MongoDB instance is configured to use TLS, click on the Use TLS for database connection check box and fill in TLS certificates and keys. If you use TLS, the authentication mechanism is automatically set to MONGODB-X509.

!

On the command line

Look for your service in the output of this command.

pmm-admin inventory list services --service-type=mongodb

Check data

  1. Open the MongoDB Instances Overview dashboard.
  2. Set the Service Name to the newly-added service.

Query Analytics

  1. Open PMM Query Analytics.
  2. In the Filters panel:
    1. Under Service Name, select your service.
    2. Under Service Type select mongodb.

Remove service

With the user interface

  1. Select {{icon.configuration}} Configuration → {{icon.inventory}} Inventory.
  2. In the first column, click the tick box for the service you want to remove.
  3. Click Delete.
  4. On the Confirm action dialog window:
    1. (Optional) Select Force mode to also delete associated agents.
    2. Click Proceed.

On the command line

pmm-admin remove mongodb SERVICE_NAME
  • SERVICE_NAME: The name the service was added as. (Find it with pmm-admin list.)

See also

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