MongoDB

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

Before you start

Check that:

• PMM Server is installed and running with a known IP address or hostname accessible from the client node.
• PMM Client is installed and the node is registered with PMM Server.
• You have superuser (root) access on the client host.
• You have adminUserAnyDatabase or superuser role privilege to any database servers that you want to monitor.
• Your MongoDB server is version 4.0 or higher.

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

Important

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": [
            "collStats",
            "dbHash",
            "dbStats",
            "find",
            "listIndexes",
            "listCollections"
         ]
     },
     {
         "resource": {
            "db": "",
            "collection": "system.profile"
         },
         "actions": [
            "dbStats",
            "collStats",
            "indexStats"
         ]
      },
      {
         "resource": {
            "db": "",
            "collection": "system.version"
         },
         "actions": [
            "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: "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 like usage statistics for collection and indexes, use the following to provide additional privileges to an existing PMM user:

db.getSiblingDB("admin").updateRole(
  "explainRole",
  {
    privileges: [
      {
        resource: { db: "", collection: "" },
        actions: ["collStats", "dbStats", "indexStats"]
      }
    ]
  }
)

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.

Important

Profiling is disabled by default as it may negatively impact the performance of the database server under specific circumstances, such as when busy servers are profiling all queries.

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 100^th 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})

Important

If you have already added the MongoDB service to PMM, make sure to restart the PMM agent service after adjusting the profiling level.

Add service

After configuring your database server, you can add a MongoDB service either through the user interface or via the command line.

Important

To monitor MongoDB sharded clusters, PMM requires access to all cluster components. Make sure to add all the config servers, shards, and at least 1-2 mongos routers. Otherwise, PMM will not be able to correctly collect metrics and populate dashboards. Keep in mind that adding all mongos routers may cause excessive overhead.

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 to a sharded cluster, ensure to add each node separately using the --cluster mycluster option. This allows the MongoDB Cluster Summary dashboard to populate correctly.
• You can also use the --replication-set option to specify a replication set, altough they are automatically detected. For instance, you can use --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.

Examples

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

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

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 \
--cluster=mycluster \
--enable-all-collectors

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.

With the PMM interface

Use this option when you don’t have direct access to the underlying host to install pmm-agent locally.

1. Select Configuration → Inventory.

2. Select MongoDB – Add a remote instance.

3. Enter or select values for the fields.

4. Click Add service.

Check the service

On the command line

Look for your service in the output of this command.

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

With the PMM interface

1. Select Configuration → 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.

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

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.)

With the PMM interface

Use this option only top remove agents installed through the PMM interface.

1. Select Configuration → 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.

See also

• pmm-admin add mongodb
• Troubleshooting connection difficulties

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