The MongoDB exporter for MongoDB 4.0 and above was causing a "log bloat" condition.

Low-priority log bloat issue.

In 4.0 an "authorizedCollections" option was added to the listCollections command. In mongodb_exporter this server command is is used whenever a collector iterates all collections (e.g. in the collection_status.go and indexusage.go files).

Since then (or possibly only since 4.2, I haven't confirmed 4.0) attempting to run the following command in the "admin" db as the "clusterMonitor" role-granted user that mongodb_exporter uses causes an authorization error and a message in the log every time the collector runs.

db.adminCommand({"listCollections": 1, "nameOnly": 1})

It is just the "admin" db. So only one log line per collection.

It is not a permissions issue because "clusterMonitor" is the only suitable built-in role for mongodb_exporter to use.

The fix is to add the "authorizedCollections" option as well.

db.adminCommand({"listCollections": 1, "nameOnly": 1, "authorizedCollections": true})

The above is just how it is represented as mongo shell code; the actual mongodb_exporter code is go is currently lines like this:

c, err := client.Database(db).ListCollections(context.TODO(), bson.M{}, options.ListCollections().SetNameOnly(true))

DOC: since this is an exporter change, it will not affect PMM Documentation for now. But if needed Exporter documentation can be changed