Mongo Large Collections Test

MongoDB stores documents in collections. Collections are analogous to tables in relational databases. Collections are leading consumers of database space. Larger the collection, larger will be the database size.

If the Mongo Databases test reveals that a particular database is growing in size rapidly, you can use the Mongo Large Collections test to precisely pinpoint the collection in that database, which is contributing to the abnormal database growth. This test auto-discovers the databases on a target MongoDB server and reports the number of collections that exceed a configured size. Detailed diagnostics of this test lists the large collections.

Target of the test : A MongoDB server

Agent deploying the test : An internal/remote agent

Outputs of the test : One set of results for each database in the server being monitored.

Configurable parameters for the test
Parameter Description

Authentication Mechanism

Typically, the MongoDB supports multiple authentication mechanisms that users can use to verify their identity. In environments where multiple authentication mechanisms are used, this test enables the users to select the authentication mechanism of their interest using this list box. By default, this is set to None. However, you can modify this settings as per the requirement.


By default, the SSL flag is set to No, indicating that the target MongoDB server is not SSL-enabled by default. To enable the test to connect to an SSL-enabled MongoDB server, set the SSL flag to Yes.

CA File

A certificate authority (CA) file contains root and intermediate certificates that are electronically signed to affirm that a public key belongs to the owner named in the certificate. If you are looking to monitor the certificates contained within a CA file, then provide the full path to this file in the CA File text box. For example, the location of this file may be: C:\cert\rootCA.pem. If you do not want to monitor the certificates in a CA file, set this parameter to none.

Certificate Key File

A Certificate Key File specifies the path on the server where your private key is stored. If you are looking to monitor the Certificate Key File, then provide the full path to this file in the Certificate Key File text box. For example, the location of this file may be: C:\cert\mongodb.pem. If you do not want to monitor the certificates in a CA file, set this parameter to none.

Test period

How often should the test be executed.


The host for which the test is to be configured.


The port number at which the specified host listens.

Database Name

The test connects to a specific Mongo database to run API commands and pull metrics of interest. Specify the name of this database here. The default value of this parameter is admin.

Username and Password

The eG agent has to be configured with the credentials of a user who has the required privileges to monitor the target MongoDB instance, if the MongoDB instance is access control enabled. To know how to create such a user, refer to How to monitor access control enabled MongoDB database?. If the target MongoDB instance is not access control enabled, then, specify none against the Username and Password parameters.

Confirm Password

Confirm the password by retyping it here.

Collection Size in GB

This test counts all those collections that are of a size larger than the value specified here as large collections. By default, this is set to 10 GB. This means that by default, those collections that are over 10 GB in size will be counted as a large collection by this test. You can change this value, if required.

Detailed Diagnosis

To make diagnosis more efficient and accurate, the eG Enterprise suite embeds an optional detailed diagnostic capability. With this capability, the eG agents can be configured to run detailed, more elaborate tests as and when specific problems are detected. To enable the detailed diagnosis capability of this test for a particular server, choose the On option. To disable the capability, click on the Off option.

The option to selectively enable/disable the detailed diagnosis capability will be available only if the following conditions are fulfilled:

  • The eG manager license should allow the detailed diagnosis capability
  • Both the normal and abnormal frequencies configured for the detailed diagnosis measures should not be 0.
Measurements made by the test
Measurement Description Measurement Unit Interpretation

Large collections

Indicates the number of collections in this database that are of a size larger than the value configured against Collection Size in GB parameter.


Use the detailed diagnosis of this test to know which are the large collections.

Largest collection size

Indicates the size of the largest collection.