Mongo Cursors Test

A cursor is a pointer to the result set of a query. Clients can iterate through a cursor to retrieve results. By default, cursors timeout after 10 minutes of inactivity. Cursors that remain open for long periods of time can drain valuable memory resources; so can those cursors that have been configured to not timeout at all. To avoid the unnecessary memory drain, the Mongo Cursors test instantly alerts administrators to an abnormally large number of open cursors and notimeout cursors.

Target of the test : A MongoDB server

Agent deploying the test : An internal/remote agent

Outputs of the test : One set of results for the MongoDB server monitored.

Configurable parameters for the test
Parameter Description

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.

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.

Measurements made by the test
Measurement Description Measurement Unit Interpretation

Open cursors

Indicates the number of cursors that are currently opened by MongoDB for clients.


A gradual increase in the number of open cursors without a corresponding growth of traffic is often symptomatic of poorly indexed queries. It can also be the result of long running queries due to large result sets. You should take a look to see how you could optimize them.

Timeout cursor

Indicates the number of cursors that timed out.


The value of this measure is incremented when a client connection has died without having gracefully closed the cursor. This cursor remains open on the server, consuming memory. By default MongoDB reaps these cursors after 10 minutes of inactivity. You should check if you have a large amount of memory being consumed from non-active cursors. A high number of timed out cursors can be related to application issues.

Timeout disabled cursor

Indicates the number of open cursors with timeout disabled.


The value 0 is desired for this measure. This is because, cursors with no timeout can prevent resources to be freed as it should and slow down internal system processes; hence, they should be avoided. A non-zero value for this measure is hence a cause for concern.

The DBQuery.Option.noTimeout flag (until v3.0) or the cursor.noCursorTimeout() method can be used to prevent the server to timeout cursors after a period of inactivity (idle cursors).