Mongo IO Test

To reduce expensive disk reads and to improve cache usage, the MongoDB cache should be populated with data that is frequently accessed. This is why, its important that data read from disk is quickly written to the cache. Any delay when reading from disk to cache can result in a high incidence of cache misses, as key data objects may not be present in the cache. Likewise, latencies when writing cache updates to the disk can result in significant data loss in the event of the database server crashes. It is therefore imperative that administrators are promptly notified if any slowness is observed in reads from disk to cache or writes from cache to disk. The Mongo IO test provides these useful alerts to administrators!

This test monitors reads from and writes to disk, and reports the time taken by the server to perform these read/write activities. In the process, the test proactively alerts administrators to potential latencies in reading from and/or writing to disk.

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.
Host	The host for which the test is to be configured.
Port	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.
SSL	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
Pages read from disk	Indicates the number of pages read from disk to cache during the last measurement period. .	Number
Pages read time from disk	Indicates the total time taken to read pages from disk to cache during the last measurement period.	Seconds
Disk read latency	Indicates the time taken to perform a single read from the disk to the cache.	Seconds/read	A low value is desired for this measure. A high value implies that it is taking a long time for a single page to be read from the disk and written to the cache. This can indicate slowness in reading from disk to cache, which in turn can result in cache misses.
Pages written to disk	Indicates the number of pages written from cache to disk during the last measurement period.	Number
Pages write time to disk	Indicates the total time taken to write pages from the cache into the disk during the last measurement period.	Seconds
Disk write latency	Indicates the time taken to perform a single write to the disk from the cache.	Seconds/write	A low value is desired for this measure. A high value could imply that the server is slow when writing cache updates to disk. Ideally, the data in the cache and disk should be in sync. Slowness in writing to disk can cause the data in disk to be out of sync with the data in cache. In such a situation, significant data loss may occur when disaster strikes.