MongoDB Cluster Availability Test

MongoDB uses sharding to support deployments with very large data sets and high throughput operations. A shard contains a subset of sharded data for a sharded cluster. Together, the cluster's shards hold the entire data set for the cluster. MongoDB partitions sharded data into chunks. Each chunk has an inclusive lower and exclusive upper range based on the shard key. The MongoDB balancer is a background process that monitors the number of chunks on each shard. When the number of chunks on a given shard reaches specific migration thresholds, the balancer attempts to automatically migrate chunks between shards and reach an equal number of chunks per shard. For example, if one shard of your cluster contains too many chunks of your sharded collection, that particular shard can receive more traffic in comparison to other shards. The migration process ensures consistency and maximizes the availability of chunks during balancing. Chunk migrations can have an impact on disk space, as the source shard automatically archives the migrated documents by default. Chunk migrations carry some overhead in terms of bandwidth and workload, both of which can impact database performance. Hence, it is very crucial for the administrators to keep an eye on the balancer process and chunk migration across shards.

This test reports whether/not the target MongoDB is clustered and if so, it reveals the type of cluster. This test also shed light on the balancer process by reporting whether/not the balancer is enabled and running. In addition, this test also reports the statistics pertaining to the failed balancer count, number of successful and failed migrations, and number of shards. This way, administrators are able to detect any aberrations in the balancer process and chunk migration, which in turn, helps them to proactively resolve any issues related to balancing the data before it affect the database performance.

Target of the test : A MongoDB Cluster

Agent deploying the test : An external agent

Outputs of the test : One set of results for the target MongoDB Cluster database server being 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.

Cluster Node IPs

By default, the eG agent connects to any of the available nodes in the target MongoDB cluster to collect the required metrics. Therefore, in the Cluster Node IPs text box, provide a comma-separated list of all the nodes in the target cluster. By default, this parameter is set to none. This parameter should be specified in the following format: HOSTNAME1:PORT1,HOSTNAME2:PORT2,.... For example, you can configure this parameter as: ac-zcguoqj-shard-00-00.e5ahzxy.mongodb.net:27017,ac-zcguoqj-shard-00-01.e5ahzxy.mongodb.net:27017.

Database Name

The test connects to a specific Mongo Cluster to run API commands and pull metrics of interest. Specify the name of a database on the target MongoDB Cluster database server being monitored 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 cluster, 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 Authentication Mechanism 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 Cluster server is not SSL-enabled by default. To enable the test to connect to an SSL-enabled MongoDB Cluster server, set the SSL flag to Yes.

CA PEM 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. A .pem file is a container that may just include the public certificate or the entire certificate chain (private key, public key and root certificates). If the connection requires server authentication and the server certificate is in the .pem format, then, the target instance presents the CA PEM File that contains the server certificate to its clients to establish the instance's identity. Therefore, you should specify the full path to the CA PEM file available in the target MongoDB cluster in the CA PEM File text box. For example, the location of this file may be: C:\app\openSSL\SSLcert\test-ca.pem.

Client PEM File

If the target instance requires a certificate key file that is in .pem format from the client to verify the client's identity, then, to establish a connection with the target cluster, the eG agent should access the client certificate. For this, specify the full path to the Client PEM file in the Client PEM File text box. For example, the location of this file may be: C:\app\openSSL\SSLcert\test-client.pem.

CA Cert File

This parameter is applicable only if the target MongoDB Cluster is SSL-enabled and CA PEM File parameter is set to none.The certificate file is a public-key certificate following the x.509 standard. It contains information about the identity of the server, such as its name, geolocation, and public key. Each nodes of the target cluster can have individual certificate files or a single certificate can be used to access all the nodes in the cluster. Essentially, it’s a certificate that the server serves to the connecting users to prove that they are what they claim to be. Therefore, specify the full path to the server root certificate or certificate file that is signed by the CA in .crt file format for all/each node in the CA Cert File text box. For example, the location of this file may be: C:\app\eGurkha\JRE\lib\security\mongodb-test-ca.crt. By default, this parameter is set to none.

This parameter specification differs according to the type of cluster and configuration:

  • If the certificate file is available for each node of the MongoDB Cluster then, provide a comma-seperated list of full path to the certificates in CA Cert File text box:

    For example:C:\app\eGurkha\JRE\lib\security\mongodb-test-ca.crt,C:\app\eGurkha\JRE\lib\security\mongodb-test-ca2.crt,C:\app\eGurkha\JRE\lib\security\mongodb-test-ca3.crt

  • Specify the full path to the certificate file of the target MongoDB cluster if a single certificate is used to access all nodes.

    For example: C:\app\eGurkha\JRE\lib\security\mongodb-test-ca.crt

Client Cert File

This parameter is applicable only if the target MongoDB Cluster is SSL-enabled and Client PEM File parameter is set to none.In order to collect metrics from the target MongoDB cluster, the eG agent requires client certificate in .p12 format. Hence, specify the full path to the Client certificate file in .p12 format in the Client Cert File text box. For example, the location of this file may be: C:\app\eGurkha\JRE\lib\security\test-client.p12 . To know how to generate .p12 file from Client PEM file, refer to How to import a Certificate that is in the PEM Format?. By default, this parameter is set to none.

Client Cert Password

Provide the password for .p12 Client certificate file in the Client Cert Password text box.

RS Node Cert Info

By default, the this parameter is set to none. This indicates that the test will report metrics for all the nodes in the cluster. However, you should specify this parameter with a comma-seperated list of the nodes in the cluster, provided, separate certificate file is required to access each node of the MongoDB cluster. The format of this configuration is: HOSTNAME1:PORT1,HOSTNAME2:PORT2,...

For example: 192.168.0.1:27011,192.168.0.2:27012,192.168.0.2:27013

Note:

The nodes should be listed in the same order corresponding to the list of certificates specified against CA Cert File.

AWS Key ID, AWS Secret Key,Confirm Password

If you are monitoring MongoDB clusters hosted on the AWS cloud, the eG agent has to be configured with the AWS AccessKey ID and Secret Key to connect with the AWS cloud and collect the required metrics. Therefore, Specify the AWS Key ID and AWS Secret Key and confirm the password by re-typing it in the Confirm Password text box. To obtain the AWS Access key and secret key, refer to Obtaining AWS Access Key and Obtaining AWS Secret Key.

Atlas URI

MongoDB Atlas is a NoSQL Database-as-a-Service offering in the public cloud. If the target MongoDB Cluster is deployed and managed in MongoDB Atlas, then the eG agent has to be configured with the MongoDB Atlas connection URI,a unique identifier for connecting to a MongoDB replica set or a sharded cluster, in the Atlas URI text box to access the target MongoDB Cluster hosted on Atlas and collect the required metrics.

Report Manager Time

By default, this flag is set to Yes, indicating that, by default, the detailed diagnosis of this test, if enabled, will report the shutdown and reboot times of the device in the manager's time zone.

If this flag is set to No, then the shutdown and reboot times are shown in the time zone of the system where the agent is running(i.e., the system being managed for agent-based monitoring, and the system on which the remote agent is running - for agentless monitoring).

Detailed Diagnosis

To make diagnosis more efficient and accurate, the eG Enterprise 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

Is cluster?

Indicates whether/not the target MongoDB is clustered.

 

The values reported by this measure and their numeric equivalents are available in the table below:

Measure Value Numeric Value
No 0
Yes 1

Note:

This measure reports the Measure Values listed in the table above to indicate whether/not the target MongoDB is clustered. However, in the graph, this measure is indicated using the Numeric Values listed in the table above.

Cluster type

Indicates the type of cluster.

 

In MongoDB, you can have two different types of clusters for a database. it can be either replica sets or sharded cluster.

The values reported by this measure and their numeric equivalents are available in the table below:

Measure Value Numeric Value
Single instance 0
Sharded cluster 1
Replica-set cluster 2

Note:

This measure reports the Measure Values listed in the table above to indicate the type of cluster. However, in the graph, this measure is indicated using the Numeric Values listed in the table above.

Is balancer enabled?

Indicates whether/not the balancer is enabled.

 

Even if, the balancer is enabled it will not start the balancer process, but it will ensures that chunk balancing won’t be blocked when the balancer process runs the next time.

The values reported by this measure and their numeric equivalents are available in the table below:

Measure Value

Numeric Value

No 0
Yes 1

Note:

This measure reports the Measure Values listed in the table above to indicate whether/not the balancer is enabled. However, in the graph, this measure is indicated using the Numeric Values listed in the table above.

Is balancer running?

Indicates whether/not the balancer is running.

 

The values reported by this measure and their numeric equivalents are available in the table below:

Measure Value Numeric Value
No 0
Yes 1

Note:

This measure reports the Measure Values listed in the table above to indicate whether/not the balancer is running. However, in the graph, this measure is indicated using the Numeric Values listed in the table above.

Failed balancer count in last 5 attempts

Indicates the number of balancer process failed in last 5 attempts.

Number

A low value is desired for this measure.

Successful migration count

Indicates the number of successful chunk migration process.

Number

 

Failed migration count

Indicates the number of failed chunk migration process.

Number

A low value is desired for this measure.

Shards count

Indicates the number of shards in the cluster.

Number

Use the detailed diagnosis of this measure to find out the details of nodes in the shard such as Shard ID, IP, Port and Node state.