PostgreSQL Cluster Replication RPO Test

The PostgreSQL Cluster Replication RPO Test helps administrators assess the effectiveness of data replication across the PostgreSQL cluster, particularly focusing on the lag between primary and standby nodes. This test monitors the amount of data that has yet to be replicated to standby nodes by reporting minimum, maximum, and average replication lag sizes. These measures are crucial for evaluating replication health and ensuring that standby nodes are nearly in sync with the primary. Significant lag may indicate network issues, I/O bottlenecks, or insufficient replication tuning, which can put data consistency and failover readiness at risk. By continuously tracking replication lag, this test aids in identifying nodes that are falling behind and helps optimize replication settings. Proactive detection of high lag conditions enables administrators to maintain low recovery point objectives (RPO), reduce data loss risks, and improve overall cluster reliability and disaster recovery preparedness.

Target of the test : A PostgreSQL Cluster

Agent deploying the test: An external agent

Outputs of the test :One set of results for each node on the target PostgreSQL cluster being monitored.

Configurable parameters for the test
Parameter	Description
Test period	How often should the test be executed
Host	The IP address of the host for which this test is to be configured.
Port	The port on which the server is listening. The default port is 5432.
Username	To monitor a PostgreSQL cluster, you must manually create a dedicated database user account on each PostgreSQL instance that you wish to monitor. To know how to create such a user based on where the target PostgreSQL cluster is installed (whether on-premises or hosted on Cloud), refer to How does eG Enterprise Monitor PostgreSQL Server?.
Password	The password associated with the above Username (can be ‘NULL’). Here, ‘NULL’ means that the user does not have any password.
Confirm Password	Confirm the Password (if any) by retyping it here.
DB Name	The name of the target database to connect to. The default is “postgres”.
SSL	This indicates that the eG agent will communicate with the PostgreSQL cluster via HTTPS or not. By default, this flag is set to No, as the target PostGreSQL database is not SSL-enabled by default. If the target cluster is SSL-enabled, then set this flag to Yes.
Verify CA	If the eG agent is required to establish an encrypted connection with the target PostgreSQL cluster by authenticating the server's identity through verifying the server CA certificate, set Verify CA flag to Yes. By default, this flag is set to No.
CA Cert File	This parameter is applicable only if the target PostgreSQL cluster is SSL-enabled.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\PostGreQL-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 PostgreSQL Cluster then, provide a comma-separated list of full path to the certificates in CA Cert File text box: For example:C:\app\eGurkha\JRE\lib\security\postgresql-test-ca.crt,C:\app\eGurkha\JRE\lib\security\postgresql-test-ca2.crt,C:\app\eGurkha\JRE\lib\security\postgresql-test-ca3.crt Specify the full path to the certificate file of the target PostgreSQL Cluster if a single certificate is used to access all nodes. For example: C:\app\eGurkha\JRE\lib\security\postgresql-test-ca.crt
Client Cert File	This parameter is applicable only if the target PostgreSQL Cluster is SSL-enabled. In order to collect metrics from the target PostgreSQL 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.
Client Key File	A client key file refers to a file containing the private key that corresponds to the public key used by a client. Provide full path of the file containing client key.
Include Available Nodes	In the Include Available Nodes text box, provide a comma-separated list of all the available nodes to be included for monitoring. This way, the test monitor and collect metrics from all the available nodes in the cluster. By default, this parameter is set to none. The format of this configuration is: HOSTNAME:PORT, for example, 172.16.8.136:3306,172.16.8.139:3306
DD Frequency	Refers to the frequency with which detailed diagnosis measures are to be generated for this test. The default is 1:1. This indicates that, by default, detailed measures will be generated every time this test runs, and also every time the test detects a problem. You can modify this frequency, if you so desire. Also, if you intend to disable the detailed diagnosis capability for this test, you can do so by specifying none against DD frequency.
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
Replication lag size	Indicates the amount of data that is yet to be replicated from the primary node to this standby node.	MB	This measure is not reported for Summary descriptor. This measure is applicable only for the standby/slave node. A consistently high lag size may indicate replication delays, slow network or disk I/O, or replica overload. This could compromise data consistency and delay failover readiness. Ideally, this value should be low and stable. The detailed diagnosis of this measure gives the PID, User OID, User name, Application name, Sent location and Replay location.
Maximum replication lag size	Indicates the maximum replication lag size across all replicas in the cluster.	MB	This measure is reported only for the Summary descriptor. A high maximum lag suggests that at least one replica is significantly out of sync with the primary. This can impact recovery point objectives (RPOs) and pose risks in disaster recovery or failover scenarios. Using the detailed diagnosis, the current node with maximum replication lag size in the cluster can be identified.
Minimum replication lag size	Indicates the minimum replication lag size among all replicas in the cluster.	MB	This measure is reported only for the Summary descriptor. A low or zero minimum lag is a good sign, indicating that at least one replica is nearly caught up. Comparing minimum and maximum lag sizes helps assess the consistency of replication performance across the cluster. Using the detailed diagnosis, the current node with minimum replication lag size in the cluster can be identified.