MongoDB Replication Lag Alert - Issues

Problem 1

• Install PMM v2.42.0

• Connect it to the portal so that you will get additional alert rules

• Identify the “MongoDB Replication Lag is high“ from the “Alert rule templates” tab and click on “+” to add this alert in your PMM

• From the “alert rules” tab, open the alert by clicking by clicking on the command “view” related to this alert

• As soon as it is opened, you will see the error of the attached image (or, you will not see it in the fixed version)

Problem 2

• After the alert is added

• You have to simulate a lag on one of your replica. For instance, you can use cfg.members[1].secondaryDelaySecs = 20 - where the [1] is the ID of the node you want to increase the lag on. This ID can be found using rs.conf() . You can verify that the lag increased with rs. printSecondaryReplicationInfo() 

• After the lag increased you should get the alert (ensure it is higher than the threshold you have)

• Verify that instead of getting “[ var='A' labels={cluster=***, name=***, set=***} value=*** ] you get something like

  • MongoDB Replication Lag on your_node_here (replicaSet your_replica_set_here) is above the defined threshold of your_threadshold_here secs. Current value is 20secs.

No new doc needed - this is a fix. However, in general, we have this: and is missing this alert - should be added