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MongoDB for Oracle DBA’s Part 10 : Switchover & Role Transition between Primary and Secondary

In MongoDB as like Oracle Dataguard switchover is possible to but in different way.

You can ask Primary to stepdown and let nodes elect a new primary in replicaset. This can be done using rs.stepDown() method.

Before stepping down primary, one must know the below

The procedure blocks all writes to primary while it runs
Terminates all sessions and running jobs, index rebuilts etc
Disconnects all connections
If the wait period to elect a new primary exceeds then primary will not step down.

Let's take a look of the same,

I have opened three sessions and in one sessions querying a table which is running (the right top most one in screenshot)
In another session tail the log file so can understand what happens when a step down is initiated
In the session that left side , initiated the stepdown of primary , immediately disconnects the current session and also the session that running a query on the database (top left side)
In the log it shows the primary is transitioning to secondary
as per rs.status() the 47018 (original primary) becomes secondary.

Screenshot

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