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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