Chapter 8. Performing a switchover with repmgr

Miscellaneous: Check for Sync in standby

In Chicago(primary) server as postgres user :
Create a Database , a table and insert set of records

Bash
# create a database called lendingapp
createdb -U postgres lendingapp

# create a schema called myschema
psql -U postgres -d lendingapp -c "CREATE SCHEMA myschema;"

# create a table called employees
psql -U postgres -d lendingapp -c "CREATE TABLE myschema.employees (id SERIAL PRIMARY KEY,name TEXT NOT NULL,salary NUMERIC);"

# insert few sample records
psql -U postgres -d lendingapp -c "INSERT INTO myschema.employees (name, salary) VALUES
    ('Alice', 60000),
    ('Bob', 75000),
    ('Charlie', 50000);"
    
# check for the records in the table
psql -U postgres -d lendingapp -c "select * from myschema.employees";
screenshot

In Boston(standby) server as postgres user

Bash
# check for the records in the table
psql -U postgres -d lendingapp -c "select * from myschema.employees";

You should be seeing the same records from Primary (chicago) is being shipped and applied at the Standby(boston) server.

8.1. Preparing for switchover

we will follow the steps as per preparing-for-switchover
Docs to read for pg_rewind , pg_rewind_in_repmgr
On both Primary & Standby (chicago & boston) host as postgres user:

Bash
repmgr -f /etc/repmgr/16/onboarding_repmgr.conf  node service --list-actions --action=stop
repmgr -f /etc/repmgr/16/onboarding_repmgr.conf  node service --list-actions --action=start
repmgr -f /etc/repmgr/16/onboarding_repmgr.conf  node service --list-actions --action=restart
Bash
psql -U postgres -c "SHOW wal_log_hints;"

psql -U postgres -c "ALTER SYSTEM SET wal_log_hints = 'on';"

sudo systemctl restart postgresql-onboarding

psql -U postgres -c "SHOW wal_log_hints;"
screenshot

chicago – screenshot

boston – screenshot

On Standby (boston) as postgres user – dry run to check if standby is ready for switchover

Bash
repmgr standby switchover -f /etc/repmgr/16/onboarding_repmgr.conf --dry-run
8.2. Executing the switchover command

we will follow the steps as per Executing the switchover command
In Standby (boston) host as postgres user :

Bash
repmgr -f /etc/repmgr/16/onboarding_repmgr.conf standby switchover
screenshot
Bash
repmgr -f /etc/repmgr.conf cluster show
screenshot

Congratulations on the switchover test ,
now the primary is boston and standby is chicago

For the below topics, read the official documentation
8.3. Caveats
8.4. Troubleshooting switchover issues

Chapter 5. Cloning standbys
Chapter 9. Event Notifications

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