Find Primary

[simontuohy]

HI
I am running a django web app and I am using routing to determine which database to use (primary or backup).
To do this I have a script that gets the output of pg_autoctl show state --monitor etc --json showing all the nodes that I am running. Then the python script searches the json output to find what is the primary and it's ip.

Is there away to just get the ip of the primary from a single command to pg_autoctl ?

[DimCitus]

See #875 and also the blog post at https://www.citusdata.com/blog/2021/02/12/reconnecting-your-app-after-a-postgres-failover/ which addresses the same question. The idea is to use multi-hosts connection strings, and use the target-session-attrs=read-write to ensure that if connected first to a standby, then the connection is dropped and attempted again with the next host on the list, until a primary is reached.

If the following connection string snippet makes sense when using Django (I just don't know), then I think it would make sense to allow for a specific switch such as pg_autoctl show uri --django that would output just that:

DATABASES = {
    'default': {
        'ENGINE': _db_engine,
        'NAME': environment.DB,
        'USER': environment.DB_USER,
        'PASSWORD': environment.DB_PASSWD,
        'HOST': environment.DB_HOSTS,
        'CONN_MAX_AGE': 0,
        'PORT': environment.DB_PORTS,
        'OPTIONS': {
            'application_name': f'applicationname',
            'options': f'-c search_path={environment.DB_SCHEMA}',
            'target_session_attrs': 'read-write',
            'connect_timeout': '30',
            'keepalives_idle': '300',
            'keepalives_interval': '75'
        },
        'ATOMIC_REQUESTS': True
    }
}

[simontuohy]

Thank you for your reply. This seems like a much better solution. Thanks again for the software