PostgreSQL Replication - Second Edition

Checking for operating system processes

Once we have checked the archives and our system views, we are ready to check for system processes. Checking for system processes might look a little crude, but it has been proven to be highly effective.

On the master, we can simply check for a process called wal_sender. On the slave, we have to check for a process called wal_receiver.

Let's check out what we are supposed to see on the master first. The following command does the job:

ps ax | grep "wal sender"

Here is the output:

9314   ??  Ss     0:00.00 postgres: wal sender process
hs ::1(61498) idle

On Linux, we can see that the process carries not only its purpose (in this case, wal_sender) but also the name of the end user and network-related information. In our ...