Once we have checked out 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 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 us check what we are supposed to see on the master first:

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

On Linux we can see that the process does not only carry its purpose (in this case, wal_sender) but also the name of the end user as well as network-related information. In our case we can see that somebody has connected from localhost through port 61498.

The situation on the slave is pretty simple as well:

9313   ??  Ss     0:00.00 postgres: wal receiver process     

All we see is a process, informing us that we are consuming XLOG.

If both processes are here, you have got a pretty good indicator already that your replication setup is working nicely.