Re: system views for walsender activity

Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> I'm of the opinion that this is a 9.1 problem. It needs more thought
> than we can put into it now --- one obvious question is what about
> monitoring on the slave side? Another is who should be able to see the
> data?

Sure. We should research user's demands for monitoring and management
of replication. I'll report some voices from users as of this moment:

* Managers often ask DBAs "How long standby servers are behind the master?"
We should provide such methods for DBAs. We have pg_xlog_location()
functions, but they should be improved for:
- The returned values are "xxx/yyy" texts, but more useful information
is the difference of two values. Subtraction functions are required.
- For easier management, the master server should provide not only
sent/flush locations but also received/replayed locations for each
standby servers. Users don't want to access both master and slaves.

* Some developers want to pause and restart replication from the master
server. They're going to use replication for application version
managements. They'll pause all replications, and test their new features
at the master, and restart replication to spread the changes to slaves.

Regards,
---
Takahiro Itagaki
NTT Open Source Software Center