Subject: Postgres is still not working...

From: [email-masked] (Marc Mazuhelli)
Date: Wed, 20 Nov 91 17:13:24 EST

Hi there,

I'm the one who sent a message yesterday about a problem with
Postgres.

This morning, after trying a lot of different things, I decided to
restore the data directory from the previous day's backups.  It
worked ... the backend startend responding again.

But at the end of the afternoon, we started getting error messages
again.  Here is a sample session:

========================

postgres@roselin (~) monitor
Welcome to the C POSTGRES terminal monitor

Go 
* retrieve (pg_user.all) \g

Query sent to backend is "retrieve (pg_user.all) "
Error: No response from the backend, exiting...

postgres@roselin (~)

========================

Killing and restarting the postmaster (after waiting for the port to
be freed) didn't help.

A retreive (pg_user.all) entered while talking directly to the backend
works.

Before a few days ago we were using Postgres very lightly, and only
one person at a time.  Now a bunch of students are using it, and the
problems have started since that time.  For the time being, we have
maybe 3-5 people each using their own mini database at the same time.
The number of users could grow though (but it won't if it keeps
crashing like it does now...).

It seems that we have a problem with multiuser access to Postgres.  I
thought that version 3 had fixed these problems...  If anyone can help
me with this problem, I would appreciate it as I'm stuck...

Thank you.

-- 
{  Marc Mazuhelli                 |  analyst in charge of computer labs     }
{  internet: [email-masked]   |  Departement of math and comp. science  }
{  <this space intentionaly ..    |  Universite de Sherbrooke               }
{                 ... left blank> |  Sherbrooke, Quebec, Canada             }

---

From: postarch (Postgres Mailing Archive)
Date: Wed, 20 Nov 91 14:53:03 PST

> crashing like it does now...).

When a backend crashes the postmaster detects the condition and signals
all other currently running backends to die gracefully.  This is done
because it's possible that one of the backends that crashed could have
corrupted shared buffers and you don't want any of that to make it to
the disk.  From the problems you describe it sounds like this is what
might be happening.  Has anyone received an error message that tries
to explain _why_ it is dying? Something like:

  "I have been signalled by the postmaster."
  "Some backend process has died unexpectedly and possibly"
  "corrupted shared memory.  The current transaction was"
  "aborted, and I am going to exit.  Please resend the"
  "last query. -- The postgres backend"

If not then there is something wrong with the clean up utlities at your
installation.

> me with this problem, I would appreciate it as I'm stuck...

version 3 fixed many of the multi-user problems. It did not apparently
fix all of them.  Its a little difficult to simulate all situations that
could arise in a multi-user installation.

Jeff Meredith
[email-masked]