Re: Cannot connect to one specific postgres database on a server

Yes, you are correct, but you can have multiple _clusters_ with
different ports,
so there would a separate postmaster for each cluster on a
server/machine with
a different port.

Keep in mind the port for the database was not specified in the original
description
so it s entirely possible the unaccessible database was due to the
postmaster for that
port being down.

BTW, we do have several servers/systems/machines running multiple
postmasters on multiple ports
so even of my "understanding" of postgresql is different than yours,
I must be doing something right. :)

-----Original Message-----
From: Andy Shellam (Mailing Lists)
[mailto:andy(dot)shellam-lists(at)mailnetwork(dot)co(dot)uk]
Sent: Monday, January 22, 2007 2:35 PM
To: Melvin Davidson
Cc: Matt Busby; pgadmin-support(at)postgresql(dot)org
Subject: Re: [pgadmin-support] Cannot connect to one specific postgres
database on a server

Melvin,

Your understanding of how to set up a PostgreSQL server is wrong.
One server process (it was called the postmaster up to 8.1, since 8.2
it's now called the Server process) can run any number of databases, you
don't need multiple postmasters for multiple databases or your server is
going to die quickly when you start adding more and more databases, not
to mention the admin overhead of managing all the ports, and handling
backups.

Using PgAdmin you connect to a particular server, connecting to the
"postgres" database by default, then once you're connected to a
PostgreSQL server, you choose which database/s to connect to.

Melvin Davidson wrote:
> When you say "The site that is using the database is also running
> fine", Do you mean users are accessing that database? If so, that
> check the port # you are using to connect.
This should be 5432 unless specifically changed during the build.
> You might also try adding a new server connection to that database in
> pgadmin.
If the OP can connect to one database, he should be able to connect to
another on the same server.
> postmaster is the postgresql process that is needed to access the
> database.
> Telnet to the server and do
> ps -ef | grep postmaster
> You should see something like
> admin 2986 1 0 Jan12 ? 00:00:00
> /home/pgsql/postgresql-8.0.6/bin/postmaster
There are various processes for PostgreSQL, such as the auto-vacuum,
stats-gatherer and background writer processes.
> You will have a process for each database on a separate port.
No - if yours is set up this way, your server is going to be
unnecessarily overloaded. One PostgreSQL postmaster/server process can
run any number of databases on one port. It's only advisable to run more
than one PostgreSQL server process on different ports if you want to run
two different versions of PostgreSQL, or want to dump one set of
databases to a different server (popular during a major version
upgrade.)
> If all postmaster(s) are running, then perhaps someone or
> something(gremlins) :) has modified the pg_hba.conf file in the
> $PGDATA directory?
If the OP can connect to one database on the same server, there's no
reason (aside from data corruption) why he shouldn't be able to connect
to the required one, especially if nothing has changed - he'd get an "no
pg_hba.conf entry for <such and such> if the pg_hba.conf file was
mis-configured.

I'd advise the OP to either turn on debug logging in PgAdmin and
re-create the crash, or dump the database from the server, restore as a
different database on the same machine and try to connect to it again.
Matt, if you follow this method, it won't take the database down as long
as you restore the dump to a different database name. If it works, I'd
then advise to dump the original database again, drop it and re-create
it. That will take it down for as long as the dump takes place.

Hope this helps!

Andy.
> ----------------------------------------------------------------------
> --
> *From:* Matt Busby [mailto:busby(at)condodomain(dot)com]
> *Sent:* Monday, January 22, 2007 12:10 PM
> *To:* Melvin Davidson
> *Cc:* pgadmin-support(at)postgresql(dot)org
> *Subject:* RE: [pgadmin-support] Cannot connect to one specific
> postgres database on a server
>
> I can telnet to the database and query the database.... The site that
is
> using the database is also running fine
>
> Not sure what postmaster is.... How can I check if its running? I did
a
> google search for it, but not sure how to check it on my postgres db
> server
>
> I don't get any errors using telnet ... I can access the db every
other
> way it seems, just using postgres
>
> If I restore/rebuild the db, will that cause the database to go down
> at all? I will try anything to get pgadmin working with the db... it
> makes my life SOOO much easier!
>
> Thanks very much for taking the time to help me with this issue! Much
> appreciated!
>
> Matt
>