Обсуждение: Giving postgres roles 'sudo'-like access

I need to have postgres role to be able to cancel queries run by that
same role.

I know that I can kill the client connection that started the query, but
I also need to have that role connect to postgres and kill some of it's
running queries.

It's on postgres 9.1.1, running on Debian Squeeze.

One idea that comes to mind is to have a special user account on the box
which would have sudo privileges to the script which will issue 'sh
postgres -c 'psql -c "select pg_cancel_backend(<pid>)"', but before that
run checks that <pid> is actually owned by correct role, etc, etc. But,
all that seems very fishy.

Has anyone had similar requests, and maybe solved them somehow?

    Mario

On 12/19/11 10:04 AM, Mario Splivalo wrote:
> I need to have postgres role to be able to cancel queries run by that
> same role.
>
> I know that I can kill the client connection that started the query, but
> I also need to have that role connect to postgres and kill some of it's
> running queries.
>
> It's on postgres 9.1.1, running on Debian Squeeze.
>
> One idea that comes to mind is to have a special user account on the box
> which would have sudo privileges to the script which will issue 'sh
> postgres -c 'psql -c "select pg_cancel_backend(<pid>)"', but before that
> run checks that<pid>  is actually owned by correct role, etc, etc. But,
> all that seems very fishy.
>
> Has anyone had similar requests, and maybe solved them somehow?
Yes.

First of all, you really don't want to do this.  If there's any other way, find it.

In our case, we use a third-party library that sometimes gets stuck on problems that would take a virtually infinite
timeto solve, and for reasons having to do with NP-complete theory, you can't easily detect them ahead of time.  So.... 

Backend Postgres processes run as the Postgres user, so they have permission to kill each other.  You write an add-on
functionthat just kills a process: 

   select my_kill_backend(pid);

Naturally, this is very dangerous. There are all sorts of security implications.  You want to use signal 2 or 15, not
9. And so forth. 

Craig

On 12/19/2011 07:46 PM, Craig James wrote:
> Backend Postgres processes run as the Postgres user, so they have
> permission to kill each other.  You write an add-on function that just
> kills a process:
>
>   select my_kill_backend(pid);
>
> Naturally, this is very dangerous. There are all sorts of security
> implications.  You want to use signal 2 or 15, not 9.  And so forth.

That 'my_kill_backend' actually calls kill, not pg_cancel/terminate_backend?

I'm thinking into creating this function, and granting particular role
access to it, and then make sure, in the function, that it can kill only
processes 'owned' by that role.

    Mario

On 12/19/2011 01:04 PM, Mario Splivalo wrote:
> I need to have postgres role to be able to cancel queries run by that
> same role.
>

This feature is close to commit as a new one for PostgreSQL 9.2:
http://archives.postgresql.org/message-id/4EEB3A2B.8090102@2ndQuadrant.com
http://archives.postgresql.org/pgsql-hackers/2011-12/msg00822.php

You might use some of that code and make your own pg_cancel_backend-like
function that loads into the database.

--
Greg Smith   2ndQuadrant US    greg@2ndQuadrant.com   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support  www.2ndQuadrant.us