Archive for ‘database administration’

4 May, 2015

SCALE 13x and “You are not the database Superuser”

by gorthx

Another followup from my talk at SCALE 13x.

This isn’t to pick on RDS in particular; you’ll likely have these or similar issues with other “database as managed service” options.

Specific problems you should be aware of:

1a – As I discussed in my post about upgrading an RDS db to Pg 9.4, you can’t pg_dumpall; access to roles & credentials is restricted.
1b – … which means you can’t extract roles & credentials. (I’m told the RDS devs are working on a way to handle this.)

2 – Lots of in pg_stat_activity. You can’t see what the actual superuser is doing, of course; so far this is an annoyance more than a true problem, because I wouldn’t be able to smash a query the actual superuser is running, anyway.

3 – You can’t VACUUM a database, only individual tables.

4 – Oops: “FATAL: remaining connection slots are reserved for non-replication superuser connections”. This does not include you :), so you are effectively locked out of your instance. You can try calling Amazon support for this; my experience with this was that even a request for information about existing connections had to be escalated, and I was told they wouldn’t terminate connections for me. So you’re looking at killing them from the app side, or restarting the instance (with a higher max_connections, perhaps). This makes troubleshooting this issue particularly challenging.

5 – If you’re fond of using SET ROLE [rolename] to troubleshoot, you have to do the extra step of adding yourself to the role:
gabrielle=> SET ROLE db_rw;
ERROR: permission denied to set role "db_rw"
gabrielle=> GRANT db_rw TO gabrielle ;
GRANT ROLE
gabrielle=> SET ROLE db_rw;

2 March, 2015

SCALE 13x and “Yes, you still need a DBA”

by gorthx

Last weekend, I got to give a talk at SCALE‘s LA PgDay for the second year in a row. PGDay was two days this year, and unfortunately I had to miss Thursday – looks like I missed some great talks, too, dangit!

I reprised my RDS talk from PDXPUG’s January meeting. It certainly sparked some interesting discussions later.

(If you are too shy to ask questions in my talk, it is totally ok to come up afterwards and ask them, or stop by the Postgres booth & talk to me. That’s what I’m there for!)

I mentioned something in my talk that I want to throw out here because it’s been coming up in conversations recently:

If you have production data that you want to protect, you need a database adminstrator. Even if you are using a managed database service (RDS, Heroku, what have you), you need someone to:

– Choose an appropriate instance size for your workload
– Configure Postgres appropriately (as much as is possible on a managed service, anyway)
– Secure and audit databases
– Ensure data quality
– Tune queries (e.g. figure out what in [Sam Hill] the ORM is doing)
– Mentor devs
– …add your own here…

None of these tasks go away just because you’re using a managed database solution. You still need someone who can hop in there & get her hands dirty. You may disagree, but please keep this list handy http://www.postgresql.org/support/professional_support/.