What does it mean when a PostgreSQL process is "idle in transaction"?
On a server that I'm looking at, the output of "ps ax | grep postgres" I see 9 PostgreSQL processes that look like the following:
postgres: user db 127.0.0.1(55658) idle in transaction
Does this mean that some of the processes are hung, waiting for a transaction to be committed? Any pointers to relevant documentation are appreciated.
The PostgreSQL manual indicates that this means the transaction is open (inside BEGIN) and idle. It's most likely a user connected using the monitor who is thinking or typing. I have plenty of those on my system, too.
If you're using Slony for replication, however, the Slony-I FAQ suggests idle in transaction may mean that the network connection was terminated abruptly. Check out the discussion in that FAQ for more details.
As mentioned here: Re: BUG #4243: Idle in transaction it is probably best to check your pg_locks table to see what is being locked and that might give you a better clue where the problem lies.
Related
I have a Postgres installed in a Centos and another application is using Postgres the save data.
For sometime, and I can't find the reason, all the database tables become empty on the weekends.
I have been searching a lot to try to find some clues of the reason of that behaviour, but logs are not giving me that info.
I am pretty sure the application is not executing anything to clean the records, my thoughts are pointing to some process for some reason in the Postgres side.
The pg_log only shows this warning the day it happens:
HINT: Consider increasing the configuration parameter "checkpoint_segments".
LOG: checkpoints are occurring too frequently (11 seconds apart)
Apart from that I have no other clues.
Performing a VACUUM ANALYZE VERBOSE it says there is no dead data so it has nothing to delete.
Can you tell me what should I look to get the reason? Should it be any Postgres process to do it?
LOG: checkpoints are occurring too frequently (11 seconds apart)
This log message should also include all the information log_line_prefix tells it to include. So you should set log_line_prefix to include more information, like application name (voluntarily supplied by the client), database username, and host name/IP from which the connection came.
But perhaps more directly at issue, if things are connecting to your database and doing things you don't understand or approve of, it is time to change your passwords.
I have this issue that is driving me nuts. Despite all my efforts, I am not able to force my postgres server to shut down. I have followed those instructions : http://www.question-defense.com/2008/10/17/pg_ctl-server-does-not-shut-down-force-postgres-to-shutdown
but still, nothing happens and all I got in the shell is
waiting for server to shut down............................................................... failed
pg_ctl: server does not shut down
Any help much appreciated.
Update: Checking the logs, I have this recurring error :
LOG: checkpoints are occurring too frequently (25 seconds apart)
HINT: Consider increasing the configuration parameter "checkpoint_segments".
After giving it a lot of thoughts especially on the way I installed it at the first place, I realize that I set up the install so the daemon would launch postgres at the start of my machine. Thus, any manual killing would simply result in the recreation of those process by the same daemon.
To resolve this problem you need to stop the daemon from working using launchctl and remove a .plist file in your postgres directory.
Good luck if you face the same problem.
You probably run with the default setting of "checkpoint_segments = 3", that produces the warnings. Your database does many writes, right? It takes some time to write all of this to disk, and your database is quite busy rotating the logfiles, instead doing real work.
If you increase checkpint_segments, you will see performance improvements, and less I/O.
For further readings: https://wiki.postgresql.org/wiki/Tuning_Your_PostgreSQL_Server
I was debugging a PostgreSQL 9.2 database corruption issue (on Solaris, but I doubt it matters) recently, and I found that we could reproduce it reliably if the client died in the middle of a transaction and then I shut down PostgreSQL by doing pkill postgres (which basically sends SIGTERM to every running postgres process). If instead we did pkill -QUIT postgres to send SIGQUIT, the database would shut down cleanly and no corruption would occur.
Based on the PostgreSQL 9.2 docs, I think that SIGTERM should be 100% expected by the database server, so why is it not safe to shut down like this? Is it a bug in PostgreSQL, or could I be doing something (configuration, etc.) that would allow the corruption to occur?
I don't think sigterm is what is causing your problem. Again, recommend you ask on dba.stackexchange instead.
If the client dies in the middle of a transacction, then the problem is that the network connection hangs? And then when you kill it you get corruption during WAL replay?
This is a complicated area to troubleshoot but here are some places to begin:
What is going on conncurrently when this happens? What sort of transaction commit load?
How often do WAL logs normally get rotated?
It is possible you could be running into a rare, obscure bug with PostgreSQL (possibly somewhere between the db, kernel, and filesystem), but if so please start by upgrading to latest 9.2 and try to reproduce again. Term and even kill signals are supposed to be 100% safe on PostgreSQL so if you are seeing database corruption, that is not expected.
I've been a MySQL guy, and now I'm working with Postgres so I am learning. Wondering if someone can tell me why my postgres process on my macbook is sending and receiving data over my network. I am just noticing this is happening for the first time - so maybe it's been going on before this and I just never noticed postgres does this.
What has me a bit nervous, is that I pulled down a production datadump from our server which is set up with replication and I imported it to my local postgres db. The settings in my postgresql.conf don't indicate replication is turned on. So it shouldn't be streaming out to anything, right?
If someone has some insight into what may be happening, or why postgres is sending/receiving packets, I'd love to hear the easy answer (and the complex one if there's more to what's happening).
This is a postgres install via Homebrew on MacOSX.
Thanks in advance!
Some final thoughts: It's entirely possible, I guess, that Mac's activity monitor also shows local 'network' traffic stats. Maybe this isn't going out to the internets.....
In short, I would not expect replication to be enabled for a DB that was dumped from a server that had it if the server to which it was restored had no replication configured at all.
More detail:
Normally, to get a local copy of a database in Postgres, one would do a pg_dump of the remote database (this could be done from your laptop, pointing at your server), followed by a createdb on your laptop to create the database stub and then a pg_restore pointed at the dump to populate its contents. [Edit: Re-reading your post, it seems like you may perhaps have done this, but meant that the dump you used had replication enabled.)]
That would be entirely local (assuming no connections into the DB from off-box), so long as you didn't explicitly setup any replication or anything else that would go off-box. Can you elaborate on what exactly you mean by importing with replication?
Also, if you're concerned about remote traffic coming from Postgres, try running this command a few times over the period of a minute or two (when you are seeing the traffic):
netstat | grep postgres
In general, replication in Postgres in configured at a server level, and has to do with things such as the master server shipping WAL files to the standby server (for streaming replication). You would have almost certainly have had to setup entries in postgresql.conf and pg_hba.conf to ensure that the standby server had access (such as a replication entry in the latter conf file). Assuming you didn't do steps such as this, I think it can pretty safely be concluded that there's no replication going on (especially in conjunction with double-checking via netstat).
You might also double-check the Postgres log to see if it's doing anything replication related. In a default install, that'd probably be in /var/log/postgresql (although I'm not 100% sure if Homebrew installs put it somewhere else).
If it's UDP traffic, to and from a high port, it's likely to be PostgreSQL's internal statistics collector.
These are pre-bound to prevent interference and should not be accessible outside of PostgreSQL.
I am performing a bulk copy into postgres with about 80GB of data.
\copy my_table FROM '/path/csv_file.csv' csv DELIMITER ','
Before the transaction is committed I get the following error.
Server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
In the PostgreSQL logs:
LOG:server process (PID 21122) was terminated by signal 9: Killed
LOG:terminating any other active server processes
WARNING:terminating connection because of crash of another server process
DETAIL:The postmaster has commanded this server process to roll back the current transaction and exit, because another server process exited abnormally and possibly corrupted shared memory.
HINT: In a moment you should be able to reconnect to the database and repeat your command.
Your backend process receiving a signal 9 (SIGKILL). This can happen if:
Somebody sends a kill -9 manually;
A cron job is set up to send kill -9 under some circumstances (very unsafe, do not do this); or
the Linux out-of-memory (OOM) killer triggers and terminates the process.
In the latter case you will see reports of OOM killer activity in the kernel's dmesg output. I expect this is what you'll see in your case.
PostgreSQL servers should be configured without virtual memory overcommit so that the OOM killer does not run and PostgreSQL can handle out-of-memory conditions its self. See the PostgreSQL documentation on Linux memory overcommit.
The separate question "why is this using so much memory" remains. Answering that requires more knowledge of your setup: how much RAM the server has, how much of it is free, what your work_mem and maintenance_work_mem settings are, etc. It isn't a very interesting problem to look into until you upgrade to the current PostgreSQL 8.4 patch release to make sure the problem isn't one that's already fixed.