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Re: Cron DB Bounce causes index problems && Help rotating logs

From: "Chris Hoover" <revoohc(at)sermonaudio(dot)com>
To: "A(dot)M(dot)" <agentm(at)themactionfaction(dot)com>,<pgsql-admin(at)postgresql(dot)org>
Subject: Re: Cron DB Bounce causes index problems && Help rotating logs
Date: 2005-01-14 23:02:28
Message-ID: 41E84F84.1090201@sermonaudio.com (view raw or flat)
Thread:
Lists: pgsql-admin
We are doing "real" backups using pg_dump every night.  The problem is
that we need to provide for an absolute minimum data loss.  We are using
the logging of the sql for this.  Right now, we can not change the
version of the db we are on (7.3.4), so we are trying to make the most
of what we have.

All the pg_dump allows you to do is to give a starting point.  You would
still lose any work done since the last backup.

A.M. wrote:

> What you are trying to do is emulate point-in-time recovery (WAL 
> backup) which is available in 8.0. The problem you face is that sql 
> logging just does that- logging all input. That is, if I connect to 
> your DB and send the query "skdfjhsdkf"- that will end up in  the logs 
> too. In addition, there is a limit on the number of characters logged 
> from the statement.
>
> The solution is to use pg_dump for real backups or upgrade to 8.0 for 
> PITR. Good luck.
>
> On Friday, January 14, 2005, at 03:16 PM, Chris Hoover wrote:
>
>> Hi all,
>>
>> We are having an issue here trying to automate our db log rotations.  
>> We were using the Apache rotatelogs program and we thought it was 
>> working fine.  However, when we had a server crash and had to recover 
>> and roll forward using the postgresql logs (we are logging all sql), 
>> we discovered that some of the sql records in the log were being over 
>> written.  This has caused us to go back to just having postgresql log 
>> directly to the drives.  (The problem with rotatelogs looked like 
>> this "[2005-01-14 08:00:01] [123]  LOG: query: select * fr[2005-01-14 
>> 08:00:01] ....")
>>
>> Anyway, we are now manually rotating the logs.  We tried to rotate 
>> the logs via a simple script and cron, but we ended up causing 
>> strange index issues.  The data would be in the tables and would show 
>> if a table scan was forced.  But many tables would not show the data 
>> if an index scan (esp. if the primary key was used) was used.  We 
>> also had issues with system allowing records to be inserted that 
>> violated the primary key.
>>
>> Manually logging into the servers and running the same script from 
>> the shell prompt works fine and does not cause any index issues.
>>
>> Any ideas on what is going on here?  We do not have any postgresql 
>> related environmental variables set in the shell.  Do we need to 
>> execute a db bounce via cron with a "special" call from cron?
>>
>> Also, has anyone else seen the rotatelogs issue?
>>
>> Is there a better way to rotate the logs w/o bouncing the db every 
>> night?  Due to recovery requirements, we must have the sql logged to 
>> the postgresql log.  These logs grow to between 2 and 5 GB every 
>> day.  Running for more than 2 days without rotating the logs tends to 
>> cause a noticable slowdown to our users.
>>
>> Any help would be appreciated.
>>
>> Chris
>>
>> P.S.
>>
>> Here is the cron line:
>> 01 20 * * * /pgsql/tmp/bin/rotate_logs.sh 50001
>>
>> Here is the rotate_log.sh script:
>>
>> source ~postgres/etc/dba.profile
>>
>> PORT=$1
>>
>> LOGPATH=${LOG_PATH}/${PORT}/pg_log
>>
>> echo "`date` - `hostname` - log rotation started" | mail -s 
>> "`hostname` rotation" $DBAPAGER
>>
>> ## shutdown the database
>> ${POSTGRES_BIN}/pg_ctl -D ${DB_PATH}/${PORT} -m fast stop > 
>> ~postgres/db_${PORT}_stop.log 2>&1
>>
>> STOPPED=`cat ~postgres/db_${PORT}_stop.log | grep "postmaster 
>> successfully shut down" | wc -l`
>> if [ $STOPPED != 1 ]
>> then
>>   echo "POSTGRES DID NOT STOP" | mail -s "`hostname` stop fail" 
>> $DBAPAGER
>>   exit
>> fi
>>
>> sleep 150
>>
>> mv $LOGPATH/postgres.log $LOGPATH/postgres.log.`date +%m%d%y%H%M`
>>
>> sleep 150
>>
>> ${POSTGRES_BIN}/pg_ctl -D ${DB_PATH}/${PORT} -l 
>> ${LOGPATH}/postgres.log start > ~postgres/db_${PORT}_start.log 2>&1
>> STARTED=`grep "successfully start" ~postgres/db_${PORT}_start.log | 
>> wc -l `
>> if [ $STARTED != 1 ]
>> then
>>   echo "POSTGRES DID NOT START" | mail -s "`hostname` start fail" 
>> $DBAPAGER
>> fi
>>
>> echo "`date` - `hostname` - log rotation finished" | mail -s 
>> "`hostname` rotation" $DBAPAGER
>>
>>
>> Here is the dba.profile file:
>> DBAPAGER=<my pager number>
>>
>> POSTGRES=/pgsql/
>>
>> POSTGRES_BIN=${POSTGRES}/bin
>>
>> DB_PATH=/data
>>
>> LOG_PATH=/data
>>
>>
>>
>> ---------------------------(end of broadcast)---------------------------
>> TIP 4: Don't 'kill -9' the postmaster
>
>
>
>
>




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