6.5. mkservice

6.5.1. slon-mkservice.sh

Create a slon service directory for use with svscan from daemontools. This uses multilog in a pretty basic way, which seems to be standard for daemontools / multilog setups. If you want clever logging, see logrep below. Currently this script has very limited error handling capabilities.

For non-interactive use, set the following environment variables. BASEDIR SYSUSR PASSFILE DBUSER HOST PORT DATABASE CLUSTER SLON_BINARY If any of the above are not set, the script asks for configuration information interactively.

• BASEDIR where you want the service directory structure for the slon to be created. This should not be the /var/service directory.

• SYSUSR the unix user under which the slon (and multilog) process should run.

• PASSFILE location of the .pgpass file to be used. (default ~sysusr/.pgpass)

• DBUSER the postgres user the slon should connect as (default slony)

• HOST what database server to connect to (default localhost)

• PORT what port to connect to (default 5432)

• DATABASE which database to connect to (default dbuser)

• CLUSTER the name of your Slony1 cluster? (default database)

• SLON_BINARY the full path name of the slon binary (default which slon)

6.5.2. logrep-mkservice.sh

This uses tail -F to pull data from log files allowing you to use multilog filters (by setting the CRITERIA) to create special purpose log files. The goal is to provide a way to monitor log files in near realtime for "interesting" data without either hacking up the initial log file or wasting CPU/IO by re-scanning the same log repeatedly.

For non-interactive use, set the following environment variables. BASEDIR SYSUSR SOURCE EXTENSION CRITERIA If any of the above are not set, the script asks for configuration information interactively.

• BASEDIR where you want the service directory structure for the logrep to be created. This should not be the /var/service directory.

• SYSUSR unix user under which the service should run.

• SOURCE name of the service with the log you want to follow.

• EXTENSION a tag to differentiate this logrep from others using the same source.

• CRITERIA the multilog filter you want to use.

A trivial example of this would be to provide a log file of all slon ERROR messages which could be used to trigger a nagios alarm. EXTENSION='ERRORS' CRITERIA="'-*' '+* * ERROR*'" (Reset the monitor by rotating the log using svc -a $svc_dir)

A more interesting application is a subscription progress log. EXTENSION='COPY' CRITERIA="'-*' '+* * ERROR*' '+* * WARN*' '+* * CONFIG enableSubscription*' '+* * DEBUG2 remoteWorkerThread_* prepare to copy table*' '+* * DEBUG2 remoteWorkerThread_* all tables for set * found on subscriber*' '+* * DEBUG2 remoteWorkerThread_* copy*' '+* * DEBUG2 remoteWorkerThread_* Begin COPY of table*' '+* * DEBUG2 remoteWorkerThread_* * bytes copied for table*' '+* * DEBUG2 remoteWorkerThread_* * seconds to*' '+* * DEBUG2 remoteWorkerThread_* set last_value of sequence*' '+* * DEBUG2 remoteWorkerThread_* copy_set*'"

If you have a subscription log then it's easy to determine if a given slon is in the process of handling copies or other subscription activity. If the log isn't empty, and doesn't end with a "CONFIG enableSubscription: sub_set:1" (or whatever set number you've subscribed) then the slon is currently in the middle of initial copies.

If you happen to be monitoring the mtime of your primary slony logs to determine if your slon has gone brain-dead, checking this is a good way to avoid mistakenly clobbering it in the middle of a subscribe. As a bonus, recall that since the the slons are running under svscan, you only need to kill it (via the svc interface) and let svscan start it up again laster. I've also found the COPY logs handy for following subscribe activity interactively.