config_log is an experimental extension which implements a custom
background worker to monitor postgresql.conf and record any changes to
a database table.
config_log requires PostgreSQL 9.3 or later and will not work in earlier
versions.
To build config_log, just do this:
make
make install
If you encounter an error such as:
"Makefile", line 8: Need an operator
You need to use GNU make, which may well be installed on your system as
gmake:
gmake
gmake install
gmake installcheck
If you encounter an error such as:
make: pg_config: Command not found
Be sure that you have pg_config installed and in your path. If you used a
package management system such as RPM to install PostgreSQL, be sure that the
-devel package is also installed. If necessary tell the build process where
to find it:
env PG_CONFIG=/path/to/pg_config make && make install
Once config_log is compiled and installed, it needs to be added to a database
in the PostgreSQL database cluster whose postgresql.conf you wish to monitor.
It can only be installed in one database within the cluster.
By default, config_log expects to be installed into the default postgres
database's public schema. The default values can be overridden by changing
the following GUC settings:
config_log.database = 'some_other_db'
config_log.schema = 'different_schema'
Note that the schema must appear in the superuser's search path.
Connect to the target database as a superuser and execute:
CREATE EXTENSION config_log
This will install the database objects required for this extension.
Following this step, the module must be added to postgresql.conf's
shared_preload_libraries parameter and the server restarted.
config_log will produce some log output, prefixed by config_log: .
Following a successful startup, it will output the following:
LOG: config_log: initialized, database objects validated
LOG: config_log: pg_settings_logger() executed
LOG: config_log: no configuration changes detected
Following a SIGHUP, it will output something like the following:
LOG: received SIGHUP, reloading configuration files
LOG: parameter "temp_buffers" changed to "64MB"
LOG: config_log: received sighup
LOG: config_log: pg_settings_logger() executed
LOG: config_log: configuration changes recorded
For more information please see these blog posts:
- sql-info.de: Custom Background Worker: a practical example
- sql-info.de: Logging changes to postgresql.conf
- config_log repository at Github
- config_log project page at PGXN
- PostgreSQL documentation: Background Worker Processes