pgagroal: setting configuration at run-time

I’m happy since today my contribution to pgagroal has been merged. The last year I added the config-get command to pgagroal-cli: such command allowed users to get information about how pgagroal was configured. The natural improvement over the above work would have been the config-set command, and now pgagroal-cli has one (see this commit ! It took me a few months to complete the work, since I was very busy on my day job: I had a working prototype working before Christmas, but then I let it there for the future me to have some time to complete the effort. And in the last month, I had some spare time, so I completed it!

pgagroal-cli config-set

The new command allows to dynamically change some configuration values. Clearly, not everything can be changed at run-time without a daemon restart. I wanted the command to be useful also in automating scripts, so I thought it could be useful for the command to report back the actual value of a configuration parameter. Therefore, checking the desiring value and the obtained value can confirm if the change has been applied or not. Similarly to the config-get command, also config-set accepts contexts:

• pgagroal (or nothing) means that the specified configuration parameter is within the [pgagroal] configuration section;
• limit means that the user requested to change a limit entry;
• server the user wants to change something about a server section;
• hba the user wants to change an HBA entry.

In the case of limit, hba and server contexts, the entry to modify must be identified with a name. While in a server configuration the name must be unique, the limits and hbas could not have unique names, so the first match wins. As an example, imagine the user wants to change the max_connection setting. Such setting is within the [pgagroal] section, so the following are two identical commands:



In both the above cases, the system is returning 40 instead of the desired value 100. That’s normal, since the max_connections requires a restart of the daemon, and can be better understood using the --verbose flag:



Clearly the system reports there was an error, and provides the information that max_connections is set at 40. Another example could be when the user decides to change a server or limit value, where he has to specify the context:



In the above, the user changes the venkman server port, and the pgbench user limit entry. If the system, that is the pgagroal daemon, cannot apply the requested change on the fly, the logs will be populated accordingly:



Clearly the messages may vary depending on the log level configuration. For more information, please see the official documentation .