RFC: configuration versioning metrics

[James Peach <jp...@apache.org>]

Hi all,

This is a proposal to make configuration versioning a little easier in the context of deploying Traffic Server with configuration management automation. When we do this, we find that it is common to need to know things like "what version of the config is running", and "do I need to restart Traffic Server". Answers to these questions can be derived from the metrics proposed below.

To assist with versioning records.config, we should add the following new metrics:

   proxy.node.config.version.current
   proxy.node.config.version.initial

Both these metrics are strings, and we ought to be able to set them from records.config like this:

    NODE proxy.node.config.version.current STRING bar

(I'm pretty sure that this syntax will work, but I have not verified it experimentally).

The semantics of proxy.node.config.version.initial must be that it is updated to the value of proxy.node.config.version.current once at traffic_server start time. proxy.node.config.version.current is updated to the new value whenever records.config is loaded.

To assist with versioning remap.config, we should add a new ".version" directive to remap.config. The syntax for this directive is:

   .version NAME STRING

When remap.config is successfully loaded, this directive will cause the following metrics to be created:

   proxy.node.remap.NAME.version.current STRING
   proxy.node.remap.NAME.version.initial STRING

Just like the remap.config metrics, the initial variant of this metric is only populated from the current version when remap.config is first loaded.


cheers,
James