prometheus.exporter.snmp to support multiple config files

[ptodev]

Request

The config_file (and maybe config) options can be changed from string to list(string), so that users can specify more than one config file. This is a feature which was added upstream some time ago.

This was requested by @bastischubert

Use case

It could be helpful to split out a config file into multiple files.

[rfratto]

Is there a way that this can be done without a breaking change, like a new config_files argument that becomes mutually exclusive with the config_file argument?

[hainenber]

That's also more intuitive, imo. From user perspective, it'd be pretty weird passing a list of SNMP config files to config_file rather config_files

Or maybe we can mark config_file as deprecated and enforce people passing single-entry list of SNMP config file to config_files? 🤔

[ptodev]

Is there a way that this can be done without a breaking change, like a new config_files argument that becomes mutually exclusive with the config_file argument?

I would be happy with that. I also think we should document the config_file argument as "deprecated", as @hainenber suggested. Having both arguments side by side will give people time to migrate prior to 2.0.

From user perspective, it'd be pretty weird passing a list of SNMP config files to config_file rather config_files

True! It was sort of implied in the original issue above, but I didn't mention it. Thanks for clearing it. up :)

Btw I don't think this is super high priority, because in theory config_file accepts a glob pattern. So even with the current config it should be possible for folks to use multiple files. I haven't tested it though. Hopefully we can use the integration tests in #954 for this purpose in the future.