Constance metrics

[msalaban-reef]

This PR allows for exporting django-constance config variables as Prometheus metrics.

1. It supports int, float, bool and decimal.Decimal types by default.
2. It skips variables listed in CONSTANCE_PROMETHEUS_BLACKLIST setting.
3. It processes variables listed in CONSTANCE_PROMETHEUS_WHITELIST setting by adding their string representation to the metric's name. (May cause problems in multiprocess mode.)

This is a review request, esp. to @ppolewicz

[lgtm-com[bot]]

This pull request introduces 3 alerts and fixes 1 when merging e8aa7a762ce8b80dede0113334bf74b7952a5b5f into c85cafedf83d864b3b597069cbfec01107447c5d - view on LGTM.com

new alerts:

• 2 for Syntax error
• 1 for Unused import

fixed alerts:

• 1 for Syntax error

[lgtm-com[bot]]

This pull request introduces 2 alerts and fixes 1 when merging 95da931a1d828eaa4aef825fabcd7bf0fe72a233 into c85cafedf83d864b3b597069cbfec01107447c5d - view on LGTM.com

new alerts:

• 2 for Syntax error

fixed alerts:

• 1 for Syntax error

[lgtm-com[bot]]

This pull request introduces 2 alerts and fixes 1 when merging a1b416d3898a95ce76ebcdf0a7c20cb3625369f0 into b54e5b648a61a690b9191753491e9c90916b37a9 - view on LGTM.com

new alerts:

• 2 for Syntax error

fixed alerts:

• 1 for Syntax error

[lgtm-com[bot]]

This pull request introduces 2 alerts and fixes 1 when merging c02cd1cb365c59be34605453e847633546370823 into b54e5b648a61a690b9191753491e9c90916b37a9 - view on LGTM.com

new alerts:

• 2 for Syntax error

fixed alerts:

• 1 for Syntax error

[msalaban-reef]

I updated the code after your review. Please re-check. The important outstanding issue is unregistering metrics in multiprocess environment, however for that I'd like to consult someone with practical experience.

[lgtm-com[bot]]

This pull request introduces 2 alerts and fixes 1 when merging 8f48671917c3ac6f2b233d9f1e4127f6e0db359b into b54e5b648a61a690b9191753491e9c90916b37a9 - view on LGTM.com

new alerts:

• 2 for Syntax error

fixed alerts:

• 1 for Syntax error

[msalaban-reef]

Another idea here is to keep the following types permitted by constance as:

• datetime: .totimestamp(), .fromtimestamp()
• date: .toordinal(), fromordinal()
• timedelta: td / timedelta(microseconds=1)
• time: in microseconds, but the conversion methods aren't provided explicitly

The advantage is that we could keep them as floats, at the cost of additional conversion on both ends. Problems arise, however, when timezones are used and need to be conserved (otherwise we could normalize to UTC).

@ppolewicz what do you think about it?

[ppolewicz]

Always use UTC time.

I'd rather cast it to int and have a 1s precision.

[lgtm-com[bot]]

This pull request introduces 3 alerts and fixes 1 when merging 016937f767a413ccf87cd10d86a770e49a9d01f0 into b54e5b648a61a690b9191753491e9c90916b37a9 - view on LGTM.com

new alerts:

• 2 for Syntax error
• 1 for Unused import

fixed alerts:

• 1 for Syntax error

[lgtm-com[bot]]

This pull request introduces 2 alerts and fixes 1 when merging 740fd699bed037d637c044f87848bb109a70f99e into b54e5b648a61a690b9191753491e9c90916b37a9 - view on LGTM.com

new alerts:

• 2 for Syntax error

fixed alerts:

• 1 for Syntax error

[lgtm-com[bot]]

This pull request introduces 3 alerts and fixes 1 when merging 15cd1fc062399b0755fd33ac239af2bea31a96ba into b54e5b648a61a690b9191753491e9c90916b37a9 - view on LGTM.com

new alerts:

• 2 for Syntax error
• 1 for Unused import

fixed alerts:

• 1 for Syntax error

[lgtm-com[bot]]

This pull request introduces 2 alerts and fixes 1 when merging 38690b16c220054fc299a880e0432c5f74db0eb5 into b54e5b648a61a690b9191753491e9c90916b37a9 - view on LGTM.com

new alerts:

• 2 for Syntax error

fixed alerts:

• 1 for Syntax error

[msalaban-reef]

Any progress with reviewing this, guys?