Add CpuTime and Duration quantiles to worker metrics

[m0ar]

This PR extends the worker metrics by providing quantiles for used CPU time and duration for invocations:

I also took the liberty of resolving the errors for trying to fetch non-free metrics on free zones:

zone 'xxx' does not have access to the path

This is done by adding a free_tier variable/flag which disables non-free metric polling. It's backwards compatible, if not explicitly set the default behaviour is to scrape everything. Currently, this leaves only worker metrics. In the future, one can imagine allowing to configure scraping of httpRequestGroups1h (instead of 1m) for free tier metrics but didn't want to scope creep too much. :)

[m0ar]

This alias was unused before

[m0ar]

same here

[m0ar]

@martinhaus Do you want me to add any janitorial changes to this PR? Updating versions somewhere and whatnot :)

[martinhaus]

LGTM, thanks @m0ar! I'll make a release and update the versions in Heml :)

[m0ar]

@martinhaus Sweet, thanks yourself. :)

There is one thing I'm still trying to figure out, and that is how the heck to set up the API token. Whenever I try using this service without the global API key, I get nothing...

[martinhaus]

@m0ar You should be able to create a token here: https://dash.cloudflare.com/profile/api-tokens
I use the Read analytics and logs template and it works fine.

[m0ar]

@martinhaus Yeah, I've set that up. The issue is that we only pay for worker subscriptions, meaning our zone is on the free tier. This is why I added the free-tier flag, to squelch our errors. However, it seems that the fetchAccounts function from #21 yields an empty slice for me (which fails the worker metrics silently), so there is some other permission that seems to be missing... I'll send another PR when I figure it out :)

[martinhaus]

@m0ar perfect, PR would be very welcomed :)

[m0ar]

Hmm, the hickup seems to be that api.Accounts working as "returns all accounts the logged in user has access to", which doesn't really make sense without X-AUTH-EMAIL identifying the user. I'm not able to query this endpoint with curl either using the bearer token. :/

[m0ar]

I think this might be an upstream issue related to auth tokens.. I've posted a bug report with cloudflare-go: cloudflare/cloudflare-go#725

[m0ar]

@martinhaus Found the issue! Account Settings:Read is required on the token for the account listing to work. :)