Makes extensible metrics in remotecv

[devppjr]

This PR aims to create metrics for remotecv and make it extensive for defining upstream metrics. So was added the metrics bellow:

For each detector:

• latency (ms) - (worker.face.time, worker.feature.time, worker.glasses.time, worker.profile.time)
• detected (if found points) - (worker.face.detected, worker.feature.detected, worker.glasses.detected, worker.profile.detected)

For original image, such as Thumbor does:

• response_bytes - (worker.original_image.response_bytes)
• status_code + host + latency - (worker.original_image.fetch.{code}.{netloc})
• status_code + host + count - (worker.original_image.fetch.{code}.{netloc})
• status_code + count - (worker.original_image.status.{code})

For each task (image to detect):

• time (total time of detection) - (worker.pyres_task.time, worker.celery_task.time)
• count - (worker.pyres_task.total, worker.celery_task.total)

closes #60

[coveralls]

Pull Request Test Coverage Report for Build 3704449885

• 33 of 74 (44.59%) changed or added relevant lines in 10 files are covered.
• 3 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-2.0%) to 59.905%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
remotecv/importer.py	3	5	60.0%
remotecv/celery_tasks.py	0	5	0.0%
remotecv/worker.py	3	9	33.33%
remotecv/metrics/init.py	0	7	0.0%
remotecv/metrics/logger_metrics.py	0	7	0.0%
remotecv/http_loader.py	0	14	0.0%

Files with Coverage Reduction	New Missed Lines	%
remotecv/http_loader.py	1	0%
remotecv/celery_tasks.py	2	0%

Totals
Change from base Build 3677248203:	-2.0%
Covered Lines:	305
Relevant Lines:	516

---

💛 - Coveralls

[heynemann]

Really good stuff, apart from how to measure time. Let's create a function in an utils.py file that returns current time for measurements (using time.perf_counter_ns). Then we can use it everywhere, instead of duplicating the code. If we decide to change it in the future it's easy. Also add a function to get the difference in seconds (get_interval_seconds(perf_counter_ns_start, perf_counter_ns_end)). This way if we want to change the function that returns the timings in the future, we can also change this one and the whole codebase just works.

[heynemann]

Approved by mistake. See comments in approval.

[heynemann]

Looks great! TYVM!

[heynemann]

Will leave merge to after @guilhermef review :)

[guilhermef]

It doesn't have to be done in this one, but I suggest a more modern approach like Prometheus metrics and taking advantage of the HTTP server we have running on the worker.
I'm also fine with the logger metrics.

[codeclimate]

Code Climate has analyzed commit 704a2e4 and detected 0 issues on this pull request.

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[guilhermef]

Awesome work @devppjr

[RaphaelVRossi]

Great job @devppjr 🚀