refactor kqueen metrics mechanism.

previously i cant get users/orgs metrics with:
'''localhost:5000/metrics/'''

- kqueen metrics updating
- logging for above operation (info level)

Notes:
We export all application metrics on /metrics and this metric can scraped by any external Prometheus instance. There two ways to authenticate to get this endpoint:

1. Provided valid token in header

TOKEN=$(curl -s -H "Content-Type: application/json" --data '{"username":"admin","password":"default"}' -X POST localhost:5000/api/v1/auth | jq -r '.access_token'); echo $TOKEN; curl -H "Authorization: Bearer $TOKEN"
And then go to localhost:5000/metrics

2. Add scraper IP address to PROMETHEUS_WHITELIST configuration and then

Go to {prometheus_ip}:{port}/metrics

review-docs: https://docs.google.com/document/d/1Bnor6D78fVzOndie52wFHVVbgV0daTOHrVP1IgKZvic/edit#

test: travis checks, demo

.travis.yml

@@ -28,13 +28,16 @@ jobs:
     - pip install -e ".[dev]"
     script:
     - export prometheus_multiproc_dir=$(mktemp -d)
+    - ls -al $prometheus_multiproc_dir
     - python3 -m pytest --cov=. --cov-report=term-missing:skip-covered
+    - ls -al $prometheus_multiproc_dir
     - coverage xml
     - coveralls
     - |
         [ ! -z "${CODACY_PROJECT_TOKEN}" ] && python-codacy-coverage -r coverage.xml || echo "Codacy coverage NOT exported"
     - pip3 install --editable .
     - python3 -m kqueen &
+    - ls -al $prometheus_multiproc_dir
     - sleep 2
     - wget -O - http://localhost:5000/api/v1/health
   - stage: build

kqueen/blueprints/metrics/views.py

@@ -5,12 +5,15 @@
 from flask_jwt import _jwt_required
 from ipaddress import ip_address
 from ipaddress import ip_network
-from prometheus_client import CollectorRegistry
+from kqueen.blueprints.metrics.helpers import MetricUpdater
 from prometheus_client import CONTENT_TYPE_LATEST
+from prometheus_client import CollectorRegistry
 from prometheus_client import generate_latest
 from prometheus_client import multiprocess
+import logging
 
 metrics = Blueprint('metrics', __name__)
+logger = logging.getLogger('kqueen_api')
 
 
 @metrics.route('/')
@@ -20,6 +23,7 @@ def root():
     if ip_address(request.remote_addr) not in ip_whitelist:
         _jwt_required(current_app.config['JWT_DEFAULT_REALM'])
 
+    MU = MetricUpdater()
     registry = CollectorRegistry()
     multiprocess.MultiProcessCollector(registry)
 
@@ -28,5 +32,7 @@ def root():
     response = make_response(data)
     response.headers['Content-Type'] = CONTENT_TYPE_LATEST
     response.headers['Content-Length'] = str(len(data))
+    logger.info('Kqueen metrics updating')
+    MU.update_metrics()
 
     return response