prometheus-flask-exporter 0.3.0

Prometheus metrics exporter for Flask

Prometheus Flask exporter
=========================

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This library provides HTTP request metrics to export into
`Prometheus <https://prometheus.io/>`__. It can also track method
invocations using convenient functions.

Usage
-----

.. code:: python

from flask import Flask, request
from prometheus_flask_exporter import PrometheusMetrics

app = Flask(__name__)
metrics = PrometheusMetrics(app)

# static information as metric
metrics.info('app_info', 'Application info', version='1.0.3')

@app.route('/')
def main():
pass # requests tracked by default

@app.route('/skip')
@metrics.do_not_track()
def skip():
pass # default metrics are not collected

@app.route('/<item_type>')
@metrics.do_not_track()
@metrics.counter('invocation_by_type', 'Number of invocations by type',
labels={'item_type': lambda: request.view_args['type']})
def by_type(item_type):
pass # only the counter is collected, not the default metrics

@app.route('/long-running')
@metrics.gauge('in_progress', 'Long running requests in progress')
def long_running():
pass

@app.route('/status/<int:status>')
@metrics.do_not_track()
@metrics.summary('requests_by_status', 'Request latencies by status',
labels={'status': lambda r: r.status_code})
@metrics.histogram('requests_by_status_and_path', 'Request latencies by status and path',
labels={'status': lambda r: r.status_code, 'path': lambda: request.path})
def echo_status(status):
return 'Status: %s' % status, status

Default metrics
---------------

The following metrics are exported by default (unless the
``export_defaults`` is set to ``False``).

- ``flask_http_request_duration_seconds`` (Histogram) Labels:
``method``, ``path`` and ``status``. Flask HTTP request duration in
seconds for all Flask requests.
- ``flask_http_request_total`` (Counter) Labels: ``method`` and
``status``. Total number of HTTP requests for all Flask requests.
- ``flask_exporter_info`` (Gauge) Information about the Prometheus
Flask exporter itself (e.g. ``version``).

Configuration
-------------

By default, the metrics are exposed on the same Flask application on the
``/metrics`` endpoint and using the core Prometheus registry. If this
doesn't suit your needs, set the ``path`` argument to ``None`` and/or
the ``export_defaults`` argument to ``False`` plus change the
``registry`` argument if needed. The ``group_by_endpoint`` constructor
flag makes the default request duration metric tracked by endpoint
(function) instead of URI path.

The ``register_endpoint`` allows exposing the metrics endpoint on a
specific path. It also allows passing in a Flask application to register
it on but defaults to the main one if not defined.

Similarly, the ``start_http_server`` allows exposing the endpoint on an
independent Flask application on a selected HTTP port. It also supports
overriding the endpoint's path and the HTTP listen address.

Labels
------

When defining labels for metrics on functions, the following values are
supported in the dictionary:

- A simple static value
- A no-argument callable
- A single argument callable that will receive the Flask response as
the argument

Label values are evaluated within the request context.

Application information
-----------------------

The ``PrometheusMetrics.info(..)`` method provides a way to expose
information as a ``Gauge`` metric, the application version for example.

The metric is returned from the method to allow changing its value from
the default ``1``:

.. code:: python

metrics = PrometheusMetrics(app)
info = metrics.info('dynamic_info', 'Something dynamic')
...
info.set(42.1)

Examples
--------

See some simple examples visualized on a Grafana dashboard by running
the demo in the
`examples/sample-signals <https://github.com/rycus86/prometheus_flask_exporter/tree/master/examples/wsgi>`__
folder.

.. figure:: examples/sample-signals/dashboard.png
:alt: Example dashboard

Example dashboard
App Factory Pattern
-------------------

This library also supports the flask `app factory
pattern <http://flask.pocoo.org/docs/1.0/patterns/appfactories/>`__. Use
the ``init_app`` method to attach the library to one or more application
objects. Note, that to use this mode, you'll need to pass in ``None``
for the ``app`` in the constructor.

.. code:: python

metrics = PrometheusMetrics(app=None, ...)
# then later:
metrics.init_app(app)

Debug mode
----------

Please note, that changes being live-reloaded, when running the Flask
app with ``debug=True``, are not going to be reflected in the metrics.
See https://github.com/rycus86/prometheus_flask_exporter/issues/4 for
more details.

WSGI
----

Getting accurate metrics for WSGI apps might require a bit more setup.
See a working sample app in the ``examples`` folder, and also the
`prometheus\_flask\_exporter#5 <https://github.com/rycus86/prometheus_flask_exporter/issues/5>`__
issue.

License
-------

MIT

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:target: https://travis-ci.org/rycus86/prometheus_flask_exporter
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:target: https://pypi.python.org/pypi/prometheus-flask-exporter
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:target: https://pypi.python.org/pypi/prometheus-flask-exporter
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:target: https://coveralls.io/github/rycus86/prometheus_flask_exporter?branch=master
.. |Code Climate| image:: https://codeclimate.com/github/rycus86/prometheus_flask_exporter/badges/gpa.svg
:target: https://codeclimate.com/github/rycus86/prometheus_flask_exporter