Add promethes-flask-exporter

fence/__init__.py

@@ -66,16 +66,20 @@
 import fence.blueprints.register
 import fence.blueprints.ga4gh
 
-
-# for some reason the temp dir does not get created properly if we move
-# this statement to `_setup_prometheus()`
-PROMETHEUS_TMP_COUNTER_DIR = tempfile.TemporaryDirectory()
+# Prometheus metrics exporter
+from prometheus_flask_exporter import PrometheusMetrics
 
 
 app = flask.Flask(__name__)
 CORS(app=app, headers=["content-type", "accept"], expose_headers="*")
 
 
+metrics = PrometheusMetrics(app, path=None)
+
+# Serve metrics on port 9090
+metrics.start_http_server(9090)
+
+
 def warn_about_logger():
     raise Exception(
         "Flask 0.12 will remove and replace all of our log handlers if you call "
@@ -366,13 +370,6 @@ def app_config(
     _load_keys(app, root_dir)
     _set_authlib_cfgs(app)
 
-    app.prometheus_counters = {}
-    if config["ENABLE_PROMETHEUS_METRICS"]:
-        logger.info("Enabling Prometheus metrics...")
-        _setup_prometheus(app)
-    else:
-        logger.info("Prometheus metrics are NOT enabled.")
-
     app.storage_manager = StorageManager(config["STORAGE_CREDENTIALS"], logger=logger)
 
     app.debug = config["DEBUG"]
@@ -511,27 +508,6 @@ def _setup_audit_service_client(app):
     )
 
 
-def _setup_prometheus(app):
-    # This environment variable MUST be declared before importing the
-    # prometheus modules (or unit tests fail)
-    # More details on this awkwardness: https://github.com/prometheus/client_python/issues/250
-    os.environ["prometheus_multiproc_dir"] = PROMETHEUS_TMP_COUNTER_DIR.name
-
-    from prometheus_client import (
-        CollectorRegistry,
-        multiprocess,
-        make_wsgi_app,
-    )
-
-    app.prometheus_registry = CollectorRegistry()
-    multiprocess.MultiProcessCollector(app.prometheus_registry)
-
-    # Add prometheus wsgi middleware to route /metrics requests
-    app.wsgi_app = DispatcherMiddleware(
-        app.wsgi_app, {"/metrics": make_wsgi_app(registry=app.prometheus_registry)}
-    )
-
-
 @app.errorhandler(Exception)
 def handle_error(error):
     """

pyproject.toml

@@ -63,6 +63,7 @@ cachelib = "^0.2.0"
 azure-storage-blob = "^12.6.0"
 Flask-WTF = "^1.0.0"
 boto = "*"
+prometheus-flask-exporter = "^0.23.0"
 
 [tool.poetry.dev-dependencies]
 addict = "^2.2.1"