Add prometheus support

app/blueprints/metrics/__init__.py

@@ -0,0 +1,74 @@
+# Content DB
+# Copyright (C) 2020  rubenwardy
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+from flask import Blueprint, make_response
+from app.models import Package, PackageRelease, db, User, UserRank
+from sqlalchemy.sql.expression import func
+
+bp = Blueprint("metrics", __name__)
+
+def generate_metrics(full=False):
+	def write_single_stat(name, help, type, value):
+		fmt = "# HELP {name} {help}\n# TYPE {name} {type}\n{name} {value}\n\n"
+
+		return fmt.format(name=name, help=help, type=type, value=value)
+
+	def gen_labels(labels):
+		pieces = [key + "=" + str(val) for key, val in labels.items()]
+		return (",").join(pieces)
+
+
+	def write_array_stat(name, help, type, data):
+		ret = ("# HELP {name} {help}\n# TYPE {name} {type}\n") \
+				.format(name=name, help=help, type=type)
+
+		for entry in data:
+			assert(len(entry) == 2)
+			ret += ("{name}{{{labels}}} {value}\n") \
+					.format(name=name, labels=gen_labels(entry[0]), value=entry[1])
+
+		return ret + "\n"
+
+
+	downloads_result = db.session.query(func.sum(PackageRelease.downloads)).one_or_none()
+	downloads = 0 if not downloads_result or not downloads_result[0] else downloads_result[0]
+
+	packages = Package.query.filter_by(approved=True, soft_deleted=False).count()
+	users = User.query.filter(User.rank != UserRank.NOT_JOINED).count()
+
+	ret = ""
+	ret += write_single_stat("contentdb_packages", "Total packages", "counter", packages)
+	ret += write_single_stat("contentdb_users", "Number of registered users", "counter", users)
+	ret += write_single_stat("contentdb_downloads", "Total downloads", "counter", downloads)
+
+	if full:
+		scores = Package.query.join(User).with_entities(User.username, Package.name, Package.score) \
+			.filter(Package.approved==True, Package.soft_deleted==False).all()
+
+		ret += write_array_stat("contentdb_package_score", "Package score", "gauge", \
+			[({ "author": score[0], "name": score[1] }, score[2])  for score in scores])
+	else:
+		score_result = db.session.query(func.sum(Package.score)).one_or_none()
+		score = 0 if not score_result or not score_result[0] else score_result[0]
+		ret += write_single_stat("contentdb_score", "Total package score", "gauge", score)
+
+	return ret
+
+@bp.route("/metrics")
+def metrics():
+    response = make_response(generate_metrics(), 200)
+    response.mimetype = "text/plain"
+    return response

app/flatpages/help.md

@@ -1,9 +1,15 @@
 title: Help
 
+## Content
+
 * [Package Tags](package_tags)
 * [Ranks and Permissions](ranks_permissions)
 * [Content Ratings and Flags](content_flags)
 * [Reporting Content](reporting)
 * [Top Packages Algorithm](top_packages)
+
+## Developers
+
 * [API](api)
+* [Metrics](metrics)
 * [Creating Releases using Webhooks](release_webhooks)

app/flatpages/help/metrics.md

@@ -0,0 +1,16 @@
+title: Prometheus Metrics
+
+## What is Prometheus?
+
+[Prometheus](https://prometheus.io) is an "open-source monitoring system with a
+dimensional data model, flexible query language, efficient time series database
+and modern alerting approach".
+
+Prometheus Metrics can be accessed at [/metrics](/metrics).
+
+## Metrics
+
+* `contentdb_packages` - Total packages (counter).
+* `contentdb_users` - Number of registered users (counter).
+* `contentdb_downloads` - Total downloads (counter).
+* `contentdb_score` - Total package score (gauge).