From aeb9b2179eaa4b468bec937570d3ac7de7ccaaea Mon Sep 17 00:00:00 2001
From: Amber Brown <hawkowl@atleastfornow.net>
Date: Tue, 10 Sep 2019 00:14:58 +1000
Subject: [PATCH] Add a build info metric to Prometheus (#6005)

---
 changelog.d/6005.feature    |  1 +
 synapse/metrics/__init__.py | 12 ++++++++++++
 tests/test_metrics.py       | 22 ++++++++++++++++++++--
 3 files changed, 33 insertions(+), 2 deletions(-)
 create mode 100644 changelog.d/6005.feature

diff --git a/changelog.d/6005.feature b/changelog.d/6005.feature
new file mode 100644
index 0000000000..ed6491d3e4
--- /dev/null
+++ b/changelog.d/6005.feature
@@ -0,0 +1 @@
+The new Prometheus metric `synapse_build_info` exposes the Python version, OS version, and Synapse version of the running server.
diff --git a/synapse/metrics/__init__.py b/synapse/metrics/__init__.py
index 488280b4a6..b5c9595cb9 100644
--- a/synapse/metrics/__init__.py
+++ b/synapse/metrics/__init__.py
@@ -29,11 +29,13 @@ from prometheus_client.core import REGISTRY, GaugeMetricFamily, HistogramMetricF
 
 from twisted.internet import reactor
 
+import synapse
 from synapse.metrics._exposition import (
     MetricsResource,
     generate_latest,
     start_http_server,
 )
+from synapse.util.versionstring import get_version_string
 
 logger = logging.getLogger(__name__)
 
@@ -385,6 +387,16 @@ event_processing_last_ts = Gauge("synapse_event_processing_last_ts", "", ["name"
 # finished being processed.
 event_processing_lag = Gauge("synapse_event_processing_lag", "", ["name"])
 
+# Build info of the running server.
+build_info = Gauge(
+    "synapse_build_info", "Build information", ["pythonversion", "version", "osversion"]
+)
+build_info.labels(
+    " ".join([platform.python_implementation(), platform.python_version()]),
+    get_version_string(synapse),
+    " ".join([platform.system(), platform.release()]),
+).set(1)
+
 last_ticked = time.time()
 
 
diff --git a/tests/test_metrics.py b/tests/test_metrics.py
index 2edbae5c6d..270f853d60 100644
--- a/tests/test_metrics.py
+++ b/tests/test_metrics.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 # Copyright 2018 New Vector Ltd
+# Copyright 2019 Matrix.org Foundation C.I.C.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -13,8 +14,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-
-from synapse.metrics import InFlightGauge
+from synapse.metrics import REGISTRY, InFlightGauge, generate_latest
 
 from tests import unittest
 
@@ -111,3 +111,21 @@ class TestMauLimit(unittest.TestCase):
             }
 
         return results
+
+
+class BuildInfoTests(unittest.TestCase):
+    def test_get_build(self):
+        """
+        The synapse_build_info metric reports the OS version, Python version,
+        and Synapse version.
+        """
+        items = list(
+            filter(
+                lambda x: b"synapse_build_info{" in x,
+                generate_latest(REGISTRY).split(b"\n"),
+            )
+        )
+        self.assertEqual(len(items), 1)
+        self.assertTrue(b"osversion=" in items[0])
+        self.assertTrue(b"pythonversion=" in items[0])
+        self.assertTrue(b"version=" in items[0])