feat(prometheus): add /metrics endpoint for monitoring

.github/workflows/pylint.yml

@@ -30,6 +30,7 @@ jobs:
           pip install flask
           pip install requests
           pip install vcrpy
+          pip install prometheus_client
       - name: Analysing the code with pylint
         run: |
           pylint $(git ls-files '*.py')

fixtures/vcr_cassettes/metrics.yaml

@@ -0,0 +1,108 @@
+interactions:
+  - request:
+      body: null
+      headers:
+        Accept:
+          - "*/*"
+        Accept-Encoding:
+          - gzip, deflate
+        Connection:
+          - keep-alive
+        User-Agent:
+          - python-requests/2.31.0
+      method: GET
+      uri: http://127.0.0.1:5000/metrics
+    response:
+      body:
+        string:
+          '# HELP python_gc_objects_collected_total Objects collected during gc
+
+          # TYPE python_gc_objects_collected_total counter
+
+          python_gc_objects_collected_total{generation="0"} 424.0
+
+          python_gc_objects_collected_total{generation="1"} 24.0
+
+          python_gc_objects_collected_total{generation="2"} 0.0
+
+          # HELP python_gc_objects_uncollectable_total Uncollectable objects found during
+          GC
+
+          # TYPE python_gc_objects_uncollectable_total counter
+
+          python_gc_objects_uncollectable_total{generation="0"} 0.0
+
+          python_gc_objects_uncollectable_total{generation="1"} 0.0
+
+          python_gc_objects_uncollectable_total{generation="2"} 0.0
+
+          # HELP python_gc_collections_total Number of times this generation was collected
+
+          # TYPE python_gc_collections_total counter
+
+          python_gc_collections_total{generation="0"} 33.0
+
+          python_gc_collections_total{generation="1"} 2.0
+
+          python_gc_collections_total{generation="2"} 0.0
+
+          # HELP python_info Python platform information
+
+          # TYPE python_info gauge
+
+          python_info{implementation="CPython",major="3",minor="13",patchlevel="1",version="3.13.1"}
+          1.0
+
+          # HELP process_virtual_memory_bytes Virtual memory size in bytes.
+
+          # TYPE process_virtual_memory_bytes gauge
+
+          process_virtual_memory_bytes 4.6829568e+07
+
+          # HELP process_resident_memory_bytes Resident memory size in bytes.
+
+          # TYPE process_resident_memory_bytes gauge
+
+          process_resident_memory_bytes 4.0833024e+07
+
+          # HELP process_start_time_seconds Start time of the process since unix epoch
+          in seconds.
+
+          # TYPE process_start_time_seconds gauge
+
+          process_start_time_seconds 1.74983991025e+09
+
+          # HELP process_cpu_seconds_total Total user and system CPU time spent in seconds.
+
+          # TYPE process_cpu_seconds_total counter
+
+          process_cpu_seconds_total 3.46
+
+          # HELP process_open_fds Number of open file descriptors.
+
+          # TYPE process_open_fds gauge
+
+          process_open_fds 6.0
+
+          # HELP process_max_fds Maximum number of open file descriptors.
+
+          # TYPE process_max_fds gauge
+
+          process_max_fds 1.048576e+06
+
+          '
+      headers:
+        Connection:
+          - close
+        Content-Length:
+          - "1893"
+        Content-Type:
+          - text/plain; version=0.0.4; charset=utf-8; charset=utf-8
+        Date:
+          - Fri, 13 Jun 2025 19:27:04 GMT
+        Server:
+          - Werkzeug/3.1.3 Python/3.13.1
+      status:
+        code: 200
+        message: OK
+version: 1

main.py

@@ -1,5 +1,6 @@
 '''Module containing the main function of the app.'''
-from flask import Flask
+from flask import Flask, Response
+from prometheus_client import generate_latest, CONTENT_TYPE_LATEST
 import opensense
 #import test_main
 
@@ -19,6 +20,11 @@ def get_temperature():
     '''Function to get the current temperature.'''
     return opensense.get_temperature()
 
+@app.route('/metrics')
+def metrics():
+    '''Function to return Prometheus metrics.'''
+    return Response(generate_latest(), mimetype=CONTENT_TYPE_LATEST)
+
 ### Test module ###
 # @app.route('/test')
 # def test():

requirements.in

@@ -1,16 +1,3 @@
-blinker==1.9.0
-certifi==2025.1.31
-charset-normalizer==3.4.1
-click==8.1.8
-DateTime==5.5
-Flask==3.1.0
-idna==3.10
-itsdangerous==2.2.0
-Jinja2==3.1.6
-MarkupSafe==3.0.2
-pytz==2025.1
-requests==2.32.3
-setuptools==76.1.0
-urllib3==2.3.0
-Werkzeug==3.1.3
-zope.interface==7.2
+Flask==3.1.1
+requests==2.32.4
+prometheus-client==0.22.1