feat(base): Add exporter to gunicorn

ref: #156 #469

includes/etc/gunicorn.conf.py

@@ -1,3 +1,15 @@
+import logging
+import os
+
+from pathlib import Path
+
+from django.conf import settings
+
+from prometheus_client import CollectorRegistry, multiprocess, start_http_server
+
+
+
+os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'app.settings')
 
 access_logfile = '-'
 access_log_format = '%(h)s %(l)s %(u)s %(t)s "%(r)s" %(s)s %(b)s "%(f)s" "%(a)s" "%({x-forwarded-for}i)s"'
@@ -7,4 +19,63 @@ bind = 'unix:/run/gunicorn.sock'
 forwarded_allow_ips = "*"
 forwarder_headers = "X-REAL-IP,X-FORWARDED-FOR,X-FORWARDED-PROTO"
 
+logger = logging.getLogger(__name__)
+
+preload_app = False
+
 workers = 10
+
+
+def when_ready(_):
+
+    if not getattr(settings, 'METRICS_ENABLED', False):
+        return
+
+    proc_path = None
+
+    try:
+        proc_path = os.environ["PROMETHEUS_MULTIPROC_DIR"]
+    except:
+        pass
+
+
+    if not proc_path:
+
+        os.environ["PROMETHEUS_MULTIPROC_DIR"] = settings.METRICS_MULTIPROC_DIR
+
+        proc_path = os.environ["PROMETHEUS_MULTIPROC_DIR"]
+
+
+    logger.info(f'Setting up prometheus metrics HTTP server on port {str(settings.METRICS_EXPORT_PORT)}.')
+
+    multiproc_folder_path = _setup_multiproc_folder()
+
+    registry = CollectorRegistry()
+
+    logger.info(f'Setting up prometheus metrics directory.')
+
+    multiprocess.MultiProcessCollector(registry, path=multiproc_folder_path)
+
+    logger.info(f'Starting prometheus metrics server.')
+
+    start_http_server( settings.METRICS_EXPORT_PORT, registry=registry)
+
+    logger.info(f'Starting prometheus serving on port {str(settings.METRICS_EXPORT_PORT)}.')
+
+
+
+def _setup_multiproc_folder():
+
+    coordination_dir = Path(os.environ["PROMETHEUS_MULTIPROC_DIR"])
+    coordination_dir.mkdir(parents=True, exist_ok=True)
+
+    for filepath in coordination_dir.glob("*.db"):
+
+        filepath.unlink()
+
+    return coordination_dir
+
+
+def child_exit(_, worker):
+
+    multiprocess.mark_process_dead(worker.pid)