Implement Prometheus metrics

src/bottle_plugins/prometheus_plugin.py

@@ -0,0 +1,53 @@
+import logging
+import os
+import urllib.parse
+
+from dtos import V1ResponseBase
+from metrics import start_metrics_http_server, REQUEST_COUNTER, REQUEST_DURATION
+
+PROMETHEUS_ENABLED = os.environ.get('PROMETHEUS_ENABLED', 'false').lower() == 'true'
+PROMETHEUS_PORT = int(os.environ.get('PROMETHEUS_PORT', 8192))
+
+
+def setup():
+    if PROMETHEUS_ENABLED:
+        start_metrics_http_server(PROMETHEUS_PORT)
+
+
+def prometheus_plugin(callback):
+    """
+    Bottle plugin to expose Prometheus metrics
+    http://bottlepy.org/docs/dev/plugindev.html
+    """
+    def wrapper(*args, **kwargs):
+        actual_response = callback(*args, **kwargs)
+
+        if PROMETHEUS_ENABLED:
+            try:
+                export_metrics(actual_response)
+            except Exception as e:
+                logging.warning("Error exporting metrics: " + str(e))
+
+        return actual_response
+
+    def export_metrics(actual_response):
+        res = V1ResponseBase(actual_response)
+
+        domain = "unknown"
+        if res.solution and res.solution.url:
+            parsed_url = urllib.parse.urlparse(res.solution.url)
+            domain = parsed_url.hostname
+
+        run_time = (res.endTimestamp - res.startTimestamp) / 1000
+        REQUEST_DURATION.labels(domain=domain).observe(run_time)
+
+        result = "unknown"
+        if res.message == "Challenge solved!":
+            result = "solved"
+        elif res.message == "Challenge not detected!":
+            result = "not_detected"
+        elif res.message.startswith("Error"):
+            result = "error"
+        REQUEST_COUNTER.labels(domain=domain, result=result).inc()
+
+    return wrapper

src/flaresolverr.py

@@ -8,6 +8,7 @@ from bottle import run, response, Bottle, request, ServerAdapter
 
 from bottle_plugins.error_plugin import error_plugin
 from bottle_plugins.logger_plugin import logger_plugin
+from bottle_plugins import prometheus_plugin
 from dtos import V1RequestBase
 import flaresolverr_service
 import utils
@@ -24,10 +25,6 @@ class JSONErrorBottle(Bottle):
 
 app = JSONErrorBottle()
 
-# plugin order is important
-app.install(logger_plugin)
-app.install(error_plugin)
-
 
 @app.route('/')
 def index():
@@ -101,6 +98,13 @@ if __name__ == "__main__":
     # test browser installation
     flaresolverr_service.test_browser_installation()
 
+    # start bootle plugins
+    # plugin order is important
+    app.install(logger_plugin)
+    app.install(error_plugin)
+    prometheus_plugin.setup()
+    app.install(prometheus_plugin.prometheus_plugin)
+
     # start webserver
     # default server 'wsgiref' does not support concurrent requests
     # https://github.com/FlareSolverr/FlareSolverr/issues/680

src/metrics.py

@@ -0,0 +1,32 @@
+import logging
+
+from prometheus_client import Counter, Histogram, start_http_server
+import time
+
+REQUEST_COUNTER = Counter(
+    name='flaresolverr_request',
+    documentation='Total requests with result',
+    labelnames=['domain', 'result']
+)
+REQUEST_DURATION = Histogram(
+    name='flaresolverr_request_duration',
+    documentation='Request duration in seconds',
+    labelnames=['domain'],
+    buckets=[0, 10, 25, 50]
+)
+
+
+def serve(port):
+    start_http_server(port=port)
+    while True:
+        time.sleep(600)
+
+
+def start_metrics_http_server(prometheus_port: int):
+    logging.info(f"Serving Prometheus exporter on http://0.0.0.0:{prometheus_port}/metrics")
+    from threading import Thread
+    Thread(
+        target=serve,
+        kwargs=dict(port=prometheus_port),
+        daemon=True,
+    ).start()