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+.. SPDX-License-Identifier: GPL-3.0-or-later
+
+.. _mod-http-prometheus:
+
+Prometheus metrics endpoint
+---------------------------
+
+The :ref:`HTTP module <mod-http>` exposes ``/metrics`` endpoint that serves metrics
+from :ref:`mod-stats` in Prometheus_ text format.
+You can use it as soon as HTTP module is configured:
+
+.. code-block:: bash
+
+	$ curl -k https://localhost:8453/metrics | tail
+	# TYPE latency histogram
+	latency_bucket{le=10} 2.000000
+	latency_bucket{le=50} 2.000000
+	latency_bucket{le=100} 2.000000
+	latency_bucket{le=250} 2.000000
+	latency_bucket{le=500} 2.000000
+	latency_bucket{le=1000} 2.000000
+	latency_bucket{le=1500} 2.000000
+	latency_bucket{le=+Inf} 2.000000
+	latency_count 2.000000
+	latency_sum 11.000000
+
+You can namespace the metrics in configuration, using `http.prometheus.namespace` attribute:
+
+.. code-block:: lua
+
+        modules.load('http')
+        -- Set Prometheus namespace
+        http.prometheus.namespace = 'resolver_'
+
+You can also add custom metrics or rewrite existing metrics before they are returned to Prometheus client.
+
+.. code-block:: lua
+
+        modules.load('http')
+        -- Add an arbitrary metric to Prometheus
+        http.prometheus.finalize = function (metrics)
+        	table.insert(metrics, 'build_info{version="1.2.3"} 1')
+        end
+
+.. _Prometheus: https://prometheus.io