Add container-based config discovery support for haproxy (#24572)

* Add container-based config discovery support for haproxy

Enables Autodiscovery to generate the OpenMetrics V2 instance config
(port 8404, /metrics) from a discovered haproxy container's exposed
ports.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

* Add changelog entry for haproxy discovery PR

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>

Author: martavicentenavarro

haproxy/assets/configuration/spec.yaml

@@ -2,6 +2,14 @@ name: HAProxy
 fleet_configurable: true
 files:
 - name: haproxy.yaml
+  discovery:
+    strategies:
+    - strategy: from_ports
+      port_hints:
+      - 8404
+      candidates:
+      - use_openmetrics: "true"
+        openmetrics_endpoint: "http://{service.host}:{port.number}/metrics"
   options:
   - template: init_config
     options:
@@ -237,3 +245,10 @@ files:
       port: 514
       service: haproxy
       source: haproxy
+- name: auto_conf.yaml
+  options:
+  - template: ad_identifiers
+    overrides:
+      value.example:
+      - haproxy
+  - template: auto_conf/discovery

haproxy/changelog.d/24572.added

@@ -0,0 +1 @@
+Add container-based config discovery support.

haproxy/datadog_checks/haproxy/config_models/discovery.py

@@ -0,0 +1,43 @@
+# (C) Datadog, Inc. 2026-present
+# All rights reserved
+# Licensed under a 3-clause BSD style license (see LICENSE)
+
+# This file is autogenerated.
+# To change this file you should edit assets/configuration/spec.yaml and then run the following commands:
+#     ddev -x validate config -s <INTEGRATION_NAME>
+#     ddev -x validate models -s <INTEGRATION_NAME>
+
+from __future__ import annotations
+
+from collections.abc import Iterator
+from typing import Any
+
+from datadog_checks.base.utils.discovery import Service, candidate_ports
+from datadog_checks.haproxy.config_models import discovery_overrides
+from datadog_checks.haproxy.config_models.instance import InstanceConfig
+from datadog_checks.haproxy.config_models.shared import SharedConfig
+
+
+def _generated_candidates(service: Service) -> Iterator[dict[str, Any]]:
+    shared = SharedConfig.model_validate({}, context={'configured_fields': frozenset()}).model_dump(
+        by_alias=True, mode='json', exclude_none=True
+    )
+    # discovery[0]: from_ports
+    for port in candidate_ports(service, [8404]):
+        ctx = {'port': port}
+        instance_data = {
+            'use_openmetrics': 'true',
+            'openmetrics_endpoint': 'http://{service.host}:{port.number}/metrics'.format(service=service, **ctx),
+        }
+        instance = InstanceConfig.model_validate(
+            instance_data, context={'configured_fields': frozenset(instance_data)}
+        ).model_dump(by_alias=True, mode='json', exclude_none=True)
+        yield {'init_config': shared, 'instances': [instance]}
+
+
+def candidates(service: Service) -> Iterator[dict[str, Any]]:
+    override = getattr(discovery_overrides, 'candidates', None)
+    if override is None:
+        yield from _generated_candidates(service)
+    else:
+        yield from override(service, default=_generated_candidates)

haproxy/datadog_checks/haproxy/config_models/discovery_overrides.py

@@ -0,0 +1,12 @@
+# (C) Datadog, Inc. 2026-present
+# All rights reserved
+# Licensed under a 3-clause BSD style license (see LICENSE)
+
+# Override the generated discovery candidates() for this integration.
+#
+# Define a candidates(service, default) function to wrap or replace the generated
+# candidate generation. `default` is the generated generator; call it to reuse
+# the spec-driven candidates, or ignore it to replace them entirely.
+#
+# def candidates(service, default):
+#     yield from default(service)

haproxy/datadog_checks/haproxy/config_models/discovery_strategies.py

@@ -0,0 +1,18 @@
+# (C) Datadog, Inc. 2026-present
+# All rights reserved
+# Licensed under a 3-clause BSD style license (see LICENSE)
+
+# Here you can define custom (local:) discovery strategies for this integration.
+#
+# Decorate a generator with @discovery_strategy (imported from
+# datadog_checks.base.utils.discovery) and reference it from the spec discovery
+# stanza as `strategy: local:<function_name>`. The function receives the
+# discovered Service plus the inputs declared in the spec and yields one context
+# (ctx) mapping per candidate, exposing the keys listed in `provides`.
+#
+# from datadog_checks.base.utils.discovery import discovery_strategy
+#
+# @discovery_strategy(provides=('svc',))
+# def from_some_config(service, config_path):
+#     ...
+#     yield {'svc': ...}

haproxy/datadog_checks/haproxy/data/auto_conf.yaml

@@ -0,0 +1,19 @@
+## @param ad_identifiers - list of strings - required
+## A list of container identifiers that are used by Autodiscovery to identify
+## which container the check should be run against. For more information, see:
+## https://docs.datadoghq.com/agent/guide/ad_identifiers/
+#
+ad_identifiers:
+  - haproxy
+
+## Enables configuration discovery
+#
+discovery: {}
+
+## Unused init configuration
+#
+init_config:
+
+## Unused instance configuration
+#
+instances: []

haproxy/pyproject.toml

@@ -28,7 +28,7 @@ classifiers = [
     "Private :: Do Not Upload",
 ]
 dependencies = [
-    "datadog-checks-base>=37.33.0",
+    "datadog-checks-base>=37.41.0",
 ]
 dynamic = [
     "version",

haproxy/tests/conftest.py

@@ -14,7 +14,7 @@
 import requests
 from packaging import version
 
-from datadog_checks.dev import TempDir, WaitFor, docker_run
+from datadog_checks.dev import TempDir, WaitFor, docker_run, get_e2e_discovery_metadata
 from datadog_checks.haproxy import HAProxyCheck
 from datadog_checks.haproxy.metrics import METRIC_MAP
 
@@ -49,7 +49,7 @@ def dd_environment():
             yield e
     else:
         with docker_run(compose_file=os.path.join(HERE, 'docker', 'haproxy.yaml'), endpoints=[ENDPOINT_PROMETHEUS]):
-            yield INSTANCE
+            yield INSTANCE, get_e2e_discovery_metadata()
 
 
 @pytest.fixture(scope='session')

haproxy/tests/test_e2e.py

@@ -4,7 +4,9 @@
 import pytest
 
 from datadog_checks.base import is_affirmative
+from datadog_checks.dev.docker import assert_all_discovery_candidates_stable
 from datadog_checks.dev.utils import get_metadata_metrics
+from datadog_checks.haproxy import HAProxyCheck
 
 from .common import ENDPOINT_PROMETHEUS, HAPROXY_LEGACY, requires_new_environment
 
@@ -40,3 +42,19 @@ def test_checkv2(dd_agent_check, instancev2, prometheus_metricsv2):
 
     aggregator.assert_all_metrics_covered()
     aggregator.assert_metrics_using_metadata(get_metadata_metrics())
+
+
+def test_e2e_discovery(dd_agent_check_discovery, prometheus_metricsv2):
+    aggregator = dd_agent_check_discovery(rate=True)
+
+    # discovery resolves the container's internal network address, which differs from
+    # ENDPOINT_PROMETHEUS's host-mapped one, so the endpoint tag isn't asserted here.
+    for metric in prometheus_metricsv2:
+        aggregator.assert_metric('haproxy.{}'.format(metric))
+
+    aggregator.assert_all_metrics_covered()
+    aggregator.assert_metrics_using_metadata(get_metadata_metrics())
+
+
+def test_e2e_discovery_all_candidates(dd_agent_check):
+    assert_all_discovery_candidates_stable(dd_agent_check, HAProxyCheck)