Remove the Prometheus HAProxy exporter image

- The source code is no longer maintained [1]
- HAProxy provides its own Prometheus metrics source [2]
- In Kolla Ansible, we have merged support for using the built in
  metrics source [3]

For these reasons, particularly the first, we should remove it immediately.

[1] https://github.com/prometheus/haproxy_exporter
[2] https://www.haproxy.com/blog/haproxy-exposes-a-prometheus-metrics-endpoint
[3] https://review.opendev.org/c/openstack/kolla-ansible/+/877118

Change-Id: Ia30e0fc367841df3726562b57b57df0f6fbb3a81

docker/prometheus/prometheus-haproxy-exporter/Dockerfile.j2

@@ -1,23 +0,0 @@
-FROM {{ namespace }}/{{ image_prefix }}prometheus-base:{{ tag }}
-{% block labels %}
-LABEL maintainer="{{ maintainer }}" name="{{ image_name }}" build-date="{{ build_date }}"
-{% endblock %}
-
-{% block haproxy_exporter_header %}{% endblock %}
-
-{% block haproxy_exporter_repository_version %}
-ARG haproxy_exporter_version=0.15.0
-ARG haproxy_exporter_url=https://github.com/prometheus/haproxy_exporter/releases/download/v${haproxy_exporter_version}/haproxy_exporter-${haproxy_exporter_version}.linux-{{debian_arch}}.tar.gz
-{% endblock %}
-
-{% block haproxy_exporter_install %}
-RUN curl -o /tmp/haproxy_exporter.tar.gz ${haproxy_exporter_url} \
-    && tar xvf /tmp/haproxy_exporter.tar.gz -C /opt/ \
-    && rm -f /tmp/haproxy_exporter.tar.gz \
-    && ln -s /opt/haproxy_exporter* /opt/haproxy_exporter
-{% endblock %}
-
-{% block haproxy_exporter_footer %}{% endblock %}
-{% block footer %}{% endblock %}
-
-USER prometheus

releasenotes/notes/remove-prometheus-haproxy-exporter-22d5af88af7e4a9d.yaml

@@ -0,0 +1,8 @@
+---
+upgrade:
+  - |
+    HAProxy Prometheus metrics are now available directly from HAProxy. As
+    such, the standalone Prometheus HAProxy exporter was archived in March
+    2023, is no longer supported and the Docker image has been removed from
+    Kolla. For further details see `here
+    <https://www.haproxy.com/blog/haproxy-exposes-a-prometheus-metrics-endpoint>`__.