Event listener fails with "invalid semantic version" when HAProxy is installed from distribution packages #415

Description

The HAProxy event listener fails to start when HAProxy is installed from distribution
packages, because the version string reported by the runtime API cannot be parsed as
a valid semantic version.

Log output:

level=error msg="Failed to start HAProxy's event listener:invalid semantic version"

This prevents ACME certificate persistence: HAProxy emits acme newcert events to the
dpapi ring, but the Data Plane API never consumes them, so renewed certificates stay
in memory only and are lost on reload.

Environment

Failing:

Working:

Data Plane API v3.4.2 (also reproduced with v3.2.15).

Configuration

Same in both failing and working cases:

haproxy:
  config_file: /etc/haproxy/haproxy.cfg
  haproxy_bin: /usr/sbin/haproxy
  master_worker_mode: true
  master_runtime: /run/haproxy-master.sock

The working container uses an equivalent configuration, so this does not appear to be
a configuration issue.

Analysis

GetVersion() in client-native/runtime/runtime_client.go:118 runs show info and
passes the version string to ParseHAProxyVersion(), which relies on
Masterminds/semver/v3. Distribution packaging suffixes are rejected — note the
double + in 3.4.3-0+ha34+ubuntu24.04u1, which is not valid semver.

The subsequent check in client-native/events.go only uses Major() and Minor():

if version.Major() < 3 || (version.Major() == 3 && version.Minor() < 2) {
    return nil, ErrOldVersion
}

So strict semver parsing appears unnecessary here — truncating the string at the first
- or + before parsing would be enough.

Steps to reproduce

1. Install HAProxy 3.4 from the official HAProxy Technologies repository on Ubuntu 24.04
2. Install Data Plane API v3.4.2
3. Configure master_worker_mode: true and master_runtime
4. Start the service and check the log

Version output

$ haproxy -v | head -1
HAProxy version 3.4.3-0+ha34+ubuntu24.04u1 2026/07/29 - https://haproxy.org/

$ echo "@1 show info" | socat /run/haproxy-master.sock - | grep -i version
Version: 3.4.3-0+ha34+ubuntu24.04u1

$ dataplaneapi --version
HAProxy Data Plane API v3.4.2 8613429f

Note that the version string is correctly retrieved from the runtime API —
the failure happens when parsing it, not when reading it.