Failed to start HAProxy's event listener:version data not found

I'd like to make event listener work to avoid reloading haproxy frequently.

Similar to #387

time="2025-10-04T02:51:09Z" level=info msg="HAProxy Data Plane API v3.2.4 1eed677a"
time="2025-10-04T02:51:09Z" level=info msg="Build from: https://github.com/haproxytech/dataplaneapi"
time="2025-10-04T02:51:09Z" level=info msg="Build date: 2025-09-23T08:14:28Z"
time="2025-10-04T02:51:09Z" level=info msg="Reload strategy: systemd"
time="2025-10-04T02:51:09Z" level=error msg="Failed to start HAProxy's event listener:version data not found"
time="2025-10-04T02:51:09Z" level=debug msg="discovery job starting" ID=8328ca23-c6e4-4e9e-815f-1489baf2baf3 ServiceDiscovery=AWS
time="2025-10-04T02:51:09Z" level=debug msg="-- command socket updating client_native client"
time="2025-10-04T02:51:09Z" level=info msg="Serving data plane at http://[::]:5555"
time="2025-10-04T02:51:09Z" level=debug msg="-- command socket Server. conf ready..."
time="2025-10-04T02:51:10Z" level=debug msg="-- command socket handleClientNativeClientUpdate stopped"
time="2025-10-04T02:51:10Z" level=debug msg="-- command socket not set (--debug_socket_path). Not running the command socket server"
time="2025-10-04T02:51:10Z" level=debug msg="Mode: single"
time="2025-10-04T02:51:19Z" level=debug msg="discovery job update triggered" ID=8328ca23-c6e4-4e9e-815f-1489baf2baf3 ServiceDiscovery=AWS
time="2025-10-04T02:51:20Z" level=debug msg="discovery job reconciliation completed" ID=8328ca23-c6e4-4e9e-815f-1489baf2baf3 ServiceDiscovery=AWS
time="2025-10-04T02:51:20Z" level=debug msg="Scheduling a new reload..." reload_id=2025-10-04-0
time="2025-10-04T02:51:24Z" level=debug msg="Reload started" reload_id=2025-10-04-0
time="2025-10-04T02:51:24Z" level=debug msg="Reload successful" reload_id=2025-10-04-0
time="2025-10-04T02:51:24Z" level=debug msg="Reload finished in 108.304043ms" reload_id=2025-10-04-0

Just as the logs said, Data Plane API failed to start HAProxy's event listener because "version data not found".

I have traced that "version data not found" is supposed to be returned by client-native/v6.
I unit tested GetVersion() of client-native/v6 on the same server and it worked.

package main

import (
	"context"
	"fmt"
	"log"
	"os"

	// Updated import paths for v6
	runtime_api "github.com/haproxytech/client-native/v6/runtime"
	"github.com/haproxytech/client-native/v6/runtime/options"
)

func main() {
	ctx := context.Background()
	
	// Check if socket exists (for local testing)
	socketPath := "/var/run/haproxy.sock"
	if _, err := os.Stat(socketPath); os.IsNotExist(err) {
		fmt.Printf("HAProxy socket not found at %s\n", socketPath)
		return
	}

	// Create runtime client with socket options
	socketOption := options.Socket(socketPath)
	runtimeClient, err := runtime_api.New(ctx, socketOption)
	if err != nil {
		log.Fatalf("Error creating runtime client: %v", err)
	}

	// Get the HAProxy version.
	version, err := runtimeClient.GetVersion()
	if err != nil {
		log.Fatalf("Error getting HAProxy version: %v", err)
	}

	// Print the version. The version string might include the release date.
	fmt.Printf("HAProxy Version: %s\n", version)
}

HAProxy Version: {ba0fd6b 3.2.5-ba0fd6b %!s(int=3) %!s(int=2) %!s(int=5)}

my dataplaneapi.yml

dataplaneapi:
  host: 0.0.0.0
  port: 5555
  userlist:
    userlist: dataplaneapi
  resources:
    maps_dir: /etc/haproxy/maps
    ssl_certs_dir: /etc/haproxy/ssl
    general_storage_dir: /etc/haproxy/general
    spoe_dir: /etc/haproxy/spoe
  transaction:
    transaction_dir: /var/lib/dataplaneapi/transactions
    backups_number: 10
    backups_dir: /var/lib/dataplaneapi/backups
haproxy:
  config_file: /etc/haproxy/haproxy.cfg
  haproxy_bin: /usr/sbin/haproxy
  master_runtime: /var/run/haproxy.sock
  master_worker_mode: true
  reload:
    reload_delay: 5
    service_name: haproxy
    reload_strategy: systemd
log_targets:
- log_to: file
  log_file: /var/log/dataplaneapi.log
  log_level: info
  log_types:
  - access
  - app

I guess it is some kind of misconfigure issue but I have lost in the code of dataplaneapi.
Any help?

I have tried 3.2.3

time="2025-10-04T04:10:35Z" level=info msg="HAProxy Data Plane API v3.2.3 daff5f5e"
time="2025-10-04T04:10:35Z" level=info msg="Reload strategy: systemd"
time="2025-10-04T04:10:35Z" level=info msg="Build from: https://github.com/haproxytech/dataplaneapi"
time="2025-10-04T04:10:35Z" level=info msg="Build date: 2025-08-07T14:07:34Z"
time="2025-10-04T04:10:35Z" level=debug msg="discovery job starting" ID=8328ca23-c6e4-4e9e-815f-1489baf2baf3 ServiceDiscovery=AWS
time="2025-10-04T04:10:35Z" level=debug msg="-- command socket updating client_native client"
time="2025-10-04T04:10:35Z" level=info msg="Serving data plane at http://[::]:5555"
time="2025-10-04T04:10:35Z" level=debug msg="-- command socket Server. conf ready..."
time="2025-10-04T04:10:35Z" level=debug msg="-- command socket handleClientNativeClientUpdate stopped"
time="2025-10-04T04:10:35Z" level=debug msg="Mode: single"
time="2025-10-04T04:10:35Z" level=debug msg="-- command socket not set (--debug_socket_path). Not running the command socket server"

The error message doesn't show but dataplaneapi still reloads haproxy when changes in service discovery happen.

FYI, the EventListener only starts if HAProxy runs in master/worker mode. It is only used during ACME renewals for now.

Thank you for the information.
I misunderstood the EventListener relevant logs. I thought it meant dataplaneapi failed to use the admin socket.

Still, thanks for the report. I will investigate because this should not happen. The EventListener is just a permanent connection to the Master socket.

@oliwer

@oliwer I used the version 3.2.8 with haproxy started in master worker mode:

root       218   215  0 18:10 ?        00:00:00 /usr/local/sbin/haproxy -W -db -f /etc/haproxy/haproxy.cfg
root       220   215  0 18:10 ?        00:00:01 /usr/local/sbin/dataplaneapi -f /etc/haproxy/dataplaneapi.yaml
jboss      227   218  0 18:10 ?        00:00:00 /usr/local/sbin/haproxy -W -db -f /etc/haproxy/haproxy.cfg

but i noticed the error during startup and all runtime APIs fail:

time="2026-02-19T18:10:28+01:00" level=info msg="HAProxy Data Plane API v3.2.8 9a2438ba"
time="2026-02-19T18:10:28+01:00" level=info msg="Build from: https://github.com/haproxytech/dataplaneapi"
time="2026-02-19T18:10:28+01:00" level=info msg="Build date: 2026-01-29T16:36:17Z"
time="2026-02-19T18:10:28+01:00" level=info msg="Reload strategy: custom"
time="2026-02-19T18:10:28+01:00" level=error msg="Failed to start HAProxy's event listener:version data not found"
time="2026-02-19T18:10:28+01:00" level=debug msg="-- command socket updating client_native client"
time="2026-02-19T18:10:29+01:00" level=info msg="Serving data plane at http://[::]:9010"
time="2026-02-19T18:10:29+01:00" level=debug msg="-- command socket Server. conf ready..."
time="2026-02-19T18:10:29+01:00" level=debug msg="Mode: single"
time="2026-02-19T18:10:29+01:00" level=info msg="-- command socket Starting on /data/external/haproxy/run/dataplane-debug.sock"

Marcello

@cello86

@cello86 This means dataplaneapi was not able to determine which version of HAProxy is running. It's the first thing it tries to do at startup when connecting to the master socket. When that fails, nothing using the socket will work.

@oliwer

@oliwer I configured the socket:

  stats socket /data/external/haproxy/run/haproxy.sock mode 660 level admin expose-fd listeners
  stats timeout 2m

I tested it via socat:

# echo "show info" | sudo socat stdio unix-connect:/data/external/haproxy/run/haproxy.sock | grep -i version
Version: 3.2.12-6011f448e

I can't find the solution for this issue. I also noticed that if I update the configuration via API the file haproxy.cfg changes but the reload command doesn't be executed.

Marcello

I think I found what's wrong: you've run haproxy with -W but did not specify the master socket address with -S. So dataplaneapi is talking to you stats socket thinking it's a master socket.

I think you want to run: haproxy -W -S /data/external/haproxy/run/master.sock -db -f /etc/haproxy/haproxy.cfg and use that address to configure the master_runtime option in dataplaneapi.yml.

This chapter is useful: https://docs.haproxy.org/3.3/management.html#9.4

I think I found what's wrong: you've run haproxy with -W but did not specify the master socket address with -S. So dataplaneapi is talking to you stats socket thinking it's a master socket.

I think you want to run: haproxy -W -S /data/external/haproxy/run/master.sock -db -f /etc/haproxy/haproxy.cfg and use that address to configure the master_runtime option in dataplaneapi.yml.

Hi, from the source code it seems that only supports UNIX sockets and not TCP4/TCP6, right?

That is correct and it is by design. UNIX socket only.

That is correct and it is by design. UNIX socket only.

Ok, thank you. I noticed it because stats socket supports tcp sockets.

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Failed to start HAProxy's event listener:version data not found #391

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Failed to start HAProxy's event listener:version data not found #391

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islue commented on Oct 4, 2025

oliwer commented on Oct 6, 2025

islue commented on Oct 6, 2025

oliwer commented on Oct 6, 2025

cello86 commented on Feb 19, 2026

oliwer commented on Feb 19, 2026

cello86 commented on Feb 19, 2026

oliwer commented on Feb 19, 2026

oliwer commented on Feb 19, 2026

ema-pe commented on Apr 2, 2026

oliwer commented on Apr 2, 2026

ema-pe commented on Apr 2, 2026

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