Using avahi to expose consul server via mdns

Consul
1

Hi everybody,

I would like to configure my consul client to use an “auto-discovered consul server”. In the doc most of the examples show a config with: “retry_join”:[ “192.168.1.1”] but I would like to avoid hard-coding ip or name.

To try to do this:

  • I’ve installed avahi and consul on a linux machine.
  • I’ve defined an avahi service on this machine using this config file:
    sudo nano /etc/avahi/services/evs-hwfw-consul-server.service
> <?xml version="1.0" standalone='no'?>
> <!DOCTYPE service-group SYSTEM "avahi-service.dtd">
> <service-group>
>   <name replace-wildcards="yes">Xts Consul Server on %h</name>
>   <service>
>     <type>_evs-hwfw-xts-consul-server._tcp</type>
>     <port>8300</port>
>   </service>
> </service-group>
  • I can see my service using avahi-browse on that linux machine or from another linux pc in the same Lan
  • I launch my consul server on this machine and all is ok from consul side.

After that, I

  • I install consul on another linux machine
  • I launch it as a client with the following config:
    {
    “advertise_addr”: “10.129.170.14”,
    “bind_addr”: “10.129.170.14”,
    “bootstrap_expect”: 1,
    “client_addr”: “0.0.0.0”,
    “datacenter”: “bha_dc”,
    “data_dir”: “/home/bha/grafana/consul/data”,
    “domain”: “consul”,
    “enable_script_checks”: true,
    “dns_config”: {
    “enable_truncate”: true,
    “only_passing”: true
    },
    “enable_syslog”: false,
    “encrypt”: “”,
    “leave_on_terminate”: true,
    “log_level”: “DEBUG”,
    “rejoin_after_leave”: true,
    “retry_join”: [
    “provider=mdns”,
    “service=_evs-hwfw-xts-consul-server._tcp.local”
    ],
    “server”: true,
    “ui_config”: {
    “enabled”: true
    }
    }

When i launch consul i can see in the log:
2024-06-21T15:15:30.172+0200 [INFO] agent: Retry join is supported for the following discovery methods: cluster=LAN discovery_methods=“aliyun aws azure digitalocean gce hcp k8s linode mdns os packet scaleway softlayer tencentcloud triton vsphere”
2024-06-21T15:15:30.172+0200 [INFO] agent: Joining cluster…: cluster=LAN
2024-06-21T15:15:30.172+0200 [DEBUG] agent: discover: Using provider “mdns”: cluster=LAN
2024-06-21T15:15:30.172+0200 [WARN] agent.router.manager: No servers available
2024-06-21T15:15:30.172+0200 [ERROR] agent.anti_entropy: failed to sync remote state: error=“No known Consul servers”
2024-06-21T15:15:30.172+0200 [ERROR] agent: Cannot discover address: cluster=LAN address=provider=mdns error="discover-mdns: Service record not provided. Please specify a service record for the mDNS lookup."
2024-06-21T15:15:30.172+0200 [INFO] agent: (LAN) joining: lan_addresses=[“service=_evs-hwfw-xts-consul-server._tcp.local”]
2024-06-21T15:15:30.192+0200 [WARN] agent.client.memberlist.lan: memberlist: Failed to resolve service=_evs-hwfw-xts-consul-server._tcp.local: lookup service=_evs-hwfw-xts-consul-server._tcp.local: no such host
2024-06-21T15:15:30.192+0200 [WARN] agent: (LAN) couldn’t join: number_of_nodes=0
error=
| 1 error occurred:
| \t* Failed to resolve service=_evs-hwfw-xts-consul-server._tcp.local: lookup service=_evs-hwfw-xts-consul-server._tcp.local: no such host
|

2024-06-21T15:15:30.192+0200 [WARN] agent: Join cluster failed, will retry: cluster=LAN retry_interval=30s
error=
| 1 error occurred:
| \t* Failed to resolve service=_evs-hwfw-xts-consul-server._tcp.local: lookup service=_evs-hwfw-xts-consul-server._tcp.local: no such host
|

If i type avahi-browse -rt _evs-hwfw-xts-consul-server._tcp on this machine:

  • enp1s0f0 IPv6 Xts Consul Server on fw-xta2 _evs-hwfw-xts-consul-server._tcp local
  • enp1s0f0 IPv4 Xts Consul Server on fw-xta2 _evs-hwfw-xts-consul-server._tcp local
    = enp1s0f0 IPv6 Xts Consul Server on fw-xta2 _evs-hwfw-xts-consul-server._tcp local
    hostname = [fw-xta2.local]
    address = [fe80::ec4:7aff:fe57:9238]
    port = [8300]
    txt =
    = enp1s0f0 IPv4 Xts Consul Server on fw-xta2 _evs-hwfw-xts-consul-server._tcp local
    hostname = [fw-xta2.local]
    address = [10.129.170.14]
    port = [8300]
    txt =

i can see the _evs-hwfw-xts-consul-server._tcp service, so i a little bit lost/disappointed :-):

Why consul is not able to see/use my mdns avahi service ?

  • Am i missing something ?
  • Is what i try to do is possible with consul/avahi ?
  • Is it a better way to do this ?

Any ideas, suggestions and/or comments are welcome

Best regards

2

Nobody can help ?
Please, can you just tell me if what i want to do is possible, or stupid :slight_smile: