peer_discovery_backend requires module name specified (at least for Consul)

[tj90241]

Compiled 3.10.12 from source and configured it for use with the Consul discovery plugin per documentation, which states:

"To use Consul for peer discovery, set the cluster_formation.peer_discovery_backend to consul or its module name, rabbit_peer_discovery_consul"

So, this should work:

{rabbit, [
  {cluster_formation, [
    {peer_discovery_backend, consul},
    {consul, [
...

However, when booting rabbitmq-server, it failed with:

BOOT FAILED
===========
Exception during startup:

error:undef

    consul:supports_registration/0
        args: []
    rabbit_peer_discovery:maybe_register/0, line 124
    rabbit_mnesia:init/0, line 82
    rabbit_boot_steps:-run_step/2-lc$^0/1-0-/2, line 41
    rabbit_boot_steps:run_step/2, line 48
    rabbit_boot_steps:-run_boot_steps/1-lc$^0/1-0-/1, line 19
    rabbit_boot_steps:run_boot_steps/1, line 20
    rabbit:start/2, line 906

Kernel pid terminated (application_controller) ({application_start_failure,rabbit,{undef,{rabbit,start,[normal,[]]}}})

Crash dump is being written to: /var/log/rabbitmq/erl_crash.dump...done

So clearly, it can't find the plugin. Which led me to make no other changes to my configuration, other than changing peer_discovery_backend to the module name (rabbitmq_peer_discovery_consul). This worked, and there was no more error:undef thrown for consul:supports_registration/0.

[tj90241]

The configuration schema also seems to be namespaced differently?

I'm groking: https://www.rabbitmq.com/cluster-formation.html

which says e.g.:

cluster_formation.peer_discovery_backend = consul

cluster_formation.consul.host = consul.eng.example.local
cluster_formation.consul.acl_token = acl-token-value

However, I had to namespace everything like this based on the source code, which worked:

{rabbit, [
  {cluster_formation, [
    {peer_discovery_backend, rabbitmq_peer_discovery_consul},
    {peer_discovery_consul, [
      {consul_host, "consul.service.consul.<REDACTED>"},
      {consul_acl_token, "<REDACTED>"},
      {consul_port, 8501},
      {consul_scheme, https},
      {consul_ssl_options, [
        {cacertfile, "/etc/rabbitmq/ssl/consul_chain.pem"},
        {certfile,   "/etc/rabbitmq/ssl/consul_cert.pem"},
        {keyfile,    "/etc/rabbitmq/ssl/consul_privkey.pem"}
      ]},
      {consul_svc, rabbitmq},
      {consul_svc_addr_auto, false},
      {consul_svc_addr, "<REDACTED>"},
      {consul_use_longname, true}

except consul_ssl_options -- those don't seem to be respected, anymore after having been added in 8f8a138

[lukebakken]

The configuration you have provided, that begins with {rabbit, [, is in Erlang term format, and goes into the advanced.config file.

In general, the documentation refers to the ini-style configuration that should be in the rabbitmq.conf file. You should be able to provide all of your Consul configuration in that file and not use the Erlang term format configuration.

https://www.rabbitmq.com/cluster-formation.html#peer-discovery-consul

So, in your /etc/rabbitmq/rabbitmq.conf file, have the following contents:

cluster_formation.peer_discovery_backend = consul

cluster_formation.consul.host = consul.eng.example.local
cluster_formation.consul.acl_token = acl-token-value
cluster_formation.consul.port = 8501
cluster_formation.consul.scheme = https
cluster_formation.consul.ssl_options.cacertfile = /etc/rabbitmq/ssl/consul_chain.pem
cluster_formation.consul.ssl_options.certfile = /etc/rabbitmq/ssl/consul_cert.pem
cluster_formation.consul.ssl_options.keyfile = /etc/rabbitmq/ssl/consul_privkey.pem
cluster_formation.consul.svc = rabbitmq
cluster_formation.consul.svc_addr_auto = false
cluster_formation.consul.svc_addr = <REDACTED>
cluster_formation.consul.use_longname = true

[tj90241]

hmm, thanks -- sorry for wasting your time!

[lukebakken]

No worries, let us know if you have issues with the configuration I provided. The fact you can configure RabbitMQ two different ways is not amenable to new users.