DNS Peer Discovery Backend and rabbit@IP

[Adrien.]

Hello there,

I'm using mesos / marathon to spawn my cluster, and I'm trying to
automatically disover nodes.
I found that mesos use a internal DNS to provide access to all nodes

extract:
dig test-rmq.marathon.mesos +short
172.16.17.3
172.16.6.3

but there is no reverse lookup for these ip in the internal mesos DNS.

So I found a way to start RMQ with rabbot@IP mode,
Working fine, my hosts start as rab...@172.16.17.3
My issue, is when I start my second node, I can't resolve the DNS lookup
and fail.

Any idea how to prevent it ?

I'm think about a small script that will edit the config file with the
rights entries

Some log from the startup of the second node:

/rmq/test> 2018-05-06 20:49:21.193 [info] <0.193.0> Node database directory
at /var/lib/rabbitmq/mnesia/rab...@172.16.6.3 is empty. Assuming we need to
join an existing cluster or initialise from scratch...
/rmq/test> 2018-05-06 20:49:21.193 [info] <0.193.0> Configured peer
discovery backend: rabbit_peer_discovery_dns
/rmq/test> 2018-05-06 20:49:21.193 [info] <0.193.0> Will try to lock with
peer discovery backend rabbit_peer_discovery_dns
/rmq/test> 2018-05-06 20:49:21.193 [info] <0.193.0> Peer discovery backend
does not support locking, falling back to randomized delay
/rmq/test> 2018-05-06 20:49:21.193 [info] <0.193.0> Peer discovery backend
rabbit_peer_discovery_dns does not support registration, skipping
randomized startup delay.
/rmq/test> 2018-05-06 20:49:21.202 [info] <0.193.0> Addresses discovered
via AAAA records of test-rmq.marathon.mesos:
/rmq/test> 2018-05-06 20:49:21.196 [info] <0.193.0> Addresses discovered
via A records of test-rmq.marathon.mesos: 172.16.17.3
/rmq/test> 2018-05-06 20:49:21.201 [error] <0.193.0> Reverse DNS lookup for
address 172.16.17.3 failed: nxdomain
/rmq/test> 2018-05-06 20:49:21.202 [info] <0.193.0> All discovered existing
cluster peers:
/rmq/test> 2018-05-06 20:49:21.202 [info] <0.193.0> Discovered no peer
nodes to cluster with
/rmq/test> 2018-05-06 20:49:21.204 [info] <0.33.0> Application mnesia
exited with reason: stopped
/rmq/test> 2018-05-06 20:49:21.321 [info] <0.33.0> Application mnesia
started on node 'rab...@172.16.6.3'
/rmq/test> 2018-05-06 20:49:22.999 [info] <0.193.0> Peer discovery backend
rabbit_peer_discovery_dns does not support registration, skipping
registration.
/rmq/test> 2018-05-06 20:49:23.075 [info] <0.193.0> message_store upgrades:
No durable queues found. Skipping message store migration
/rmq/test> 2018-05-06 20:49:23.075 [info] <0.193.0> message_store upgrades:
Removing the old message store data
/rmq/test> 2018-05-06 20:49:23.143 [info] <0.193.0> Creating user 'stagging'

Thank you

[Michael Klishin]

This is a Mesos IP management question more than anything else.

Are you sure the DNS backend is what you want if you don't control hostname resolution?

Are you aware of Erlang's inetrc feature? [1]

1. http://erlang.org/doc/apps/erts/inet_cfg.html

2. https://groups.google.com/d/msg/rabbitmq-users/QYrtYmGZavg/g3lSPd47AQAJ

On Sun, May 6, 2018 at 4:14 PM, Adrien. <adrien...@gmail.com> wrote:

Hello there,

I'm using mesos / marathon to spawn my cluster, and I'm trying to
automatically disover nodes.
I found that mesos use a internal DNS to provide access to all nodes

extract:
dig test-rmq.marathon.mesos +short
172.16.17.3
172.16.6.3

but there is no reverse lookup for these ip in the internal mesos DNS.

So I found a way to start RMQ with rabbot@IP mode,
Working fine, my hosts start as rab...@172.16.17.3
My issue, is when I start my second node, I can't resolve the DNS lookup
and fail.

Any idea how to prevent it ?

I'm think about a small script that will edit the config file with the
rights entries

Some log from the startup of the second node:

/rmq/test> 2018-05-06 20:49:21.193 [info] <0.193.0> Node database directory

at /var/lib/rabbitmq/mnesia/rabbit...@172.16.6.3 is empty. Assuming we need to

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MK

Staff Software Engineer, Pivotal/RabbitMQ