Node names and cluster with CouchDB 2.0

[Simon Keary]

Hi All,

I'm trying to setup a test CouchDB cluster across two machines and struggling to get it working and understanding how the node names work. I'm am able to sucessfully call the _nodes endpoint on one of the machines to add the other but I don't think this is doing the right thing since the cluster_nodes array is updated with the new node but the all_nodes array isn't...

Where I think I'm going wrong is setting the node names in the the vm.args files and then specifying the correct node name when trying to add the second machine to the first instance. In my case the machines have host names but neither machine can contact the other via this and can only contact the other via IP address. Ideally I'd only like the machines to connect to each other via IP and not host name as this will make maintenance of the cluster much simpler going forward. In this situation I'm not sure of:

* Whether I should be setting -sname or -name in vm.args. When using -name, my testing suggests I should use a name of the form "node1" with no @ symbol. Is this right?
* For -name I'm not sure whether it's supposed to be "node1@<the ip address>" or "node1@<the hostname>" or "node1@localhost"?
* Once I've set the name I'm not sure how to refer to the other node when trying to add it via curl. If I've used -sname should I just use the short name (e.g. "node2") or "node2@<the ip address>"? If -name is used in vm.args is the correct thing to do to use "node2@<the ip address>"?

I don't believe I have a connectivity issue between the nodes but the ports that are open between them are 4369, 5984, 5986, 9100-9200 (all TCP) and all UDP.

When trying to remove the node, to try further variants to see if they work, I get an error about a document conflict. I suspect this is because CouchDB is getting into a strange state but this makes a trial and error process of figuring out how the node names work as difficult to say the least.

Any help would be appreciated - Thanks!
Simon




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[Adam Kocoloski]

Hi Simon, if your nodes need to find each other by IP address you should use -name. You can specify it in VM.args like

-name couchdb@<the IP address>

There shouldn't be a need to change the "couchdb@" element for each node unless you want to run multiple nodes on the same IP (not recommended).

When you add the peer nodes into the _nodes database you should use the same format; each document should have an ID like "couchdb@<the IP address>".

The firewall ports look fine provided that your vm.args file includes these lines

-kernel inet_dist_listen_min 9100
-kernel inet_dist_listen_max 9200

Cheers, Adam

[Simon Keary]

Hi Adam,

Thanks so much - I have a cluster working now!

A key part I was missing was adding these lines to vm.args:

-kernel inet_dist_listen_min 9100
-kernel inet_dist_listen_max 9200

I had incorrectly assumed that these were the default settings based on the documentation.

I'm (obviously) very new to clustering but I'll see if I can suggest a couple of tweaks to the documentation via a PR .

Thanks again,
Simon

[Adam Kocoloski]

That would be _most_ welcome. Glad we got this sorted out. Cheers,

Adam