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Running Multiple Nodes per machine

During testing or development, you might want to run more than one node per box. For example, you might want to run two nodes ("ns_1" and "ns_2") on your development laptop. To do so requires priv/config file propery overrides. Here are the step by step instructions...

There are helper scripts that help generate the right multi-node configuration files. To get a 5 node cluster config file, so that all the nodes (n_0, n_1, ...) run on 127.0.0.1...

./test/gen_cluster_scripts.rb 5

To start the cluster...

./cluster_run.sh

Now, you can point your web browser to...

http://localhost:9000
http://localhost:9001
...
http://localhost:9004

And, you can join the nodes together with the web console UI.

The memcached direct servers will be running on even port numbers...

12000, 12002, 12004, ...

The emoxi servers will be running on odd port numbers

12001, 12003, 12005, ...

To stop the cluster press Ctrl-D or Ctrl-C.

After you've joined nodes together, they will remember their join configuration (in the ./config directory) and when you start/stop the cluster, they should automatically rejoin.


Below are the old manual instructions for joining nodes together into a cluster...

Make a copy of the priv/config file...

cp priv/config priv/config2

Start erlang...

erl -name ns_1

Make a note of your "node name" at erlang's shell prompt. For example, below my node name is "ns_1@stevenmb.gateway.2wire.net"...

stevenmb:ns_server steveyen$ erl -name ns_1
Erlang R13B03 (erts-5.7.4) [source]
Eshell V5.7.4  (abort with ^G)
(ns_1@stevenmb.gateway.2wire.net)1>

Quit/ctrl-C from the erlang shell.

Next, open up your favorite text editor to edit the priv/config2 file. You'll need to edit everywhere you see a port number, and add extra "per-node" entries. One by one...

In your priv/config2 file, if you see...

{rest, [{'_ver', {0, 0, 0}},
        {port, 8091}
       ]}.

Add an additional "per-node" entry right below it, so it looks like...

{rest, [{'_ver', {0, 0, 0}},
        {port, 8091}
       ]}.
{{node, 'ns_2@stevenmb.gateway.2wire.net', rest},
     [{'_ver', {0, 0, 0}},
      {port, 8081}
     ]}.

With the above change, the priv/config2 file is saying that by default the rest key has a port value of 8091. And, on node ns_2@stevenmb.gateway.2wire.net, the value of the rest key will have a port number of 8081. So, when ns_1 and ns_2 run on the same machine, they won't have a REST admin api port conflict.

By the way, you can add more than one "per-node" entries, which is useful in case you move your machine between networks. For example, I have 3 extra entries, one for the office, one for home, and one for when I'm not connected. So, my per-node overrides in my priv/config2 file look like...

{rest, [{'_ver', {0, 0, 0}},
        {port, 8091}
       ]}.
{{node, 'ns_2@stevenmb.gateway.2wire.net', rest},
     [{'_ver', {0, 0, 0}},
      {port, 8081}
     ]}.
{{node, 'ns_2@stevenmb.hsd1.ca.comcast.net', rest},
     [{'_ver', {0, 0, 0}},
      {port, 8081}
     ]}.
{{node, 'ns_2@stevenmb.local', rest},
     [{'_ver', {0, 0, 0}},
      {port, 8081}
     ]}.

Let's keep going, as there are more "per-node" entries to handle more port conflicts...

Do the same for the "port_servers" key. For example...

{port_servers,
  [{'_ver', {0, 0, 0}},
   {memcached, "./memcached",
    [
     "-E", "engines/default_engine.so",
     "-p", "11212"
     ],
    [{env, [{"MEMCACHED_CHECK_STDIN", "thread"},
            {"ISASL_PWFILE", "/tmp/isasl.pw"} % Also isasl_path above.
           ]}]
   }
  ]}.
{{node, 'ns_2@stevenmb.gateway.2wire.net', port_servers},
  [{'_ver', {0, 0, 0}},
   {memcached, "./memcached",
    [
     "-E", "engines/default_engine.so",
     "-p", "11222"
     ],
    [{env, [{"MEMCACHED_CHECK_STDIN", "thread"},
            {"ISASL_PWFILE", "/tmp/isasl.pw"} % Also isasl_path above.
           ]}]
   }
  ]}.

Above, ns_1 will start a memcached running on port 11212 since that's the default setting; and ns_2 will start a memcached running on port 11222.

And, the same for your pools port number. This one is a little special, where the per-node overrides are inside the nested value.

So, instead of the default config...

{pools, [
  {'_ver', {0, 0, 0}},
  {"default", [
    {port, 11213},
    {buckets, [
      {"default", [
        {auth_plain, undefined},
        {size_per_node, 64} % In MB.
      ]}
    ]}
  ]}
]}.

You will make it instead look like, adding per-node port overrides inside the value.

{pools, [
  {'_ver', {0, 0, 0}},
  {"default", [
    {port, 11213},
    {{node, 'ns_2@stevenmb.gateway.2wire.net', port}, 11223},
    {{node, 'ns_2@stevenmb.hsd1.ca.comcast.net', port}, 11223},
    {{node, 'ns_2@stevenmb.local', port}, 11223},
    {buckets, [
      {"default", [
        {auth_plain, undefined},
        {size_per_node, 64} % In MB.
      ]}
    ]}
  ]}
]}.

Copyright (c) 2011, Couchbase, Inc.

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