By Dmytro Nasyrov, Founder, CTO at Pharos Production Inc. And Pharos Production Inc. - Web3, blockchain, fintech, defi software development services

nodefinder: Strategies for automatic node discovery in Erlang

Description

All strategies have been combined into this Erlang application after being refactored.

(The source code is a fork of http://code.google.com/p/nodefinder/)

EC2 tags and groups selection are selected with the following syntax (if a tuple doesn't make the boolean expression explicitly AND or OR the list is implicitly an OR):

[Entry... |
 {'AND', [Entry...]} |
 {'OR', [Entry...]}]
 
  tags: Entry == "key" |
                 ["key1", "key2"] |
                 {"key3", "value3"} |
                 {["key4", "key5"], "value4"} |
                 {"key6", ["value6", "value7"]} |
                 {["key8", "key9"], ["value9", "value8"]}
 
groups: Entry == "security_group_name"

Build

rebar compile

Example

LAN multicast (requires that ntpd is running)

$ erl -sname foo1@localhost -pz ebin/
(foo1@localhost)1> application:ensure_all_started(nodefinder).
{ok,[inets,xmerl,crypto,asn1,public_key,ssl,nodefinder]}
(foo1@localhost)2> nodes(). 
[]
(foo1@localhost)3> nodefinder:multicast_start().
{ok,<0.52.0>}
(foo1@localhost)4> nodes().
[foo2@localhost]
(foo1@localhost)5> nodefinder:multicast_discover(5000).
ok
(foo1@localhost)6> nodes().
[foo2@localhost]
(foo1@localhost)7> nodefinder:multicast_stop().
ok
(foo1@localhost)8> nodefinder:multicast_stop().
{error,not_found}

$ erl -sname foo2@localhost -pz ebin/
(foo2@localhost)1> application:ensure_all_started(nodefinder).
{ok,[inets,xmerl,crypto,asn1,public_key,ssl,nodefinder]}
(foo2@localhost)2> nodes(). 
[]
(foo2@localhost)3> nodefinder:multicast_start().
{ok,<0.52.0>}
(foo2@localhost)4> nodes().
[foo1@localhost]
(foo2@localhost)5> nodefinder:multicast_discover(5000).
ok
(foo2@localhost)6> nodes().
[foo1@localhost]
(foo2@localhost)7> nodefinder:multicast_stop().
ok

EC2

Functionality details:

• The same Erlang distributed node name is used (separate Erlang VMs must be on separate EC2 instances)
• Connections between regions are not supported due to the high latency

Add security group TCP rules for:

• port 4369 (epmd) 10.0.0.0/8
• ports 4374-4474 (inet_dist_listen) 10.0.0.0/8

Example:

$ cat << EOF > sys.config
[{kernel, [
    {inet_dist_listen_min, 4374},
    {inet_dist_listen_max, 4474}]}].
EOF
$ erl -name test -config sys.config -pz ebin/
> application:ensure_all_started(nodefinder).
> nodes().
> Host = "ec2.amazonaws.com".
> Key = "".
> SecretKey = "".
> nodefinder:ec2_start(Key, SecretKey, Host, ["www"], []).
> nodefinder:ec2_stop().
> nodes().
> [net_kernel:disconnect(N) || N <- nodes()].
> nodefinder:ec2_start(Key, SecretKey, Host, [], [{"Tag1", "Value1"}]).
> nodefinder:ec2_stop().
> nodes().
> [net_kernel:disconnect(N) || N <- nodes()].
> nodefinder:ec2_start(Key, SecretKey, Host, [], ["Tag1"]).
> nodefinder:ec2_stop().
> nodes().
> [net_kernel:disconnect(N) || N <- nodes()].

• First, connect to all EC2 instances in the "www" security group that are running with a 'test' node name
• Second, connect to all EC2 instances with a tag Tag1=Value1 that are running with a 'test' node name
• Third, connect to all EC2 instances with a tag Tag1 that are running with a 'test' node name

Tests

rebar compile
rebar eunit skip_deps=true

License

MIT License