# process_group
[](https://github.com/relayr/erl-process-group/actions?query=workflow%3A%22Erlang+CI%22) [](https://hex.pm/packages/process_group) [](https://coveralls.io/github/relayr/erl-process-group?branch=master)
Application for managing of distributed process groups with API compatible with [OTP 'pg2' module](http://erlang.org/doc/man/pg2.html).
Each process group is managed by a single gen_server that creates protected ETS table for faster access. This allows to remove bottleneck of 'pg2' of each call going through gen_server.
Process group gen_server is responsible for monitoring of attached processes and removing them from ETS if any of these processes went down.
## Usage
#### create/1
Create new named process group
```
1> process_group:create(my_group).
ok
```
#### join/1,2
Add new process to specified group
```
2> PID = self().
<0.170.0>
3> process_group:join(my_group, PID).
ok
```
#### join/3
Add new process to specified group and attach some static process state to it. This state can be used when passing notification function as an argument to `notify_members/2`.
```
4> process_group:join(my_group, PID, #{reply => true}).
ok
```
#### get_members/1
Get members of process group
```
5> process_group:get_members(my_group).
[<0.170.0>]
```
#### notify_members/2
Send message to all processes in specific group
```
6> process_group:notify_members(my_group, {data, [test_msg]}).
ok
7> flush().
Shell got {data,[test_msg]}
ok
```
The above is equivalent to using function and sending notification message in it:
```
8> process_group:notify_members(my_group, fun(PID, _State) -> PID ! {data, [test_msg]}, ok end).
ok
```
Based on state passed to this function you can decide not to send any notification at all and invoke additional functions e.g.
```
9> process_group:notify_members(my_group,
fun(PID, State) ->
case maps:get(reply, State) of
true ->
PID ! {data, [test_msg]},
ok;
_ ->
logger:warning("Process ~p not replied", [PID]),
ok
end
end).
ok
```
#### leave/1,2
Remove process from specific group
```
10> process_group:leave(my_group, PID).
ok
```
#### delete/1
Delete process group
```
11> process_group:delete(my_group).
ok
```
