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lib/phoenix/topic/server.ex

defmodule Phoenix.Topic.Server do
use GenServer.Behaviour
alias Phoenix.Topic
alias Phoenix.Topic.Server
alias Phoenix.Topic.GarbageCollector
defstruct role: :slave,
gc_buffer: [],
garbage_collect_after_ms: 60_000..300_000
def start_link do
:gen_server.start_link __MODULE__, [], []
end
def leader_pid, do: :global.whereis_name(__MODULE__)
def init(_) do
case :global.register_name(Phoenix.Topic.Server, self) do
:no ->
Process.link(leader_pid)
{:ok, %Server{role: :slave}}
:yes ->
send(self, :garbage_collect_all)
{:ok, %Server{role: :leader}}
end
end
def handle_call(_message, _from, %Server{role: :slave}) do
{:stop, :error, nil, :slave}
end
def handle_call({:exists?, group}, _from, state) do
{:reply, exists?(group), state}
end
def handle_call({:active?, group}, _from, state) do
{:reply, active?(group), state}
end
def handle_call({:create, group}, _from, state) do
if exists?(group) do
{:reply, :ok, state}
else
:ok = :pg2.create(group)
{:reply, :ok, GarbageCollector.mark(state, group)}
end
end
def handle_call({:subscribe, pid, group}, _from, state) do
{:reply, :pg2.join(group, pid), state}
end
def handle_call({:unsubscribe, pid, group}, _from, state) do
{:reply, :pg2.leave(group, pid), state}
end
def handle_call({:delete, group}, _from, state) do
{:reply, delete(group), state}
end
def handle_info(_message, %Server{role: :slave}), do: {:stop, :error, nil, :slave}
def handle_info({:garbage_collect, groups}, state) do
active_groups = Enum.filter groups, fn group ->
if active?(group) do
true
else
delete(group)
false
end
end
{:noreply, GarbageCollector.mark(state, active_groups)}
end
def handle_info(:garbage_collect_all, state) do
{:noreply, GarbageCollector.mark(state, Topic.list)}
end
defp exists?(group) do
case :pg2.get_closest_pid(group) do
pid when is_pid(pid) -> true
{:error, {:no_process, _}} -> true
{:error, {:no_such_group, _}} -> false
end
end
defp active?(group) do
case :pg2.get_closest_pid(group) do
pid when is_pid(pid) -> true
_ -> false
end
end
defp delete(group), do: :pg2.delete(group)
end