Here some code example I ran with livebook:
For the server side:
defmodule Listener do
use GenServer
def start_link(arg) do
GenServer.start_link(__MODULE__, arg)
end
def init(arg) do
port = Keyword.get(arg, :port)
{:ok, listen_socket} =
:gen_tcp.listen(port, [
:binary,
{:packet, 4},
{:active, :once},
{:reuseaddr, true},
{:backlog, 500}
])
Enum.each(1..100, fn _ ->
spawn(fn -> accept_loop(listen_socket) end)
end)
{:ok, %{listen_socket: listen_socket}}
end
def accept_loop(listen_socket) do
case :gen_tcp.accept(listen_socket) do
{:ok, socket} ->
{:ok, pid} = AcceptedConnection.start_link(socket: socket)
:gen_tcp.controlling_process(socket, pid)
accept_loop(listen_socket)
{:error, _} = e ->
e
end
end
end
defmodule AcceptedConnection do
use GenServer
def start_link(arg) do
GenServer.start_link(__MODULE__, arg)
end
def init(arg) do
socket = Keyword.get(arg, :socket)
{:ok, %{socket: socket}}
end
def handle_info({:tcp, socket, data}, state) do
:inet.setopts(socket, active: :once)
# Reply back the message
:gen_tcp.send(socket, data)
{:noreply, state}
end
def handle_info({:tcp_closed, _}, state) do
{:stop, :normal, state}
end
end
For the client:
defmodule Connection do
use GenServer
def start_link(arg) do
GenServer.start_link(__MODULE__, arg)
end
def send_message(pid, msg) do
GenServer.call(pid, {:send_message, msg})
end
def init(arg) do
ip = Keyword.get(arg, :ip)
port = Keyword.get(arg, :port)
Registry.register(ConnectionRegistry, :connections, _value = nil)
{:ok, socket} = :gen_tcp.connect(ip, port, [:binary, {:packet, 4}, {:active, :once}])
{:ok, %{socket: socket, requests: %{}, next_id: 1}}
end
def handle_call({:send_message, data}, from, state = %{socket: socket, next_id: next_id}) do
:gen_tcp.send(socket, <<next_id::32, data::binary>>)
new_state =
state
|> Map.update!(:next_id, &(&1 + 1))
|> Map.update!(:requests, &Map.put(&1, next_id, from))
{:noreply, new_state}
end
def handle_info(
{:tcp, _, <<id::32, data::binary>>},
state = %{socket: socket, requests: requests}
) do
:inet.setopts(socket, active: :once)
{from, requests} = Map.pop(requests, id)
GenServer.reply(from, {:ok, data})
{:noreply, %{state | requests: requests}}
end
def handle_info({:tcp_closed, _}, state) do
Registry.unregister(ConnectionRegistry, :connections)
{:stop, :normal, state}
end
end
Benchmark suite:
port = 10_000
{:ok, pid} = Listener.start_link(port: port)
%{listen_socket: listen_socket} = :sys.get_state(pid)
Registry.start_link(name: ConnectionRegistry, keys: :duplicate)
{:ok, conn1} = Connection.start_link(ip: {127, 0, 0, 1}, port: port)
{:ok, conn2} = Connection.start_link(ip: {127, 0, 0, 1}, port: port)
{:ok, conn2} = Connection.start_link(ip: {127, 0, 0, 1}, port: port)
{:ok, socket1} = :gen_tcp.connect({127, 0, 0, 1}, port, [:binary, {:packet, 4}, {:active, false}])
{:ok, socket2} = :gen_tcp.connect({127, 0, 0, 1}, port, [:binary, {:packet, 4}, {:active, false}])
{:ok, socket3} = :gen_tcp.connect({127, 0, 0, 1}, port, [:binary, {:packet, 4}, {:active, false}])
if :ets.info(:connections) == :undefined do
:ets.new(:connections, [:named_table, :public, read_concurrency: true])
end
:ets.insert(:connections, {{{127, 0, 0, 1}, port}, socket1})
Benchee.run(
%{
"single genserver" => fn ->
Connection.send_message(conn1, "hello")
end,
"pool of genserver" => fn ->
connections = Registry.lookup(ConnectionRegistry, :connections)
{pid, _} = Enum.random(connections)
Connection.send_message(pid, "hello")
end,
"ets" => fn ->
{_, socket_ets} = :ets.lookup(:connections, {{127, 0, 0, 1}, port}) |> Enum.random()
:gen_tcp.send(socket_ets, "hello")
:gen_tcp.recv(socket_ets, 0)
end
},
parallel: 4
)
:ets.delete(:connections)
:gen_tcp.close(listen_socket)
Benchmarks results
Operating System: macOS
CPU Information: Intel(R) Core(TM) i5-7500 CPU @ 3.40GHz
Number of Available Cores: 4
Available memory: 16 GB
Elixir 1.12.3
Erlang 24.1.2
Benchmark suite executing with the following configuration:
warmup: 2 s
time: 5 s
memory time: 0 ns
parallel: 4
inputs: none specified
Estimated total run time: 21 s
Benchmarking ets...
Benchmarking pool of genserver...
Benchmarking single genserver...
Name ips average deviation median 99th %
ets 22.47 K 44.50 μs ±311.73% 29 μs 211 μs
single genserver 9.67 K 103.43 μs ±58.76% 93 μs 268 μs
pool of genserver 8.43 K 118.64 μs ±130.49% 98 μs 323 μs
Comparison:
ets 22.47 K
single genserver 9.67 K - 2.32x slower +58.93 μs
pool of genserver 8.43 K - 2.67x slower +74.14 μs
However, if I’m increasing the parallel execution number, the latency between ETS and pool of GenServer is reducing, but it requires few connections instead of a single one.
