Initial commit

This commit is contained in:
Jordan Bracco 2020-05-08 01:55:49 +02:00
commit 554524db9b
8 changed files with 180 additions and 0 deletions

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.formatter.exs Normal file
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# Used by "mix format"
[
inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
]

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.gitignore vendored Normal file
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# The directory Mix will write compiled artifacts to.
/_build/
# If you run "mix test --cover", coverage assets end up here.
/cover/
# The directory Mix downloads your dependencies sources to.
/deps/
# Where third-party dependencies like ExDoc output generated docs.
/doc/
# Ignore .fetch files in case you like to edit your project deps locally.
/.fetch
# If the VM crashes, it generates a dump, let's ignore it too.
erl_crash.dump
# Also ignore archive artifacts (built via "mix archive.build").
*.ez
# Ignore package tarball (built via "mix hex.build").
limiter-*.tar

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lib/limiter.ex Normal file
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defmodule Limiter do
@ets __MODULE__.ETS
def new(name, max_running, max_waiting) do
name = atom_name(name)
:persistent_term.put(name, {max_running, max_waiting})
:ets.new(name, [:public, :named_table])
:ok
end
def limit(name, fun) do
{max_running, max_waiting} = :persistent_term.get(atom_name(name))
max = max_running + max_waiting
counter = inc(name)
cond do
counter <= max_running ->
fun.()
counter > max ->
{:error, :overload}
counter > max_running ->
wait(name, fun)
end
after
dec(name)
end
defp wait(name, fun) do
Process.sleep(150)
dec(name)
limit(name, fun)
end
defp inc(name) do
name = atom_name(name)
:ets.update_counter(name, name, {2, 1}, {name, 0})
end
def dec(name) do
name = atom_name(name)
:ets.update_counter(name, name, {2, -1}, {name, 0})
end
defp atom_name(suffix), do: Module.concat(@ets, suffix)
end

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mix.exs Normal file
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defmodule Limiter.MixProject do
use Mix.Project
def project do
[
app: :limiter,
version: "0.1.0",
elixir: "~> 1.10",
start_permanent: Mix.env() == :prod,
deps: deps()
]
end
# Run "mix help compile.app" to learn about applications.
def application do
[
extra_applications: [:logger]
]
end
# Run "mix help deps" to learn about dependencies.
defp deps do
[
{:benchee, "~> 1.0", only: [:dev, :test]}
# {:dep_from_hexpm, "~> 0.3.0"},
# {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"}
]
end
end

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%{
"benchee": {:hex, :benchee, "1.0.1", "66b211f9bfd84bd97e6d1beaddf8fc2312aaabe192f776e8931cb0c16f53a521", [:mix], [{:deep_merge, "~> 1.0", [hex: :deep_merge, repo: "hexpm", optional: false]}], "hexpm", "3ad58ae787e9c7c94dd7ceda3b587ec2c64604563e049b2a0e8baafae832addb"},
"deep_merge": {:hex, :deep_merge, "1.0.0", "b4aa1a0d1acac393bdf38b2291af38cb1d4a52806cf7a4906f718e1feb5ee961", [:mix], [], "hexpm", "ce708e5f094b9cd4e8f2be4f00d2f4250c4095be93f8cd6d018c753894885430"},
}

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defmodule LimiterTest do
use ExUnit.Case
doctest Limiter
defp test_ets(name, max, sleep, fun) do
count = :ets.update_counter(:limiter_test, name, {2, 1}, {name, 0})
if count <= max do
fun.({:ok, count})
Process.sleep(sleep)
else
fun.(:fail)
end
after
:ets.update_counter(:limiter_test, name, {2, -1}, {name, 1})
end
test "limits with ets" do
:ets.new(:limiter_test, [:public, :named_table])
ets = "test"
test = self()
spawn_link(fn -> test_ets(ets, 2, 500, fn result -> send(test, result) end) end)
spawn_link(fn -> test_ets(ets, 2, 750, fn result -> send(test, result) end) end)
spawn_link(fn -> test_ets(ets, 2, 500, fn result -> send(test, result) end) end)
assert_receive {:ok, 1}
assert_receive {:ok, 2}
assert_receive :fail
Process.sleep(500)
spawn_link(fn -> test_ets(ets, 2, 500, fn result -> send(test, result) end) end)
assert_receive {:ok, 2}
end
test "limiter" do
name = "test1"
self = self()
Limiter.set(name, 2, 2)
sleepy = fn sleep ->
case Limiter.limit(name, fn ->
send(self, :ok)
Process.sleep(sleep)
:ok
end) do
:ok -> :ok
other -> send(self, other)
end
end
spawn_link(fn -> sleepy.(500) end)
spawn_link(fn -> sleepy.(500) end)
spawn_link(fn -> sleepy.(500) end)
spawn_link(fn -> sleepy.(500) end)
spawn_link(fn -> sleepy.(500) end)
assert_receive :ok, 2000
assert_receive :ok, 2000
assert_receive {:error, :overload}, 2000
assert_receive :ok, 2000
assert_receive :ok, 2000
end
end

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:ets.new(:limiter_bench, [:public, :named_table])
Limiter.new(:bench, 1_000_000_000_000_000_000_000_000_000_000_000_000_000_000_000, 0)
Benchee.run(%{
"update_counter" => fn ->
:ets.update_counter(:limiter_bench, "bench", {2, 1}, {"bench", 0})
end,
"limit" => fn ->
Limiter.limit(:bench, fn -> :ok end)
end
})

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ExUnit.start()