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Feature: Request Rate Limiter with ETS #3

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Feature: Request Rate Limiter with ETS #3

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52860db
update config
mudssrali Mar 27, 2022
e116d04
use ets to keep log of user requests
mudssrali Mar 27, 2022
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3 changes: 2 additions & 1 deletion config/config.exs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,4 +4,5 @@ import Config
config :ex_banking,
max_requests: 20,
rate_units: :seconds,
sweep_rate: 60
sweep_rate: 60,
ets_table: :rater_limiter_requests
45 changes: 29 additions & 16 deletions lib/ex_banking/rate_limiter.ex
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Expand Up @@ -10,35 +10,44 @@ defmodule ExBanking.RateLimiter do
GenServer.start_link(__MODULE__, [], name: __MODULE__)
end

def log_request(uid) do
GenServer.call(__MODULE__, {:log_request, uid})
@spec log_request( user :: String.t()) :: :ok | {:error, :too_many_requests_to_user}
def log_request(user) do
ets_table = get_ets_table()
max_requests = Application.get_env(:ex_banking, :max_requests)

case :ets.update_counter(ets_table, user, {2, 1}, {user, 0}) do
count when count > max_requests -> {:error, :too_many_requests_to_user}
_count -> :ok
end
end

@impl true
@spec init(any) :: {:ok, %{requests: %{}}}
@spec init(any) :: {:ok, %{}}
def init(_) do
ets_table = get_ets_table()

:ets.new(ets_table, [
:set,
:named_table,
:public,
read_concurrency: true,
write_concurrency: true
])

schedule_sweep()
{:ok, %{requests: %{}}}
{:ok, %{}}
end

@impl true
def handle_info(:sweep, state) do
Logger.debug("Sweeping requests")
schedule_sweep()
{:noreply, %{state | requests: %{}}}
end

@impl true
def handle_call({:log_request, uid}, _from, state) do
max_requests = Application.get_env(:ex_banking, :max_requests)
ets_table = get_ets_table()
:ets.delete_all_objects(ets_table)

case state.requests[uid] do
count when is_nil(count) or count < max_requests ->
{:reply, :ok, put_in(state, [:requests, uid], (count || 0) + 1)}
schedule_sweep()

count when count >= max_requests ->
{:reply, {:error, :too_many_requests_to_user}, state}
end
{:noreply, state}
end

defp schedule_sweep do
Expand All @@ -47,4 +56,8 @@ defmodule ExBanking.RateLimiter do

Process.send_after(self(), :sweep, sweep_after)
end

defp get_ets_table do
Application.get_env(:ex_banking, :ets_table)
end
end