Handling external APIs with Elixir - Alex Rozumii
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This document discusses handling external APIs with Elixir. It describes using OTP behaviors and agents to build a robust system that can handle errors from external APIs. Key points covered include: 1. Using agents to store messages in a queue when an API call fails or hits rate limits. 2. Implementing a TelegramMessageQueue agent to push and pull messages from the queue. 3. Having a process pull from the queue on a timer and retry sending messages if API calls fail, hitting retry thresholds to avoid overloading the external API.
![defmodule Telegram.MessageQueue do
def start_link do
Agent.start_link(fn -> [] end, name: __MODULE__)
end
# @doc Flushes all existing records
def flush! do
Agent.cast(__MODULE__, fn(_) -> [] end)
end
# @doc Pushes message for given receiver to queue
def push_message(tlg_id, message, opts) do
item = {tlg_id, message, opts}
# Agent.get(GosuObs.Telegram.MessageQueue, fn set -> set end)
Agent.update(__MODULE__, &( [item | &1 ]))
end
# @doc Gets a top message, grouped if possible
def pull_top_message do
Agent.get_and_update(__MODULE__, fn queue ->
case List.last(queue) do
nil ->
{nil, []}
msg ->
end
end
end
end](https://image.slidesharecdn.com/externalapis-elixir-171027142058/85/Handling-external-APIs-with-Elixir-Alex-Rozumii-9-320.jpg)
Handling external APIs with Elixir - Alex Rozumii
- 1. HANDLING EXTERNAL APIS WITH ELIXIR ALEX ROZUMII
- 2. ТЕКСТ WHY? ▸ Because: ▸ External API fail (50x) ▸ Network fails ▸ Have rate limits
- 5. TelegramInterface.pull_messages(Keyword.get(state, :offset, 0)) Enum.each(items, fn(update) -> case update do %Nadia.Model.Update{message: %Nadia.Model.Message{date: the_date}} -> #IT WORKS _ -> Rollbax.report() end end end
- 6. case Dota.live_league_games do {:ok, curr_state} -> # REAL LOGIC {:noreply, tick(prev_state, curr_state)} {:error, %Nadia.Model.Error{reason: :connect_timeout}} -> Process.send_after(self, :timer_event, @wait_ms_before_next_polling_error) {:noreply, tick(prev_state, prev_state)} {:error, {:error, %HTTPoison.Error{id: nil, reason: _reason}}} -> Process.send_after(self, :timer_event, @wait_ms_before_next_empty_response) {:noreply, tick(prev_state, prev_state)} {:error, {:ok, %HTTPoison.Response{status_code: 500}}} -> Process.send_after(self, :timer_event, @wait_ms_before_next_500_error) {:noreply, tick(prev_state, prev_state)} end
- 8. ТЕКСТ HOW? ▸ OTP ▸ Agents ▸ Behaviours
- 9. defmodule Telegram.MessageQueue do def start_link do Agent.start_link(fn -> [] end, name: __MODULE__) end # @doc Flushes all existing records def flush! do Agent.cast(__MODULE__, fn(_) -> [] end) end # @doc Pushes message for given receiver to queue def push_message(tlg_id, message, opts) do item = {tlg_id, message, opts} # Agent.get(GosuObs.Telegram.MessageQueue, fn set -> set end) Agent.update(__MODULE__, &( [item | &1 ])) end # @doc Gets a top message, grouped if possible def pull_top_message do Agent.get_and_update(__MODULE__, fn queue -> case List.last(queue) do nil -> {nil, []} msg -> end end end end
- 10. def handle_info(:timer_event, state) do case Telegram.MessageQueue.pull_top_message do {tlg_id, message, opts} -> case send_message(tlg_id, message, opts) do :ok -> Process.send_after(self, :timer_event, @wait_ms_before_next_message_send) nil :error -> Process.send_after(self, :timer_event, @wait_ms_before_next_message_send) nil :wait -> Process.send_after(self, :timer_event, @wait_ms_before_next_message_send_limit) nil :retry -> Process.send_after(self, :timer_event, @wait_ms_before_next_message) GosuObs.Telegram.MessageQueue.push_message(tlg_id, message, opts) end {:noreply, state} nil -> Process.send_after(self, :timer_event, @wait_ms_before_next_message_pull) {:noreply, state} end end
- 11. defp send_message(t, message, opts) do case Nadia.send_message(t, message, opts) do {:ok, _result} -> :ok {:error, %Nadia.Model.Error{reason: "Please wait»}} -> :wait result -> Rollbax.report() :retry end end
- 13. THANKS!