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Add ratelimit backoff to HTTP get

This commit is contained in:
FloatingGhost 2023-12-20 16:45:35 +00:00
parent cc1efd2182
commit 14ff522b67
2 changed files with 38 additions and 6 deletions

View file

@ -9,14 +9,24 @@ defp next_backoff_timestamp(%{headers: headers}) when is_list(headers) do
# figure out from the 429 response when we can make the next request
# mastodon uses the x-ratelimit-reset header, so we will use that!
# other servers may not, so we'll default to 5 minutes from now if we can't find it
case Enum.find_value(headers, fn {"x-ratelimit-reset", value} -> value end) do
nil ->
default_5_minute_backoff =
DateTime.utc_now()
|> Timex.shift(seconds: 5 * 60)
case Enum.find_value(headers, fn {"x-ratelimit-reset", value} -> value end) do
nil ->
Logger.error("Rate limited, but couldn't find timestamp! Using default 5 minute backoff until #{default_5_minute_backoff}")
default_5_minute_backoff
value ->
{:ok, stamp} = DateTime.from_iso8601(value)
with {:ok, stamp, _} <- DateTime.from_iso8601(value) do
Logger.error("Rate limited until #{stamp}")
stamp
else
_ ->
Logger.error("Rate limited, but couldn't parse timestamp! Using default 5 minute backoff until #{default_5_minute_backoff}")
default_5_minute_backoff
end
end
end
@ -28,6 +38,7 @@ def get(url, headers \\ [], options \\ []) do
# this ensures that we don't hammer the server with requests, and instead wait for the backoff to expire
# this is a very simple implementation, and can be improved upon!
%{host: host} = URI.parse(url)
case @cachex.get(@backoff_cache, host) do
{:ok, nil} ->
case HTTP.get(url, headers, options) do
@ -49,6 +60,7 @@ def get(url, headers \\ [], options \\ []) do
end
_ ->
Logger.error("Request not made to #{host} because we are rate limited!")
{:error, %Tesla.Env{status: 429, body: "Rate limited (internal backoff)"}}
end
end

View file

@ -9,6 +9,7 @@ test "should return {:ok, env} when not rate limited" do
%Tesla.Env{url: "https://akkoma.dev/api/v1/instance"} ->
{:ok, %Tesla.Env{status: 200, body: "ok"}}
end)
assert {:ok, env} = Backoff.get("https://akkoma.dev/api/v1/instance")
assert env.status == 200
end
@ -30,5 +31,24 @@ test "should insert a value into the cache when rate limited" do
assert env.status == 429
assert {:ok, true} = Cachex.get(@backoff_cache, "ratelimited.dev")
end
test "should parse the value of x-ratelimit-reset, if present" do
ten_minutes_from_now =
DateTime.utc_now() |> Timex.shift(minutes: 10) |> DateTime.to_iso8601()
Tesla.Mock.mock_global(fn
%Tesla.Env{url: "https://ratelimited.dev/api/v1/instance"} ->
{:ok,
%Tesla.Env{
status: 429,
body: "Rate limited",
headers: [{"x-ratelimit-reset", ten_minutes_from_now}]
}}
end)
assert {:error, env} = Backoff.get("https://ratelimited.dev/api/v1/instance")
assert env.status == 429
assert {:ok, true} = Cachex.get(@backoff_cache, "ratelimited.dev")
end
end
end