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|
# Pleroma: A lightweight social networking server
# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only
defmodule Pleroma.Web.FedSockets.FetchRegistry do
@moduledoc """
The FetchRegistry acts as a broker for fetch requests and return values.
This allows calling processes to block while waiting for a reply.
It doesn't impose it's own process instead using `Cachex` to handle fetches in process, allowing
multi threaded processes to avoid bottlenecking.
Normally outside modules will have no need to call or use the FetchRegistry themselves.
The `Cachex` parameters can be controlled from the config. Since exact timeout intervals
aren't necessary the following settings are used by default:
config :pleroma, :fed_sockets,
fed_socket_fetches: [
default: 12_000,
interval: 3_000,
lazy: false
]
"""
defmodule FetchRegistryData do
defstruct uuid: nil,
sent_json: nil,
received_json: nil,
sent_at: nil,
received_at: nil
end
alias Ecto.UUID
require Logger
@fetches :fed_socket_fetches
@doc """
Registers a json request wth the FetchRegistry and returns the identifying UUID.
"""
def register_fetch(json) do
%FetchRegistryData{uuid: uuid} =
json
|> new_registry_data
|> save_registry_data
uuid
end
@doc """
Reports on the status of a Fetch given the identifying UUID.
Will return
* {:ok, fetched_object} if a fetch has completed
* {:error, :waiting} if a fetch is still pending
* {:error, other_error} usually :missing to indicate a fetch that has timed out
"""
def check_fetch(uuid) do
case get_registry_data(uuid) do
{:ok, %FetchRegistryData{received_at: nil}} ->
{:error, :waiting}
{:ok, %FetchRegistryData{} = reg_data} ->
{:ok, reg_data}
e ->
e
end
end
@doc """
Retrieves the response to a fetch given the identifying UUID.
The completed fetch will be deleted from the FetchRegistry
Will return
* {:ok, fetched_object} if a fetch has completed
* {:error, :waiting} if a fetch is still pending
* {:error, other_error} usually :missing to indicate a fetch that has timed out
"""
def pop_fetch(uuid) do
case check_fetch(uuid) do
{:ok, %FetchRegistryData{received_json: received_json}} ->
delete_registry_data(uuid)
{:ok, received_json}
e ->
e
end
end
@doc """
This is called to register a fetch has returned.
It expects the result data along with the UUID that was sent in the request
Will return the fetched object or :error
"""
def register_fetch_received(uuid, data) do
case get_registry_data(uuid) do
{:ok, %FetchRegistryData{received_at: nil} = reg_data} ->
reg_data
|> set_fetch_received(data)
|> save_registry_data()
{:ok, %FetchRegistryData{} = reg_data} ->
Logger.warn("tried to add fetched data twice - #{uuid}")
reg_data
{:error, _} ->
Logger.warn("Error adding fetch to registry - #{uuid}")
:error
end
end
defp new_registry_data(json) do
%FetchRegistryData{
uuid: UUID.generate(),
sent_json: json,
sent_at: :erlang.monotonic_time(:millisecond)
}
end
defp get_registry_data(origin) do
case Cachex.get(@fetches, origin) do
{:ok, nil} ->
{:error, :missing}
{:ok, reg_data} ->
{:ok, reg_data}
_ ->
{:error, :cache_error}
end
end
defp set_fetch_received(%FetchRegistryData{} = reg_data, data),
do: %FetchRegistryData{
reg_data
| received_at: :erlang.monotonic_time(:millisecond),
received_json: data
}
defp save_registry_data(%FetchRegistryData{uuid: uuid} = reg_data) do
{:ok, true} = Cachex.put(@fetches, uuid, reg_data)
reg_data
end
defp delete_registry_data(origin),
do: {:ok, true} = Cachex.del(@fetches, origin)
end
|
