[#3213] Background migration infrastructure refactoring.

Extracted BaseMigrator and BaseMigratorState.

lib/pleroma/migrators/support/base_migrator.ex

@@ -0,0 +1,210 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Migrators.Support.BaseMigrator do
+  @moduledoc """
+  Base background migrator functionality.
+  """
+
+  @callback perform() :: any()
+  @callback retry_failed() :: any()
+  @callback feature_config_path() :: list(atom())
+  @callback query() :: Ecto.Query.t()
+  @callback fault_rate_allowance() :: integer() | float()
+
+  defmacro __using__(_opts) do
+    quote do
+      use GenServer
+
+      require Logger
+
+      import Ecto.Query
+
+      alias __MODULE__.State
+      alias Pleroma.Config
+      alias Pleroma.Repo
+
+      @behaviour Pleroma.Migrators.Support.BaseMigrator
+
+      defdelegate data_migration(), to: State
+      defdelegate data_migration_id(), to: State
+      defdelegate state(), to: State
+      defdelegate persist_state(), to: State, as: :persist_to_db
+      defdelegate get_stat(key, value \\ nil), to: State, as: :get_data_key
+      defdelegate put_stat(key, value), to: State, as: :put_data_key
+      defdelegate increment_stat(key, increment), to: State, as: :increment_data_key
+
+      @reg_name {:global, __MODULE__}
+
+      def whereis, do: GenServer.whereis(@reg_name)
+
+      def start_link(_) do
+        case whereis() do
+          nil ->
+            GenServer.start_link(__MODULE__, nil, name: @reg_name)
+
+          pid ->
+            {:ok, pid}
+        end
+      end
+
+      @impl true
+      def init(_) do
+        {:ok, nil, {:continue, :init_state}}
+      end
+
+      @impl true
+      def handle_continue(:init_state, _state) do
+        {:ok, _} = State.start_link(nil)
+
+        data_migration = data_migration()
+        manual_migrations = Config.get([:instance, :manual_data_migrations], [])
+
+        cond do
+          Config.get(:env) == :test ->
+            update_status(:noop)
+
+          is_nil(data_migration) ->
+            message = "Data migration does not exist."
+            update_status(:failed, message)
+            Logger.error("#{__MODULE__}: #{message}")
+
+          data_migration.state == :manual or data_migration.name in manual_migrations ->
+            message = "Data migration is in manual execution or manual fix mode."
+            update_status(:manual, message)
+            Logger.warn("#{__MODULE__}: #{message}")
+
+          data_migration.state == :complete ->
+            on_complete(data_migration)
+
+          true ->
+            send(self(), :perform)
+        end
+
+        {:noreply, nil}
+      end
+
+      @impl true
+      def handle_info(:perform, state) do
+        State.reinit()
+
+        update_status(:running)
+        put_stat(:iteration_processed_count, 0)
+        put_stat(:started_at, NaiveDateTime.utc_now())
+
+        perform()
+
+        fault_rate = fault_rate()
+        put_stat(:fault_rate, fault_rate)
+        fault_rate_allowance = fault_rate_allowance()
+
+        cond do
+          fault_rate == 0 ->
+            set_complete()
+
+          is_float(fault_rate) and fault_rate <= fault_rate_allowance ->
+            message = """
+            Done with fault rate of #{fault_rate} which doesn't exceed #{fault_rate_allowance}.
+            Putting data migration to manual fix mode. Try running `#{__MODULE__}.retry_failed/0`.
+            """
+
+            Logger.warn("#{__MODULE__}: #{message}")
+            update_status(:manual, message)
+            on_complete(data_migration())
+
+          true ->
+            message = "Too many failures. Try running `#{__MODULE__}.retry_failed/0`."
+            Logger.error("#{__MODULE__}: #{message}")
+            update_status(:failed, message)
+        end
+
+        persist_state()
+        {:noreply, state}
+      end
+
+      defp on_complete(data_migration) do
+        if data_migration.feature_lock || feature_state() == :disabled do
+          Logger.warn(
+            "#{__MODULE__}: migration complete but feature is locked; consider enabling."
+          )
+
+          :noop
+        else
+          Config.put(feature_config_path(), :enabled)
+          :ok
+        end
+      end
+
+      @doc "Approximate count for current iteration (including processed records count)"
+      def count(force \\ false, timeout \\ :infinity) do
+        stored_count = get_stat(:count)
+
+        if stored_count && !force do
+          stored_count
+        else
+          processed_count = get_stat(:processed_count, 0)
+          max_processed_id = get_stat(:max_processed_id, 0)
+          query = where(query(), [entity], entity.id > ^max_processed_id)
+
+          count = Repo.aggregate(query, :count, :id, timeout: timeout) + processed_count
+          put_stat(:count, count)
+          persist_state()
+
+          count
+        end
+      end
+
+      def failures_count do
+        with {:ok, %{rows: [[count]]}} <-
+               Repo.query(
+                 "SELECT COUNT(record_id) FROM data_migration_failed_ids WHERE data_migration_id = $1;",
+                 [data_migration_id()]
+               ) do
+          count
+        end
+      end
+
+      def feature_state, do: Config.get(feature_config_path())
+
+      def force_continue do
+        send(whereis(), :perform)
+      end
+
+      def force_restart do
+        :ok = State.reset()
+        force_continue()
+      end
+
+      def set_complete do
+        update_status(:complete)
+        persist_state()
+        on_complete(data_migration())
+      end
+
+      defp update_status(status, message \\ nil) do
+        put_stat(:state, status)
+        put_stat(:message, message)
+      end
+
+      defp fault_rate do
+        with failures_count when is_integer(failures_count) <- failures_count() do
+          failures_count / Enum.max([get_stat(:affected_count, 0), 1])
+        else
+          _ -> :error
+        end
+      end
+
+      defp records_per_second do
+        get_stat(:iteration_processed_count, 0) / Enum.max([running_time(), 1])
+      end
+
+      defp running_time do
+        NaiveDateTime.diff(
+          NaiveDateTime.utc_now(),
+          get_stat(:started_at, NaiveDateTime.utc_now())
+        )
+      end
+    end
+  end
+end

lib/pleroma/migrators/support/base_migrator_state.ex

@@ -0,0 +1,116 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Migrators.Support.BaseMigratorState do
+  @moduledoc """
+  Base background migrator state functionality.
+  """
+
+  @callback data_migration() :: Pleroma.DataMigration.t()
+
+  defmacro __using__(_opts) do
+    quote do
+      use Agent
+
+      alias Pleroma.DataMigration
+
+      @behaviour Pleroma.Migrators.Support.BaseMigratorState
+      @reg_name {:global, __MODULE__}
+
+      def start_link(_) do
+        Agent.start_link(fn -> load_state_from_db() end, name: @reg_name)
+      end
+
+      def data_migration, do: raise("data_migration/0 is not implemented")
+      defoverridable data_migration: 0
+
+      defp load_state_from_db do
+        data_migration = data_migration()
+
+        data =
+          if data_migration do
+            Map.new(data_migration.data, fn {k, v} -> {String.to_atom(k), v} end)
+          else
+            %{}
+          end
+
+        %{
+          data_migration_id: data_migration && data_migration.id,
+          data: data
+        }
+      end
+
+      def persist_to_db do
+        %{data_migration_id: data_migration_id, data: data} = state()
+
+        if data_migration_id do
+          DataMigration.update_one_by_id(data_migration_id, data: data)
+        else
+          {:error, :nil_data_migration_id}
+        end
+      end
+
+      def reset do
+        %{data_migration_id: data_migration_id} = state()
+
+        with false <- is_nil(data_migration_id),
+             :ok <-
+               DataMigration.update_one_by_id(data_migration_id,
+                 state: :pending,
+                 data: %{}
+               ) do
+          reinit()
+        else
+          true -> {:error, :nil_data_migration_id}
+          e -> e
+        end
+      end
+
+      def reinit do
+        Agent.update(@reg_name, fn _state -> load_state_from_db() end)
+      end
+
+      def state do
+        Agent.get(@reg_name, & &1)
+      end
+
+      def get_data_key(key, default \\ nil) do
+        get_in(state(), [:data, key]) || default
+      end
+
+      def put_data_key(key, value) do
+        _ = persist_non_data_change(key, value)
+
+        Agent.update(@reg_name, fn state ->
+          put_in(state, [:data, key], value)
+        end)
+      end
+
+      def increment_data_key(key, increment \\ 1) do
+        Agent.update(@reg_name, fn state ->
+          initial_value = get_in(state, [:data, key]) || 0
+          updated_value = initial_value + increment
+          put_in(state, [:data, key], updated_value)
+        end)
+      end
+
+      defp persist_non_data_change(:state, value) do
+        with true <- get_data_key(:state) != value,
+             true <- value in Pleroma.DataMigration.State.__valid_values__(),
+             %{data_migration_id: data_migration_id} when not is_nil(data_migration_id) <- state() do
+          DataMigration.update_one_by_id(data_migration_id, state: value)
+        else
+          false -> :ok
+          _ -> {:error, :nil_data_migration_id}
+        end
+      end
+
+      defp persist_non_data_change(_, _) do
+        nil
+      end
+
+      def data_migration_id, do: Map.get(state(), :data_migration_id)
+    end
+  end
+end