Message recovery client (#55)

* Add messaging method to retrieve distinct origin_host from topics

* Add rescuer client and adapter to list undelivered messages

* Implement delete method on rescuer client

lib/postoffice/messaging.ex

@@ -204,4 +204,9 @@ defmodule Postoffice.Messaging do
     from(p in PublisherFailures, where: p.message_id == ^message_id)
     |> Repo.all()
   end
+
+  def get_topic_origin_hosts() do
+    from(t in Topic, distinct: true, select: t.origin_host)
+    |> Repo.all()
+  end
 end

lib/postoffice/rescuer/adapters/http.ex

@@ -0,0 +1,21 @@
+defmodule Postoffice.Rescuer.Adapters.Http do
+  require Logger
+
+  @behaviour Postoffice.Rescuer.Adapters.Impl
+
+  @impl true
+  def list(host) do
+    Logger.info("Listing undelivered messages from #{host}")
+    HTTPoison.get(host)
+  end
+
+  @impl true
+  def delete(host, message_id) do
+    build_message_path(host, message_id)
+    |> HTTPoison.delete()
+  end
+
+  defp build_message_path(host, message_id) do
+    host <> message_id <> "/"
+  end
+end

lib/postoffice/rescuer/adapters/impl.ex

@@ -0,0 +1,6 @@
+defmodule Postoffice.Rescuer.Adapters.Impl do
+  @moduledoc false
+
+  @callback list(host :: String) :: {:ok, list} | {:error, reason :: String}
+  @callback delete(host :: String, message_id :: Integer) :: {:ok, status :: Atom } | {:error, reason :: String}
+end

lib/postoffice/rescuer/client.ex

@@ -0,0 +1,52 @@
+defmodule Postoffice.Rescuer.Client do
+  require Logger
+
+  alias Postoffice.Rescuer.Adapters.Http
+
+  def list(host) do
+    case impl().list(host) do
+      {:ok, %HTTPoison.Response{status_code: status_code, body: body}}
+      when status_code in 200..299 ->
+        Logger.info("Succesfully listed pending messages from #{host}")
+        {:ok, Poison.decode!(body)}
+
+      {:ok, %HTTPoison.Response{status_code: status_code, body: body}} ->
+        Logger.info(
+          "Non successful response list pending messages from #{host} with status code: #{
+            status_code
+          }"
+        )
+
+        {:error, []}
+
+      {:error, %HTTPoison.Error{reason: reason}} ->
+        Logger.info("Error trying to list pending messages #{reason}")
+        {:error, []}
+    end
+  end
+
+  def delete(host, message_id) do
+    case impl().delete(host, message_id) do
+      {:ok, %HTTPoison.Response{status_code: status_code}}
+      when status_code in 200..299 ->
+        Logger.info("Successfully deleted message #{message_id} from #{host}")
+        {:ok, :deleted}
+      {:ok, %HTTPoison.Response{status_code: status_code, body: body}} ->
+        Logger.info(
+          "Non successful response deleting message from #{host} with status code: #{
+            status_code
+          }"
+        )
+
+        {:error, "Request status code #{status_code}"}
+
+      {:error, %HTTPoison.Error{reason: reason}} ->
+        Logger.info("Error trying to delete message #{host}: #{reason}")
+        {:error, reason}
+    end
+  end
+
+  defp impl do
+    Application.get_env(:postoffice, :rescuer_client, Http)
+  end
+end

test/postoffice/messaging_test.exs

@@ -290,5 +290,19 @@ defmodule Postoffice.MessagingTest do
       loaded_publisher_failures = Messaging.get_publisher_failures_for_message(message.id)
       assert Kernel.length(loaded_publisher_failures) == 1
     end
+
+    test "get_topic_origin_hosts returns unique hosts" do
+      _topic = Fixtures.create_topic()
+
+      _second_topic =
+        Fixtures.create_topic(%{
+          name: "second_test",
+          origin_host: "example.com"
+        })
+
+      hosts = Messaging.get_topic_origin_hosts()
+
+      assert Kernel.length(hosts) == 1
+    end
   end
 end

test/postoffice/rescuer/client_test.exs

@@ -0,0 +1,96 @@
+defmodule Postoffice.Rescuer.ClientTest do
+  use ExUnit.Case
+
+  import Mox
+
+  alias Postoffice.Rescuer.Adapters.HttpMock
+  alias Postoffice.Rescuer.Client
+
+  @origin_host "http://fake_origin.host"
+  @wrong_message_id 9999
+  @external_message_id 1
+  @one_message_response "[{\"id\": 1, \"topic\": \"test\", \"payload\": {\"products\": [{\"code\": \"1234\"}, {\"code\": 2345}], \"reference\": 1234}, \"attributes\": null}]"
+  @two_messages_response "[{\"id\": 1, \"topic\": \"test\", \"payload\": {\"products\": [{\"code\": \"1234\"}, {\"code\": 2345}], \"reference\": 1234}, \"attributes\": null}, {\"id\": 2, \"topic\": \"test2\", \"payload\": {\"products\": [{\"code\": \"1234\"}, {\"code\": 2345}], \"reference\": 1234}, \"attributes\": null}]"
+
+  setup [:set_mox_from_context, :verify_on_exit!]
+
+  setup do
+    :ok = Ecto.Adapters.SQL.Sandbox.checkout(Postoffice.Repo)
+  end
+
+  describe "list undelivered messages" do
+    test "non successful response from origin host" do
+      expect(HttpMock, :list, fn @origin_host ->
+        {:ok, %HTTPoison.Response{status_code: 300}}
+      end)
+
+      {:error, pending_messages} = Client.list(@origin_host)
+      assert pending_messages == []
+    end
+
+    test "origin host returns an error" do
+      expect(HttpMock, :list, fn @origin_host ->
+        {:error, %HTTPoison.Error{reason: "test error"}}
+      end)
+
+      {:error, pending_messages} = Client.list(@origin_host)
+      assert pending_messages == []
+    end
+
+    test "no pending messages returned" do
+      expect(HttpMock, :list, fn @origin_host ->
+        {:ok, %HTTPoison.Response{status_code: 200, body: "[]"}}
+      end)
+
+      {:ok, pending_messages} = Client.list(@origin_host)
+      assert pending_messages == []
+    end
+
+    test "one pending message received" do
+      expect(HttpMock, :list, fn @origin_host ->
+        {:ok, %HTTPoison.Response{status_code: 200, body: @one_message_response}}
+      end)
+
+      {:ok, pending_messages} = Client.list(@origin_host)
+      assert Kernel.length(pending_messages) == 1
+    end
+
+    test "two pending messages received" do
+      expect(HttpMock, :list, fn @origin_host ->
+        {:ok, %HTTPoison.Response{status_code: 200, body: @two_messages_response}}
+      end)
+
+      {:ok, pending_messages} = Client.list(@origin_host)
+      assert Kernel.length(pending_messages) == 2
+    end
+  end
+
+  describe "delete undelivered messages" do
+    test "trying to delete non existing message" do
+      expect(HttpMock, :delete, fn @origin_host, @wrong_message_id ->
+        {:ok, %HTTPoison.Response{status_code: 404, body: ""}}
+      end)
+
+      {:error, reason} = Client.delete(@origin_host, @wrong_message_id)
+      assert reason == "Request status code 404"
+    end
+
+    test "errors are handled from our side" do
+      expect(HttpMock, :delete, fn @origin_host, @wrong_message_id ->
+        {:error, %HTTPoison.Error{reason: "Something weird happened"}}
+      end)
+
+      {:error, reason} = Client.delete(@origin_host, @wrong_message_id)
+      assert reason == "Something weird happened"
+    end
+
+    test "messages are successfuly deleted" do
+      expect(HttpMock, :delete, fn @origin_host, @external_message_id ->
+        {:ok, %HTTPoison.Response{status_code: 204, body: ""}}
+      end)
+
+      {:ok, :deleted} = Client.delete(@origin_host, @external_message_id)
+
+    end
+  end
+end

test/test_helper.exs

@@ -3,6 +3,7 @@ Ecto.Adapters.SQL.Sandbox.mode(Postoffice.Repo, :manual)
 
 Mox.defmock(Postoffice.Adapters.HttpMock, for: Postoffice.Adapters.Impl)
 Mox.defmock(Postoffice.Adapters.PubsubMock, for: Postoffice.Adapters.Impl)
+Mox.defmock(Postoffice.Rescuer.Adapters.HttpMock, for: Postoffice.Rescuer.Adapters.Impl)
 
 Application.put_env(
   :postoffice,
@@ -15,3 +16,9 @@ Application.put_env(
   :pubsub_consumer_impl,
   Postoffice.Adapters.PubsubMock
 )
+
+Application.put_env(
+  :postoffice,
+  :rescuer_client,
+  Postoffice.Rescuer.Adapters.HttpMock
+)