MVP implementation

Author: ajuvercr

lib/cache/cache.ex

@@ -17,22 +17,25 @@ defmodule Cache.Registry do
     end
   end
 
-  def create_coalescer(key) do
-    GenServer.call(__MODULE__, {:start_coalesce, key})
+  def get_or_create_coalescer(key) do
+    GenServer.call(__MODULE__, {:get_or_create_coalescer, key})
   end
 
   def get_coalesce_pid(key) do
-    GenServer.call(__MODULE__, {:get_coalesce, key})
+    IO.inspect(key, label: "Getting coalesce")
+
+    case GenServer.call(__MODULE__, {:get_coalesce, key})
+         |> IO.inspect(label: "got return value") do
+      {:ok, response} -> response
+      {:not_found} -> nil
+    end
   end
 
   def remove_coalesce_key(key) do
     GenServer.call(__MODULE__, {:remove_coalesce, key})
   end
 
   def store({_method, _full_path, _get_params, _allowed_groups} = key, response) do
-    # IO.puts "Going to store new content"
-    # IO.inspect( key, label: "Key to store under" )
-    # IO.inspect( response, label: "Response to save" )
     GenServer.call(__MODULE__, {:store, key, response})
   end
 
@@ -53,18 +56,18 @@ defmodule Cache.Registry do
     {:ok, %{cache: %{}, caches_by_key: %{}, coalesce_handlers: %{}}}
   end
 
+  def handle_call({:get_or_create_coalescer, key}, _from, state) do
+    case Map.get(state.coalesce_handlers, key, nil) do
+      nil ->
+        {:ok, pid} = Coalesce.Registry.start(%{})
+        new_state = put_in(state[:coalesce_handlers][key], pid)
+        {:reply, {:created, pid}, new_state}
 
-  def handle_call({:start_coalesce, key}, _from, state) do
-    if Map.has_key?(state.coalesce_handlers, key) do
-      {:reply, {:alread_started}, state}
-    else
-      {:ok, pid} = Coalesce.Registry.start(%{})
-      new_state = put_in(state[:coalesce_handlers][key], pid)
-      {:reply, {:ok, pid}, new_state}
+      pid ->
+        {:reply, {:attach, pid}, state}
     end
   end
 
-
   def handle_call({:get_coalesce, key}, _from, state) do
     if Map.has_key?(state.coalesce_handlers, key) do
       {:reply, {:ok, Map.get(state.coalesce_handlers, key)}, state}
@@ -73,10 +76,8 @@ defmodule Cache.Registry do
     end
   end
 
-
   def handle_call({:remove_coalesce, key}, _from, state) do
     if Map.has_key?(state.coalesce_handlers, key) do
-      handlers = Map.pop(state.coalesce_handlers, key)
       {_, new_state} = pop_in(state[:coalesce_handlers][key])
       {:reply, {:ok}, new_state}
     else
@@ -85,23 +86,21 @@ defmodule Cache.Registry do
   end
 
   def handle_call({:find_cache, key}, _from, state) do
-    if Map.has_key?(state.cache, key) do
+    if has_key?(state, key) do
       {:reply, {:ok, Map.get(state.cache, key)}, state}
     else
       {:reply, {:not_found}, state}
     end
   end
 
   def handle_call({:store, request_key, response}, _from, state) do
-
     %{cache_keys: cache_keys, clear_keys: clear_keys} = response
 
     state =
       state
       # update state for clear_keys
       |> clear_keys!(clear_keys)
 
-
     if cache_keys == [] do
       {:reply, :ok, state}
     else
@@ -135,6 +134,7 @@ defmodule Cache.Registry do
     cache =
       Enum.reduce(clear_keys, cache, fn clear_key, cache ->
         keys_to_remove = Map.get(caches_by_key, clear_key, [])
+
         cache = Map.drop(cache, keys_to_remove)
         cache
       end)

lib/cache/coalesce.ex

@@ -5,8 +5,10 @@ defmodule Coalesce.Registry do
 
   # TODO define coalesce status
   # With headers, body (in chunks), status code something else?
-
-
+  def add_connection(pid, connection) do
+    {:ok, conn} = GenServer.call(pid, {:add_conn, connection})
+    conn
+  end
 
   use GenServer
   ###
@@ -16,51 +18,97 @@ defmodule Coalesce.Registry do
     GenServer.start(__MODULE__, [%{}])
   end
 
+  def assure_status_sent(state, status) do
+    if not is_nil(status) and is_nil(state.status) and not is_nil(state.headers) do
+      # First time there was a status
+      conns =
+        state.connections
+        |> Enum.map(fn {conn, from} ->
+          conn =
+            Plug.Conn.merge_resp_headers(conn, state.headers)
+            |> Plug.Conn.send_chunked(status)
+
+          {conn, from}
+        end)
+        |> Enum.flat_map(fn {conn, from} ->
+          case push_body_parts(conn, state.body) do
+            nil -> []
+            conn -> [{conn, from}]
+          end
+        end)
+
+      %{state | connections: conns, status: status}
+    else
+      state
+    end
+  end
+
+  def push_body_parts(conn, body_parts) do
+    Enum.reduce_while(body_parts, conn, fn ch, conn ->
+      case Plug.Conn.chunk(conn, ch) do
+        {:ok, conn} -> {:cont, conn}
+        {:error, :closed} -> {:halt, nil}
+      end
+    end)
+  end
+
   @impl true
   def init(s) do
     IO.inspect(s, label: "init config")
-    {:ok, %{connections: [], state: %{headers: nil, body: []}}}
+    {:ok, %{connections: [], headers: nil, body: [], status: nil}}
   end
 
   # TODO
   @impl true
-  def handle_call({:add_conn, _connection}, _from, state) do
-    # Put connection in state
-    # Make connection up to date
+  def handle_call({:add_conn, conn}, from, state) do
+    IO.inspect("adding connection to coalescer")
+
+    if not is_nil(state.status) and not is_nil(state.headers) do
+      conn =
+        Plug.Conn.merge_resp_headers(conn, state.headers)
+        |> Plug.Conn.send_chunked(state.status)
+        |> push_body_parts(state.body)
+    end
 
-    {:reply, :ok, state}
+    conns = [{conn, from} | state.connections]
+
+    new_state = %{state | connections: conns}
+
+    {:noreply, new_state}
   end
 
   @impl true
-  def handle_cast({:headers, headers}, state) do
-    IO.inspect(headers, label: "coalescing cast headers")
+  def handle_cast({:headers, headers, status}, state) do
+    state_with_headers = %{state | headers: headers}
+    new_state = assure_status_sent(state_with_headers, status)
 
-    {:noreply, put_in(state.state.headers, headers)}
+    {:noreply, new_state}
   end
 
-
   # TODO
   @impl true
-  def handle_cast({:chunk, data}, state) do
-    IO.inspect(data, label: "coalescing cast chunk")
+  def handle_cast({:chunk, data, status}, state) do
+    new_state = assure_status_sent(state, status)
 
-    # foreach connection
-      # frontend_conn
-      # |> Plug.Conn.chunk(chunk)
+    conns =
+      Enum.flat_map(new_state.connections, fn {conn, from} ->
+        case Plug.Conn.chunk(conn, data) do
+          {:ok, conn} -> [{conn, from}]
+          {:error, :closed} -> []
+        end
+      end)
 
-    {:noreply, state}
-  end
+    new_state = %{new_state | connections: conns}
 
+    {:noreply, new_state}
+  end
 
-  # TODO
   @impl true
   def handle_cast({:finished, status}, state) do
-    IO.inspect({state, status}, label: "coalescing cast finish")
-    # foreach connection
-      # frontend_conn
-      # |> Plug.Conn.send_resp(return_status, "")
+    new_state = assure_status_sent(state, status)
+
+    Enum.each(state.connections, fn {conn, from} -> GenServer.reply(from, {:ok, conn}) end)
 
-      {:noreply, state}
-    # {:stop, :normal, state}
+    {:stop, :normal, state}
   end
 end

lib/manipulators/coalesce_response.ex

@@ -11,26 +11,26 @@ defmodule Manipulators.CoalesceResponse do
       all_response_headers
       |> Enum.find({nil, "[]"}, &match?({"mu-auth-allowed-groups", _}, &1))
       |> elem(1)
+      |> Poison.decode!()
 
     key = {conn_in.method, conn_in.request_path, conn_in.query_string, allowed_groups}
 
-    {:ok, pid} = Cache.create_coalescer(key) |> IO.inspect(label: "did it make the journey?")
+    pid = Cache.get_coalesce_pid(key) |> IO.inspect(label: "did it make the journey?")
 
-    conn_out = conn_out
-        |> Mint.HTTP.put_private(:coalesce_pid, pid)
-        |> Mint.HTTP.put_private(:coalesce_key, key)
+    conn_out =
+      conn_out
+      |> Mint.HTTP.put_private(:coalesce_pid, pid)
+      |> Mint.HTTP.put_private(:coalesce_key, key)
 
-    GenServer.cast(pid, {:headers, headers})
+    GenServer.cast(pid, {:headers, headers, conn_in.status})
 
     {headers, {conn_in, conn_out}}
   end
 
   @impl true
-  def chunk(chunk, {_conn_in, conn_out}) do
-    IO.inspect({chunk, nil}, label: "chunk")
-
+  def chunk(chunk, {conn_in, conn_out}) do
     pid = Mint.HTTP.get_private(conn_out, :coalesce_pid)
-    GenServer.cast(pid, {:chunk, chunk})
+    GenServer.cast(pid, {:chunk, chunk, conn_in.status})
 
     :skip
   end

lib/manipulators/store_response.ex

@@ -66,6 +66,7 @@ defmodule Manipulators.StoreResponse do
           all_response_headers
           |> Enum.find({nil, "[]"}, &match?({"mu-auth-allowed-groups", _}, &1))
           |> elem(1)
+          |> Poison.decode!()
 
         cache_keys =
           all_response_headers
@@ -79,8 +80,6 @@ defmodule Manipulators.StoreResponse do
           |> elem(1)
           |> Poison.decode!()
 
-        # IO.inspect( {conn_in.method, conn_in.request_path, conn_in.query_string, allowed_groups}, label: "Signature to store" )
-
         Cache.store(
           {conn_in.method, conn_in.request_path, conn_in.query_string, allowed_groups},
           %{
@@ -109,8 +108,6 @@ defmodule Manipulators.StoreResponse do
           |> elem(1)
           |> Poison.decode!()
 
-        IO.inspect(clear_keys, label: "Clear keys")
-
         Cache.clear_keys(clear_keys)
 
       true ->

lib/mu_cache_plug.ex

@@ -52,15 +52,16 @@ defmodule MuCachePlug do
         ConnectionForwarder.forward(conn, path, "http://backend/", @manipulators)
 
       cached_value =
-          Cache.find_cache({conn.method, full_path, conn.query_string, known_allowed_groups}) ->
+          Cache.find_cache({conn.method, full_path, conn.query_string, Poison.decode!(known_allowed_groups)}) ->
         # with allowed groups and a cache, we should use the cache
         respond_with_cache(conn, cached_value)
 
       true ->
-        # without a cache, we should consult the backend
-        # IO.inspect(
-        #   {conn.method, full_path, conn.query_string, known_allowed_groups}, label: "Cache miss for signature")
-        ConnectionForwarder.forward(conn, path, "http://backend/", @manipulators)
+        key = {conn.method, full_path, conn.query_string, Poison.decode!(known_allowed_groups)}
+        case Cache.get_or_create_coalescer(key) do
+          {:created, _pid} -> ConnectionForwarder.forward(conn, path, "http://backend/", @manipulators)
+          {:attach, pid} -> Coalesce.Registry.add_connection(pid, conn)
+        end
     end
   end