fix: prevent client <-> db locking (#195)

VERSION

@@ -1 +1 @@
-0.9.22
+0.9.23

lib/supavisor/client_handler.ex

@@ -26,8 +26,8 @@ defmodule Supavisor.ClientHandler do
   @impl true
   def callback_mode, do: [:handle_event_function]
 
-  def client_call(pid, bin, ready?) do
-    :gen_statem.call(pid, {:client_call, bin, ready?}, 5000)
+  def client_cast(pid, bin, ready?) do
+    :gen_statem.cast(pid, {:client_cast, bin, ready?})
   end
 
   @impl true
@@ -303,7 +303,7 @@ defmodule Supavisor.ClientHandler do
   end
 
   def handle_event(_, {proto, _, bin}, :busy, data) when proto in [:tcp, :ssl] do
-    case Db.call(data.db_pid, bin) do
+    case Db.call(data.db_pid, self(), bin) do
       :ok ->
         Logger.debug("DB call success")
         :keep_state_and_data
@@ -366,11 +366,11 @@ defmodule Supavisor.ClientHandler do
     end
   end
 
-  # emulate handle_call
-  def handle_event({:call, from}, {:client_call, bin, ready?}, _, data) do
+  # emulate handle_cast
+  def handle_event(:cast, {:client_cast, bin, ready?}, _, data) do
     Logger.debug("--> --> bin #{inspect(byte_size(bin))} bytes")
 
-    reply = {:reply, from, HH.sock_send(data.sock, bin)}
+    :ok = HH.sock_send(data.sock, bin)
 
     if ready? do
       Logger.debug("Client is ready")
@@ -382,15 +382,15 @@ defmodule Supavisor.ClientHandler do
 
       actions =
         if data.idle_timeout > 0 do
-          [reply, idle_check(data.idle_timeout)]
+          idle_check(data.idle_timeout)
         else
-          reply
+          []
         end
 
       {:next_state, :idle, %{data | db_pid: db_pid, stats: stats}, actions}
     else
       Logger.debug("Client is not ready")
-      {:keep_state_and_data, reply}
+      :keep_state_and_data
     end
   end
 

lib/supavisor/db_handler.ex

@@ -19,9 +19,9 @@ defmodule Supavisor.DbHandler do
     :gen_statem.start_link(__MODULE__, config, hibernate_after: 5_000)
   end
 
-  @spec call(pid(), binary()) :: :ok | {:error, any()} | {:buffering, non_neg_integer()}
-  def call(pid, msg) do
-    :gen_statem.call(pid, {:db_call, msg})
+  @spec call(pid(), pid(), binary()) :: :ok | {:error, any()} | {:buffering, non_neg_integer()}
+  def call(pid, caller, msg) do
+    :gen_statem.call(pid, {:db_call, caller, msg}, 15_000)
   end
 
   @impl true
@@ -240,32 +240,33 @@ defmodule Supavisor.DbHandler do
     {:keep_state, %{data | buffer: []}}
   end
 
-  def handle_event(:info, {_proto, _, bin}, _, data) do
+  def handle_event(:info, {_proto, _, bin}, _, %{caller: caller} = data) when is_pid(caller) do
     # check if the response ends with "ready for query"
     ready = String.ends_with?(bin, Server.ready_for_query())
-    :ok = Client.client_call(data.caller, bin, ready)
+    Logger.debug("Db ready #{inspect(ready)}")
+    :ok = Client.client_cast(caller, bin, ready)
 
     if ready do
       {_, stats} = Telem.network_usage(:db, data.sock, data.id, data.stats)
-      {:keep_state, %{data | stats: stats}}
+      {:keep_state, %{data | stats: stats, caller: nil}}
     else
       :keep_state_and_data
     end
   end
 
-  def handle_event({:call, {pid, _} = from}, {:db_call, bin}, :idle, %{sock: sock} = data) do
+  def handle_event({:call, from}, {:db_call, caller, bin}, :idle, %{sock: sock} = data) do
     reply = {:reply, from, sock_send(sock, bin)}
-    {:keep_state, %{data | caller: pid}, reply}
+    {:keep_state, %{data | caller: caller}, reply}
   end
 
-  def handle_event({:call, {pid, _} = from}, {:db_call, bin}, state, %{buffer: buff} = data) do
+  def handle_event({:call, from}, {:db_call, caller, bin}, state, %{buffer: buff} = data) do
     Logger.debug(
-      "state #{state} <-- <-- bin #{inspect(byte_size(bin))} bytes, caller: #{inspect(pid)}"
+      "state #{state} <-- <-- bin #{inspect(byte_size(bin))} bytes, caller: #{inspect(caller)}"
     )
 
     new_buff = [bin | buff]
     reply = {:reply, from, {:buffering, IO.iodata_length(new_buff)}}
-    {:keep_state, %{data | caller: pid, buffer: new_buff}, reply}
+    {:keep_state, %{data | caller: caller, buffer: new_buff}, reply}
   end
 
   def handle_event(:info, {:tcp_closed, sock}, state, %{sock: sock} = data) do

test/supavisor/db_handler_test.exs

@@ -97,7 +97,7 @@ defmodule Supavisor.DbHandlerTest do
     data = %{sock: {:gen_tcp, sock}, caller: nil, buffer: []}
     from = {self(), :test_ref}
     event = {:call, from}
-    payload = {:db_call, "test_data"}
+    payload = {:db_call, self(), "test_data"}
 
     {:keep_state, new_data, reply} = Db.handle_event(event, payload, :idle, data)
 
@@ -107,10 +107,10 @@ defmodule Supavisor.DbHandlerTest do
   end
 
   test "handle_event/4 with non-idle state" do
-    data = %{sock: nil, caller: nil, buffer: []}
+    data = %{sock: nil, caller: self(), buffer: []}
     from = {self(), :test_ref}
     event = {:call, from}
-    payload = {:db_call, "test_data"}
+    payload = {:db_call, self(), "test_data"}
     state = :non_idle
 
     {:keep_state, new_data, reply} = Db.handle_event(event, payload, state, data)