From 345860c779e5edf544b3c6052eb244cc78706d71 Mon Sep 17 00:00:00 2001
From: Sebastian Serth <Sebastian.Serth@hpi.de>
Date: Sun, 17 Oct 2021 13:15:52 +0200
Subject: [PATCH] Adapt output buffering to Poseidon and DCP * Refactor
 flushing of messages * Introduce two separate buffers for stdout and stderr

---
 app/controllers/submissions_controller.rb | 13 ++++------
 lib/runner/connection.rb                  | 31 +++++++++++++----------
 lib/runner/strategy/poseidon.rb           |  2 +-
 3 files changed, 24 insertions(+), 22 deletions(-)

diff --git a/app/controllers/submissions_controller.rb b/app/controllers/submissions_controller.rb
index f0ebd2ec..06456a77 100644
--- a/app/controllers/submissions_controller.rb
+++ b/app/controllers/submissions_controller.rb
@@ -96,14 +96,11 @@ class SubmissionsController < ApplicationController
       end
 
       client_socket.onmessage do |raw_event|
-        event = if raw_event == "\n"
-                  # Obviously, this is just flushing the current connection.
-                  # We temporarily wrap it and then forward the original event intentionally.
-                  {cmd: 'result'}
-                else
-                  # We expect to receive a JSON
-                  JSON.parse(raw_event).deep_symbolize_keys
-                end
+        # Obviously, this is just flushing the current connection: Filtering.
+        next if raw_event == "\n"
+
+        # Otherwise, we expect to receive a JSON: Parsing.
+        event = JSON.parse(raw_event).deep_symbolize_keys
 
         case event[:cmd].to_sym
           when :client_kill
diff --git a/lib/runner/connection.rb b/lib/runner/connection.rb
index 03368ab7..ab3f5279 100644
--- a/lib/runner/connection.rb
+++ b/lib/runner/connection.rb
@@ -22,7 +22,8 @@ class Runner::Connection
     @status = :established
     @event_loop = event_loop
     @locale = locale
-    @buffer = Buffer.new
+    @stdout_buffer = Buffer.new
+    @stderr_buffer = Buffer.new
 
     # For every event type of Faye WebSockets, the corresponding
     # RunnerConnection method starting with `on_` is called.
@@ -83,14 +84,7 @@ class Runner::Connection
 
   def on_message(raw_event)
     Rails.logger.debug { "#{Time.zone.now.getutc}: Receiving from #{@socket.url}: #{raw_event.data.inspect}" }
-    @buffer.store raw_event.data
-    @buffer.events.each do |event_data|
-      forward_message event_data
-    end
-  end
-
-  def forward_message(event_data)
-    event = decode(event_data)
+    event = decode(raw_event.data)
     return unless BACKEND_OUTPUT_SCHEMA.valid?(event)
 
     event = event.deep_symbolize_keys
@@ -102,7 +96,6 @@ class Runner::Connection
       close(:error)
     end
   end
-  private :forward_message
 
   def on_open(_event)
     @start_callback.call
@@ -112,7 +105,7 @@ class Runner::Connection
 
   def on_close(_event)
     Rails.logger.debug { "#{Time.zone.now.getutc}: Closing connection to #{@socket.url} with status: #{@status}" }
-    forward_message @buffer.flush unless @buffer.empty?
+    flush_buffers
 
     # Depending on the status, we might want to destroy the runner at management.
     # This ensures we get a new runner on the next request.
@@ -149,11 +142,17 @@ class Runner::Connection
   end
 
   def handle_stdout(event)
-    @stdout_callback.call event[:data]
+    @stdout_buffer.store event[:data]
+    @stdout_buffer.events.each do |event_data|
+      @stdout_callback.call event_data
+    end
   end
 
   def handle_stderr(event)
-    @stderr_callback.call event[:data]
+    @stderr_buffer.store event[:data]
+    @stderr_buffer.events.each do |event_data|
+      @stderr_callback.call event_data
+    end
   end
 
   def handle_error(_event); end
@@ -163,4 +162,10 @@ class Runner::Connection
   def handle_timeout(_event)
     @status = :timeout
   end
+
+  def flush_buffers
+    @stdout_callback.call @stdout_buffer.flush unless @stdout_buffer.empty?
+    @stderr_callback.call @stderr_buffer.flush unless @stderr_buffer.empty?
+  end
+  private :flush_buffers
 end
diff --git a/lib/runner/strategy/poseidon.rb b/lib/runner/strategy/poseidon.rb
index 2c186e1f..10ce2a60 100644
--- a/lib/runner/strategy/poseidon.rb
+++ b/lib/runner/strategy/poseidon.rb
@@ -166,7 +166,7 @@ class Runner::Strategy::Poseidon < Runner::Strategy
     end
 
     def encode(data)
-      data
+      "#{data}\n"
     end
   end
 end