Handle client disconnect during live streaming

.. even when the producer is blocked for a write.

1 files changed, 48 insertions, 0 deletions

diff --git a/actionpack/lib/action_controller/metal/live.rb b/actionpack/lib/action_controller/metal/live.rb
index 4c0554d27b..67875141cb 100644
--- a/actionpack/lib/action_controller/metal/live.rb
+++ b/actionpack/lib/action_controller/metal/live.rb
@@ -107,12 +107,25 @@ module ActionController
         end
     end
 
+    class ClientDisconnected < RuntimeError
+    end
+
     class Buffer < ActionDispatch::Response::Buffer #:nodoc:
       include MonitorMixin
 
+      # Ignore that the client has disconnected.
+      #
+      # If this value is `true`, calling `write` after the client
+      # disconnects will result in the written content being silently
+      # discarded. If this value is `false` (the default), a
+      # ClientDisconnected exception will be raised.
+      attr_accessor :ignore_disconnect
+
       def initialize(response)
         @error_callback = lambda { true }
         @cv = new_cond
+        @aborted = false
+        @ignore_disconnect = false
         super(response, SizedQueue.new(10))
       end
 
@@ -123,6 +136,17 @@ module ActionController
         end
 
         super
+
+        unless connected?
+          @buf.clear
+
+          unless @ignore_disconnect
+            # Raise ClientDisconnected, which is a RuntimeError (not an
+            # IOError), because that's more appropriate for something beyond
+            # the developer's control.
+            raise ClientDisconnected, "client disconnected"
+          end
+        end
       end
 
       def each
@@ -133,6 +157,10 @@ module ActionController
         @response.sent!
       end
 
+      # Write a 'close' event to the buffer; the producer/writing thread
+      # uses this to notify us that it's finished supplying content.
+      #
+      # See also #abort.
       def close
         synchronize do
           super
@@ -141,6 +169,26 @@ module ActionController
         end
       end
 
+      # Inform the producer/writing thread that the client has
+      # disconnected; the reading thread is no longer interested in
+      # anything that's being written.
+      #
+      # See also #close.
+      def abort
+        synchronize do
+          @aborted = true
+          @buf.clear
+        end
+      end
+
+      # Is the client still connected and waiting for content?
+      #
+      # The result of calling `write` when this is `false` is determined
+      # by `ignore_disconnect`.
+      def connected?
+        !@aborted
+      end
+
       def await_close
         synchronize do
           @cv.wait_until { @closed }