Fix broken pipe when closing UNIX Socket in HTTP::Server

spec/std/http/server/request_processor_spec.cr

@@ -2,6 +2,7 @@ require "spec"
 require "log/spec"
 require "http/server/request_processor"
 require "../../../support/io"
+require "../../../support/tempfile"
 
 private def requestize(string)
   string.gsub('\n', "\r\n")
@@ -268,6 +269,22 @@ describe HTTP::Server::RequestProcessor do
     logs.entry.exception.should be_a(IO::Error)
   end
 
+  it "handles closed UNIXSocket without broken pipe" do
+    with_tempfile("request_processor.sock") do |path|
+      server = UNIXServer.new(path)
+      client = UNIXSocket.new(path)
+      server.accept do |sock|
+        sock.sync = false
+        client.send "GET / HTTP/1.1\r\n\r\n"
+        processor = HTTP::Server::RequestProcessor.new do |context|
+          client.close
+          context.response.puts "hello"
+        end
+        processor.process(sock, sock)
+      end
+    end
+  end
+
   it "catches raised error on handler and retains context from handler" do
     exception = Exception.new "OH NO"
     processor = HTTP::Server::RequestProcessor.new { Log.context.set foo: "bar"; raise exception }

src/http/server/request_processor.cr

@@ -48,7 +48,13 @@ class HTTP::Server::RequestProcessor
         context = Context.new(request, response)
 
         Log.with_context do
-          @handler.call(context)
+          begin
+            @handler.call(context)
+          ensure
+            if output.is_a?(IO::Buffered)
+              output.sync = true
+            end
+          end
         rescue ex : ClientError
           Log.debug(exception: ex.cause) { ex.message }
         rescue ex