flush method in HttpServer::Response doesn't seem to work

[unplugandplay]

Hi, I 'm trying to replicate the Server Side Event example from https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events , using this code :

require "http/server"

port = 5000

server = HTTP::Server.new do |context|
  puts "Got request"
  # `context.response.headers["Transfer-Encoding"] = "chunked"` is default.
   context.response.headers["Content-Type"] = "text/event-stream"
  context.response.headers["Access-Control-Allow-Origin"] = "*"
  context.response.headers["Access-Control-Allow-Methods"] = "GET, HEAD, POST, PUT"
  context.response.headers["Access-Control-Allow-Headers"] = "Content-Type, Accept, Origin, Authorization"
  context.response.headers["Access-Control-Max-Age"] = "86400"
  loop do
    context.response.puts "event: ping\n";
    context.response.puts "data: hello\n"
    context.response.flush
    puts "Writing"
    sleep 5
    context.response.puts "data: world\n"
    context.response.flush
    puts "Writing"
  end
end

address = server.bind_tcp 5000
puts "Listening on http://#{address}"
server.listen

I was hoping that

crystal/src/http/server/response.cr

Line 109 in 639e476

def flush

would do a similar job as

ob_end_flush();
  flush()

in the PHP example part, I mean, sending (flushing) response while keeping the http connexion open

Am I missing something or is the flush method just not design to do that ?

crystal --version
Crystal 0.27.2 (2019-02-05)

LLVM: 6.0.1
Default target: x86_64-apple-macosx

[vladfaust]

I'm not much sure, but it might be a good idea to debug the request processor, adding pp as breakpoints to the HTTP::Server::RequestProcessor#process method to find out what's going on...

[straight-shoota]

Yes, #flush should write the buffer to the IO which means currently queued data should be send.

Unfortunately, your post lacks sufficient information to be able to help you. Could you provide a full description how you're actually testing this server code, what you expect it to do and what exactly goes wrong?

[straight-shoota]

@vladfaust Your suggestion is not very helpful. It's based on a wild guess that RequestProcessor#process might be faulted, which is almost impossible to be relevant here. If there is actually a bug somewhere, it's in the IO stack. But without any information about how the server is supposed to behave and what it actually does, there is no way to tell what's actually the issue here.

[unplugandplay]

In fact it was me, as this code is perfectly working with the EventSource javascript part :

  3.times do |i_times|
    #context.response.puts "id: #{i_times+1}\n"
    #context.response.puts "event: ping\n"
    context.response.puts "data: hello"
    context.response.puts "data: world"
    context.response.puts "\n\n"
    puts "Writing"
    context.response.flush
    sleep 1
  end