Yielding in body_filter_by_lua

[domanjiri]

I'm curious to know why you didn't provide async facilities in body_filter_by_lua. Is there any hard barrier in Nginx? I guess it would be possible to suspend a request within a body filter by blocking its read and write event handlers and then deleting timers. Maybe we also need a small patch for ngx_http_finalize_request() to do nothing with that request. Have I missed anything?