evhttp_write_buffer() used by evhttp_send_reply_chunk() can take callback
executed when (part of) the buffer has been written. Using this callback to
schedule the next chunk avoids buffering large amounts of data in memory.
The callback will be executed if a failure (timeout, read error) is detected
on an incoming connection.
This can be used to detect a client closing the connection while engaged in a
chunked reply and actively pushing chunks to the client. Without this
notification, it is impossible to know if/when a connection gets closed and
react appropriately (ie. stop pushing chunks) resulting in a segfault.
Julien BLACHE