Emit the HTTP response headers that turn the current response into a
Server-Sent Events stream and write the blank line that ends the
headers. After this call the CGI stream is in event_stream
transfer mode and each sse_send/1 or sse_send/2 is flushed to the
client. The mandatory headers emitted are:
Content-Type: text/event-streamCache-Control: no-cacheX-Accel-Buffering: no (disables nginx response buffering)
cors_enable/0 is called after the mandatory headers, so the
http:cors setting controls whether an Access-Control-Allow-Origin
header is emitted. Browser-based EventSource clients on a different
origin need this; non-browser clients do not.
Options:
- headers(+List)
- Additional response headers to emit, given as a list of
Name-Value pairs. Both Name and Value are written with
format/3 using `~w`.
- retry(+Seconds)
- After the headers, emit an initial `retry: Millis\n\n` field,
which sets the client's reconnect delay in milliseconds,
computed from Seconds.
