From 8459bebceb9533948193774371cbd9fd571b78ea Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Lo=C3=AFc=20Hoguin?= Date: Wed, 16 Oct 2019 09:48:31 +0200 Subject: Cowboy 2.7.0 --- docs/en/cowboy/2.7/guide/streams.asciidoc | 75 +++++++++++++++++++++++++++++++ 1 file changed, 75 insertions(+) create mode 100644 docs/en/cowboy/2.7/guide/streams.asciidoc (limited to 'docs/en/cowboy/2.7/guide/streams.asciidoc') diff --git a/docs/en/cowboy/2.7/guide/streams.asciidoc b/docs/en/cowboy/2.7/guide/streams.asciidoc new file mode 100644 index 00000000..39b52039 --- /dev/null +++ b/docs/en/cowboy/2.7/guide/streams.asciidoc @@ -0,0 +1,75 @@ +[[streams]] +== Streams + +A stream is the set of messages that form an HTTP +request/response pair. + +The term stream comes from HTTP/2. In Cowboy, it is +also used when talking about HTTP/1.1 or HTTP/1.0. +It should not be confused with streaming the request +or response body. + +All versions of HTTP allow clients to initiate +streams. HTTP/2 is the only one also allowing servers, +through its server push feature. Both client and +server-initiated streams go through the same process +in Cowboy. + +=== Stream handlers + +link:man:cowboy_stream(3)[Stream handlers] +must implement five different callbacks. +Four of them are directly related; one is special. + +All callbacks receives the stream ID as first argument. + +Most of them can return a list of commands to be executed +by Cowboy. When callbacks are chained, it is possible to +intercept and modify these commands. This can be useful +for modifying responses for example. + +The `init/3` callback is invoked when a new request +comes in. It receives the Req object and the protocol options +for this listener. + +The `data/4` callback is invoked when data from the request +body is received. It receives both this data and a flag +indicating whether more is to be expected. + +The `info/3` callback is invoked when an Erlang message is +received for this stream. They will typically be messages +sent by the request process. + +Finally the `terminate/3` callback is invoked with the +terminate reason for the stream. The return value is ignored. +Note that as with all terminate callbacks in Erlang, there +is no strong guarantee that it will be called. + +The special callback `early_error/5` is called when an error +occurs before the request headers were fully received and +Cowboy is sending a response. It receives the partial Req +object, the error reason, the protocol options and the response +Cowboy will send. This response must be returned, possibly +modified. + +=== Built-in handlers + +Cowboy comes with two handlers. + +link:man:cowboy_stream_h(3)[cowboy_stream_h] is the default +stream handler. It is the core of much of the functionality +of Cowboy. All chains of stream handlers should call it last. + +link:man:cowboy_compress_h(3)[cowboy_compress_h] will +automatically compress responses when possible. It is not +enabled by default. It is a good example for writing your +own handlers that will modify responses. + +link:man:cowboy_metrics_h(3)[cowboy_metrics_h] gathers +metrics about a stream then passes them to a configurable +function. It is not enabled by default. + +link:man:cowboy_tracer_h(3)[cowboy_tracer_h] can be used to +conditionally trace streams based on the contents of the +request or its origin. Trace events are passed to a +configurable function. It is not enabled by default. -- cgit v1.2.3