http_sse_wire_stream.h File Reference

WireStream transport over HTTP Server-Sent Events. More...

#include <cstdint>
#include <functional>
#include <memory>
#include <optional>
#include <string>
#include <absl/base/nullability.h>
#include <absl/status/status.h>
#include <absl/status/statusor.h>
#include <absl/time/time.h>
#include "a11/concurrency/future.h"
#include "a11/data/types.h"
#include "a11/net/describe_endpoint.h"
#include "a11/net/http2.h"
#include "a11/net/in_process_wire_stream.h"
#include "a11/net/server_headers.h"
#include "a11/net/wire_stream.h"

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Classes
struct	a11::net::HttpSseOptions
	Endpoint paths and transport tuning for an HTTP SSE wire stream. More...
class	a11::net::HttpSseWireStream
	Common base for the client and server HTTP SSE wire streams. More...
class	a11::net::HttpSseClientWireStream
	The client-side HTTP SSE wire stream, dialing out to a server URL. More...
class	a11::net::HttpSseServerWireStream
	The server-side HTTP SSE wire stream, accepted from a client. More...
class	a11::net::HttpSseServer
	Hosts HTTP SSE wire streams on top of an HTTP/2 server. More...

Namespaces
namespace	a11
namespace	a11::net

Typedefs
using	a11::net::OnHttpSseConnect = std::function< a11::Task(std::shared_ptr< HttpSseServerWireStream >)>
	Callback invoked with each accepted server-side SSE wire stream.
using	a11::net::HttpSseWireStreamServer = HttpSseServer
	Alias for HttpSseServer, spelled to match the WireStream naming family.

Enumerations
enum class	a11::net::SseOutboundDelivery { a11::net::kPost , a11::net::kStream }
	How an SSE client hands its outbound WireMessages to the server. More...

Variables
constexpr std::string_view	a11::net::kSseStreamIdHeader = "x-a11-stream-id"
	Response header naming the stream id assigned to an SSE connection.
constexpr std::string_view	a11::net::kSseHttpHeaderPrefix = "x-a11-http-"
	Prefix under which application HTTP headers are tunneled over SSE.
constexpr std::string_view	a11::net::kSseOutboundModesHeader = "x-a11-outbound"
	Response header on the connect response listing the outbound delivery modes the server accepts, comma-separated – post, stream.
constexpr std::string_view	a11::net::kSseOutboundPostToken = "post"
	Token for one-POST-per-message outbound delivery.
constexpr std::string_view	a11::net::kSseOutboundStreamToken = "stream"
	Token for long-lived-request-body outbound delivery.
constexpr std::string_view	a11::net::kSseWireStreamContentType
	Content type of a streamed outbound request body.
constexpr std::string_view	a11::net::kDefaultSseConnectEndpoint = "/connect"
	Default path on which a client opens the SSE event stream.
constexpr std::string_view	a11::net::kDefaultSseMessageEndpoint
	Default message-post path template ({id} is the stream id).

Detailed Description

WireStream transport over HTTP Server-Sent Events.

An HttpSseWireStream carries A11 WireMessage traffic over an HTTP channel: the server streams messages back as Server-Sent Events while the client posts outgoing messages to a companion endpoint. Pick this transport when only ordinary HTTP is available – it is a firewall- and proxy-friendly alternative to WebSockets. HttpSseClientWireStream dials out, HttpSseServerWireStream is the accepted counterpart, and HttpSseServer hosts them. Delivery carries no global ordering guarantee but is synchronised on closure – a reader observes every delivered message before the stream completes.

HTTP/2 and HTTP/1.1

Over HTTP/2 the event stream and the outbound direction are streams on one connection. HTTP/1.1 has no multiplexing and an A11 client connection carries a single request, so the outbound direction needs a connection of its own: either one for all of it (a streamed request body, which a non-multiplexed connection prefers whenever the server advertises it) or one per message (POST delivery, the interop fallback). Nothing about the protocol changes – only how many sockets it takes.