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* Add Server::CustomRoute() for HTTP methods outside the built-in set parse_request_line validates the request method against a fixed whitelist and rejects anything else with 400 before routing runs. That blocks WebDAV, where PROPFIND, PROPPATCH, MKCOL, COPY, MOVE, LOCK and UNLOCK are ordinary methods defined by RFC 4918, and it blocks extension methods such as UPnP's SUBSCRIBE. The need has been open since #847. Registering a handler is now what makes the server accept a method: svr.CustomRoute("PROPFIND", "/dav/:id", handler); Because custom methods go through the normal dispatch path, patterns work the way they do for Get() and friends, and the request body is available in req.body. Serving these methods through set_pre_routing_handler was never enough: the body has not been read at that point, so PROPPATCH and LOCK, which require one, could not be implemented at all. A HandlerWithContentReader overload is available too. The content reader gate in routing() also fires when a custom method carries no body, matching what expect_content() does unconditionally for POST/PUT/PATCH/DELETE, so a body-less PROPFIND (RFC 4918 treats one as allprop) reaches its handler instead of falling through to 404. Method names are validated as RFC 9110 tokens, and the ten built-in methods are refused. Seven of them are dispatched by the if/else chain in routing() before the custom tables are consulted, so a route registered for one could never fire; CONNECT, TRACE and PRI carry protocol-level meaning this library does not route. A refused registration makes is_valid() return false, so listen() fails rather than starting a server holding a handler that would never run. This is also why SSLServer::is_valid() now chains to Server::is_valid() instead of only checking ctx_. Servers that never call CustomRoute() keep the previous per-request cost: the built-in method set is checked first and short-circuits, and the custom lookup returns early on an empty map. * Add cookbook recipe for custom HTTP methods The CustomRoute() docs were a section inside S01, which pushed that page to 90 lines, the longest in the cookbook, and mixed a separate feature into a page about registering GET/POST/PUT/DELETE handlers. Move the section into its own recipe and give it room for the part that was missing: the OPTIONS handler returning DAV: and Allow, which WebDAV clients probe for before anything else. S01 goes back to 68 lines and keeps a pointer to the new page. The recipe is titled after the API rather than after WebDAV, and says outright that generating the 207 Multi-Status XML, interpreting Depth and managing locks are the reader's job. Routing the method is all the library does. S23 takes order 42, so the TLS, SSE and WebSocket recipes shift to 43-57. That only moves the sort key. Filenames, the T01/E01/W01 labels, the published URLs and every cross-reference are untouched.
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3.5 KiB
title, order, status
| title | order | status |
|---|---|---|
| E01. SSEサーバーを実装する | 48 | draft |
Server-Sent Events（SSE）は、サーバーからクライアントへイベントを一方向にプッシュするためのシンプルなプロトコルです。長時間の接続を保ったまま、サーバーが好きなタイミングでデータを送れます。WebSocketより軽量で、HTTPの範囲で完結するのが魅力です。
cpp-httplibにはSSE専用のサーバーAPIはありませんが、set_chunked_content_provider()とtext/event-streamを組み合わせれば実装できます。
基本のSSEサーバー
svr.Get("/events", [](const httplib::Request &req, httplib::Response &res) {
res.set_chunked_content_provider(
"text/event-stream",
[](size_t offset, httplib::DataSink &sink) {
std::string message = "data: hello\n\n";
sink.write(message.data(), message.size());
std::this_thread::sleep_for(std::chrono::seconds(1));
return true;
});
});
ポイントは3つです。
- Content-Typeを
text/event-streamにする - メッセージは
data: <内容>\n\nの形式で書く（\n\nで1イベントの区切り） sink.write()で送るたびに、クライアントが受け取る
接続が生きている限り、プロバイダラムダが繰り返し呼ばれ続けます。
イベントを送り続ける例
サーバーの現在時刻を1秒ごとに送るシンプルな例です。
svr.Get("/time", [](const httplib::Request &req, httplib::Response &res) {
res.set_chunked_content_provider(
"text/event-stream",
[&req](size_t offset, httplib::DataSink &sink) {
if (req.is_connection_closed()) {
sink.done();
return true;
}
auto now = std::chrono::system_clock::now();
auto t = std::chrono::system_clock::to_time_t(now);
std::string msg = "data: " + std::string(std::ctime(&t)) + "\n";
sink.write(msg.data(), msg.size());
std::this_thread::sleep_for(std::chrono::seconds(1));
return true;
});
});
クライアントが切断したらsink.done()で終了します。詳しくはS16. クライアントが切断したか検出するを参照してください。
コメント行でハートビート
:で始まる行はSSEのコメントで、クライアントは無視しますが、接続を生かしておく役割があります。プロキシやロードバランサが無通信接続を切ってしまうのを防げます。
// 30秒ごとにハートビート
if (tick_count % 30 == 0) {
std::string ping = ": ping\n\n";
sink.write(ping.data(), ping.size());
}
スレッドプールとの関係
SSEは接続がつなぎっぱなしなので、1クライアントあたり1ワーカースレッドを消費します。同時接続数が多くなりそうなら、スレッドプールを動的スケーリングにしておきましょう。
svr.new_task_queue = [] {
return new httplib::ThreadPool(8, 128);
};
詳しくはS21. マルチスレッド数を設定するを参照してください。
Note:
data:の後ろに改行が含まれる場合、各行の先頭にdata:を付けて複数のdata:行として送ります。SSEの仕様で決まっているフォーマットです。
イベント名を使い分けたい場合はE02. SSEでイベント名を使い分けるを、クライアント側はE04. SSEをクライアントで受信するを参照してください。