yhirose
9bfd2ddf1c
Bring the READMEs and the docs pages (en and ja) in line with the current header: - Fix the client sample that does not compile, the Transfer-Encoding statement for default headers, the verifier callback comment, the thread pool spawn rule, the sanitize_filename description, and the inverted Accept-Encoding sentence. - Describe recent behaviour: TLS errors behind Read/Write failures, Host validation, Connection: close for a body without length, content_reader rules, refused CONNECT, WebSocketClient proxies, CPPHTTPLIB_INTERIM_RESPONSE_MAX_COUNT, the SSE event size limit, and the payload limit of the Stream API. - Complete the API references of WebSocket, WebSocketClient and the stream:: helpers, and the SSE reconnect rules. - Fix cookbook pages: keychain loading on every backend, received Close status, a multipart sample that trusted the client's file name, an echo sample that sent binary as text, SNI, pre-request handler scope, stop() with WebSocket handlers, and the thread pool notes. - Restore the mutex in the LLM app's Chapter 5 code.
1.9 KiB
title, order, status
| title | order | status |
|---|---|---|
| S20. Tune Keep-Alive | 39 | draft |
httplib::Server enables HTTP/1.1 Keep-Alive automatically. From the client's perspective, connections are reused — so they don't pay the TCP handshake cost on every request. When you need to tune the behavior, there are two setters.
What you can configure
| API | Default | Meaning |
|---|---|---|
set_keep_alive_max_count |
100 | Max requests served over a single connection (0 for no limit) |
set_keep_alive_timeout |
5s | How long an idle connection is kept before closing |
Basic usage
httplib::Server svr;
svr.set_keep_alive_max_count(20);
svr.set_keep_alive_timeout(10); // 10 seconds
svr.listen("0.0.0.0", 8080);
set_keep_alive_timeout() also has a std::chrono overload.
using namespace std::chrono_literals;
svr.set_keep_alive_timeout(10s);
Tuning ideas
Too many idle connections eating resources
Shorten the timeout so idle connections drop and release their worker threads.
svr.set_keep_alive_timeout(2s);
API is hammered and you want max reuse
Raising the per-connection request cap improves benchmark numbers.
svr.set_keep_alive_max_count(1000);
Never reuse connections
Set set_keep_alive_max_count(1) and every request gets its own connection. Mostly only useful for debugging or compatibility testing.
Relationship with the thread pool
A Keep-Alive connection holds a worker thread for its entire lifetime. The pool adds threads under load, up to its maximum thread count (4× the base count by default). If open connections outnumber that maximum, new connections wait in the queue until one closes. For thread counts, see S21. Configure the thread pool.
Note: For the client side, see C14. Understand connection reuse and Keep-Alive behavior. Even when the server closes the connection on timeout, the client reconnects automatically.