mirror of
https://github.com/yhirose/cpp-httplib.git
synced 2026-10-19 11:19:36 +00:00
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.
58 lines
1.9 KiB
Markdown
58 lines
1.9 KiB
Markdown
---
|
||
title: "S20. Tune Keep-Alive"
|
||
order: 39
|
||
status: "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
|
||
|
||
```cpp
|
||
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.
|
||
|
||
```cpp
|
||
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.
|
||
|
||
```cpp
|
||
svr.set_keep_alive_timeout(2s);
|
||
```
|
||
|
||
**API is hammered and you want max reuse**
|
||
Raising the per-connection request cap improves benchmark numbers.
|
||
|
||
```cpp
|
||
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](../s21-thread-pool).
|
||
|
||
> **Note:** For the client side, see [C14. Understand connection reuse and Keep-Alive behavior](../c14-keep-alive). Even when the server closes the connection on timeout, the client reconnects automatically.
|