yhirose
ebcd5551fd
A failed request could reach the client's error logger twice: once from the step that failed, without a request when that was the TLS setup or the proxy CONNECT, and again from send_() with the request. A content receiver or progress callback that canceled was reported twice too, a CONNECT answered with 407 only without a request, and a stream that failed to open not at all unless TLS failed. Report a failure in one place instead. The outermost send() reports the request's error once, with the request the caller made, also when the failure happened on a redirect (a redirect client no longer gets the error logger) and when an answer carries an error, such as a proxy's 407. open_stream() reports a stream that fails to open the same way. Only an upload body compressed before send() still reports where it fails.
2.2 KiB
title, order, status
| title | order | status |
|---|---|---|
| C19. Set a Logger on the Client | 19 | draft |
To log requests sent and responses received by the client, use set_logger(). If you only care about errors, there's a separate set_error_logger().
Log requests and responses
httplib::Client cli("https://api.example.com");
cli.set_logger([](const httplib::Request &req, const httplib::Response &res) {
std::cout << req.method << " " << req.path
<< " -> " << res.status << std::endl;
});
auto res = cli.Get("/users");
The callback you pass to set_logger() fires once for each completed request. You get both the request and the response as arguments — so you can log the method, path, status, headers, body, or whatever else you need.
Catch errors only
When a network-layer error happens (like Error::Connection), set_logger() is not called — there's no response to log. For those cases, use set_error_logger().
cli.set_error_logger([](const httplib::Error &err, const httplib::Request *req) {
std::cerr << "error: " << httplib::to_string(err);
if (req) {
std::cerr << " (" << req->method << " " << req->path << ")";
}
std::cerr << std::endl;
});
Each failed request is reported once, with the request you made, also when it failed on a redirect. A stream that fails to open with open_stream() or stream::Get() is reported the same way; errors while reading its body come back through read_error() instead. req is null only in a server's error logger, for errors that belong to no request.
Use both together
A nice pattern is to log successes through one, failures through the other.
cli.set_logger([](const auto &req, const auto &res) {
std::cout << "[ok] " << req.method << " " << req.path
<< " " << res.status << std::endl;
});
cli.set_error_logger([](const auto &err, const auto *req) {
std::cerr << "[ng] " << httplib::to_string(err);
if (req) std::cerr << " " << req->method << " " << req->path;
std::cerr << std::endl;
});
Note: The log callbacks run synchronously on the same thread as the request. Heavy work inside them slows the request down — push it to a background queue if you need to do anything expensive.