Structured Lifecycle Events ​
HTTPX uses an event-driven observability model for client requests and server connections. Instead of printing unconditionally to standard output, HTTPX delivers structured event payloads to user-defined callback hooks.
Overview ​
The zero-output default design guarantees that library internals never clutter console logs or disrupt terminal protocols. When observability is needed, attach an event handler at initialization time.
Client Request Events ​
const std = @import("std");
const httpx = @import("httpx");
fn onClientEvent(event: httpx.logging.ClientEvent) void {
switch (event.kind) {
.requestCompleted => std.debug.print("[Client] {s} {s} -> {d}\n", .{
event.method, event.url, event.status,
}),
.requestFailed => std.debug.print("[Client] {s} {s} failed: {s}\n", .{
event.method, event.url, event.message,
}),
else => {},
}
}
pub fn main() !void {
var gpa: std.heap.DebugAllocator(.{}) = .init;
defer _ = gpa.deinit();
const allocator = gpa.allocator();
const io = std.Io.Threaded.global_single_threaded.io();
var client = httpx.Client.init(allocator, io, .{
.eventCallback = &onClientEvent,
});
defer client.deinit();
var res = try client.get("https://httpbun.com/get", .{});
defer res.deinit();
}The client callback currently emits requestCompleted with the method, URL, and response status, or requestFailed with the method, URL, and error name. ClientEventKind also defines requestStarted, redirect, retry, dnsLookup, dnsCacheHit, connectionEstablished, connectionReused, tlsHandshake, timeout, and cancellation, but the high-level client does not currently emit those kinds.
Event slices are borrowed for the callback duration only. Copy any value you need to retain.
Server Request Events ​
fn onServerEvent(event: httpx.logging.ServerEvent) void {
switch (event.kind) {
.serverStarted => std.debug.print("[Server] listening\n", .{}),
.requestCompleted => std.debug.print("[Server] {s} {s} -> {d} in {d}ms\n", .{
event.method, event.path, event.status, event.durationMs,
}),
.tlsHandshakeFailed => std.debug.print("[Server] TLS failure: {s}\n", .{
event.message,
}),
.serverStopped => std.debug.print("[Server] stopped\n", .{}),
else => {},
}
}The server callback currently emits serverStarted, serverStopped, requestCompleted, and tlsHandshakeFailed. ServerEventKind also defines connection, routing, middleware, handler, and worker kinds for applications that need to extend instrumentation, but the high-level server does not emit them today.
Pass .logging = .{ .callback = &onServerEvent } in the options passed to httpx.Server.init. The .logging.level field filters events below the configured severity.