49 lines
2.3 KiB
Go
49 lines
2.3 KiB
Go
package mw
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import (
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"net/http"
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"code.nochebuena.dev/einherjar/core/logz"
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)
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// RequestIDFrom injects a per-request ID into the context (via [logz.WithRequestID])
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// and the X-Request-ID response header, using the ID that resolve returns for the
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// request.
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//
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// resolve receives the request so the application can decide the ID from it — most
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// importantly, to continue a correlation ID a client already sent, so a distributed
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// trace survives this boundary. The framework deliberately does not read a header,
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// choose a header name, or validate the value: acceptability is per-service. A
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// service that persists the ID in a typed column must reject what it cannot store
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// and mint its own; a service that only logs an opaque string need not care. Reading
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// the header here would accept, on a service's behalf, a value that service may be
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// unable to store — so resolution is the application's to own, and generation is
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// merely the fallback branch a resolver takes when there is no usable inbound ID.
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//
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// resolve is called exactly once per request and is expected to return a non-empty
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// ID. When it returns "", no ID is attached — the response header is omitted and the
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// context carries none — rather than propagating an empty value; supplying a resolver
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// that can resolve to "" (e.g. one with no generation fallback) is a caller error.
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func RequestIDFrom(resolve func(r *http.Request) string) func(http.Handler) http.Handler {
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return func(next http.Handler) http.Handler {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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if id := resolve(r); id != "" {
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r = r.WithContext(logz.WithRequestID(r.Context(), id))
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w.Header().Set("X-Request-ID", id)
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}
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next.ServeHTTP(w, r)
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})
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}
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}
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// RequestID injects a freshly generated request ID into the context (via
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// [logz.WithRequestID]) and sets the X-Request-ID response header. generator is
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// called once per request — pass uuid.NewString or a custom function.
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//
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// It always generates and ignores any inbound X-Request-ID. To continue a
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// correlation ID the client supplied, use [RequestIDFrom] with a resolver that
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// reads and validates it.
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func RequestID(generator func() string) func(http.Handler) http.Handler {
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return RequestIDFrom(func(*http.Request) string { return generator() })
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}
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