Create global attributes

Sometimes you want a sub-function to be able to "pass back" attributes to the parent. An example of this is when using middleware to log errors. In the situation below, the handler h may handle parsing the req and pull out certain fields that should be logged if there is an error. Unfortunately, because WithAttrs(...) only attaches the attrs to a child context, the parent function will not have access to these attrs.

func logMiddleware(ctx context.Context, h Handler, req []byte) {
    err := h(ctx, req)
    if err != nil {
        slog.ErrorContext(ctx, "request error")
    }
}

ctxlog provides a way to pass back these attributes for logging through global attributes.

func logMiddleware(ctx context.Context, h Handler, req []byte) {
    // First, set the anchor point/root of global attrs. This allows us to
    // scope global attrs to each request.
    ctx = ctxlog.AnchorGlobalAttrs(ctx) 
    err := h(ctx, req)
    if err != nil {
        slog.ErrorContext(ctx, "request error")
    }
}

func myHandler(ctx context.Context, req []byte) error {
    parsedReq := parseRequest(req)

    // Use ctxlog.WithGlobalAttrs to "pass back" attrs to the anchor point
    ctx = ctxlog.WithGlobalAttrs(ctx, slog.String("request_id", parsedReq.request_id))
    // ...
    return nil
}