Function ExposeNodeHeader

core/http/middleware/node_header.go:96–127

ExposeNodeHeader installs a per-request response writer wrapper that stamps the X-LocalAI-Node header from the per-request holder published by the distributed router on the first write. Off by default; opted in via --expose-node-header / LOCALAI_EXPOSE_NODE_HEADER. Attribution is per-request correc

(appCfg *config.ApplicationConfig)

// shared loader state, no overwriting across concurrent requests for the
// same model on multiple replicas.
func ExposeNodeHeader(appCfg *config.ApplicationConfig) echo.MiddlewareFunc {
	return func(next echo.HandlerFunc) echo.HandlerFunc {
		return func(c echo.Context) error {
			if appCfg == nil || !appCfg.ExposeNodeHeader {
				return next(c)
			}

			// One holder per request. The pointer is captured both in
			// the wrapper closure (read side) and in the request
			// context (write side, accessed by the router via
			// distributedhdr.Stamp). Both sides point at the same
			// atomic slot.
			holder := distributedhdr.NewHolder()

			req := c.Request()
			c.SetRequest(req.WithContext(distributedhdr.WithHolder(req.Context(), holder)))

			orig := c.Response().Writer
			wrapper := &nodeHeaderWriter{
				ResponseWriter: orig,
				resolve: func() string {
					return distributedhdr.Load(holder)
				},
			}
			c.Response().Writer = wrapper
			defer func() {
				c.Response().Writer = orig
			}()
			return next(c)
		}
	}
}