Decouple MetricsMiddleware from downstream handlers (#206)

* Decouple MetricsMiddleware from downstream handlers

Remove ls-real-model-name optimization. Within proxyOAIHandler the
request body's bytes are required for various rewriting features
anyways. This negated any benefits from trying not to parse it twice.

proxy/metrics_middleware.go

@@ -17,6 +17,7 @@ func MetricsMiddleware(pm *ProxyManager) gin.HandlerFunc {
 		bodyBytes, err := io.ReadAll(c.Request.Body)
 		if err != nil {
 			pm.sendErrorResponse(c, http.StatusBadRequest, "could not ready request body")
+			c.Abort()
 			return
 		}
 		c.Request.Body = io.NopCloser(bytes.NewBuffer(bodyBytes))
@@ -24,15 +25,16 @@ func MetricsMiddleware(pm *ProxyManager) gin.HandlerFunc {
 		requestedModel := gjson.GetBytes(bodyBytes, "model").String()
 		if requestedModel == "" {
 			pm.sendErrorResponse(c, http.StatusBadRequest, "missing or invalid 'model' key")
+			c.Abort()
 			return
 		}
 
 		realModelName, found := pm.config.RealModelName(requestedModel)
 		if !found {
 			pm.sendErrorResponse(c, http.StatusBadRequest, fmt.Sprintf("could not find real modelID for %s", requestedModel))
+			c.Abort()
 			return
 		}
-		c.Set("ls-real-model-name", realModelName)
 
 		writer := &MetricsResponseWriter{
 			ResponseWriter: c.Writer,

proxy/proxymanager.go

@@ -14,6 +14,7 @@ import (
 	"time"
 
 	"github.com/gin-gonic/gin"
+	"github.com/tidwall/gjson"
 	"github.com/tidwall/sjson"
 )
 
@@ -367,9 +368,15 @@ func (pm *ProxyManager) proxyOAIHandler(c *gin.Context) {
 		return
 	}
 
-	realModelName := c.GetString("ls-real-model-name") // Should be set in MetricsMiddleware
-	if realModelName == "" {
-		pm.sendErrorResponse(c, http.StatusInternalServerError, "ls-real-model-name not set")
+	requestedModel := gjson.GetBytes(bodyBytes, "model").String()
+	if requestedModel == "" {
+		pm.sendErrorResponse(c, http.StatusBadRequest, "missing or invalid 'model' key")
+		return
+	}
+
+	realModelName, found := pm.config.RealModelName(requestedModel)
+	if !found {
+		pm.sendErrorResponse(c, http.StatusBadRequest, fmt.Sprintf("could not find real modelID for %s", requestedModel))
 		return
 	}