Middleware upgrade (#554)

* Adds root level middleware

* Added todo

* Better way for extensions to be added.

* Bad conflict merge?

api/server/gin_middlewares.go

@@ -0,0 +1,96 @@
+// This is middleware we're using for the entire server.
+
+package server
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"github.com/fnproject/fn/api"
+	"github.com/fnproject/fn/api/common"
+	"github.com/fnproject/fn/api/models"
+	"github.com/gin-contrib/cors"
+	"github.com/gin-gonic/gin"
+	opentracing "github.com/opentracing/opentracing-go"
+	"github.com/opentracing/opentracing-go/ext"
+	"github.com/sirupsen/logrus"
+)
+
+func optionalCorsWrap(r *gin.Engine) {
+	// By default no CORS are allowed unless one
+	// or more Origins are defined by the API_CORS
+	// environment variable.
+	corsStr := getEnv(EnvAPICORS, "")
+	if len(corsStr) > 0 {
+		origins := strings.Split(strings.Replace(corsStr, " ", "", -1), ",")
+
+		corsConfig := cors.DefaultConfig()
+		corsConfig.AllowOrigins = origins
+
+		logrus.Infof("CORS enabled for domains: %s", origins)
+
+		r.Use(cors.New(corsConfig))
+	}
+}
+
+// we should use http grr
+func traceWrap(c *gin.Context) {
+	// try to grab a span from the request if made from another service, ignore err if not
+	wireContext, _ := opentracing.GlobalTracer().Extract(
+		opentracing.HTTPHeaders,
+		opentracing.HTTPHeadersCarrier(c.Request.Header))
+
+	// Create the span referring to the RPC client if available.
+	// If wireContext == nil, a root span will be created.
+	// TODO we should add more tags?
+	serverSpan := opentracing.StartSpan("serve_http", ext.RPCServerOption(wireContext), opentracing.Tag{Key: "path", Value: c.Request.URL.Path})
+	serverSpan.SetBaggageItem("fn_appname", c.Param(api.CApp))
+	serverSpan.SetBaggageItem("fn_path", c.Param(api.CRoute))
+	defer serverSpan.Finish()
+
+	ctx := opentracing.ContextWithSpan(c.Request.Context(), serverSpan)
+	c.Request = c.Request.WithContext(ctx)
+	c.Next()
+}
+
+func panicWrap(c *gin.Context) {
+	defer func(c *gin.Context) {
+		if rec := recover(); rec != nil {
+			err, ok := rec.(error)
+			if !ok {
+				err = fmt.Errorf("fn: %v", rec)
+			}
+			handleErrorResponse(c, err)
+			c.Abort()
+		}
+	}(c)
+	c.Next()
+}
+
+func loggerWrap(c *gin.Context) {
+	ctx, _ := common.LoggerWithFields(c.Request.Context(), extractFields(c))
+
+	if appName := c.Param(api.CApp); appName != "" {
+		c.Set(api.AppName, appName)
+		ctx = context.WithValue(ctx, api.AppName, appName)
+	}
+
+	if routePath := c.Param(api.CRoute); routePath != "" {
+		c.Set(api.Path, routePath)
+		ctx = context.WithValue(ctx, api.Path, routePath)
+	}
+
+	c.Request = c.Request.WithContext(ctx)
+	c.Next()
+}
+
+func appWrap(c *gin.Context) {
+	appName := c.GetString(api.AppName)
+	if appName == "" {
+		handleErrorResponse(c, models.ErrAppsMissingName)
+		c.Abort()
+		return
+	}
+	c.Next()
+}