Make HTTP middleware easier to use

appengine/tsmon/middleware.go

 // Copyright 2016 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 // Package tsmon adapts common/tsmon library to GAE environment.
 //
 // It configures tsmon state with a monitor and store suitable for GAE
 // environment and controls when metric flushes happen.
 package tsmon
 
 import (
         "fmt"
-        "net/http"
         "strings"
         "sync"
         "time"
 
         "github.com/golang/protobuf/proto"
-        "github.com/julienschmidt/httprouter"
         "golang.org/x/net/context"
 
         "github.com/luci/gae/service/info"
         gaeauth "github.com/luci/luci-go/appengine/gaeauth/client"
         "github.com/luci/luci-go/common/clock"
         gcps "github.com/luci/luci-go/common/gcloud/pubsub"
         "github.com/luci/luci-go/common/logging"
         "github.com/luci/luci-go/common/tsmon"
         "github.com/luci/luci-go/common/tsmon/monitor"
         "github.com/luci/luci-go/common/tsmon/store"
         "github.com/luci/luci-go/common/tsmon/target"
-        "github.com/luci/luci-go/server/middleware"
+        "github.com/luci/luci-go/server/router"
 )
 
 // State holds the configuration of the tsmon library for GAE.
 //
 // Define it as a global variable and inject it in the request contexts using
 // State.Middleware().
 //
 // It will initialize itself from the tsmon state in the passed context on
 // a first use, mutating it along the way. Assumes caller is consistently using
 // contexts configured with exact same tsmon state (in a vast majority of cases
@@ skipping 12 matching lines @@
         lastFlushed time.Time
 
         // testingMonitor is mocked monitor used in unit tests.
         testingMonitor monitor.Monitor
         // testingSettings if not nil are used in unit tests.
         testingSettings *tsmonSettings
 }
 
 // Middleware returns a middleware that must be inserted into the chain to
 // enable tsmon metrics to be sent on App Engine.
-func (s *State) Middleware(h middleware.Handler) middleware.Handler {
-        return func(c context.Context, rw http.ResponseWriter, r *http.Request, p httprouter.Params) {
-                state, settings := s.checkSettings(c)
-                h(c, rw, r, p)
+func (s *State) Middleware() router.Handler {
+        return func(c *router.Context) {
+                state, settings := s.checkSettings(c.Context)
+                c.Next()
                 if settings.Enabled {
-                        s.flushIfNeeded(c, state, settings)
+                        s.flushIfNeeded(c.Context, state, settings)
                 }
         }
 }
 
 // checkSettings fetches tsmon settings and initializes, reinitializes or
 // deinitializes tsmon, as needed.
 //
 // Returns current tsmon state and settings. Panics if the context is using
 // unexpected tsmon state.
 func (s *State) checkSettings(c context.Context) (*tsmon.State, *tsmonSettings) {
@@ skipping 208 matching lines @@
                 }
         }
 
         if err := state.Flush(c, mon); err != nil {
                 return err
         }
 
         state.ResetGlobalCallbackMetrics(c)
         return nil
 }