Add support for Pull Queues to prod implementation.

filter/featureBreaker/tq.go

 // Copyright 2015 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 featureBreaker
 
 import (
         "golang.org/x/net/context"
 
         tq "github.com/luci/gae/service/taskqueue"
 )
 
 type tqState struct {
         *state
 
         tq tq.RawInterface
 }
 
 var _ tq.RawInterface = (*tqState)(nil)
 
 func (t *tqState) AddMulti(tasks []*tq.Task, queueName string, cb tq.RawTaskCB) error {
         return t.run(func() (err error) { return t.tq.AddMulti(tasks, queueName, cb) })
 }
 
 func (t *tqState) DeleteMulti(tasks []*tq.Task, queueName string, cb tq.RawCB) error {
         return t.run(func() error { return t.tq.DeleteMulti(tasks, queueName, cb) })
 }
 
+func (t *tqState) Lease(maxTasks int, queueName string, leaseTime int) (tasks []*tq.Task, err error) {
+        err = t.run(func() (err error) {
+                tasks, err = t.tq.Lease(maxTasks, queueName, leaseTime)
+                return
+        })
+        if err != nil {
+                tasks = nil
+        }
+        return
+}
+
+func (t *tqState) LeaseByTag(maxTasks int, queueName string, leaseTime int, tag string) (tasks []*tq.Task, err error) {
+        err = t.run(func() (err error) {
+                tasks, err = t.tq.LeaseByTag(maxTasks, queueName, leaseTime, tag)
+                return
+        })
+        if err != nil {
+                tasks = nil
+        }
+        return
+}
+
+func (t *tqState) ModifyLease(task *tq.Task, queueName string, leaseTime int) error {
+        return t.run(func() error { return t.tq.ModifyLease(task, queueName, leaseTime) })
+}
+
 func (t *tqState) Purge(queueName string) error {
         return t.run(func() error { return t.tq.Purge(queueName) })
 }
 
 func (t *tqState) Stats(queueNames []string, cb tq.RawStatsCB) error {
         return t.run(func() error { return t.tq.Stats(queueNames, cb) })
 }
 
 func (t *tqState) GetTestable() tq.Testable {
         return t.tq.GetTestable()
 }
 
 // FilterTQ installs a featureBreaker TaskQueue filter in the context.
 func FilterTQ(c context.Context, defaultError error) (context.Context, FeatureBreaker) {
         state := newState(defaultError)
         return tq.AddRawFilters(c, func(ic context.Context, tq tq.RawInterface) tq.RawInterface {
                 return &tqState{state, tq}
         }), state
 }