Simple memory testing for gae/wrapper

go/src/infra/gae/libs/wrapper/memory/context.go

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package memory
+
+import (
+        "fmt"
+        "infra/gae/libs/wrapper"
+        "math/rand"
+        "sync"
+
+        "golang.org/x/net/context"
+
+        "appengine/datastore"
+)
+
+type memContextObj interface {
+        sync.Locker
+        canApplyTxn(m memContextObj) bool
+        applyTxn(rnd *rand.Rand, m memContextObj)
+
+        endTxn()
+        mkTxn(*datastore.TransactionOptions) (memContextObj, error)
+}
+
+type memContext []memContextObj
+
+func newMemContext() memContext {
+        return memContext{
+                newTaskQueueData(),
+                newDataStoreData(),
+        }
+}
+
+var memContextIndices = map[string]int{
+        "TQ": 0,

[M-A Ruel, 2015/05/29 16:16:18]

Did you plan to have this list be dynamic? Otherwise you could use a type with
const, e.g.

type ContextType string
const TQ ContextType = "TQ"

but then you don't even need strings anymore and would just use indexes, so no
need for memContextIndices. I'd prefer that.

[iannucci, 2015/05/29 16:33:14]

sgtm

+        "DS": 1,
+}
+
+func (m memContext) Get(item string) memContextObj {
+        if i, ok := memContextIndices[item]; ok {
+                return m[i]
+        }
+        panic(fmt.Errorf("wrapper/memory: cannot get context item %q", item))
+}
+
+func (m memContext) Lock() {
+        for _, itm := range m {
+                itm.Lock()
+        }
+}
+
+func (m memContext) Unlock() {
+        for i := len(m) - 1; i >= 0; i-- {
+                m[i].Unlock()
+        }
+}
+
+func (m memContext) endTxn() {
+        for _, itm := range m {
+                itm.endTxn()
+        }
+}
+
+func (m memContext) mkTxn(o *datastore.TransactionOptions) (memContext, error) {
+        ret := make(memContext, len(m))
+        for i, itm := range m {
+                newItm, err := itm.mkTxn(o)
+                if err != nil {
+                        return nil, err
+                }
+                ret[i] = newItm
+        }
+        return ret, nil
+}
+
+func (m memContext) canApplyTxn(txnCtx memContext) bool {
+        for i := range m {
+                if !m[i].canApplyTxn(txnCtx[i]) {
+                        return false
+                }
+        }
+        return true
+}
+
+func (m memContext) applyTxn(rnd *rand.Rand, txnCtx memContext) {
+        for i := range m {
+                m[i].applyTxn(rnd, txnCtx[i])
+        }
+}
+
+// Enable adds a new memory context to c. This new memory context will have
+// a zeroed state.
+func Enable(c context.Context) context.Context {
+        return context.WithValue(
+                context.WithValue(c, memContextKey, newMemContext()),
+                giContextKey, &globalInfoData{})
+}
+
+// Use calls ALL of this packages Use* methods on c. This enables all
+// gae/wrapper Get* api's.
+func Use(c context.Context) context.Context {
+        return UseTQ(UseDS(UseMC(UseGI(c))))
+}
+
+func cur(c context.Context) (p memContext) {
+        p, _ = c.Value(memContextKey).(memContext)
+        return
+}
+
+type memContextKeyType int
+
+var memContextKey memContextKeyType
+
+// weird stuff
+
+// RunInTransaction is here because it's really a service-wide transaction, not
+// just in the datastore. TaskQueue behaves differently in a transaction in
+// a couple ways, for example.
+//
+// It really should have been appengine.Context.RunInTransaction(func(tc...)),
+// but because it's not, this method is on dsImpl instead to mirror the official
+// API.
+//
+// The fake implementation also differs from the real implementation because the
+// fake TaskQueue is NOT backed by the fake Datastore. This is done to make the
+// test-access API for TaskQueue better (instead of trying to reconstitute the
+// state of the task queue from a bunch of datastore accesses).
+func (d *dsImpl) RunInTransaction(f func(context.Context) error, o *datastore.TransactionOptions) error {
+        curMC := cur(d.c)
+
+        txnMC, err := curMC.mkTxn(o)
+        if err != nil {
+                return err
+        }
+
+        defer func() {
+                txnMC.Lock()
+                defer txnMC.Unlock()
+
+                txnMC.endTxn()
+        }()
+
+        if err = f(context.WithValue(d.c, memContextKey, txnMC)); err != nil {
+                return err
+        }
+
+        txnMC.Lock()
+        defer txnMC.Unlock()
+
+        if curMC.canApplyTxn(txnMC) {
+                curMC.applyTxn(wrapper.GetMathRand(d.c), txnMC)
+        } else {
+                return datastore.ErrConcurrentTransaction
+        }
+        return nil
+}