我正在学习 golang 和谷歌应用引擎数据存储。

我计划调用一个简单的 rest api 来保存和检索数据存储中的数据。

我遵循了一些 hello world 教程和官方入门指南。最后我想到的是这个。

`

package hello

import (
        "fmt"
        "log"
        "net/http"
        "encoding/json"
        "cloud.google.com/go/datastore"
        "golang.org/x/net/context"
        "github.com/gorilla/mux"
        "time"
)
type Task struct {
        Description    string    `datastore:"description"`
        Created time.Time `datastore:"created"`
        id      int64
}
func saveData(w http.ResponseWriter, r *http.Request){
        fmt.Println("Endpoint Hit: saveData")
        input := r.URL.Query().Get("input")
        fmt.Println(input)

        ctx := context.Background()
        projectID := "api-project-426361742627"
        client, err := datastore.NewClient(ctx, projectID)
        if err != nil {
                log.Fatalf("Failed to create client: %v", err)
        }
        kind := "Task"
        task := Task{
                Description: input,
                Created: time.Now(),
        }
        taskKey := datastore.IncompleteKey(kind, nil)

        if _, err := client.Put(ctx, taskKey, &task); err != nil {
                log.Fatalf("Failed to save task: %v", err)
        }

        fmt.Printf("Saved %v: %v\n", taskKey, task.Description)
        json.NewEncoder(w).Encode(task)
}
func returnAll(w http.ResponseWriter, r *http.Request){
        fmt.Println("Endpoint Hit: returnAll")

        ctx := context.Background()
        projectID := "api-project-426361742627"
        client, err := datastore.NewClient(ctx, projectID)
        if err != nil {
                log.Fatalf("Failed to create client: %v", err)
        }

        query := datastore.NewQuery("Task").Order("description")

        var tasks []*Task

        keys, err := client.GetAll(ctx, query, &tasks)
        for i, key := range keys {
                tasks[i].id = key.ID
        }
        // for _, t := range tasks {
        //         // fmt.Println( t.id, t.Description)
        // }

        json.NewEncoder(w).Encode(tasks)
}

func homePage(w http.ResponseWriter, r *http.Request){
        fmt.Fprintf(w, "Welcome to the HomePage!")
        fmt.Println("Endpoint Hit: homePage")
}
func handleRequests() {
        myRouter := mux.NewRouter()
        myRouter.HandleFunc("/", homePage)
        myRouter.HandleFunc("/save", saveData)
        myRouter.HandleFunc("/retrieve", returnAll)
        http.Handle("/", myRouter)
}
func init() {
        handleRequests()
}

`

现在我面临的问题是在这一行

客户端，错误:= datastore.NewClient(ctx，projectID)

我收到以下错误。

2017/09/26 07:15:16 http: panic serving 127.0.0.1:59488: not an App Engine context
goroutine 17 [running]:
net/http.(*conn).serve.func1(0xc82021e000)
    /home/aditya/google-cloud-sdk/platform/google_appengine/goroot-1.6/src/net/http/server.go:1389 +0xc1
panic(0xa44740, 0xc82018a8c0)
    /home/aditya/google-cloud-sdk/platform/google_appengine/goroot-1.6/src/runtime/panic.go:443 +0x4e9
google.golang.org/appengine/internal.fullyQualifiedAppID(0x7f4142e12be0, 0xc82000b4e0, 0x0, 0x0)
    /home/aditya/work/src/google.golang.org/appengine/internal/identity_classic.go:54 +0x8b
google.golang.org/appengine/internal.FullyQualifiedAppID(0x7f4142e12be0, 0xc82000b4e0, 0x0, 0x0)
    /home/aditya/work/src/google.golang.org/appengine/internal/api_common.go:77 +0xe2
google.golang.org/appengine/internal.AppID(0x7f4142e12be0, 0xc82000b4e0, 0x0, 0x0)
    /home/aditya/work/src/google.golang.org/appengine/internal/identity.go:13 +0x37
google.golang.org/appengine.AppID(0x7f4142e12be0, 0xc82000b4e0, 0x0, 0x0)
    /home/aditya/work/src/google.golang.org/appengine/identity.go:20 +0x37
golang.org/x/oauth2/google.FindDefaultCredentials(0x7f4142e12be0, 0xc82000b4e0, 0xc820222170, 0x1, 0x1, 0xc820222150, 0x0, 0x0)
    /home/aditya/work/src/golang.org/x/oauth2/google/default.go:92 +0x5a8
google.golang.org/api/internal.Creds(0x7f4142e12be0, 0xc82000b4e0, 0xc820248240, 0xc8202452c0, 0x0, 0x0)
    /home/aditya/work/src/google.golang.org/api/internal/creds.go:37 +0x173
google.golang.org/api/transport/grpc.Dial(0x7f4142e12be0, 0xc82000b4e0, 0xc820245638, 0x3, 0x3, 0x0, 0x0, 0x0)
    /home/aditya/work/src/google.golang.org/api/transport/grpc/dial.go:47 +0x272
cloud.google.com/go/datastore.NewClient(0x7f4142e12be0, 0xc82000b4e0, 0xc0c320, 0x18, 0x0, 0x0, 0x0, 0x9, 0x0, 0x0)
    /home/aditya/work/src/cloud.google.com/go/datastore/datastore.go:87 +0x87f
main76346.returnAll(0x7f4142dcb058, 0xc820234000, 0xc82022a000)
    hello.go:51 +0x1b8
net/http.HandlerFunc.ServeHTTP(0xcd13d8, 0x7f4142dcb058, 0xc820234000, 0xc82022a000)
    /home/aditya/google-cloud-sdk/platform/google_appengine/goroot-1.6/src/net/http/server.go:1618 +0x3a
github.com/gorilla/mux.(*Router).ServeHTTP(0xc820052660, 0x7f4142dcb058, 0xc820234000, 0xc82022a000)
    /home/aditya/work/src/github.com/gorilla/mux/mux.go:133 +0x37c
net/http.(*ServeMux).ServeHTTP(0xc82000eab0, 0x7f4142dcb058, 0xc820234000, 0xc82022a000)
    /home/aditya/google-cloud-sdk/platform/google_appengine/goroot-1.6/src/net/http/server.go:1910 +0x17d
appengine_internal.handleFilteredHTTP(0x7f4142dcb058, 0xc820234000, 0xc82022a000)
    /home/aditya/google-cloud-sdk/platform/google_appengine/goroot-1.6/src/appengine_internal/api_dev.go:102 +0x409
net/http.HandlerFunc.ServeHTTP(0xccfe48, 0x7f4142dcb058, 0xc820234000, 0xc82022a000)
    /home/aditya/google-cloud-sdk/platform/google_appengine/goroot-1.6/src/net/http/server.go:1618 +0x3a
net/http.serverHandler.ServeHTTP(0xc820078500, 0x7f4142dcb058, 0xc820234000, 0xc82022a000)
    /home/aditya/google-cloud-sdk/platform/google_appengine/goroot-1.6/src/net/http/server.go:2081 +0x19e
net/http.(*conn).serve(0xc82021e000)
    /home/aditya/google-cloud-sdk/platform/google_appengine/goroot-1.6/src/net/http/server.go:1472 +0xf2e
created by net/http.(*Server).Serve
    /home/aditya/google-cloud-sdk/platform/google_appengine/goroot-1.6/src/net/http/server.go:2137 +0x44e
INFO     2017-09-26 07:15:16,800 module.py:821] default: "GET /retrieve HTTP/1.1" 500 3349

我不确定如何解决这个问题。我尝试使用

gcloud auth application-default login 

授予对本地数据存储的访问权限，但它不工作。每当我在初始化数据存储新客户端时尝试保存数据或返回所有条目时，我都会遇到这个问题。

最佳答案

更新您的处理程序以使用从应用的处理程序请求派生的上下文而不是 context.Background()

func saveData(w http.ResponseWriter, r *http.Request){
    // ..
    fmt.Println(input)

    ctx := appengine.NewContext(r)
    projectID := "api-project-426361742627"
    // ...
}

请记住，上下文也可以用作不透明的值容器，应用引擎环境会大量使用此功能。

包裹appengine docs .

关于google-app-engine - 无法存储在数据存储 gcloud 中，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/46420331/