go - 两个客户端在 Consul 中获取相同的锁

Question

我有以下代码:

package publicservice

import (
    "time"
    "github.com/hashicorp/consul/api"
    "github.com/hashicorp/consul/testutil"
    "testing"
)

func TestAcquireLock(t *testing.T) {
    consul := testutil.NewTestServer(t)
    defer consul.Stop()

    firstClient, err := api.NewClient(&api.Config{
        Address: consul.HTTPAddr,
    })

    if err != nil {
        t.Fatalf("failed to create first client with %v", err)
    }

    secondClient, err := api.NewClient(&api.Config{
        Address: consul.HTTPAddr,
    })

    if err != nil {
        t.Fatalf("failed to create second client with %v", err)
    }

    lockKey := "sample-lock-key"

    firstLock, err := firstClient.LockOpts(&api.LockOptions{
        Key: lockKey,
    })

    if err != nil {
        t.Fatalf("failed to create first lock %v", err)
    }

    _, err = firstLock.Lock(nil)

    if err != nil {
        t.Fatalf("failed to acquire first lock %v", err)
    }

    defer firstLock.Unlock()

    secondLock, err := secondClient.LockOpts(&api.LockOptions{
        Key: lockKey,
        LockTryOnce: true,
        LockWaitTime: time.Second,
    })

    if err != nil {
        t.Fatalf("failed to create second lock %v", err)
    }

    _, err = secondLock.Lock(nil)

    if err == nil {
        t.Fatal("should not have acquired lock here")
    }
}

当我运行它时，第二次锁定调用永远不会失败，即使它应该失败，因为锁定已经被另一个客户端持有，从日志中可以看出:

2016/11/29 14:46:25 [DEBUG] http: Request GET /v1/catalog/nodes (1.115897356s) from=127.0.0.1:50492
2016/11/29 14:46:25 [DEBUG] http: Request PUT /v1/session/create (939.436µs) from=127.0.0.1:50493
2016/11/29 14:46:25 [DEBUG] http: Request GET /v1/kv/sample-lock-key?wait=15000ms (269.823µs) from=127.0.0.1:50493
2016/11/29 14:46:25 [DEBUG] http: Request PUT /v1/kv/sample-lock-key?acquire=aa8fb351-6b6e-8e17-f8d9-fb265c497a9f&flags=3304740253564472344 (899.564µs) from=127.0.0.1:50493
2016/11/29 14:46:25 [DEBUG] http: Request GET /v1/kv/sample-lock-key?consistent= (112.87µs) from=127.0.0.1:50493
2016/11/29 14:46:25 [DEBUG] http: Request PUT /v1/session/create (595.554µs) from=127.0.0.1:50494
2016/11/29 14:46:25 [DEBUG] http: Request GET /v1/kv/sample-lock-key?wait=1000ms (38.602µs) from=127.0.0.1:50494
2016/11/29 14:46:26 [DEBUG] http: Request GET /v1/kv/sample-lock-key?index=7&wait=999ms (1.007117154s) from=127.0.0.1:50494
2016/11/29 14:46:26 [DEBUG] http: Request PUT /v1/session/destroy/fd83b8f8-1757-d9d7-6f0e-5defaf26b886 (1.549558ms) from=127.0.0.1:50494
2016/11/29 14:46:26 [DEBUG] http: Request PUT /v1/kv/sample-lock-key?flags=3304740253564472344&release=aa8fb351-6b6e-8e17-f8d9-fb265c497a9f (1.56451ms) from=127.0.0.1:50495
2016/11/29 14:46:26 [DEBUG] http: Request GET /v1/kv/sample-lock-key?consistent=&index=7 (1.010637359s) from=127.0.0.1:50493

我在这里错过了什么？我还必须做些什么来确保第二个客户端不会获得锁吗？

Answer 1

问题是您必须检查从 Lock 返回的 channel ，如果锁已经被持有，则 channel 为 nil:

package publicservice

import (
    "time"
    "github.com/hashicorp/consul/api"
    "github.com/hashicorp/consul/testutil"
    "testing"
    "github.com/xtgo/uuid"
)

func TestAcquireLock(t *testing.T) {
    consul := testutil.NewTestServer(t)
    defer consul.Stop()

    firstClient, err := api.NewClient(&api.Config{
        Address: consul.HTTPAddr,
    })

    if err != nil {
        t.Fatalf("failed to create first client with %v", err)
    }

    secondClient, err := api.NewClient(&api.Config{
        Address: consul.HTTPAddr,
    })

    if err != nil {
        t.Fatalf("failed to create second client with %v", err)
    }

    lockKey := "sample-lock-key"

    firstLock, err := firstClient.LockOpts(&api.LockOptions{
        Key: lockKey,
        SessionName: uuid.NewRandom().String(),
    })

    if err != nil {
        t.Fatalf("failed to create first lock %v", err)
    }

    firstResult, err := firstLock.Lock(nil)

    t.Logf("=====> result for first lock is %v", firstResult)

    if err != nil {
        t.Fatalf("failed to acquire first lock %v", err)
    }

    defer firstLock.Unlock()

    secondLock, err := secondClient.LockOpts(&api.LockOptions{
        Key: lockKey,
        LockTryOnce: true,
        LockWaitTime: time.Second,
        SessionName: uuid.NewRandom().String(),
    })

    if err != nil {
        t.Fatalf("failed to create second lock %v", err)
    }

    secondResult, err := secondLock.Lock(nil)

    if secondResult != nil || err != nil {
        t.Fatal("should not have acquired lock here")
    }
}