使用BLPOP处理Redis队列会导致单元测试中出现竞争条件？

Question

我正在按照Go Chapter 6.4.1 of the Redis e-book中的描述实现先进先出的任​​务队列。为了进行测试，我将CommandExecutor接口传递给'worker'函数，如下所示：

package service

import (
    "context"

    "github.com/gomodule/redigo/redis"
    "github.com/pkg/errors"
    "github.com/sirupsen/logrus"
)

const commandsQueue = "queuedCommands:"

var pool = redis.Pool{
    MaxIdle:   50,
    MaxActive: 1000,
    Dial: func() (redis.Conn, error) {
        conn, err := redis.Dial("tcp", ":6379")
        if err != nil {
            logrus.WithError(err).Fatal("initialize Redis pool")
        }
        return conn, err
    },
}

// CommandExecutor executes a command
type CommandExecutor interface {
    Execute(string) error
}

func processQueue(ctx context.Context, done chan<- struct{}, executor CommandExecutor) error {
    rc := pool.Get()
    defer rc.Close()

    for {
        select {
        case <-ctx.Done():
            done <- struct{}{}
            return nil
        default:
            // If the commands queue does not exist, BLPOP blocks until another client
            // performs an LPUSH or RPUSH against it. The timeout argument of zero is
            // used to block indefinitely.
            reply, err := redis.Strings(rc.Do("BLPOP", commandsQueue, 0))
            if err != nil {
                logrus.WithError(err).Errorf("BLPOP %s %d", commandsQueue, 0)
                return errors.Wrapf(err, "BLPOP %s %d", commandsQueue, 0)
            }

            if len(reply) < 2 {
                logrus.Errorf("Expected a reply of length 2, got one of length %d", len(reply))
                return errors.Errorf("Expected a reply of length 2, got one of length %d", len(reply))
            }

            // BLPOP returns a two-element multi-bulk with the first element being the
            // name of the key where an element was popped and the second element
            // being the value of the popped element (cf. https://redis.io/commands/blpop#return-value)
            if err := executor.Execute(reply[1]); err != nil {
                return errors.Wrapf(err, "execute scheduled command: %s", reply[0])
            }
            done <- struct{}{}
        }
    }
}

我已经用此代码制作了一个小的示例存储库https://github.com/kurtpeek/process-queue，并尝试了单元测试。对于单元测试，我有两个相同的测试（名称不同）：

package service

import (
    "context"
    "testing"

    "github.com/stretchr/testify/assert"
    "github.com/stretchr/testify/require"
)

func TestProcessQueue(t *testing.T) {
    ctx, cancel := context.WithCancel(context.Background())
    defer cancel()

    executor := &CommandExecutorMock{
        ExecuteFunc: func(string) error {
            return nil
        },
    }

    done := make(chan struct{})
    go processQueue(ctx, done, executor)

    rc := pool.Get()
    defer rc.Close()

    _, err := rc.Do("RPUSH", commandsQueue, "foobar")
    require.NoError(t, err)

    <-done

    assert.Exactly(t, 1, len(executor.ExecuteCalls()))
    assert.Exactly(t, "foobar", executor.ExecuteCalls()[0].In1)
}

func TestProcessQueue2(t *testing.T) {
    ctx, cancel := context.WithCancel(context.Background())
    defer cancel()

    executor := &CommandExecutorMock{
        ExecuteFunc: func(string) error {
            return nil
        },
    }

    done := make(chan struct{})
    go processQueue(ctx, done, executor)

    rc := pool.Get()
    defer rc.Close()

    _, err := rc.Do("RPUSH", commandsQueue, "foobar")
    require.NoError(t, err)

    <-done

    assert.Exactly(t, 1, len(executor.ExecuteCalls()))
    assert.Exactly(t, "foobar", executor.ExecuteCalls()[0].In1)
}

其中CommandExecutorMock是使用moq生成的。如果我分别运行每个测试，它们将通过：

moq

但是，如果我运行所有测试，则第二次超时：

~/g/s/g/k/process-queue> go test ./... -v -run TestProcessQueue2
=== RUN   TestProcessQueue2
--- PASS: TestProcessQueue2 (0.00s)
PASS
ok      github.com/kurtpeek/process-queue/service   0.243s

[似乎在第二个测试运行时，在第一个测试中启动的goroutine仍在运行，并且从队列中

~/g/s/g/k/process-queue> 
go test ./... -v -timeout 10s
=== RUN   TestProcessQueue
--- PASS: TestProcessQueue (0.00s)
=== RUN   TestProcessQueue2
panic: test timed out after 10s

删除命令，因此第二个测试中的BLPOP行将无限期地阻塞。尽管在第一个测试的父上下文上调用了<-done。

我如何“隔离”这些测试，以便它们一起运行时都能通过？ （我尝试将cancel()标志传递给-p 1，但无济于事。）>

我正在按照Go中Redis电子书的6.4.1章中的描述实现先进先出的任​​务队列。为了进行测试，我将CommandExecutor接口传递给'worker'...

Answer 1

尽管在第一个测试的父上下文上调用了cancel（）。