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sudo apt install go
go env -w GO111MODULE=on
go env -w GOPROXY=https://goproxy.io,direct

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git clone git://g.csail.mit.edu/6.824-golabs-2020 6.824
cd 6.824
go mod init 6.824-lab

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# 运行方式
# 初始状态下 反注释worker.go 中CallExample() 可以得到用rpc调用的y=x+1
go run mrmaster.go pg-*.txt
go run mrworker.go wc.so

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cd src/main
# modify src/mrapps/wc.go import "6.824-lab/src/mr" before build    see [2]
# by default, we replace all "../mr" with "6.824-lab/src/mr"
go build -buildmode=plugin ../mrapps/wc.go
go run mrsequential.go wc.so pg*.txt

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// 任务结束 更新task状态 重新调度
func (m *Master) TaskCompleted(task *Task, reply *ExampleReply) error {
	// worker可能断连后重新连接
	// 如果是worker和master在不同阶段 或者 在相同阶段但task状态为已完成
	// 则直接返回 让worker认为自己提交成功 然后尝试获取下一个任务(充分利用计算资源)
	if task.TaskState != m.MasterPhase || m.TaskMeta[task.TaskNumber].TaskStatus == Completed {
		return nil
	}

	m.mu.Lock()
	m.TaskMeta[task.TaskNumber].TaskStatus = Completed
	// 此处手动释放锁 否则下方函数中尝试获取锁永远失败
	m.mu.Unlock()

	switch task.TaskState {
	case Map:
		// 将该worker的nReduce个临时文件路径放到对应reducer的文件列表中
		for i := 0; i < task.NReducer; i++ {
			m.LocIntermediate[i] = append(m.LocIntermediate[i], task.Intermediates[i])
		}
		// for _, v := range m.LocIntermediate {
		// 	fmt.Println(v)
		// }
		if m.allTaskDone() {
			// 该函数里面也尝试上锁 但是前面已经上锁 导致该函数里面永远获取不到锁 所以一直等待
			m.createReduceTask()
			// fmt.Println(len(m.TaskQueue))
			m.MasterPhase = Reduce
		}
	case Reduce:
		if m.allTaskDone() {
			m.MasterPhase = Exit
		}
	}
	return nil
}

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dialing:dial unix /var/tmp/824-mr-0: connect: connection refused

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*** Starting wc test.
2022/03/11 13:07:44 rpc.Register: method "Done" has 1 input parameters; needs exactly three
--- wc test: PASS
*** Starting indexer test.
2022/03/11 13:07:50 rpc.Register: method "Done" has 1 input parameters; needs exactly three
--- indexer test: PASS
*** Starting map parallelism test.
2022/03/11 13:07:54 rpc.Register: method "Done" has 1 input parameters; needs exactly three
--- map parallelism test: PASS
*** Starting reduce parallelism test.
2022/03/11 13:08:02 rpc.Register: method "Done" has 1 input parameters; needs exactly three
--- reduce parallelism test: PASS
*** Starting crash test.
2022/03/11 13:08:11 rpc.Register: method "Done" has 1 input parameters; needs exactly three
--- crash test: PASS
*** PASSED ALL TESTS