workflow源码解析：ThreadTask

1、使用程序，一个简单的加法运算程序

cpp 复制代码

#include <iostream>
#include <workflow/WFTaskFactory.h>
#include <errno.h>

// 直接定义thread_task三要素
// 一个典型的后端程序由三个部分组成，并且完全独立开发。即：程序=协议+算法+任务流。

// 定义INPUT
struct AddInput
{
    int x;
    int y;
};

// 定义OUTPUT
struct AddOutput
{
    int res;
};

// 加法流程
void add_routine(const AddInput *input, AddOutput *output)
{
    output->res = input->x + input->y;
}

using AddTask = WFThreadTask<AddInput, AddOutput>;

void callback(AddTask *task)
{
	auto *input = task->get_input();
	auto *output = task->get_output();

	assert(task->get_state() == WFT_STATE_SUCCESS);

    fprintf(stderr, "%d + %d = %d\n", input->x, input->y, output->res);
}

int main()
{
    using AddFactory = WFThreadTaskFactory<AddInput, AddOutput>;
	AddTask *task = AddFactory::create_thread_task("add_task",
												add_routine,
												callback);
	AddInput *input = task->get_input();

	input->x = 1;
	input->y = 2;

	task->start();

	getchar();
	return 0;
}

2、类继承关系

WFThreadTaskFactory代码

cpp 复制代码

// src/factory/WFTaskFactory.h
template<class INPUT, class OUTPUT>
class WFThreadTaskFactory
{
private:
	using T = WFThreadTask<INPUT, OUTPUT>;
    ...
public:
	static T *create_thread_task(const std::string& queue_name,
								 std::function<void (INPUT *, OUTPUT *)> routine,
								 std::function<void (T *)> callback);

    ...
};

cpp 复制代码

// src/factory/WFTaskFactory.inl
template<class INPUT, class OUTPUT>
WFThreadTask<INPUT, OUTPUT> *
WFThreadTaskFactory<INPUT, OUTPUT>::create_thread_task(const std::string& queue_name,
						std::function<void (INPUT *, OUTPUT *)> routine,
						std::function<void (WFThreadTask<INPUT, OUTPUT> *)> callback)
{
	return new __WFThreadTask<INPUT, OUTPUT>(WFGlobal::get_exec_queue(queue_name),
											 WFGlobal::get_compute_executor(),
											 std::move(routine),
											 std::move(callback));
}

__WFThreadTask代码

cpp 复制代码

// src/factory/WFTaskFactory.inl
template<class INPUT, class OUTPUT>
class __WFThreadTask : public WFThreadTask<INPUT, OUTPUT>
{
protected:
	virtual void execute()  //实现ExecSession的纯虚函数
	{
		this->routine(&this->input, &this->output); //执行用户程序的routine
	}

protected:
	std::function<void (INPUT *, OUTPUT *)> routine;

public:
	__WFThreadTask(ExecQueue *queue, Executor *executor,
				   std::function<void (INPUT *, OUTPUT *)>&& rt,
				   std::function<void (WFThreadTask<INPUT, OUTPUT> *)>&& cb) :
		WFThreadTask<INPUT, OUTPUT>(queue, executor, std::move(cb)),
		routine(std::move(rt))
	{
	}
};

WFThreadTask代码

cpp 复制代码

// src/factory/WFTask.h
template<class INPUT, class OUTPUT>
class WFThreadTask : public ExecRequest
{
public:
	void start();
	void dismiss();

	INPUT *get_input() { return &this->input; }
	OUTPUT *get_output() { return &this->output; }

	void *user_data;

	int get_state() const { return this->state; }
	int get_error() const { return this->error; }

	void set_callback(std::function<void (WFThreadTask<INPUT, OUTPUT> *)> cb);
protected:
	virtual SubTask *done();

protected:
	INPUT input;
	OUTPUT output;
	std::function<void (WFThreadTask<INPUT, OUTPUT> *)> callback;

public:
	WFThreadTask(ExecQueue *queue, Executor *executor,
				 std::function<void (WFThreadTask<INPUT, OUTPUT> *)>&& cb) :
		ExecRequest(queue, executor),
		callback(std::move(cb))
	{
        // 初始化
	}

protected:
	virtual ~WFThreadTask() { }
};

ExecRequest代码

cpp 复制代码

// src/kernel/ExecRequest.h
class ExecRequest : public SubTask, public ExecSession
{
public:
	ExecRequest(ExecQueue *queue, Executor *executor);
	ExecQueue *get_request_queue() const { return this->queue; }
	void set_request_queue(ExecQueue *queue) { this->queue = queue; }
	virtual void dispatch()  // 实现SubTask的纯虚函数，这个纯虚函数主要是任务的开始执行接口
	{
		this->executor->request(this, this->queue);
		...
	}

protected:
	int state;
	int error;

	ExecQueue *queue;
	Executor *executor;

protected:
	virtual void handle(int state, int error); // 实现ExecSession的纯虚函数
};

SubTask代码

cpp 复制代码

class SubTask
{
     // 子任务被调起的时机
     virtual void dispatch() = 0;
     // 子任务执行完成的时机
     virtual SubTask *done() = 0;
     // 内部实现，决定了任务流走向
     void subtask_done();
     ...
};

ExecSession代码

cpp 复制代码

/src/kernel/Executor.h
class ExecSession
{
private:
	virtual void execute() = 0;
	virtual void handle(int state, int error) = 0;

protected:
	ExecQueue *get_queue() { return this->queue; }

private:
	ExecQueue *queue;
    ...
};

继承关系图

__WFThreadTask__目前还未用到，暂不清楚

3、两个重要成员: ExecQueue, Executor

ExecQueue代码

cpp 复制代码

/src/kernel/Executor.h
class ExecQueue
{
    ...
private:
	struct list_head task_list;
	pthread_mutex_t mutex;
};

Executor代码

cpp 复制代码

/src/kernel/Executor.h
class Executor
{
public:
    // 一次要执行的接口，对于线程执行器来说，就是把一个执行任务扔进某个队列中
    int request(ExecSession *session, ExecQueue *queue);

private:
    // 执行器和系统资源，是一个包含关系
    thrdpool_t *thrdpool;
};

request() 函数把任务扔进线程池队列等待执行，线程池会从队列拿到这个任务，然后执行executor_thread_routine

cpp 复制代码

// src/kernel/Executor.cc
int Executor::request(ExecSession *session, ExecQueue *queue)
{
    ExecSessionEntry *entry = new ExecSessionEntry;

	session->queue = queue;
	entry->session = session;
	entry->thrdpool = this->thrdpool;
	queue->mutex.lock();
	list_add_tail(&entry->list, &queue->session_list);
	if (queue->session_list.next == &entry->list)
	{
		struct thrdpool_task task = {Executor::executor_thread_routine, queue};
		/*
		{
			.routine	=	Executor::executor_thread_routine,
			.context	=	queue
		};
		*/
		if (thrdpool_schedule(&task, this->thrdpool) < 0)
		{
			list_del(&entry->list);
			delete entry;
			entry = NULL;
		}
	}

	queue->mutex.unlock();
	return -!entry;
}

cpp 复制代码

struct ExecSessionEntry
{
	struct list_head list;
	ExecSession *session;
	thrdpool_t *thrdpool;
};

cpp 复制代码

// src/kernel/Executor.cc
void Executor::executor_thread_routine(void *context)
{
	ExecQueue *queue = (ExecQueue *)context;
	ExecSessionEntry *entry;
	ExecSession *session;

	queue->mutex.lock();
	entry = list_entry(queue->session_list.next, ExecSessionEntry, list);
	list_del(&entry->list);
	session = entry->session;
	if (!list_empty(&queue->session_list))
	{
		struct thrdpool_task task = {Executor::executor_thread_routine, queue};
		/*
		{
			.routine	=	Executor::executor_thread_routine,
			.context	=	queue
		};
		*/
		__thrdpool_schedule(&task, entry, entry->thrdpool);
	}
	else
		delete entry;

	queue->mutex.unlock();
	session->execute(); //这里会执行到用户routine
	session->handle(ES_STATE_FINISHED, 0);
}

4、参考链接

https://github.com/chanchann/workflow_annotation/blob/main/src_analysis/12_thread_task.md
https://blog.csdn.net/j497205974/article/details/135554164?spm=1001.2014.3001.5502