workflow 之 Prefect 基本用法（qbit）

前言

软件版本

Python  3.8.10
poetry  1.1.12
prefect 1.0.0

poetry github：https://github.com/python-poe...
prefect github：https://github.com/PrefectHQ/...

安装

用 poetry 初始化项目后在 pyproject.toml 添加以下依赖，然后运行 poetry update -vvv

# 国内镜像源（可选）
[[tool.poetry.source]]
name = "aliyun"
url = "https://mirrors.aliyun.com/pypi/simple/"
default = true

[tool.poetry.dependencies]
python = "^3.8"
prefect = "~1.0.0"

设置启用检查点环境变量

# Linux
export PREFECT__FLOWS__CHECKPOINTING=true
# Windows powershell
$env:PREFECT__FLOWS__CHECKPOINTING="true"
# Windows cmd（注意行尾不要有空格）
set PREFECT__FLOWS__CHECKPOINTING=true

测试代码

test_prefect.py

# encoding: utf-8
# author: qbit
# date: 2022-01-12
# summary: 测试 prefect，加减乘除

import os
import sys
import shutil
import prefect
from prefect import task, Flow
from prefect.engine.results import LocalResult

logger = prefect.context.get("logger")
cur_dir_fullpath = os.path.dirname(os.path.abspath(__file__))
cur_filename = os.path.basename(__file__)
dirname = f".{os.path.splitext(cur_filename)[0]}"       # 以当前 py 文件名作为缓存目录名
PrefectLocalResultDir = os.path.join(cur_dir_fullpath, dirname)

def ClearDirectory(dir):
  r""" 清空目录 """
  for filename in os.listdir(dir):
      file = os.path.join(dir, filename)
      try:
          if os.path.isfile(file) or os.path.islink(file):
              os.remove(file)
          elif os.path.isdir(file):
              shutil.rmtree(file)
      except Exception as e:
          print(f'Failed to delete{file}. Reason: {e}')

@task(target="{task_name}.target", checkpoint=True, result=LocalResult(dir=PrefectLocalResultDir))
def TaskAdd(x, y):
  result = x + y
  logger.info(f"{x} + {y} = {result}")
  return result

@task
def TaskSubtract(x):
  r""" 读入参数减 1 """
  result = x - 1
  logger.info(f"{x} - 1 = {result}")
  return result

@task
def TaskMultiply(x):
  r""" 读入参数乘以 2 """
  result = x * 2
  logger.info(f"{x} * 2 = {result}")
  print(f"result: {result}")
  return result

@task(log_stdout=True)
def TaskDivide(x, y):
  r""" 读入参数做除法 """
  result = y / x
  logger.info(f"{y} / {x} = {result}")
  return result

if __name__ == '__main__':
  if (len(sys.argv) > 1) and (sys.argv[1] == "restart"):
      print(f"****** Clear {PrefectLocalResultDir} ...")
      ClearDirectory(PrefectLocalResultDir)

  with Flow("示例: 四则运算") as flow:
      addResult = TaskAdd(2, 1)
      subResult = TaskSubtract(addResult)
      mulResult = TaskMultiply(addResult)
      TaskDivide(subResult, mulResult)

  flow_state = flow.run()

运行

第一次运行（注意第一个计算结果的 state 是 Success）

# 运行命令
poetry run python ./test_prefect.py
# 结果输出
[2022-02-24 17:35:48+0800] INFO - prefect.FlowRunner | Beginning Flow run for '示例: 四则运算'
[2022-02-24 17:35:49+0800] INFO - prefect.TaskRunner | Task 'TaskAdd': Starting task run...
[2022-02-24 17:35:49+0800] INFO - prefect | 2 + 1 = 3
[2022-02-24 17:35:49+0800] INFO - prefect.TaskRunner | Task 'TaskAdd': Finished task run for task with final state: 'Success'
[2022-02-24 17:35:49+0800] INFO - prefect.TaskRunner | Task 'TaskMultiply': Starting task run...
[2022-02-24 17:35:49+0800] INFO - prefect.TaskRunner | Task 'TaskSubtract': Starting task run...
[2022-02-24 17:35:49+0800] INFO - prefect | 3 * 2 = 6
[2022-02-24 17:35:49+0800] INFO - prefect | 3 - 1 = 2
[2022-02-24 17:35:49+0800] INFO - prefect.TaskRunner | Task 'TaskMultiply': Finished task run for task with final state: 'Success'
[2022-02-24 17:35:49+0800] INFO - prefect.TaskRunner | Task 'TaskSubtract': Finished task run for task with final state: 'Success'
[2022-02-24 17:35:49+0800] INFO - prefect.TaskRunner | Task 'TaskDivide': Starting task run...
[2022-02-24 17:35:49+0800] INFO - prefect | 6 / 2 = 3.0
[2022-02-24 17:35:49+0800] INFO - prefect.TaskRunner | result: 3.0
[2022-02-24 17:35:49+0800] INFO - prefect.TaskRunner | Task 'TaskDivide': Finished task run for task with final state: 'Success'
[2022-02-24 17:35:49+0800] INFO - prefect.FlowRunner | Flow run SUCCESS: all reference tasks succeeded

第二次运行（注意第一个计算结果的 state 是 cached）

# 运行命令
poetry run python ./test_prefect.py
# 结果输出
[2022-02-24 17:36:47+0800] INFO - prefect.FlowRunner | Beginning Flow run for '示例: 四则运算'
[2022-02-24 17:36:47+0800] INFO - prefect.TaskRunner | Task 'TaskAdd': Starting task run...
[2022-02-24 17:36:47+0800] INFO - prefect.TaskRunner | Task 'TaskAdd': Finished task run for task with final state: 'Cached'
[2022-02-24 17:36:47+0800] INFO - prefect.TaskRunner | Task 'TaskMultiply': Starting task run...
[2022-02-24 17:36:47+0800] INFO - prefect.TaskRunner | Task 'TaskSubtract': Starting task run...
[2022-02-24 17:36:47+0800] INFO - prefect | 3 * 2 = 6
[2022-02-24 17:36:47+0800] INFO - prefect | 3 - 1 = 2
[2022-02-24 17:36:47+0800] INFO - prefect.TaskRunner | Task 'TaskMultiply': Finished task run for task with final state: 'Success'
[2022-02-24 17:36:47+0800] INFO - prefect.TaskRunner | Task 'TaskSubtract': Finished task run for task with final state: 'Success'
[2022-02-24 17:36:47+0800] INFO - prefect.TaskRunner | Task 'TaskDivide': Starting task run...
[2022-02-24 17:36:47+0800] INFO - prefect | 6 / 2 = 3.0
[2022-02-24 17:36:47+0800] INFO - prefect.TaskRunner | result: 3.0
[2022-02-24 17:36:47+0800] INFO - prefect.TaskRunner | Task 'TaskDivide': Finished task run for task with final state: 'Success'
[2022-02-24 17:36:47+0800] INFO - prefect.FlowRunner | Flow run SUCCESS: all reference tasks succeeded

静态 DAG 图

官方文档：https://docs.prefect.io/core/...
下载 Graphviz 并配置到 PATH 环境变量

修改 pyproject.toml，添加 viz extra，然后运行 poetry update -vvv

[tool.poetry.dependencies]
python = "^3.8"
prefect = { version = "~1.0.0", extras = ["viz"] }

修改 test_prefect.py 的主函数

if __name__ == '__main__':
  if (len(sys.argv) > 1) and (sys.argv[1] == "restart"):
      print(f"****** Clear {PrefectLocalResultDir} ...")
      ClearDirectory(PrefectLocalResultDir)

  with Flow("示例: 四则运算") as flow:
      addResult = TaskAdd(2, 1)
      subResult = TaskSubtract(addResult)
      mulResult = TaskMultiply(addResult)
      TaskDivide(subResult, mulResult)

  flow.visualize(filename='flow_start', format='png')
  flow_state = flow.run()
  flow.visualize(flow_state=flow_state, filename='flow_end', format='png')

运行代码会生成 flow_start.png flow_end.png 两张图片
```
poetry run python ./test_prefect.py restart
```
flow_start.png
flow_end.png
颜色代表的状态：https://docs.prefect.io/api/l...

qbiter

workflow 之 Prefect 基本用法（qbit）

前言

安装

运行

静态 DAG 图