问题描述
我正在使用 Metaflow 创建一个文本处理管道，如下所示：-
___F------
______ D---| |
| |___G---| |__>
____B-----| |----->H
| |______E_________________> ^
A -| |
|____C________________________________|
根据 documentation，branch 允许并行计算步骤，它用于并行计算 (B,C)、(D,E) 和 (F,G)。最后所有的分支都在H处加入。以下是实现这个逻辑的代码：-
from Metaflow import FlowSpec,step
class TextProcessing(FlowSpec):
@step
def a(self):
....
self.next(self.b,self.c)
@step
def c(self):
result1 = {}
....
self.next(self.join)
@step
def b(self):
....
self.next(self.d,self.e)
@step
def e(self):
result2 = []
.....
self.next(self.join)
@step
def d(self):
....
self.next(self.f,self.g)
@step
def f(self):
result3 = []
....
self.next(self.join)
@step
def g(self):
result4 = []
.....
self.next(self.join)
@step
def join(self,results):
data = [results.c.result,results.e.result2,result.f.result3,result.g.result4]
print(data)
self.next(self.end)
@step
def end(self):
pass
etl = TextProcessing()
在运行 python main.py run 时，出现以下错误：-
Metaflow 2.2.10 executing TextProcessing for user:ubuntu
Validating your flow...
Validity checker found an issue on line 83:
Step join seems like a join step (it takes an extra input argument) but an incorrect number of steps (c,e,f,g) lead to it. This join was expecting 2 incoming paths,starting from splitted step(s) f,g.
有人能指出我哪里出错了吗？
解决方法
再次仔细检查 docs 后，我意识到我没有正确处理连接。根据 metaflow-2.2.10 的文档：-
注意可以任意嵌套分支，也就是可以在一个分支内分支。请记住加入您创建的所有分支。
这意味着应该加入每个分支。为了连接来自分支的值，metaflow 提供了 merge_artifacts 效用函数来帮助传播明确的值。
由于工作流中有三个分支，因此添加了三个合并步骤来合并结果。
以下更改对我有用：-
from metaflow import FlowSpec,step
class TextProcessing(FlowSpec):
@step
def a(self):
....
self.next(self.b,self.c)
@step
def c(self):
result1 = {}
....
self.next(self.merge_3)
@step
def b(self):
....
self.next(self.d,self.e)
@step
def e(self):
result2 = []
.....
self.next(self.merge_2)
@step
def d(self):
....
self.next(self.f,self.g)
@step
def f(self):
result3 = []
....
self.next(self.merge_1)
@step
def g(self):
result4 = []
.....
self.next(self.merge_1)
@step
def merge_1(self,results):
self.result = {
'result4' : results.g.result4,'result3' : results.f.result3
}
self.next(self.merge_2)
@step
def merge_2(self,results):
self.result = { 'result2' : results.e.result2,**results.merge_1.result }
self.merge_artifacts(results,include=['result'])
self.next(self.merge_3)
@step
def merge_3(self,results):
self.result = { 'c' : results.c.result1,**results.merge_2.result }
self.merge_artifacts(results,include=['result'])
self.next(self.end)
@step
def end(self):
print(self.result)
etl = TextProcessing()