Draft: Add skip decorator; A few clean ups

metaflow/plugins/__init__.py

@@ -116,7 +116,8 @@ def get_plugin_cli():
 from .frameworks.pytorch import PytorchParallelDecorator
 from .aip.aip_decorator import AIPInternalDecorator
 from .aip.accelerator_decorator import AcceleratorDecorator
-from .aip.interruptible_decorator import interruptibleDecorator
+from .aip.interruptible_decorator import InterruptibleDecorator
+from .aip.skip_decorator import SkipDecorator
 
 
 STEP_DECORATORS = [
@@ -134,8 +135,9 @@ def get_plugin_cli():
     PytorchParallelDecorator,
     InternalTestUnboundedForeachDecorator,
     AcceleratorDecorator,
-    interruptibleDecorator,
+    InterruptibleDecorator,
     AIPInternalDecorator,
+    SkipDecorator,
 ]
 _merge_lists(STEP_DECORATORS, _ext_plugins["STEP_DECORATORS"], "name")
 

metaflow/plugins/aip/aip.py

@@ -58,7 +58,7 @@
 from metaflow.plugins.aip.aip_decorator import AIPException
 from .accelerator_decorator import AcceleratorDecorator
 from .argo_client import ArgoClient
-from .interruptible_decorator import interruptibleDecorator
+from .interruptible_decorator import InterruptibleDecorator
 from .aip_foreach_splits import graph_to_task_ids
 from ..aws.batch.batch_decorator import BatchDecorator
 from ..aws.step_functions.schedule_decorator import ScheduleDecorator
@@ -106,7 +106,7 @@ def __init__(
         resource_requirements: Dict[str, str],
         aip_decorator: AIPInternalDecorator,
         accelerator_decorator: AcceleratorDecorator,
-        interruptible_decorator: interruptibleDecorator,
+        interruptible_decorator: InterruptibleDecorator,
         environment_decorator: EnvironmentDecorator,
         total_retries: int,
         minutes_between_retries: str,
@@ -741,7 +741,7 @@ def build_aip_component(node: DAGNode, task_id: str) -> AIPComponent:
                     (
                         deco
                         for deco in node.decorators
-                        if isinstance(deco, interruptibleDecorator)
+                        if isinstance(deco, InterruptibleDecorator)
                     ),
                     None,  # default
                 ),

metaflow/plugins/aip/interruptible_decorator.py

@@ -11,7 +11,7 @@ def _get_ec2_metadata(path: str) -> Optional[str]:
     return response.text
 
 
-class interruptibleDecorator(StepDecorator):
+class InterruptibleDecorator(StepDecorator):
     """
     For AIP orchestrator plugin only.
 

metaflow/plugins/aip/s3_sensor_decorator.py

@@ -1,5 +1,4 @@
 from types import FunctionType
-from typing import Tuple
 from urllib.parse import urlparse
 
 from metaflow.decorators import FlowDecorator

metaflow/plugins/aip/skip_decorator.py

@@ -0,0 +1,52 @@
+# Skip decorator is a workaround solution to implement conditional branching in metaflow.
+# When condition variable is_skipping is evaluated to True,
+# it will skip current step and execute the supplied next step.
+
+from functools import wraps
+from metaflow.decorators import StepDecorator
+
+
+class SkipDecorator(StepDecorator):
+    """
+    The @skip decorator is a workaround for conditional branching. The @skip decorator checks an artifact
+    and if it is false, skips the evaluation of the step function and jumps to the supplied next step.
+
+    **The `start` and `end` steps are always expected and should not be skipped.**
+
+    Usage:
+        class SkipFlow(FlowSpec):
+
+        condition = Parameter("condition", default=False)
+
+        @step
+        def start(self):
+            print("Should skip:", self.condition)
+            self.next(self.middle)
+
+        @skip(check='condition', next='end')
+        @step
+        def middle(self):
+            print("Running the middle step - not skipping")
+            self.next(self.end)
+
+        @step
+        def end(self):
+            pass
+    """
+
+    name = "skip"
+
+    def __init__(self, check="", next=""):
+        super().__init__()
+        self.check = check
+        self.next = next
+
+    def __call__(self, f):
+        @wraps(f)
+        def func(step):
+            if getattr(step, self.check):
+                step.next(getattr(step, self.next))
+            else:
+                return f(step)
+
+        return func

metaflow/plugins/aip/tests/flows/resources_flow.py

@@ -1,7 +1,6 @@
 import os
 import pprint
 import subprocess
-import time
 from typing import Dict, List
 from multiprocessing.shared_memory import SharedMemory
 

metaflow/plugins/aip/tests/flows/skip_flow.py

@@ -0,0 +1,42 @@
+from metaflow import Parameter, FlowSpec, step, skip
+
+
+class SkipFlow(FlowSpec):
+
+    condition_true = Parameter("condition-true", default=True)
+
+    @step
+    def start(self):
+        print("Should skip:", self.condition)
+        self.desired_step_executed = False
+        self.condition_false = False
+        self.next(self.skipped_step)
+
+    @skip(check="condition_true", next="desired_step")
+    @step
+    def skipped_step(self):
+        raise Exception(
+            "Unexpectedly ran the skipped_step step. This step should have been skipped."
+        )
+        self.next(self.unreachable_step)
+
+    @step
+    def unreachable_step(self):
+        raise Exception(
+            "Unexpectedly ran the unreachable step. This step should have been skipped."
+        )
+        self.next(self.desired_step)
+
+    @skip(check="condition_false", next="end")
+    @step
+    def desired_step(self):
+        self.desired_step_executed = True
+        self.next(self.end)
+
+    @step
+    def end(self):
+        assert self.desired_step_executed, "Desired step was not executed"
+
+
+if __name__ == "__main__":
+    SkipFlow()