feat(sdk): support more than one exit handler per pipeline (#8088)

* add compiler test pipeline with multiple exit handlers

* remove blocker of multiple exit handlers

* move exit handler builder logic to pipeline_spec_builder

* build all exit handlers per pipeline

* add compiler test with IR inspection

* prevent usage of cross-pipeline after

* test cross-pipeline after is prevented

* update existing task dependency logic and tests

* add v2 sample test

* remove cross-pipeline .after

* prevent cross-dag data dependency for dsl features

* add compiler test pipeline with nested exit handlers

* add support for nested exit handlers

* clean up pipeline with nested exit handlers

* remove sample with multiple exit handlers

* remove compiler test with nested exit handlers

* add compilation guard against nested exit handlers in subdag

* update release notes

samples/core/loop_parameter/loop_parameter_v2.py

@@ -1,4 +1,5 @@
 import os
+
 from kfp import dsl
 
 # In tests, we install a KFP package from the PR under test. Users should not
@@ -32,5 +33,4 @@ def my_pipeline(
     generate_task = generate_op()
     with dsl.ParallelFor(generate_task.output) as item:
         concat_task = concat_op(a=item.a, b=item.b)
-        concat_task.after(print_task)
         print_task_2 = print_op(text=concat_task.output)

samples/core/loop_static/loop_static_v2.py

@@ -1,7 +1,8 @@
 import os
-from kfp import dsl
 from typing import List
 
+from kfp import dsl
+
 # In tests, we install a KFP package from the PR under test. Users should not
 # normally need to specify `kfp_package_path` in their component definitions.
 _KFP_PACKAGE_PATH = os.getenv('KFP_PACKAGE_PATH')
@@ -21,12 +22,10 @@ def concat_op(a: str, b: str) -> str:
 
 @dsl.pipeline(name='pipeline-with-loop-static')
 def my_pipeline(
-    greeting: str = 'this is a test for looping through parameters',
-):
+    greeting: str = 'this is a test for looping through parameters',):
     print_task = print_op(text=greeting)
     static_loop_arguments = [{'a': '1', 'b': '2'}, {'a': '10', 'b': '20'}]
 
     with dsl.ParallelFor(static_loop_arguments) as item:
         concat_task = concat_op(a=item.a, b=item.b)
-        concat_task.after(print_task)
-        print_task_2 = print_op(text=concat_task.output)
+        print_task_2 = print_op(text=concat_task.output)

sdk/RELEASE.md

@@ -5,7 +5,6 @@
 ## Breaking Changes
 
 ### For Pipeline Authors
-* Add support for task-level retry policy [\#7867](https://github.com/kubeflow/pipelines/pull/7867)
 
 ### For Component Authors
 
@@ -14,6 +13,8 @@
 ## Bug Fixes and Other Changes
 * Enable overriding caching options at submission time [\#7912](https://github.com/kubeflow/pipelines/pull/7912)
 * Allow artifact inputs in pipeline definition. [\#8044](https://github.com/kubeflow/pipelines/pull/8044)
+* Support task-level retry policy [\#7867](https://github.com/kubeflow/pipelines/pull/7867)
+* Support multiple exit handlers per pipeline [\#8088](https://github.com/kubeflow/pipelines/pull/8088)
 
 ## Documentation Updates
 

sdk/python/kfp/compiler/_read_write_test_config.py

@@ -44,6 +44,7 @@ CONFIG = {
             'component_with_pip_index_urls',
             'container_component_with_no_inputs',
             'two_step_pipeline_containerized',
+            'pipeline_with_multiple_exit_handlers',
         ],
         'test_data_dir': 'sdk/python/kfp/compiler/test_data/pipelines',
         'config': {

sdk/python/kfp/compiler/compiler.py

@@ -148,8 +148,6 @@ class Compiler:
         if not dsl_pipeline.tasks:
             raise ValueError('Task is missing from pipeline.')
 
-        self._validate_exit_handler(dsl_pipeline)
-
         pipeline_inputs = pipeline_meta.inputs or {}
 
         # Verify that pipeline_parameters_override contains only input names
@@ -186,45 +184,6 @@ class Compiler:
 
         return pipeline_spec
 
-    def _validate_exit_handler(self,
-                               pipeline: pipeline_context.Pipeline) -> None:
-        """Makes sure there is only one global exit handler.
-
-        This is temporary to be compatible with KFP v1.
-
-        Raises:
-            ValueError if there are more than one exit handler.
-        """
-
-        def _validate_exit_handler_helper(
-            group: tasks_group.TasksGroup,
-            exiting_task_names: List[str],
-            handler_exists: bool,
-        ) -> None:
-
-            if isinstance(group, dsl.ExitHandler):
-                if handler_exists or len(exiting_task_names) > 1:
-                    raise ValueError(
-                        'Only one global exit_handler is allowed and all ops need to be included.'
-                    )
-                handler_exists = True
-
-            if group.tasks:
-                exiting_task_names.extend([x.name for x in group.tasks])
-
-            for group in group.groups:
-                _validate_exit_handler_helper(
-                    group=group,
-                    exiting_task_names=exiting_task_names,
-                    handler_exists=handler_exists,
-                )
-
-        _validate_exit_handler_helper(
-            group=pipeline.groups[0],
-            exiting_task_names=[],
-            handler_exists=False,
-        )
-
     def _create_pipeline_spec(
         self,
         pipeline_args: List[pipeline_channel.PipelineChannel],
@@ -301,49 +260,11 @@ class Compiler:
                 name_to_for_loop_group=name_to_for_loop_group,
             )
 
-        # TODO: refactor to support multiple exit handler per pipeline.
-        if pipeline.groups[0].groups:
-            first_group = pipeline.groups[0].groups[0]
-            if isinstance(first_group, dsl.ExitHandler):
-                exit_task = first_group.exit_task
-                exit_task_name = component_utils.sanitize_task_name(
-                    exit_task.name)
-                exit_handler_group_task_name = component_utils.sanitize_task_name(
-                    first_group.name)
-                input_parameters_in_current_dag = [
-                    input_name for input_name in
-                    pipeline_spec.root.input_definitions.parameters
-                ]
-                exit_task_task_spec = builder.build_task_spec_for_exit_task(
-                    task=exit_task,
-                    dependent_task=exit_handler_group_task_name,
-                    pipeline_inputs=pipeline_spec.root.input_definitions,
-                )
-
-                exit_task_component_spec = builder.build_component_spec_for_exit_task(
-                    task=exit_task)
-
-                exit_task_container_spec = builder.build_container_spec_for_task(
-                    task=exit_task)
-
-                # Add exit task task spec
-                pipeline_spec.root.dag.tasks[exit_task_name].CopyFrom(
-                    exit_task_task_spec)
-
-                # Add exit task component spec if it does not exist.
-                component_name = exit_task_task_spec.component_ref.name
-                if component_name not in pipeline_spec.components:
-                    pipeline_spec.components[component_name].CopyFrom(
-                        exit_task_component_spec)
-
-                # Add exit task container spec if it does not exist.
-                executor_label = exit_task_component_spec.executor_label
-                if executor_label not in deployment_config.executors:
-                    deployment_config.executors[
-                        executor_label].container.CopyFrom(
-                            exit_task_container_spec)
-                    pipeline_spec.deployment_spec.update(
-                        json_format.MessageToDict(deployment_config))
+        builder.build_exit_handler_groups_recursively(
+            parent_group=root_group,
+            pipeline_spec=pipeline_spec,
+            deployment_config=deployment_config,
+        )
 
         return pipeline_spec
 
@@ -705,14 +626,12 @@ class Compiler:
                     task2=task,
                 )
 
-                # If a task depends on a condition group or a loop group, it
-                # must explicitly dependent on a task inside the group. This
-                # should not be allowed, because it leads to ambiguous
-                # expectations for runtime behaviors.
+                # a task cannot depend on a task created in a for loop group since individual PipelineTask variables are reassigned after each loop iteration
                 dependent_group = group_name_to_group.get(
                     upstream_groups[0], None)
                 if isinstance(dependent_group,
-                              (tasks_group.Condition, tasks_group.ParallelFor)):
+                              (tasks_group.ParallelFor, tasks_group.Condition,
+                               tasks_group.ExitHandler)):
                     raise RuntimeError(
                         f'Task {task.name} cannot dependent on any task inside'
                         f' the group: {upstream_groups[0]}.')

sdk/python/kfp/compiler/compiler_test.py

@@ -440,7 +440,7 @@ class TestCompilePipeline(parameterized.TestCase):
             compiler.Compiler().compile(
                 pipeline_func=my_pipeline, package_path='result.yaml')
 
-    def test_invalid_after_dependency(self):
+    def test_invalid_data_dependency_loop(self):
 
         @dsl.component
         def producer_op() -> str:
@@ -451,30 +451,7 @@ class TestCompilePipeline(parameterized.TestCase):
             pass
 
         @dsl.pipeline(name='test-pipeline')
-        def my_pipeline(text: str):
-            with dsl.Condition(text == 'a'):
-                producer_task = producer_op()
-
-            dummy_op().after(producer_task)
-
-        with self.assertRaisesRegex(
-                RuntimeError,
-                'Task dummy-op cannot dependent on any task inside the group:'):
-            compiler.Compiler().compile(
-                pipeline_func=my_pipeline, package_path='result.yaml')
-
-    def test_invalid_data_dependency(self):
-
-        @dsl.component
-        def producer_op() -> str:
-            return 'a'
-
-        @dsl.component
-        def dummy_op(msg: str = ''):
-            pass
-
-        @dsl.pipeline(name='test-pipeline')
-        def my_pipeline(text: bool):
+        def my_pipeline(val: bool):
             with dsl.ParallelFor(['a, b']):
                 producer_task = producer_op()
 
@@ -483,8 +460,125 @@ class TestCompilePipeline(parameterized.TestCase):
         with self.assertRaisesRegex(
                 RuntimeError,
                 'Task dummy-op cannot dependent on any task inside the group:'):
+            with tempfile.TemporaryDirectory() as tmpdir:
+                package_path = os.path.join(tmpdir, 'pipeline.yaml')
+                compiler.Compiler().compile(
+                    pipeline_func=my_pipeline, package_path=package_path)
+
+    def test_valid_data_dependency_loop(self):
+
+        @dsl.component
+        def producer_op() -> str:
+            return 'a'
+
+        @dsl.component
+        def dummy_op(msg: str = ''):
+            pass
+
+        @dsl.pipeline(name='test-pipeline')
+        def my_pipeline(val: bool):
+            with dsl.ParallelFor(['a, b']):
+                producer_task = producer_op()
+                dummy_op(msg=producer_task.output)
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            package_path = os.path.join(tmpdir, 'pipeline.yaml')
             compiler.Compiler().compile(
-                pipeline_func=my_pipeline, package_path='result.yaml')
+                pipeline_func=my_pipeline, package_path=package_path)
+
+    def test_invalid_data_dependency_condition(self):
+
+        @dsl.component
+        def producer_op() -> str:
+            return 'a'
+
+        @dsl.component
+        def dummy_op(msg: str = ''):
+            pass
+
+        @dsl.pipeline(name='test-pipeline')
+        def my_pipeline(val: bool):
+            with dsl.Condition(val == False):
+                producer_task = producer_op()
+
+            dummy_op(msg=producer_task.output)
+
+        with self.assertRaisesRegex(
+                RuntimeError,
+                'Task dummy-op cannot dependent on any task inside the group:'):
+            with tempfile.TemporaryDirectory() as tmpdir:
+                package_path = os.path.join(tmpdir, 'pipeline.yaml')
+                compiler.Compiler().compile(
+                    pipeline_func=my_pipeline, package_path=package_path)
+
+    def test_valid_data_dependency_condition(self):
+
+        @dsl.component
+        def producer_op() -> str:
+            return 'a'
+
+        @dsl.component
+        def dummy_op(msg: str = ''):
+            pass
+
+        @dsl.pipeline(name='test-pipeline')
+        def my_pipeline(val: bool):
+            with dsl.Condition(val == False):
+                producer_task = producer_op()
+                dummy_op(msg=producer_task.output)
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            package_path = os.path.join(tmpdir, 'pipeline.yaml')
+            compiler.Compiler().compile(
+                pipeline_func=my_pipeline, package_path=package_path)
+
+    def test_invalid_data_dependency_exit_handler(self):
+
+        @dsl.component
+        def producer_op() -> str:
+            return 'a'
+
+        @dsl.component
+        def dummy_op(msg: str = ''):
+            pass
+
+        @dsl.pipeline(name='test-pipeline')
+        def my_pipeline(val: bool):
+            first_producer = producer_op()
+            with dsl.ExitHandler(first_producer):
+                producer_task = producer_op()
+
+            dummy_op(msg=producer_task.output)
+
+        with self.assertRaisesRegex(
+                RuntimeError,
+                'Task dummy-op cannot dependent on any task inside the group:'):
+            with tempfile.TemporaryDirectory() as tmpdir:
+                package_path = os.path.join(tmpdir, 'pipeline.yaml')
+                compiler.Compiler().compile(
+                    pipeline_func=my_pipeline, package_path=package_path)
+
+    def test_valid_data_dependency_exit_handler(self):
+
+        @dsl.component
+        def producer_op() -> str:
+            return 'a'
+
+        @dsl.component
+        def dummy_op(msg: str = ''):
+            pass
+
+        @dsl.pipeline(name='test-pipeline')
+        def my_pipeline(val: bool):
+            first_producer = producer_op()
+            with dsl.ExitHandler(first_producer):
+                producer_task = producer_op()
+                dummy_op(msg=producer_task.output)
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            package_path = os.path.join(tmpdir, 'pipeline.yaml')
+            compiler.Compiler().compile(
+                pipeline_func=my_pipeline, package_path=package_path)
 
     def test_use_task_final_status_in_non_exit_op(self):
 
@@ -527,7 +621,6 @@ implementation:
                 pipeline_func=my_pipeline, package_path='result.yaml')
 
 
-# pylint: disable=import-outside-toplevel,unused-import,import-error,redefined-outer-name,reimported
 class V2NamespaceAliasTest(unittest.TestCase):
     """Test that imports of both modules and objects are aliased (e.g. all
     import path variants work)."""
@@ -536,7 +629,7 @@ class V2NamespaceAliasTest(unittest.TestCase):
     # the kfp.v2 module is loaded. Due to the way we run tests in CI/CD, we cannot ensure that the kfp.v2 module will first be loaded in these tests,
     # so we do not test for the DeprecationWarning here.
 
-    def test_import_namespace(self):  # pylint: disable=no-self-use
+    def test_import_namespace(self):
         from kfp import v2
 
         @v2.dsl.component
@@ -560,7 +653,7 @@ class V2NamespaceAliasTest(unittest.TestCase):
             with open(temp_filepath, 'r') as f:
                 yaml.load(f)
 
-    def test_import_modules(self):  # pylint: disable=no-self-use
+    def test_import_modules(self):
         from kfp.v2 import compiler
         from kfp.v2 import dsl
 
@@ -584,7 +677,7 @@ class V2NamespaceAliasTest(unittest.TestCase):
             with open(temp_filepath, 'r') as f:
                 yaml.load(f)
 
-    def test_import_object(self):  # pylint: disable=no-self-use
+    def test_import_object(self):
         from kfp.v2.compiler import Compiler
         from kfp.v2.dsl import component
         from kfp.v2.dsl import pipeline
@@ -1125,5 +1218,82 @@ class TestSetRetryCompilation(unittest.TestCase):
         self.assertEqual(retry_policy.backoff_max_duration.seconds, 3600)
 
 
+from google.protobuf import json_format
+
+
+class TestMultipleExitHandlerCompilation(unittest.TestCase):
+
+    def test_basic(self):
+
+        @dsl.component
+        def print_op(message: str):
+            print(message)
+
+        @dsl.pipeline(name='pipeline-with-multiple-exit-handlers')
+        def my_pipeline():
+            first_exit_task = print_op(message='First exit task.')
+
+            with dsl.ExitHandler(first_exit_task):
+                print_op(message='Inside first exit handler.')
+
+            second_exit_task = print_op(message='Second exit task.')
+            with dsl.ExitHandler(second_exit_task):
+                print_op(message='Inside second exit handler.')
+
+        with tempfile.TemporaryDirectory() as tempdir:
+            package_path = os.path.join(tempdir, 'pipeline.yaml')
+            compiler.Compiler().compile(
+                pipeline_func=my_pipeline, package_path=package_path)
+            pipeline_spec = pipeline_spec_from_file(package_path)
+        # check that the exit handler dags exist
+        self.assertEqual(
+            pipeline_spec.components['comp-exit-handler-1'].dag
+            .tasks['print-op-2'].inputs.parameters['message'].runtime_value
+            .constant.string_value, 'Inside first exit handler.')
+        self.assertEqual(
+            pipeline_spec.components['comp-exit-handler-2'].dag
+            .tasks['print-op-4'].inputs.parameters['message'].runtime_value
+            .constant.string_value, 'Inside second exit handler.')
+        # check that the exit handler dags are in the root dag
+        self.assertIn('exit-handler-1', pipeline_spec.root.dag.tasks)
+        self.assertIn('exit-handler-2', pipeline_spec.root.dag.tasks)
+        # check that the exit tasks are in the root dag
+        self.assertIn('print-op', pipeline_spec.root.dag.tasks)
+        self.assertEqual(
+            pipeline_spec.root.dag.tasks['print-op'].inputs
+            .parameters['message'].runtime_value.constant.string_value,
+            'First exit task.')
+        self.assertIn('print-op-3', pipeline_spec.root.dag.tasks)
+        self.assertEqual(
+            pipeline_spec.root.dag.tasks['print-op-3'].inputs
+            .parameters['message'].runtime_value.constant.string_value,
+            'Second exit task.')
+
+    def test_nested_unsupported(self):
+
+        @dsl.component
+        def print_op(message: str):
+            print(message)
+
+        @dsl.pipeline(name='pipeline-with-multiple-exit-handlers')
+        def my_pipeline():
+            first_exit_task = print_op(message='First exit task.')
+
+            with dsl.ExitHandler(first_exit_task):
+                print_op(message='Inside first exit handler.')
+
+                second_exit_task = print_op(message='Second exit task.')
+                with dsl.ExitHandler(second_exit_task):
+                    print_op(message='Inside second exit handler.')
+
+        with self.assertRaisesRegex(
+                ValueError,
+                r'ExitHandler can only be used within the outermost scope of a pipeline function definition\.'
+        ):
+
+            compiler.Compiler().compile(
+                pipeline_func=my_pipeline, package_path='output.yaml')
+
+
 if __name__ == '__main__':
     unittest.main()

sdk/python/kfp/compiler/pipeline_spec_builder.py

@@ -23,6 +23,7 @@ from kfp import dsl
 from kfp.compiler import pipeline_spec_builder as builder
 from kfp.components import for_loop
 from kfp.components import pipeline_channel
+from kfp.components import pipeline_context
 from kfp.components import pipeline_task
 from kfp.components import placeholders
 from kfp.components import structures
@@ -34,6 +35,13 @@ from kfp.components.types import type_utils
 from kfp.pipeline_spec import pipeline_spec_pb2
 
 GroupOrTaskType = Union[tasks_group.TasksGroup, pipeline_task.PipelineTask]
+# must be defined here to avoid circular imports
+group_type_to_dsl_class = {
+    tasks_group.TasksGroupType.PIPELINE: pipeline_context.Pipeline,
+    tasks_group.TasksGroupType.CONDITION: tasks_group.Condition,
+    tasks_group.TasksGroupType.FOR_LOOP: tasks_group.ParallelFor,
+    tasks_group.TasksGroupType.EXIT_HANDLER: tasks_group.ExitHandler,
+}
 
 
 def _additional_input_name_for_pipeline_channel(
@@ -772,7 +780,7 @@ def build_task_spec_for_exit_task(
         pipeline_spec_pb2.PipelineTaskSpec.TriggerPolicy.TriggerStrategy
         .ALL_UPSTREAM_TASKS_COMPLETED)
 
-    for input_name, input_spec in task.component_spec.inputs.items():
+    for input_name, input_spec in (task.component_spec.inputs or {}).items():
         if type_utils.is_task_final_status_type(input_spec.type):
             pipeline_task_spec.inputs.parameters[
                 input_name].task_final_status.producer_task = dependent_task
@@ -1184,6 +1192,61 @@ def build_spec_by_group(
     )
 
 
+def build_exit_handler_groups_recursively(
+    parent_group: tasks_group.TasksGroup,
+    pipeline_spec: pipeline_spec_pb2.PipelineSpec,
+    deployment_config: pipeline_spec_pb2.PipelineDeploymentConfig,
+):
+    if not parent_group.groups:
+        return
+    for group in parent_group.groups:
+        if isinstance(group, dsl.ExitHandler):
+            exit_task = group.exit_task
+            exit_task_name = utils.sanitize_task_name(exit_task.name)
+            exit_handler_group_task_name = utils.sanitize_task_name(group.name)
+
+            exit_task_task_spec = builder.build_task_spec_for_exit_task(
+                task=exit_task,
+                dependent_task=exit_handler_group_task_name,
+                pipeline_inputs=pipeline_spec.root.input_definitions,
+            )
+
+            exit_task_component_spec = builder.build_component_spec_for_exit_task(
+                task=exit_task)
+
+            exit_task_container_spec = builder.build_container_spec_for_task(
+                task=exit_task)
+
+            # remove this if block to support nested exit handlers
+            if not parent_group.is_root:
+                raise ValueError(
+                    f'{dsl.ExitHandler.__name__} can only be used within the outermost scope of a pipeline function definition. Using an {dsl.ExitHandler.__name__} within {group_type_to_dsl_class[parent_group.group_type].__name__} {parent_group.name} is not allowed.'
+                )
+
+            parent_dag = pipeline_spec.root.dag if parent_group.is_root else pipeline_spec.components[
+                utils.sanitize_component_name(parent_group.name)].dag
+
+            parent_dag.tasks[exit_task_name].CopyFrom(exit_task_task_spec)
+
+            # Add exit task component spec if it does not exist.
+            component_name = exit_task_task_spec.component_ref.name
+            if component_name not in pipeline_spec.components:
+                pipeline_spec.components[component_name].CopyFrom(
+                    exit_task_component_spec)
+
+            # Add exit task container spec if it does not exist.
+            executor_label = exit_task_component_spec.executor_label
+            if executor_label not in deployment_config.executors:
+                deployment_config.executors[executor_label].container.CopyFrom(
+                    exit_task_container_spec)
+                pipeline_spec.deployment_spec.update(
+                    json_format.MessageToDict(deployment_config))
+        build_exit_handler_groups_recursively(
+            parent_group=group,
+            pipeline_spec=pipeline_spec,
+            deployment_config=deployment_config)
+
+
 def get_parent_groups(
     root_group: tasks_group.TasksGroup,
 ) -> Tuple[Mapping[str, List[GroupOrTaskType]], Mapping[str,

sdk/python/kfp/compiler/test_data/pipelines/pipeline_with_multiple_exit_handlers.py

@@ -0,0 +1,59 @@
+# Copyright 2022 The Kubeflow Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Pipeline using multiple ExitHandlers."""
+
+from kfp import compiler
+from kfp import dsl
+from kfp.dsl import component
+
+
+@component
+def print_op(message: str):
+    """Prints a message."""
+    print(message)
+
+
+@component
+def fail_op(message: str):
+    """Fails."""
+    import sys
+    print(message)
+    sys.exit(1)
+
+
+@dsl.pipeline(name='pipeline-with-multiple-exit-handlers')
+def my_pipeline(message: str = 'Hello World!'):
+
+    first_exit_task = print_op(message='First exit handler has worked!')
+
+    with dsl.ExitHandler(first_exit_task):
+        first_exit_print_task = print_op(message=message)
+        print(first_exit_print_task.outputs)
+        fail_op(message='Task failed.')
+
+    second_exit_task = print_op(message='Second exit handler has worked!')
+
+    with dsl.ExitHandler(second_exit_task):
+        print_op(message=message)
+
+    third_exit_task = print_op(message='Third exit handler has worked!')
+
+    with dsl.ExitHandler(third_exit_task):
+        print_op(message=message)
+
+
+if __name__ == '__main__':
+    compiler.Compiler().compile(
+        pipeline_func=my_pipeline,
+        package_path=__file__.replace('.py', '.yaml'))

sdk/python/kfp/compiler/test_data/pipelines/pipeline_with_multiple_exit_handlers.yaml

@@ -0,0 +1,387 @@
+components:
+  comp-exit-handler-1:
+    dag:
+      tasks:
+        fail-op:
+          cachingOptions:
+            enableCache: true
+          componentRef:
+            name: comp-fail-op
+          inputs:
+            parameters:
+              message:
+                runtimeValue:
+                  constant: Task failed.
+          taskInfo:
+            name: fail-op
+        print-op-2:
+          cachingOptions:
+            enableCache: true
+          componentRef:
+            name: comp-print-op-2
+          inputs:
+            parameters:
+              message:
+                componentInputParameter: pipelinechannel--message
+          taskInfo:
+            name: print-op-2
+    inputDefinitions:
+      parameters:
+        pipelinechannel--message:
+          parameterType: STRING
+  comp-exit-handler-2:
+    dag:
+      tasks:
+        print-op-4:
+          cachingOptions:
+            enableCache: true
+          componentRef:
+            name: comp-print-op-4
+          inputs:
+            parameters:
+              message:
+                componentInputParameter: pipelinechannel--message
+          taskInfo:
+            name: print-op-4
+    inputDefinitions:
+      parameters:
+        pipelinechannel--message:
+          parameterType: STRING
+  comp-exit-handler-3:
+    dag:
+      tasks:
+        print-op-6:
+          cachingOptions:
+            enableCache: true
+          componentRef:
+            name: comp-print-op-6
+          inputs:
+            parameters:
+              message:
+                componentInputParameter: pipelinechannel--message
+          taskInfo:
+            name: print-op-6
+    inputDefinitions:
+      parameters:
+        pipelinechannel--message:
+          parameterType: STRING
+  comp-fail-op:
+    executorLabel: exec-fail-op
+    inputDefinitions:
+      parameters:
+        message:
+          parameterType: STRING
+  comp-print-op:
+    executorLabel: exec-print-op
+    inputDefinitions:
+      parameters:
+        message:
+          parameterType: STRING
+  comp-print-op-2:
+    executorLabel: exec-print-op-2
+    inputDefinitions:
+      parameters:
+        message:
+          parameterType: STRING
+  comp-print-op-3:
+    executorLabel: exec-print-op-3
+    inputDefinitions:
+      parameters:
+        message:
+          parameterType: STRING
+  comp-print-op-4:
+    executorLabel: exec-print-op-4
+    inputDefinitions:
+      parameters:
+        message:
+          parameterType: STRING
+  comp-print-op-5:
+    executorLabel: exec-print-op-5
+    inputDefinitions:
+      parameters:
+        message:
+          parameterType: STRING
+  comp-print-op-6:
+    executorLabel: exec-print-op-6
+    inputDefinitions:
+      parameters:
+        message:
+          parameterType: STRING
+deploymentSpec:
+  executors:
+    exec-fail-op:
+      container:
+        args:
+        - --executor_input
+        - '{{$}}'
+        - --function_to_execute
+        - fail_op
+        command:
+        - sh
+        - -c
+        - "\nif ! [ -x \"$(command -v pip)\" ]; then\n    python3 -m ensurepip ||\
+          \ python3 -m ensurepip --user || apt-get install python3-pip\nfi\n\nPIP_DISABLE_PIP_VERSION_CHECK=1\
+          \ python3 -m pip install --quiet     --no-warn-script-location 'kfp==2.0.0-beta.1'\
+          \ && \"$0\" \"$@\"\n"
+        - sh
+        - -ec
+        - 'program_path=$(mktemp -d)
+
+          printf "%s" "$0" > "$program_path/ephemeral_component.py"
+
+          python3 -m kfp.components.executor_main                         --component_module_path                         "$program_path/ephemeral_component.py"                         "$@"
+
+          '
+        - "\nimport kfp\nfrom kfp import dsl\nfrom kfp.dsl import *\nfrom typing import\
+          \ *\n\ndef fail_op(message: str):\n    \"\"\"Fails.\"\"\"\n    import sys\n\
+          \    print(message)\n    sys.exit(1)\n\n"
+        image: python:3.7
+    exec-print-op:
+      container:
+        args:
+        - --executor_input
+        - '{{$}}'
+        - --function_to_execute
+        - print_op
+        command:
+        - sh
+        - -c
+        - "\nif ! [ -x \"$(command -v pip)\" ]; then\n    python3 -m ensurepip ||\
+          \ python3 -m ensurepip --user || apt-get install python3-pip\nfi\n\nPIP_DISABLE_PIP_VERSION_CHECK=1\
+          \ python3 -m pip install --quiet     --no-warn-script-location 'kfp==2.0.0-beta.1'\
+          \ && \"$0\" \"$@\"\n"
+        - sh
+        - -ec
+        - 'program_path=$(mktemp -d)
+
+          printf "%s" "$0" > "$program_path/ephemeral_component.py"
+
+          python3 -m kfp.components.executor_main                         --component_module_path                         "$program_path/ephemeral_component.py"                         "$@"
+
+          '
+        - "\nimport kfp\nfrom kfp import dsl\nfrom kfp.dsl import *\nfrom typing import\
+          \ *\n\ndef print_op(message: str):\n    \"\"\"Prints a message.\"\"\"\n\
+          \    print(message)\n\n"
+        image: python:3.7
+    exec-print-op-2:
+      container:
+        args:
+        - --executor_input
+        - '{{$}}'
+        - --function_to_execute
+        - print_op
+        command:
+        - sh
+        - -c
+        - "\nif ! [ -x \"$(command -v pip)\" ]; then\n    python3 -m ensurepip ||\
+          \ python3 -m ensurepip --user || apt-get install python3-pip\nfi\n\nPIP_DISABLE_PIP_VERSION_CHECK=1\
+          \ python3 -m pip install --quiet     --no-warn-script-location 'kfp==2.0.0-beta.1'\
+          \ && \"$0\" \"$@\"\n"
+        - sh
+        - -ec
+        - 'program_path=$(mktemp -d)
+
+          printf "%s" "$0" > "$program_path/ephemeral_component.py"
+
+          python3 -m kfp.components.executor_main                         --component_module_path                         "$program_path/ephemeral_component.py"                         "$@"
+
+          '
+        - "\nimport kfp\nfrom kfp import dsl\nfrom kfp.dsl import *\nfrom typing import\
+          \ *\n\ndef print_op(message: str):\n    \"\"\"Prints a message.\"\"\"\n\
+          \    print(message)\n\n"
+        image: python:3.7
+    exec-print-op-3:
+      container:
+        args:
+        - --executor_input
+        - '{{$}}'
+        - --function_to_execute
+        - print_op
+        command:
+        - sh
+        - -c
+        - "\nif ! [ -x \"$(command -v pip)\" ]; then\n    python3 -m ensurepip ||\
+          \ python3 -m ensurepip --user || apt-get install python3-pip\nfi\n\nPIP_DISABLE_PIP_VERSION_CHECK=1\
+          \ python3 -m pip install --quiet     --no-warn-script-location 'kfp==2.0.0-beta.1'\
+          \ && \"$0\" \"$@\"\n"
+        - sh
+        - -ec
+        - 'program_path=$(mktemp -d)
+
+          printf "%s" "$0" > "$program_path/ephemeral_component.py"
+
+          python3 -m kfp.components.executor_main                         --component_module_path                         "$program_path/ephemeral_component.py"                         "$@"
+
+          '
+        - "\nimport kfp\nfrom kfp import dsl\nfrom kfp.dsl import *\nfrom typing import\
+          \ *\n\ndef print_op(message: str):\n    \"\"\"Prints a message.\"\"\"\n\
+          \    print(message)\n\n"
+        image: python:3.7
+    exec-print-op-4:
+      container:
+        args:
+        - --executor_input
+        - '{{$}}'
+        - --function_to_execute
+        - print_op
+        command:
+        - sh
+        - -c
+        - "\nif ! [ -x \"$(command -v pip)\" ]; then\n    python3 -m ensurepip ||\
+          \ python3 -m ensurepip --user || apt-get install python3-pip\nfi\n\nPIP_DISABLE_PIP_VERSION_CHECK=1\
+          \ python3 -m pip install --quiet     --no-warn-script-location 'kfp==2.0.0-beta.1'\
+          \ && \"$0\" \"$@\"\n"
+        - sh
+        - -ec
+        - 'program_path=$(mktemp -d)
+
+          printf "%s" "$0" > "$program_path/ephemeral_component.py"
+
+          python3 -m kfp.components.executor_main                         --component_module_path                         "$program_path/ephemeral_component.py"                         "$@"
+
+          '
+        - "\nimport kfp\nfrom kfp import dsl\nfrom kfp.dsl import *\nfrom typing import\
+          \ *\n\ndef print_op(message: str):\n    \"\"\"Prints a message.\"\"\"\n\
+          \    print(message)\n\n"
+        image: python:3.7
+    exec-print-op-5:
+      container:
+        args:
+        - --executor_input
+        - '{{$}}'
+        - --function_to_execute
+        - print_op
+        command:
+        - sh
+        - -c
+        - "\nif ! [ -x \"$(command -v pip)\" ]; then\n    python3 -m ensurepip ||\
+          \ python3 -m ensurepip --user || apt-get install python3-pip\nfi\n\nPIP_DISABLE_PIP_VERSION_CHECK=1\
+          \ python3 -m pip install --quiet     --no-warn-script-location 'kfp==2.0.0-beta.1'\
+          \ && \"$0\" \"$@\"\n"
+        - sh
+        - -ec
+        - 'program_path=$(mktemp -d)
+
+          printf "%s" "$0" > "$program_path/ephemeral_component.py"
+
+          python3 -m kfp.components.executor_main                         --component_module_path                         "$program_path/ephemeral_component.py"                         "$@"
+
+          '
+        - "\nimport kfp\nfrom kfp import dsl\nfrom kfp.dsl import *\nfrom typing import\
+          \ *\n\ndef print_op(message: str):\n    \"\"\"Prints a message.\"\"\"\n\
+          \    print(message)\n\n"
+        image: python:3.7
+    exec-print-op-6:
+      container:
+        args:
+        - --executor_input
+        - '{{$}}'
+        - --function_to_execute
+        - print_op
+        command:
+        - sh
+        - -c
+        - "\nif ! [ -x \"$(command -v pip)\" ]; then\n    python3 -m ensurepip ||\
+          \ python3 -m ensurepip --user || apt-get install python3-pip\nfi\n\nPIP_DISABLE_PIP_VERSION_CHECK=1\
+          \ python3 -m pip install --quiet     --no-warn-script-location 'kfp==2.0.0-beta.1'\
+          \ && \"$0\" \"$@\"\n"
+        - sh
+        - -ec
+        - 'program_path=$(mktemp -d)
+
+          printf "%s" "$0" > "$program_path/ephemeral_component.py"
+
+          python3 -m kfp.components.executor_main                         --component_module_path                         "$program_path/ephemeral_component.py"                         "$@"
+
+          '
+        - "\nimport kfp\nfrom kfp import dsl\nfrom kfp.dsl import *\nfrom typing import\
+          \ *\n\ndef print_op(message: str):\n    \"\"\"Prints a message.\"\"\"\n\
+          \    print(message)\n\n"
+        image: python:3.7
+pipelineInfo:
+  name: pipeline-with-multiple-exit-handlers
+root:
+  dag:
+    tasks:
+      exit-handler-1:
+        componentRef:
+          name: comp-exit-handler-1
+        inputs:
+          parameters:
+            pipelinechannel--message:
+              componentInputParameter: message
+        taskInfo:
+          name: exit-handler-1
+      exit-handler-2:
+        componentRef:
+          name: comp-exit-handler-2
+        inputs:
+          parameters:
+            pipelinechannel--message:
+              componentInputParameter: message
+        taskInfo:
+          name: exit-handler-2
+      exit-handler-3:
+        componentRef:
+          name: comp-exit-handler-3
+        inputs:
+          parameters:
+            pipelinechannel--message:
+              componentInputParameter: message
+        taskInfo:
+          name: exit-handler-3
+      print-op:
+        cachingOptions:
+          enableCache: true
+        componentRef:
+          name: comp-print-op
+        dependentTasks:
+        - exit-handler-1
+        inputs:
+          parameters:
+            message:
+              runtimeValue:
+                constant: First exit handler has worked!
+        taskInfo:
+          name: print-op
+        triggerPolicy:
+          strategy: ALL_UPSTREAM_TASKS_COMPLETED
+      print-op-3:
+        cachingOptions:
+          enableCache: true
+        componentRef:
+          name: comp-print-op-3
+        dependentTasks:
+        - exit-handler-2
+        inputs:
+          parameters:
+            message:
+              runtimeValue:
+                constant: Second exit handler has worked!
+        taskInfo:
+          name: print-op-3
+        triggerPolicy:
+          strategy: ALL_UPSTREAM_TASKS_COMPLETED
+      print-op-5:
+        cachingOptions:
+          enableCache: true
+        componentRef:
+          name: comp-print-op-5
+        dependentTasks:
+        - exit-handler-3
+        inputs:
+          parameters:
+            message:
+              runtimeValue:
+                constant: Third exit handler has worked!
+        taskInfo:
+          name: print-op-5
+        triggerPolicy:
+          strategy: ALL_UPSTREAM_TASKS_COMPLETED
+  inputDefinitions:
+    parameters:
+      message:
+        defaultValue: Hello World!
+        parameterType: STRING
+schemaVersion: 2.1.0
+sdkVersion: kfp-2.0.0-beta.1

sdk/python/kfp/components/pipeline_context.py

@@ -118,7 +118,9 @@ class Pipeline:
         # Add the root group.
         self.groups = [
             tasks_group.TasksGroup(
-                group_type=tasks_group.TasksGroupType.PIPELINE, name=name)
+                group_type=tasks_group.TasksGroupType.PIPELINE,
+                name=name,
+                is_root=True)
         ]
         self._group_id = 0
 
@@ -174,6 +176,7 @@ class Pipeline:
 
         self.tasks[task_name] = task
         if add_to_group:
+            task.parent_task_group = self.groups[-1]
             self.groups[-1].tasks.append(task)
 
         return task_name

sdk/python/kfp/components/pipeline_task.py

@@ -69,6 +69,10 @@ class PipelineTask:
         args: Mapping[str, Any],
     ):
         """Initilizes a PipelineTask instance."""
+        # import within __init__ to avoid circular import
+        from kfp.components.tasks_group import TasksGroup
+
+        self.parent_task_group: Union[None, TasksGroup] = None
         args = args or {}
 
         for input_name, argument_value in args.items():
@@ -558,5 +562,9 @@ class PipelineTask:
                 task2 = my_component(text='2nd task').after(task1)
         """
         for task in tasks:
+            if task.parent_task_group is not self.parent_task_group:
+                raise ValueError(
+                    f'Cannot use .after() across inner pipelines or DSL control flow features. Tried to set {self.name} after {task.name}, but these tasks do not belong to the same pipeline or are not enclosed in the same control flow content manager.'
+                )
             self._task_spec.dependent_tasks.append(task.name)
         return self

sdk/python/kfp/components/pipeline_task_test.py

@@ -13,10 +13,14 @@
 # limitations under the License.
 """Tests for kfp.components.pipeline_task."""
 
+import os
+import tempfile
 import textwrap
 import unittest
 
 from absl.testing import parameterized
+from kfp import compiler
+from kfp import dsl
 from kfp.components import pipeline_task
 from kfp.components import placeholders
 from kfp.components import structures
@@ -301,5 +305,136 @@ class PipelineTaskTest(parameterized.TestCase):
         self.assertEqual('test_name', task._task_spec.display_name)
 
 
+class TestCannotUseAfterCrossDAG(unittest.TestCase):
+
+    def test_inner_task_prevented(self):
+        with self.assertRaisesRegex(ValueError,
+                                    r'Cannot use \.after\(\) across'):
+
+            @dsl.component
+            def print_op(message: str):
+                print(message)
+
+            @dsl.pipeline(name='pipeline-with-multiple-exit-handlers')
+            def my_pipeline():
+                first_exit_task = print_op(message='First exit task.')
+
+                with dsl.ExitHandler(first_exit_task):
+                    first_print_op = print_op(
+                        message='Inside first exit handler.')
+
+                second_exit_task = print_op(message='Second exit task.')
+                with dsl.ExitHandler(second_exit_task):
+                    print_op(message='Inside second exit handler.').after(
+                        first_print_op)
+
+            with tempfile.TemporaryDirectory() as tempdir:
+                package_path = os.path.join(tempdir, 'pipeline.yaml')
+                compiler.Compiler().compile(
+                    pipeline_func=my_pipeline, package_path=package_path)
+
+    def test_exit_handler_task_prevented(self):
+        with self.assertRaisesRegex(ValueError,
+                                    r'Cannot use \.after\(\) across'):
+
+            @dsl.component
+            def print_op(message: str):
+                print(message)
+
+            @dsl.pipeline(name='pipeline-with-multiple-exit-handlers')
+            def my_pipeline():
+                first_exit_task = print_op(message='First exit task.')
+
+                with dsl.ExitHandler(first_exit_task):
+                    first_print_op = print_op(
+                        message='Inside first exit handler.')
+
+                second_exit_task = print_op(message='Second exit task.')
+                with dsl.ExitHandler(second_exit_task):
+                    x = print_op(message='Inside second exit handler.')
+                    x.after(first_exit_task)
+
+            with tempfile.TemporaryDirectory() as tempdir:
+                package_path = os.path.join(tempdir, 'pipeline.yaml')
+                compiler.Compiler().compile(
+                    pipeline_func=my_pipeline, package_path=package_path)
+
+    def test_within_same_exit_handler_permitted(self):
+
+        @dsl.component
+        def print_op(message: str):
+            print(message)
+
+        @dsl.pipeline(name='pipeline-with-multiple-exit-handlers')
+        def my_pipeline():
+            first_exit_task = print_op(message='First exit task.')
+
+            with dsl.ExitHandler(first_exit_task):
+                first_print_op = print_op(
+                    message='First task inside first exit handler.')
+                second_print_op = print_op(
+                    message='Second task inside first exit handler.').after(
+                        first_print_op)
+
+            second_exit_task = print_op(message='Second exit task.')
+            with dsl.ExitHandler(second_exit_task):
+                print_op(message='Inside second exit handler.')
+
+        with tempfile.TemporaryDirectory() as tempdir:
+            package_path = os.path.join(tempdir, 'pipeline.yaml')
+            compiler.Compiler().compile(
+                pipeline_func=my_pipeline, package_path=package_path)
+
+    def test_outside_of_condition_blocked(self):
+        with self.assertRaisesRegex(ValueError,
+                                    r'Cannot use \.after\(\) across'):
+
+            @dsl.component
+            def print_op(message: str):
+                print(message)
+
+            @dsl.component
+            def return_1() -> int:
+                return 1
+
+            @dsl.pipeline(name='pipeline-with-multiple-exit-handlers')
+            def my_pipeline():
+                return_1_task = return_1()
+
+                with dsl.Condition(return_1_task.output == 1):
+                    one = print_op(message='1')
+                    two = print_op(message='2')
+                three = print_op(message='3').after(one)
+
+            with tempfile.TemporaryDirectory() as tempdir:
+                package_path = os.path.join(tempdir, 'pipeline.yaml')
+                compiler.Compiler().compile(
+                    pipeline_func=my_pipeline, package_path=package_path)
+
+    def test_inside_of_condition_permitted(self):
+
+        @dsl.component
+        def print_op(message: str):
+            print(message)
+
+        @dsl.component
+        def return_1() -> int:
+            return 1
+
+        @dsl.pipeline(name='pipeline-with-multiple-exit-handlers')
+        def my_pipeline():
+            return_1_task = return_1()
+
+            with dsl.Condition(return_1_task.output == '1'):
+                one = print_op(message='1')
+                two = print_op(message='2').after(one)
+            three = print_op(message='3')
+
+        with tempfile.TemporaryDirectory() as tempdir:
+            package_path = os.path.join(tempdir, 'pipeline.yaml')
+            compiler.Compiler().compile(
+                pipeline_func=my_pipeline, package_path=package_path)
+
+
 if __name__ == '__main__':
     unittest.main()

sdk/python/kfp/components/tasks_group.py

@@ -44,12 +44,14 @@ class TasksGroup:
         groups: A list of TasksGroups in this group.
         display_name: The optional user given name of the group.
         dependencies: A list of tasks or groups this group depends on.
+        is_root: If TasksGroup is root group.
     """
 
     def __init__(
         self,
         group_type: TasksGroupType,
         name: Optional[str] = None,
+        is_root: bool = False,
     ):
         """Create a new instance of TasksGroup.
 
@@ -62,6 +64,7 @@ class TasksGroup:
         self.groups = list()
         self.display_name = name
         self.dependencies = []
+        self.is_root = is_root
 
     def __enter__(self):
         if not pipeline_context.Pipeline.get_default_pipeline():
@@ -116,7 +119,11 @@ class ExitHandler(TasksGroup):
         name: Optional[str] = None,
     ):
         """Initializes a Condition task group."""
-        super().__init__(group_type=TasksGroupType.EXIT_HANDLER, name=name)
+        super().__init__(
+            group_type=TasksGroupType.EXIT_HANDLER,
+            name=name,
+            is_root=False,
+        )
 
         if exit_task.dependent_tasks:
             raise ValueError('exit_task cannot depend on any other tasks.')
@@ -151,6 +158,7 @@ class Condition(TasksGroup):
         self,
         condition: pipeline_channel.ConditionOperator,
         name: Optional[str] = None,
+        is_root=False,
     ):
         """Initializes a conditional task group."""
         super().__init__(group_type=TasksGroupType.CONDITION, name=name)
@@ -182,7 +190,11 @@ class ParallelFor(TasksGroup):
         name: Optional[str] = None,
     ):
         """Initializes a for loop task group."""
-        super().__init__(group_type=TasksGroupType.FOR_LOOP, name=name)
+        super().__init__(
+            group_type=TasksGroupType.FOR_LOOP,
+            name=name,
+            is_root=False,
+        )
 
         if isinstance(items, pipeline_channel.PipelineChannel):
             self.loop_argument = for_loop.LoopArgument.from_pipeline_channel(