Composer: add simple workflow example. Use 1.10beta instead of git.

composer/workflows/requirements.txt

@@ -1 +1 @@
-git+https://github.com/apache/incubator-airflow.git#egg=project[gcp_api]
+https://dist.apache.org/repos/dist/dev/incubator/airflow/1.10.0beta1/apache-airflow-1.10.0b1+incubating.tar.gz#egg=apache-airflow[gcp_api]

composer/workflows/simple.py

@@ -0,0 +1,58 @@
+# Copyright 2018 Google LLC
+#
+# 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
+#
+#     https://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.
+
+"""An example DAG demonstrating simple Apache Airflow operators."""
+
+# [START composer_simple]
+from __future__ import print_function
+
+import datetime
+
+from airflow import models
+from airflow.operators import bash_operator
+from airflow.operators import python_operator
+
+
+default_dag_args = {
+    # The start_date describes when a DAG is valid / can be run. Set this to a
+    # fixed point in time rather than dynamically, since it is evaluated every
+    # time a DAG is parsed. See:
+    # https://airflow.apache.org/faq.html#what-s-the-deal-with-start-date
+    'start_date': datetime.datetime(2018, 1, 1),
+}
+
+# Define a DAG (directed acyclic graph) of tasks.
+# Any task you create within the context manager is automatically added to the
+# DAG object.
+with models.DAG(
+        'simple_greeting',
+        default_args=default_dag_args) as dag:
+    def greeting():
+        print('Hello World!')
+
+    # An instance of an operator is called a task. In this case, the
+    # hello_python task calls the "greeting" Python function.
+    hello_python = python_operator.PythonOperator(
+        task_id='hello',
+        python_callable=greeting)
+
+    # Likewise, the goodbye_bash task calls a Bash script.
+    goodbye_bash = bash_operator.BashOperator(
+        task_id='bye',
+        bash_command='echo Goodbye.')
+
+    # Define the order in which the tasks complete by using the >> and <<
+    # operators. In this example, hello_python executes before goodbye_bash.
+    hello_python >> goodbye_bash
+# [END composer_simple]

composer/workflows/simple_test.py

@@ -0,0 +1,23 @@
+# Copyright 2018 Google LLC
+#
+# 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
+#
+#     https://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.
+
+
+def test_dag_import():
+    """Test that the DAG file can be successfully imported.
+
+    This tests that the DAG can be parsed, but does not run it in an Airflow
+    environment. This is a recommended sanity check by the official Airflow
+    docs: https://airflow.incubator.apache.org/tutorial.html#testing
+    """
+    from . import simple # noqa