[Example] Minimal containerized app example (#1212)

* Container example

* parenthesis

* Add explicit StorageMode

* lint

examples/docker/echo_app.py

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+# Example using SkyPilot python API to run the echo app in a container.
+#
+# The echo example ingests a file, prints the contents and writes it back out.
+# In this YAML, the output is mapped to a Sky Storage object, which writes to a
+# cloud bucket.
+#
+# Usage:
+#   python echo_app.py
+
+import random
+import sky
+import string
+
+with sky.Dag() as dag:
+    # The setup command to build the container image
+    setup = 'docker build -t echo:v0 /echo_app'
+
+    # The command to run - runs the container and mounts volumes
+    run = ('docker run --rm --volume="/inputs:/inputs:ro" '
+           '--volume="/outputs:/outputs:rw" '
+           'echo:v0 /inputs/README.md /outputs/output.txt')
+
+    echo_app = sky.Task(
+        setup=setup,
+        run=run,
+    )
+
+    # Configure file mounts to copy local contents to remote
+    echo_app.set_file_mounts({
+        '/inputs': './echo_app',
+        '/echo_app': './echo_app',
+    })
+
+    # Configure outputs for the task - we'll write to a bucket using Sky Storage
+    output_bucket_name = ''.join(random.choices(string.ascii_lowercase, k=15))
+    output_storage = sky.Storage(name=output_bucket_name,
+                                 mode=sky.StorageMode.MOUNT)
+    echo_app.set_storage_mounts({
+        '/outputs': output_storage,
+    })
+
+    # Set resources if required
+    # echo_app.set_resources({
+    #     sky.Resources(accelerators='V100'),
+    # })
+
+sky.launch(dag)
+
+print('Remember to clean up resources after this script is done!\n'
+      'Run sky status and sky storage ls to list current resources.\n'
+      'Run sky down <cluster_name> and sky storage delete <storage_name> to '
+      'delete resources.')

examples/docker/echo_app.yaml

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+# Runs the echo example app in a container with custom inputs and outputs
+#
+# The echo example ingests a file, prints the contents and writes it back out.
+# In this YAML, the output is mapped to a Sky Storage object, which writes to a
+# cloud bucket.
+#
+# Usage:
+#   sky launch -c myclus echo_app.yaml
+#   sky exec myclus echo_app.yaml
+#   sky down myclus
+
+file_mounts:
+  /inputs: ./echo_app
+  /echo_app: ./echo_app
+  /outputs:
+    name: # Set unique bucket name here!
+    mode: MOUNT
+
+setup: |
+  # Build docker image. If pushed to a registry, can also do docker pull here
+  docker build -t echo:v0 /echo_app
+
+run: |
+  docker run --rm \
+    --volume="/inputs:/inputs:ro" \
+    --volume="/outputs:/outputs:rw" \
+    echo:v0 /inputs/README.md /outputs/output.txt

examples/docker/echo_app/Dockerfile

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+FROM python
+
+ADD echo.py /app/echo.py
+
+WORKDIR /app
+
+ENTRYPOINT ["python", "echo.py"]

examples/docker/echo_app/README.md

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+# Echo App
+
+A simple app that ingests a file and writes it out back to a specified path.

examples/docker/echo_app/echo.py

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+"""Echo app
+
+Reads a file, echoes it and writes back to a specified path.
+"""
+import argparse
+
+
+def main():
+    """Main function"""
+    parser = argparse.ArgumentParser(description='Echo app')
+    parser.add_argument('input', type=str)
+    parser.add_argument('output', type=str)
+    args = parser.parse_args()
+
+    with open(args.input, 'r') as input_file:
+        content = input_file.read()
+    print("===== echo app =====")
+    print("Input file content:")
+    print(content)
+    with open(args.output, 'w') as output_file:
+        output_file.write(content)
+    print("Output written to {}".format(args.output))
+
+
+if __name__ == '__main__':
+    main()