sample docker image that runs a web server

Signed-off-by: Vishnu Kannan <[email protected]>

Author: vishh

Dockerfile

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+# A docker base image based on alpine linux with python 3.6.0 pre-installed.
+# Docker images can be stacked on top of each other.
+FROM library/python:3.6.0-alpine
+
+# Install tornado library.
+RUN pip install tornado
+
+# Copy the webserver python app.
+ADD web-server.py /web-server.py
+
+# Set the default execution command for this image.
+CMD ["python", "/web-server.py"]

README.md

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+# A tornado based sample python webserver in a docker image
+
+`web-server.py` is a sample python application that hosts a simple webserver that responds to `Get` requests http requests on `localhost:8888` with the hostname.
+
+To run the webserver manually,
+
+1. Install python versions `2.7` or `3.3+`. 
+2. Install Tornado - `pip install tornado`
+3. Run `python web-server.py`
+4. Try accessing <a href="http://localhost:8888/" target="_blank">http://localhost:8888</a> from your browser.
+
+Sharing and running such a simple app like this `web-server` requires many manual steps.
+Imagine packaging a real-life webserver with a lot of web content.
+
+Now, let's see how docker can help.
+Take a look at [the Dockerfile](./Dockerfile) before you begin.
+Docker allows for stacking of images on top of each other.
+Our docker image will be built on top of an existing docker image `library/python` which has python pre-installed.
+
+1. Install Docker following [these instructions](https://docs.docker.com/engine/installation/).
+
+2. Execute `docker build -t "py-web-server:v1" .` to build a docker image with web-server packaged inside of it.
+
+3. Run the webserver
+```shell
+docker run -d -p 8888:8888 -h my-web-server py-web-server:v1
+```
+
+The webserver and all its dependencies including `python` and `tornado library` have been packaged into a single docker image that can now be shared with everyone.
+`py-web-server:v1` docker image will function the same way on all docker supported OSes (OS X, Windows & Linux).
+
+Try accessing the webserver again - <a href="http://localhost:8888/" target="_blank">http://localhost:8888</a>
+
+Now let's upload the docker image to your private image repository in Google Cloud Registry (`gcr.io`).
+
+1. Store the GCP project name in an environment variable
+```shell
+export GCP_PROJECT=<your-project-name>
+```
+
+2. Rebuild the docker image with an image name that includes `gcr.io` project prefix.
+```shell
+docker build -t "gcr.io/${GCP_PROJECT}/py-web-server:v1" .
+```
+
+3. Push the image to `gcr.io`
+```shell
+gcloud docker push -- gcr.io/${GCP_PROJECT}/py-web-server:v1
+```
+
+The image is now private and people with access to `$GCP_PROJECT` used above can only access it. 
+
+Now, let's make the image accessible to everyone.
+Google Container Registry stores its images on Google Cloud storage.
+Let's update the permissions on Google Cloud Storage to make our image repository publically accessible.
+
+```shell
+gsutil defacl ch -u AllUsers:R gs://artifacts.${GCP_PROJECT}.appspot.com
+gsutil acl ch -r -u AllUsers:R gs://artifacts.${GCP_PROJECT}.appspot.com
+gsutil acl ch -u AllUsers:R gs://artifacts.${GCP_PROJECT}.appspot.com
+```
+
+The docker image can now be executed from any machine by running the following command
+```shell
+docker run -d -p 8888:8888 -h my-web-server gcr.io/${GCP_PROJECT}/py-web-server:v1
+```
+
+Detailed Dockerfile reference is available [here](https://docs.docker.com/engine/reference/builder/).

web-server.py

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+
+import tornado.ioloop
+import tornado.web
+import socket
+
+class MainHandler(tornado.web.RequestHandler):
+    def get(self):
+        self.write("Hostname: " + socket.gethostname())
+
+def make_app():
+    return tornado.web.Application([
+        (r"/", MainHandler),
+    ])
+
+if __name__ == "__main__":
+    app = make_app()
+    app.listen(8888)
+    tornado.ioloop.IOLoop.current().start()