mirror of https://github.com/knative/docs.git
Added Python Example for Knative Eventing (#2299)
* Added Python Knative Eventing Helloworld Example * Update docs/eventing/samples/helloworld/helloworld-python/Dockerfile Co-Authored-By: Matt Moore <mattmoor@vmware.com> * Update docs/eventing/samples/helloworld/helloworld-python/Dockerfile Co-Authored-By: Matt Moore <mattmoor@vmware.com> * Update docs/eventing/samples/helloworld/helloworld-python/README.md Co-Authored-By: Matt Moore <mattmoor@vmware.com> * Apply suggestions from code review Co-Authored-By: Matt Moore <mattmoor@vmware.com> Co-authored-by: Matt Moore <mattmoor@vmware.com>
This commit is contained in:
Alejandro Saucedo
GitHub
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0b86a4a7e0
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FROM python:alpine3.7
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COPY . /app
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WORKDIR /app
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RUN pip install -r requirements.txt
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EXPOSE 8080
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ENTRYPOINT [ "python" ]
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CMD [ "helloworld.py" ]
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A simple web app written in Python that you can use to test knative eventing. It shows how to consume a [CloudEvent](https://cloudevents.io/) in Knative eventing, and optionally how to respond back with another CloudEvent in the http response, by adding the Cloud Eventing headers outlined in the Cloud Events standard definition.
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We will deploy the app as a [Kubernetes Deployment](https://kubernetes.io/docs/concepts/workloads/controllers/deployment/) along with a [Kubernetes Service](https://kubernetes.io/docs/concepts/services-networking/service/).
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However, you can also deploy the app as a [Knative Serving Service](../../../../serving/README.md).
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Follow the steps below to create the sample code and then deploy the app to your
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cluster. You can also download a working copy of the sample, by running the
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following commands:
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```shell
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# Clone the relevant branch version such as "release-0.13"
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git clone -b "{{< branch >}}" https://github.com/knative/docs knative-docs
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cd knative-docs/docs/eventing/samples/helloworld/helloworld-python
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```
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## Before you begin
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- A Kubernetes cluster with [Knative Eventing](../../../getting-started.md#installing-knative-eventing) installed.
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- [Docker](https://www.docker.com) installed and running on your local machine,
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and a Docker Hub account configured (we'll use it for a container registry).
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## Recreating the sample code
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1. Create a new file named `helloworld.py` and paste the following code. This
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code creates a basic web server which listens on port 8080:
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```python
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from flask import Flask, request, make_response
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import uuid
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app = Flask(__name__)
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@app.route('/', methods=['POST'])
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def hello_world():
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app.logger.warning(request.data)
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# Respond with another event (optional)
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response = make_response({
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"msg": "Hi from helloworld-python app!"
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})
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response.headers["Ce-Id"] = str(uuid.uuid4())
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response.headers["Ce-specversion"] = "0.3"
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response.headers["Ce-Source"] = "knative/eventing/samples/hello-world"
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response.headers["Ce-Type"] = "dev.knative.samples.hifromknative"
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return response
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if __name__ == '__main__':
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app.run(debug=True, host='0.0.0.0', port=8080)
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```
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1. Add a requirements.txt file containing the following contents:
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```bash
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Flask==1.1.1
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```
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1. In your project directory, create a file named `Dockerfile` and copy the code
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block below into it. For detailed instructions on dockerizing a Go app, see
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[Deploying Go servers with Docker](https://blog.golang.org/docker).
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```docker
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FROM python:alpine3.7
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COPY . /app
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WORKDIR /app
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RUN pip install -r requirements.txt
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EXPOSE 8080
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ENTRYPOINT [ "python" ]
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CMD [ "helloworld.py" ]
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```
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1. Create a new file, `sample-app.yaml` and copy the following service definition
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into the file. Make sure to replace `{username}` with your Docker Hub
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username.
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```yaml
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# Namespace for sample application with eventing enabled
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apiVersion: v1
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kind: Namespace
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metadata:
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name: knative-samples
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labels:
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knative-eventing-injection: enabled
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---
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# Helloworld-python app deploment
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apiVersion: apps/v1
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kind: Deployment
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metadata:
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name: helloworld-python
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namespace: knative-samples
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spec:
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replicas: 1
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selector:
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matchLabels: &labels
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app: helloworld-python
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template:
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metadata:
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labels: *labels
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spec:
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containers:
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- name: helloworld-python
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image: docker.io/{username}/helloworld-python
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imagePullPolicy: IfNotPresent
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---
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# Service that exposes helloworld-python app.
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# This will be the subscriber for the Trigger
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kind: Service
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apiVersion: v1
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metadata:
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name: helloworld-python
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namespace: knative-samples
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spec:
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selector:
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app: helloworld-python
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ports:
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- protocol: TCP
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port: 80
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targetPort: 8080
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---
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# Knative Eventing Trigger to trigger the helloworld-python service
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apiVersion: eventing.knative.dev/v1alpha1
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kind: Trigger
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metadata:
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name: helloworld-python
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namespace: knative-samples
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spec:
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broker: default
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filter:
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attributes:
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type: dev.knative.samples.helloworld
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source: dev.knative.samples/helloworldsource
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subscriber:
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ref:
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apiVersion: v1
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kind: Service
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name: helloworld-python
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```
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## Building and deploying the sample
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Once you have recreated the sample code files (or used the files in the sample
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folder) you're ready to build and deploy the sample app.
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1. Use Docker to build the sample code into a container. To build and push with
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Docker Hub, run these commands replacing `{username}` with your Docker Hub
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username:
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```shell
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# Build the container on your local machine
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docker build -t {username}/helloworld-python .
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# Push the container to docker registry
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docker push {username}/helloworld-python
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```
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1. After the build has completed and the container is pushed to docker hub, you
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can deploy the sample application into your cluster. Ensure that the container image value
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in `sample-app.yaml` matches the container you built in the previous step. Apply
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the configuration using `kubectl`:
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```shell
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kubectl apply --filename sample-app.yaml
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```
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1. Above command created a namespace `knative-samples` and labelled it with `knative-eventing-injection=enabled`, to enable eventing in the namespace. Verify using the following command:
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```shell
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kubectl get ns knative-samples --show-labels
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```
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1. It deployed the helloworld-python app as a K8s Deployment and created a K8s service names helloworld-python. Verify using the following command.
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```shell
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kubectl --namespace knative-samples get deployments helloworld-python
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kubectl --namespace knative-samples get svc helloworld-python
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```
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1. It created a Knative Eventing Trigger to route certain events to the helloworld-python application. Make sure that Ready=true
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```shell
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kubectl --namespace knative-samples get trigger helloworld-python
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```
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## Send and verify CloudEvents
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Once you have deployed the application and verified that the namespace, sample application and trigger are ready, let's send a CloudEvent.
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### Send CloudEvent to the Broker
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We can send an http request directly to the [Broker](../../../broker-trigger.md) with correct CloudEvent headers set.
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1. Deploy a curl pod and SSH into it
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```shell
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kubectl --namespace knative-samples run curl --image=radial/busyboxplus:curl -it
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```
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1. Run the following in the SSH terminal
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```shell
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curl -v "default-broker.knative-samples.svc.cluster.local" \
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-X POST \
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-H "Ce-Id: 536808d3-88be-4077-9d7a-a3f162705f79" \
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-H "Ce-specversion: 0.3" \
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-H "Ce-Type: dev.knative.samples.helloworld" \
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-H "Ce-Source: dev.knative.samples/helloworldsource" \
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-H "Content-Type: application/json" \
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-d '{"msg":"Hello World from the curl pod."}'
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exit
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```
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### Verify that event is received by helloworld-python app
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Helloworld-python app logs the context and the msg of the above event, and replies back with another event.
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1. Display helloworld-python app logs
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```shell
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kubectl --namespace knative-samples logs -l app=helloworld-python --tail=50
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```
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You should see something similar to:
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```shell
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Event received. Context: Context Attributes,
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specversion: 0.3
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type: dev.knative.samples.helloworld
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source: dev.knative.samples/helloworldsource
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id: 536808d3-88be-4077-9d7a-a3f162705f79
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time: 2019-10-04T22:35:26.05871736Z
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datacontenttype: application/json
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Extensions,
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knativearrivaltime: 2019-10-04T22:35:26Z
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knativehistory: default-kn2-trigger-kn-channel.knative-samples.svc.cluster.local
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traceparent: 00-971d4644229653483d38c46e92a959c7-92c66312e4bb39be-00
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Hello World Message "Hello World from the curl pod."
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Responded with event Validation: valid
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Context Attributes,
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specversion: 0.2
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type: dev.knative.samples.hifromknative
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source: knative/eventing/samples/hello-world
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id: 37458d77-01f5-411e-a243-a459bbf79682
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Data,
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{"msg":"Hi from Knative!"}
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```
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Play around with the CloudEvent attributes in the curl command and the trigger specification to understand how [Triggers work](../../../broker-trigger.md#trigger).
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## Verify reply from helloworld-python app
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`helloworld-python` app replies back with an event of `type= dev.knative.samples.hifromknative`, and `source=knative/eventing/samples/hello-world`. This event enters the eventing mesh via the Broker and can be delivered to other services using a Trigger
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1. Deploy a pod that receives any CloudEvent and logs the event to its output.
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```shell
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kubectl --namespace knative-samples apply --filename - << END
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# event-display app deploment
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apiVersion: apps/v1
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kind: Deployment
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metadata:
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name: event-display
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namespace: knative-samples
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spec:
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replicas: 1
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selector:
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matchLabels: &labels
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app: event-display
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template:
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metadata:
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labels: *labels
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spec:
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containers:
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- name: helloworld-python
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image: gcr.io/knative-releases/github.com/knative/eventing-sources/cmd/event_display
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---
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# Service that exposes event-display app.
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# This will be the subscriber for the Trigger
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kind: Service
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apiVersion: v1
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metadata:
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name: event-display
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namespace: knative-samples
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spec:
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selector:
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app: event-display
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ports:
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- protocol: TCP
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port: 80
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targetPort: 8080
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END
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```
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1. Create a trigger to deliver the event to the above service
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```shell
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kubectl --namespace knative-samples apply --filename - << END
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apiVersion: eventing.knative.dev/v1alpha1
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kind: Trigger
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metadata:
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name: event-display
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namespace: knative-samples
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spec:
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broker: default
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filter:
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attributes:
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type: dev.knative.samples.hifromknative
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source: knative/eventing/samples/hello-world
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subscriber:
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ref:
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apiVersion: v1
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kind: Service
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name: event-display
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END
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```
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1. [Send a CloudEvent to the Broker](###Send-CloudEvent-to-the-Broker)
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1. Check the logs of event-display service
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```shell
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kubectl --namespace knative-samples logs -l app=event-display --tail=50
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```
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You should see something similar to:
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```shell
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cloudevents.Event
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Validation: valid
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Context Attributes,
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specversion: 0.3
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type: dev.knative.samples.hifromknative
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source: knative/eventing/samples/hello-world
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id: 8a7384b9-8bbe-4634-bf0f-ead07e450b2a
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time: 2019-10-04T22:53:39.844943931Z
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datacontenttype: application/json
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Extensions,
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knativearrivaltime: 2019-10-04T22:53:39Z
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knativehistory: default-kn2-ingress-kn-channel.knative-samples.svc.cluster.local
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traceparent: 00-4b01db030b9ea04bb150b77c8fa86509-2740816590a7604f-00
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Data,
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{
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"msg": "Hi from helloworld- app!"
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}
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```
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**Note: You could use the above approach to test your applications too.**
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## Removing the sample app deployment
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To remove the sample app from your cluster, delete the service record:
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```shell
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kubectl delete --filename sample-app.yaml
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```
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---
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title: "Hello World - Python"
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linkTitle: "Python"
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weight: 20
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type: "docs"
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---
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{{% readfile file="README.md" %}}
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from flask import Flask, request, make_response
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import uuid
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app = Flask(__name__)
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@app.route('/', methods=['POST'])
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def hello_world():
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app.logger.warning(request.data)
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# Respond with another event (optional)
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response = make_response({
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"msg": "Hi from helloworld-python app!"
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})
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response.headers["Ce-Id"] = str(uuid.uuid4())
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response.headers["Ce-specversion"] = "0.3"
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response.headers["Ce-Source"] = "knative/eventing/samples/hello-world"
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response.headers["Ce-Type"] = "dev.knative.samples.hifromknative"
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return response
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if __name__ == '__main__':
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app.run(debug=True, host='0.0.0.0', port=8080)
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Flask==1.1.1
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# Namespace for sample application with eventing enabled
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apiVersion: v1
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kind: Namespace
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metadata:
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name: knative-samples
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labels:
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knative-eventing-injection: enabled
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---
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# Helloworld-go app deploment
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apiVersion: apps/v1
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kind: Deployment
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metadata:
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name: helloworld-python
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namespace: knative-samples
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spec:
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replicas: 1
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selector:
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matchLabels: &labels
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app: helloworld-python
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template:
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metadata:
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labels: *labels
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spec:
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containers:
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- name: helloworld-python
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image: docker.io/axsauze/helloworld-python
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imagePullPolicy: IfNotPresent
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---
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# Service that exposes helloworld-go app.
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# This will be the subscriber for the Trigger
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kind: Service
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apiVersion: v1
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metadata:
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name: helloworld-python
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namespace: knative-samples
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spec:
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selector:
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app: helloworld-python
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ports:
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- protocol: TCP
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port: 80
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targetPort: 8080
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---
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# Knative Eventing Trigger to trigger the helloworld-go service
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apiVersion: eventing.knative.dev/v1alpha1
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kind: Trigger
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metadata:
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name: helloworld-python
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namespace: knative-samples
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spec:
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broker: default
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filter:
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attributes:
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type: dev.knative.samples.helloworld
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source: dev.knative.samples/helloworldsource
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subscriber:
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ref:
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apiVersion: v1
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kind: Service
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name: helloworld-python
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