Cloud Events - Rust

A simple web app written in Rust using Actix web that can receive CloudEvents. It supports running in two modes:

  1. The default mode has the app reply to your input events with the output event, which is simplest for demonstrating things working in isolation, but is also the model for working for the Knative Eventing Broker concept. The input event is modified assigning a new source and type attribute.

  2. K_SINK mode has the app send events to the destination encoded in $K_SINK, which is useful to demonstrate how folks can synthesize events to send to a Service or Broker when not initiated by a Broker invocation (e.g. implementing an event source). The input event is modified assigning a new source and type attribute.

The application will use $K_SINK-mode whenever the environment variable is specified.

Follow the steps below to create the sample code and then deploy the app to your cluster. You can also download a working copy of the sample by running the following commands:

git clone -b "release-0.19" https://github.com/knative/docs knative-docs
cd knative-docs/docs/serving/samples/cloudevents/cloudevents-rust

Before you begin

  • A Kubernetes cluster with Knative installed and DNS configured. Follow the installation instructions if you need to create one.
  • Docker installed and running on your local machine, and a Docker Hub account configured (we’ll use it for a container registry).
  • This guide uses Rust musl toolchain to build the image in order to create really small docker images. To install the Rust toolchain: rustup. To install musl support: MUSL support for fully static binaries.

Build and deploy the sample

To build the binary, run:

cargo build --target x86_64-unknown-linux-musl --release

This will build a statically linked binary, in order to create an image from scratch. Now build the docker image:

docker build -t <image> .

To deploy the Knative Service, look in the service.yaml and replace <image> with the deployed image name. Then run:

kubectl apply -f service.yaml

If using kn to deploy:

kn service create cloudevents-rust --image=<image>

Testing the sample

Get the URL for your Service with:

$ kubectl get ksvc
NAME                URL                                            LATESTCREATED             LATESTREADY               READY   REASON
cloudevents-rust    http://cloudevents-rust.xip.io                 cloudevents-rust-vl8fq    cloudevents-rust-vl8fq    True

Then send a CloudEvent to it with:

$ curl \
    -X POST -v \
    -H "content-type: application/json"  \
    -H "ce-specversion: 1.0"  \
    -H "ce-source: http://curl-command"  \
    -H "ce-type: curl.demo"  \
    -H "ce-id: 123-abc"  \
    -d '{"name":"Dave"}' \
    http://cloudevents-rust.xip.io

You can also send CloudEvents spawning a temporary curl pod in your cluster with:

$ kubectl run curl \
    --image=curlimages/curl --rm=true --restart=Never -ti -- \
    -X POST -v \
    -H "content-type: application/json"  \
    -H "ce-specversion: 1.0"  \
    -H "ce-source: http://curl-command"  \
    -H "ce-type: curl.demo"  \
    -H "ce-id: 123-abc"  \
    -d '{"name":"Dave"}' \
    http://cloudevents-rust.default.svc

You’ll get as result:

> POST / HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.69.1
> Accept: */*
> content-type: application/json
> ce-specversion: 1.0
> ce-source: http://curl-command
> ce-type: curl.demo
> ce-id: 123-abc
> Content-Length: 15
>
< HTTP/1.1 200 OK
< content-length: 15
< content-type: application/json
< ce-specversion: 1.0
< ce-id: 123-abc
< ce-type: dev.knative.docs.sample
< ce-source: https://github.com/knative/docs/docs/serving/samples/cloudevents/cloudevents-rust
< date: Sat, 23 May 2020 09:00:01 GMT
<
{"name":"Dave"}

Removing the sample app deployment

To remove the sample app from your cluster, delete the service.

Run:

kubectl delete --filename service.yaml

Run:

kn service delete cloudevents-rust