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AssemblyScript for Istio 1.8

An example of deploying Wasm using Istio 1.8.

Diagram

Build

To compile the AssemblyScript into build/untouched.wasm:

npm install
npm run asbuild:untouched

Deploy

First, deploy a pod. This example uses an httpbin pod, with special annotations to mount WASM files from a ConfigMap into the sidecar.

kubectl apply -f deploy/httpbin.yaml

To deploy the Wasm compiled above onto that httpbin pod:

./deploy/update-wasm.sh

Test

Execute

kubectl exec -ti deploy/httpbin -c istio-proxy -- curl -v http://httpbin.default:8000/status/418

When this is working -- it currently isn't -- we want to see the status 418 and the body from http://example.com.

Troubleshooting

  • Ignore WARNING AS201: Conversion from type 'usize' to 'u32' will require an explicit cast; this is some problem with the Solo.io runtime.
  • Use istioctl pc log <pod> --level wasm:debug to turn on debug logging.
    • Turn it off with istioctl pc log <pod> --level wasm:warning
  • Use istioctl proxy-status and verify httpbin isn't STALE.
  • Verify the mount worked using kubectl exec deployment/httpbin -c istio-proxy -- ls -l /var/local/wasm
  • Some of the WASM fields in EnvoyFilter are a bit different than in Istio 1.5-1.7. If you are porting old filters try to make them look like the example here.

Learn more

  • The spec for WebAssembly for Proxies is here. This documents vNext, not the 0.2.0 used by this example. There is no documentation for that.
  • This project uses the Solo.io Proxy Runtime to give the ABI an object-based feel.
  • Both the spec and the AssemblyScript runtime docs are written for advanced Envoy extension developers. They lack an explanation of what is going on. See Solo.io Runtime Issue 24 for links to Envoy docs and C++ header files.