Extensibility

    WebAssembly sandbox goals:

    • Efficiency - An extension adds low latency, CPU, and memory overhead.
    • Function - An extension can enforce policy, collect telemetry, and perform payload mutations.
    • Isolation - A programming error or crash in one plugin doesn’t affect other plugins.
    • Operator - An extension can be canaried and deployed as log-only, fail-open or fail-close.
    • Extension developer - The plugin can be written in several programming languages.

    Istio extensions (Proxy-Wasm plugins) have several components:

    • Filter Service Provider Interface (SPI) for building Proxy-Wasm plugins for filters.
    • Sandbox V8 Wasm Runtime embedded in Envoy.
    • Host APIs for headers, trailers and metadata.
    • Call out APIs for gRPC and HTTP calls.

    Extending Istio/Envoy