Module wasm 

proxy-wasm host (DW-055).

This module implements a proxy-wasm ABI host on top of wasmtime, allowing dwara to run community Kong/Envoy proxy-wasm filters unmodified. The host compiles unconditionally in the OSS build (there are no cargo features for it): dataplane::plugin_dispatch (DW-157) drives it on the live request path for routes that reference plugins.

Architecture

• abi — proxy-wasm ABI constants and header map serialization.
• host — the wasmtime host: engine, linker (ABI imports), plugin module, and per-request instance.

Phase contract (§9.3)

dwara’s request pipeline calls plugin phase callbacks at defined points. Each plugin declares which phase(s) it hooks. The phases relevant to HTTP filters are:

1. request_headers — after route resolution, before authn.
2. request_body — after authn/authz/rate-limit, before upstream.
3. response_headers — after the upstream responds, before masking.
4. response_body — after masking, before compression.

A plugin can short-circuit the request by calling proxy_send_http_response (returns a local response instead of forwarding to the upstream). The host catches this and returns the stored response immediately.

Fuel and epoch preemption (decision 4; §9.3)

Each plugin instance gets a fuel budget (PluginLimits::fuel). wasmtime consumes fuel on every operation; exhaustion traps the plugin, which the host converts to a 500. Memory is capped via wasmtime’s ResourceLimiter. Time caps use epoch interruption.

Done-when

A community Kong/Envoy proxy-wasm filter runs unmodified. The test suite includes a minimal proxy-wasm filter compiled from Rust source that exercises the core ABI surface (header inspection, response short-circuit, body modification).

Re-exports

pub use abi::deserialize_header_map;

pub use abi::serialize_header_map;

pub use abi::ACTION_CONTINUE;

pub use abi::ACTION_END_STREAM;

pub use callout::perform_callout;

pub use callout::CalloutError;

pub use callout::CalloutRequest;

pub use callout::CalloutResponse;

pub use callout::CALLOUT_BODY_CAP_BYTES;

pub use callout::CALLOUT_TIMEOUT_MAX_MS;

pub use callout::CALLOUT_TIMEOUT_MIN_MS;

pub use callout::MAX_CALLOUT_ROUNDS;

pub use host::LocalResponse;

pub use host::PendingCallout;

pub use host::PhaseResult;

pub use host::PluginContext;

pub use host::PluginInstance;

pub use host::PluginLimits;

pub use host::PluginMetric;

pub use host::PluginMetricType;

pub use host::PluginModule;

pub use host::WasmEngine;

pub use lifecycle::LoadError;

pub use lifecycle::LoadedPlugin;

pub use lifecycle::PluginHealth;

pub use lifecycle::PluginLifecycle;

pub use lifecycle::ValidationError;

pub use runner::PhaseOutcome;

pub use runner::PluginInstances;

pub use runner::PluginRunner;

pub use source::resolve_sources;

pub use source::SourceError;

pub use source::SourceResolutions;

pub use source::DEFAULT_CACHE_DIR;

Modules

abi

proxy-wasm ABI constants and types (DW-055).

adapter

The WASM-to-unified-chain adapter (DW-119).

callout

Plugin HTTP callout transport (DW-167, issue #285).

host

proxy-wasm host implementation (DW-055).

lifecycle

Plugin lifecycle (DW-056).

runner

Plugin runner — the integration layer between the proxy pipeline and the proxy-wasm host (DW-055).

source

Registry plugin source resolution (DW-165).