yams/examples/plugins/wasm/dr

DR WASM Plugin Example (Prototype)

This folder contains a minimal example of a WASM-based DR plugin that the YAMS WASM host can load.

Goals:

• Provide a tiny module that exports required functions so the host can scan and load it.
• Demonstrate a simple readiness call returning JSON.

Exports required by the current host prototype:

• memory: linear memory (default export) for passing buffers.
• alloc(size: i32) -> i32: guest allocator to request a region to copy inputs.
• dr_provider_v1_is_replication_ready(key_ptr: i32, key_len: i32, opts_ptr: i32, opts_len: i32) -> i64:
  • Returns a packed pointer+length: (ptr << 32) | len, where ptr points into guest memory and len is number of bytes.
  • The host copies that JSON payload out of guest memory.

Manifest sidecar (required): place a JSON file next to the module with suffix .manifest.json.

Example plugin.wasm.manifest.json:

{
  "name": "dr_wasm",
  "version": "0.1.0",
  "interfaces": ["dr_provider_v1"]
}

Build (Python + WAT, requires wat2wasm in PATH):

python3 build_wasm.py

This produces plugin.wasm and plugin.wasm.manifest.json.

Test harness (ctest):

export TEST_WASM_PLUGIN_FILE=$(pwd)/plugin.wasm
ctest -R wasm_plugin_harness_test --output-on-failure

Notes:

• This example is intentionally minimal and returns a static readiness result. Extend it to parse inputs and compute real status.
• The YAMS WASM host currently disables ambient WASI by default; add hostcalls as needed in future iterations.