Skip to main content
Version: 1.x

RPC

wasmCloud uses the ByteCode Alliance hosted project wRPC for all distributed communication between components and capability providers. wasmCloud was the first reference implementation for wRPC, and was designed to make distributed communication between components to feel exactly like composing components.

Components (via the wasmCloud host) and capability providers subscribe on NATS subjects to serve all exports as defined in their WIT interface. The subject is of the following form:

console
{lattice}.{component_id}.wrpc.{protocol_version}.{namespace}:{package}/{interface}@{version}.{function}

For example, the subject is as follows when invoking the HTTP hello world component in our quickstart:

console
default.http-hello-world.wrpc.0.0.1.wasi:http/incoming-handler@0.2.0.handle

Headers​

In order to determine the source, target and link name of an invocation, wasmCloud includes the following headers on every wRPC invocation:

console
source: <source_id>
target: <target>
link_name: <link_name>

Debugging​

You can subscribe to all traffic sent over wRPC using the following subscription:

bash
nats sub "*.*.wrpc.>"

References​

See the 0.82 RPC Documentation for information about the no-longer-supported wasmbus RPC protocol.