Module echo_plugin 

可运行示例 echo_plugin 的说明（cargo run --example echo_plugin）。

echo-plugin

A complete, runnable Flare capability plugin in about 130 lines.

It does nothing useful on purpose. Its value is that it is complete: declaration, registration, context restoration, JSON encoding, unknown-operation handling and graceful withdraw are all here, and all short enough to read in one sitting.

Every dependency comes from crates.io — no path dependencies — so it builds anywhere, not just inside the Flare multi-repo workspace.

Run it

cargo run

echo-plugin 监听 127.0.0.1:7901，对外通告 127.0.0.1:7901
已向 http://127.0.0.1:50110 声明 2 个 operation

The platform does not have to be running: if it cannot be reached the plugin says so and keeps serving. A plugin that exits because the platform is late starting is a plugin that cannot survive a rolling restart.

Variable	Default	Meaning
ECHO_PLUGIN_LISTEN	127.0.0.1:7901	Where the gRPC server binds
ECHO_PLUGIN_ADVERTISE	same as listen	The address the platform calls back on
CAPABILITY_ENDPOINT	http://127.0.0.1:50110	The platform’s capability service

ADVERTISE is separate from LISTEN because in a container they are rarely the same string, and announcing an address the platform cannot reach fails as a health-check problem rather than a configuration one.

Operations

Operation	Payload	Result
example.echo.say	{"text": "hi"}	echoes the text plus the caller’s tenant/user
example.echo.upper	{"text": "hi"}	echoes it uppercased

example.echo.say returns the tenant and user ids on purpose: it proves the plugin restored the calling context out of request metadata. The platform calls you out of process, so no framework middleware does that for you.

The test that matters

cargo test checks the declaration list against the dispatch arms. Those two drifting apart is the most common plugin bug, and it fails in two directions with completely different symptoms:

• declared but not implemented → the request arrives and you answer UNKNOWN_OPERATION, which looks like the plugin is broken
• implemented but not declared → the platform rejects it and your process never sees it, which looks like a permissions problem

Copy this test into your own plugin.