nerve/examples/senses/nerve-health.ts

/**
 * nerve-health — built-in sense that reports daemon health via IPC.
 *
 * When running inside a sense worker, this compute function sends a
 * "health-request" to the parent kernel process and merges the response into state.
 *
 * Usage in nerve.yaml:
 *   senses:
 *     nerve-health:
 *       group: internal
 *       throttle: 30s
 *       timeout: 5s
 *       interval: 30s
 */

export type NerveHealth = {
  uptime: number;
  activeSenses: string[];
  inFlightCount: number;
  workerMemoryUsage: NodeJS.MemoryUsage;
  workerUptime: number;
};

type HealthState = {
  lastCheck: number | null;
  lastHealth: NerveHealth | null;
};

export const initialState: HealthState = { lastCheck: null, lastHealth: null };

export async function compute(_state: HealthState): Promise<{
  state: HealthState;
  workflow: null;
}> {
  void _state;
  const health = await requestHealthFromKernel();
  return {
    state: { lastCheck: Date.now(), lastHealth: health },
    workflow: null,
  };
}

function requestHealthFromKernel(): Promise<NerveHealth> {
  return new Promise((resolve, reject) => {
    if (!process.send) {
      reject(new Error("nerve-health: not running as a child process with IPC"));
      return;
    }

    const timeout = setTimeout(() => {
      process.removeListener("message", onMessage);
      reject(new Error("nerve-health: health-request timed out"));
    }, 5000);

    function onMessage(msg: unknown): void {
      if (
        msg !== null &&
        typeof msg === "object" &&
        (msg as Record<string, unknown>).type === "health-response"
      ) {
        clearTimeout(timeout);
        process.removeListener("message", onMessage);
        const resp = msg as {
          senses: string[];
          inFlightCount: number;
        };
        resolve({
          uptime: process.uptime(),
          activeSenses: resp.senses,
          inFlightCount: resp.inFlightCount,
          workerMemoryUsage: process.memoryUsage(),
          workerUptime: process.uptime(),
        });
      }
    }

    process.on("message", onMessage);
    process.send({ type: "health-request" });
  });
}