Class Daemon

src/mcp/daemon.ts:167–483

 * daemons.
 */
export class Daemon {
  private server: net.Server | null = null;
  private clients = new Set<MCPSession>();
  /** Per-client peer pids from the optional client-hello, for the liveness sweep. */
  private clientPeers = new Map<MCPSession, { pid: number | null; hostPid: number | null }>();
  private idleTimer: NodeJS.Timeout | null = null;
  private idleTimeoutMs: number;
  private maxIdleMs: number;
  private lastActivityAt = Date.now();
  private maxIdleTimer: NodeJS.Timeout | null = null;
  private clientSweepTimer: NodeJS.Timeout | null = null;
  private engine: MCPEngine;
  private stopping = false;
  private socketPath: string;
  private pidPath: string;

  constructor(
    private projectRoot: string,
    opts: { idleTimeoutMs?: number; maxIdleMs?: number } = {},
  ) {
    this.socketPath = getDaemonSocketPath(projectRoot);
    this.pidPath = getDaemonPidPath(projectRoot);
    this.idleTimeoutMs = opts.idleTimeoutMs ?? resolveIdleTimeoutMs();
    this.maxIdleMs = opts.maxIdleMs ?? resolveMaxIdleMs();
    // Daemon mode serves many concurrent clients on one event loop, so off-load
    // read-tool dispatch to a worker pool — otherwise concurrent explores
    // serialize and starve the MCP transport (clients time out). Direct mode
    // (one stdio client) leaves the pool off; `CODEGRAPH_QUERY_POOL_SIZE=0`
    // disables it here too.
    this.engine = new MCPEngine({ queryPool: true });
    this.engine.setProjectPathHint(projectRoot);
  }

  /**
   * Bind the socket, kick off engine init, and register signal handlers. The
   * lockfile body was already written atomically by `tryAcquireDaemonLock`, so
   * there is nothing to write here. The promise resolves once the server is
   * listening — the daemon then sticks around until idle/shutdown.
   */
  async start(): Promise<DaemonStartResult> {
    // Engine init is deliberately backgrounded — see #172. The first session
    // to land waits on `ensureInitialized` either way, and unloaded sessions
    // (cross-project tool calls only) shouldn't pay any open cost.
    void this.engine.ensureInitialized(this.projectRoot);

    // Walk the ordered socket candidates and bind the first that works. The
    // in-project path comes first; the deterministic tmpdir path is the fallback
    // for a filesystem that can't host an AF_UNIX node at all (ExFAT/FAT external
    // volumes, some network mounts, WSL2 DrvFs → ENOTSUP/EACCES; #997, #974). The
    // `listen` closure clears a stale socket (left by a SIGKILL'd previous daemon)
    // before each attempt — safe because we hold the lockfile, so no live daemon
    // owns it; without it `listen` would wedge on EADDRINUSE.
    const candidates = getDaemonSocketCandidates(this.projectRoot);
    const listen = (socketPath: string): Promise<net.Server> =>
      new Promise<net.Server>((resolve, reject) => {
        if (process.platform !== 'win32') {
          try { fs.unlinkSync(socketPath); } catch { /* not-exists is fine */ }
        }