switched rover <-> server streams to rtsptcp, and moved mediamtx to be a server owned and configured child process!

server/src/services/mediaMtxService/supervisor.js

@@ -0,0 +1,103 @@
+// MediaMTX Child Supervisor
+// Purpose: Writes the generated runtime configuration and owns the MediaMTX child process lifecycle.
+// Scope: Starts exactly one child, forwards its logs, and lets systemd restart the coherent server/media pair.
+const fs = require('fs');
+const path = require('path');
+const { spawn } = require('child_process');
+const yaml = require('js-yaml');
+const { buildMediaMtxConfig } = require('./config');
+
+function createMediaMtxSupervisor(deps) {
+  const {
+    config,
+    serverPort,
+    logger,
+    mediaMtxBin = process.env.MEDIAMTX_BIN || '/usr/local/bin/mediamtx',
+    runtimeDir = process.env.MULTIROVER_RUNTIME_DIR || '/run/multirover',
+    snapshotWriterPath = process.env.ROVER_SNAPSHOT_WRITER_BIN || '/usr/local/bin/rover-snapshot-writer.sh',
+    spawnProcess = spawn,
+  } = deps;
+
+  let child = null;
+  let stopping = false;
+  let stoppedCallback = null;
+
+  function forwardLines(stream, level) {
+    let pending = '';
+    stream.setEncoding('utf8');
+    stream.on('data', (chunk) => {
+      pending += chunk;
+      const lines = pending.split(/\r?\n/);
+      pending = lines.pop() || '';
+      lines.filter(Boolean).forEach((line) => logger[level](line));
+    });
+    stream.on('end', () => {
+      if (pending) logger[level](pending);
+    });
+  }
+
+  function start() {
+    if (child) return child;
+
+    const runtimeConfig = buildMediaMtxConfig({ config, serverPort, snapshotWriterPath });
+    const configPath = path.join(runtimeDir, 'mediamtx.yml');
+    fs.mkdirSync(runtimeDir, { recursive: true, mode: 0o750 });
+    fs.writeFileSync(configPath, yaml.dump(runtimeConfig, { noRefs: true, lineWidth: 120 }), { mode: 0o640 });
+
+    logger.info(`Starting MediaMTX with generated config ${configPath}`);
+    child = spawnProcess(mediaMtxBin, [configPath], {
+      stdio: ['ignore', 'pipe', 'pipe'],
+    });
+
+    forwardLines(child.stdout, 'info');
+    forwardLines(child.stderr, 'warn');
+
+    child.once('error', (err) => {
+      logger.error('Unable to start MediaMTX', err);
+      if (!stopping) {
+        /*
+          A spawn failure does not reliably emit the normal exit event on every platform.
+          Fail the parent here as well so the server can never stay nominally online without
+          its required media child and systemd gets the opportunity to repair the launch.
+        */
+        process.exit(1);
+      }
+    });
+    child.once('exit', (code, signal) => {
+      child = null;
+      if (stopping) {
+        stoppedCallback?.();
+        stoppedCallback = null;
+        return;
+      }
+
+      /*
+        MediaMTX is required for every live media path. Exiting the parent is intentionally
+        simpler and safer than maintaining a second retry policy inside Node: systemd already
+        restarts multirover.service, producing one clean server/MediaMTX lifecycle.
+      */
+      logger.error(`MediaMTX exited unexpectedly (code=${code ?? 'none'} signal=${signal || 'none'})`);
+      process.exit(1);
+    });
+    return child;
+  }
+
+  function stop(onStopped) {
+    stopping = true;
+    stoppedCallback = typeof onStopped === 'function' ? onStopped : null;
+    if (!child) {
+      stoppedCallback?.();
+      stoppedCallback = null;
+      return;
+    }
+    try {
+      child.kill('SIGTERM');
+    } catch (err) {
+      logger.warn('Unable to stop MediaMTX cleanly', err);
+    }
+  }
+
+  return { start, stop };
+}
+
+module.exports = { createMediaMtxSupervisor };