Move TCP settlement to systemd worker

tcp_worker.php

@@ -0,0 +1,44 @@
+<?php
+declare(strict_types=1);
+
+require __DIR__ . '/common.php';
+
+const WORKER_IDLE_SLEEP_USEC = 200000;
+
+if (PHP_SAPI !== 'cli') {
+    fwrite(STDERR, "tcp_worker.php must run from CLI\n");
+    exit(1);
+}
+
+$lockFp = fopen('/tmp/car_tcp_worker.lock', 'c');
+if ($lockFp === false) {
+    fwrite(STDERR, "failed to open worker lock\n");
+    exit(1);
+}
+
+if (!flock($lockFp, LOCK_EX | LOCK_NB)) {
+    fwrite(STDERR, "worker already running\n");
+    exit(0);
+}
+
+register_shutdown_function(static function () use ($lockFp): void {
+    @flock($lockFp, LOCK_UN);
+    @fclose($lockFp);
+});
+
+db_ensure_tcp_queue_schema(db());
+
+while (true) {
+    try {
+        $job = tcp_queue_claim_next(db());
+        if (!$job) {
+            usleep(WORKER_IDLE_SLEEP_USEC);
+            continue;
+        }
+
+        tcp_worker_process_job($job);
+    } catch (Throwable $e) {
+        fwrite(STDERR, date('c') . ' ' . $e->getMessage() . "\n");
+        usleep(1000000);
+    }
+}