Fix liveness probe when no connections are defined (#401)

* Fix liveness probe when no connections are defined.

* Add changeset.

Author: rkistner

.changeset/orange-forks-eat.md

@@ -0,0 +1,5 @@
+---
+'@powersync/service-core': patch
+---
+
+Fix liveness probe when no connections are defined.

packages/service-core/src/replication/ReplicationEngine.ts

@@ -1,9 +1,10 @@
-import { logger } from '@powersync/lib-services-framework';
+import { container, logger } from '@powersync/lib-services-framework';
 import { AbstractReplicator } from './AbstractReplicator.js';
 import { ConnectionTestResult } from './ReplicationModule.js';
 
 export class ReplicationEngine {
   private readonly replicators: Map<string, AbstractReplicator> = new Map();
+  private probeInterval: NodeJS.Timeout | null = null;
 
   /**
    *  Register a Replicator with the engine
@@ -27,6 +28,17 @@ export class ReplicationEngine {
       logger.info(`Starting Replicator: ${replicator.id}`);
       replicator.start();
     }
+    if (this.replicators.size == 0) {
+      // If a replicator is running, the replicators update the probes.
+      // If no connections are configured, then no replicator is running
+      // Typical when no connections are configured.
+      // In this case, update the probe here to avoid liveness probe failures.
+      this.probeInterval = setInterval(() => {
+        container.probes.touch().catch((e) => {
+          logger.error(`Failed to touch probe`, e);
+        });
+      }, 5_000);
+    }
     logger.info('Successfully started Replication Engine.');
   }
 
@@ -39,6 +51,9 @@ export class ReplicationEngine {
       logger.info(`Stopping Replicator: ${replicator.id}`);
       await replicator.stop();
     }
+    if (this.probeInterval) {
+      clearInterval(this.probeInterval);
+    }
     logger.info('Successfully shut down Replication Engine.');
   }