fix(gateway): disable Redis consumers on local tier (#689)

apps/gateway/src/gc/session-gc.service.ts

@@ -1,4 +1,4 @@
-import { Inject, Injectable, Logger, type OnModuleInit } from '@nestjs/common';
+import { Inject, Injectable, Logger, Optional, type OnModuleInit } from '@nestjs/common';
 import type { QueueHandle } from '@mosaicstack/queue';
 import type { LogService } from '@mosaicstack/log';
 import { LOG_SERVICE } from '../log/log.tokens.js';
@@ -32,11 +32,21 @@ export class SessionGCService implements OnModuleInit {
   private readonly logger = new Logger(SessionGCService.name);
 
   constructor(
-    @Inject(REDIS) private readonly redis: QueueHandle['redis'],
+    // On Local tier there is no Redis — the GC module provides null for this token.
+    // NOTE: if a future feature stores Redis-backed state on Local tier, this guard
+    // would silently skip GC for those keys. Revisit when that happens.
+    @Optional()
+    @Inject(REDIS)
+    private readonly redis: QueueHandle['redis'] | null,
     @Inject(LOG_SERVICE) private readonly logService: LogService,
   ) {}
 
   onModuleInit(): void {
+    if (!this.redis) {
+      // Local tier: no Valkey — skip cold-start GC entirely (correct no-op).
+      this.logger.log('SessionGCService: Valkey GC skipped on local tier (no Redis configured)');
+      return;
+    }
     // Fire-and-forget: run full GC asynchronously so it does not block the
     // NestJS bootstrap chain.  Cold-start GC typically takes 100–500 ms
     // depending on Valkey key count; deferring it removes that latency from
@@ -60,8 +70,10 @@ export class SessionGCService implements OnModuleInit {
    * Scan Valkey for all keys matching a pattern using SCAN (non-blocking).
    * KEYS is avoided because it blocks the Valkey event loop for the full scan
    * duration, which can cause latency spikes under production key volumes.
+   * Returns empty array when Redis is not available (Local tier).
    */
   private async scanKeys(pattern: string): Promise<string[]> {
+    if (!this.redis) return [];
     const collected: string[] = [];
     let cursor = '0';
     do {
@@ -78,12 +90,14 @@ export class SessionGCService implements OnModuleInit {
   async collect(sessionId: string): Promise<GCResult> {
     const result: GCResult = { sessionId, cleaned: {} };
 
-    // 1. Valkey: delete all session-scoped keys
-    const pattern = `mosaic:session:${sessionId}:*`;
-    const valkeyKeys = await this.scanKeys(pattern);
-    if (valkeyKeys.length > 0) {
-      await this.redis.del(...valkeyKeys);
-      result.cleaned.valkeyKeys = valkeyKeys.length;
+    // 1. Valkey: delete all session-scoped keys (skipped on Local tier)
+    if (this.redis) {
+      const pattern = `mosaic:session:${sessionId}:*`;
+      const valkeyKeys = await this.scanKeys(pattern);
+      if (valkeyKeys.length > 0) {
+        await this.redis.del(...valkeyKeys);
+        result.cleaned.valkeyKeys = valkeyKeys.length;
+      }
     }
 
     // 2. PG: demote hot-tier agent_logs for this session to warm
@@ -106,6 +120,7 @@ export class SessionGCService implements OnModuleInit {
     const cleaned: GCResult[] = [];
 
     // 1. Find all session-scoped Valkey keys (non-blocking SCAN)
+    // Returns empty on Local tier — no Valkey session keys exist there.
     const allSessionKeys = await this.scanKeys('mosaic:session:*');
 
     // Extract unique session IDs from keys
@@ -136,11 +151,15 @@ export class SessionGCService implements OnModuleInit {
    */
   async fullCollect(): Promise<FullGCResult> {
     const start = Date.now();
+    let valkeyKeysCount = 0;
 
-    // 1. Valkey: delete ALL session-scoped keys (non-blocking SCAN)
-    const sessionKeys = await this.scanKeys('mosaic:session:*');
-    if (sessionKeys.length > 0) {
-      await this.redis.del(...sessionKeys);
+    if (this.redis) {
+      // 1. Valkey: delete ALL session-scoped keys (non-blocking SCAN)
+      const sessionKeys = await this.scanKeys('mosaic:session:*');
+      if (sessionKeys.length > 0) {
+        await this.redis.del(...sessionKeys);
+      }
+      valkeyKeysCount = sessionKeys.length;
     }
 
     // 2. NOTE: channel keys are NOT collected on cold start
@@ -154,7 +173,7 @@ export class SessionGCService implements OnModuleInit {
     const jobsPurged = 0;
 
     return {
-      valkeyKeys: sessionKeys.length,
+      valkeyKeys: valkeyKeysCount,
       logsDemoted,
       jobsPurged,
       tempFilesRemoved: 0,