fix(#707): scope session GC retention

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

@@ -1,4 +1,4 @@
-import { Inject, Injectable, Logger, type OnModuleInit } from '@nestjs/common';
+import { Inject, Injectable } from '@nestjs/common';
 import type { QueueHandle } from '@mosaicstack/queue';
 import type { LogService } from '@mosaicstack/log';
 import { LOG_SERVICE } from '../log/log.tokens.js';
@@ -13,49 +13,13 @@ export interface GCResult {
   };
 }
 
-export interface GCSweepResult {
-  orphanedSessions: number;
-  totalCleaned: GCResult[];
-  duration: number;
-}
-
-export interface FullGCResult {
-  valkeyKeys: number;
-  logsDemoted: number;
-  jobsPurged: number;
-  tempFilesRemoved: number;
-  duration: number;
-}
-
 @Injectable()
-export class SessionGCService implements OnModuleInit {
-  private readonly logger = new Logger(SessionGCService.name);
-
+export class SessionGCService {
   constructor(
     @Inject(REDIS) private readonly redis: QueueHandle['redis'],
     @Inject(LOG_SERVICE) private readonly logService: LogService,
   ) {}
 
-  onModuleInit(): void {
-    // 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
-    // the TTFB of the first HTTP request.
-    this.fullCollect()
-      .then((result) => {
-        this.logger.log(
-          `Full GC complete: ${result.valkeyKeys} Valkey keys, ` +
-            `${result.logsDemoted} logs demoted, ` +
-            `${result.jobsPurged} jobs purged, ` +
-            `${result.tempFilesRemoved} temp dirs removed ` +
-            `(${result.duration}ms)`,
-        );
-      })
-      .catch((err: unknown) => {
-        this.logger.error('Cold-start GC failed', err instanceof Error ? err.stack : String(err));
-      });
-  }
-
   /**
    * 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
@@ -86,79 +50,13 @@ export class SessionGCService implements OnModuleInit {
       result.cleaned.valkeyKeys = valkeyKeys.length;
     }
 
-    // 2. PG: demote hot-tier agent_logs for this session to warm
-    const cutoff = new Date(); // demote all hot logs for this session
-    const logsDemoted = await this.logService.logs.promoteToWarm(cutoff);
+    // 2. PG: demote hot-tier agent logs for this session only.
+    const cutoff = new Date();
+    const logsDemoted = await this.logService.logs.promoteSessionToWarm(sessionId, cutoff);
     if (logsDemoted > 0) {
       result.cleaned.logsDemoted = logsDemoted;
     }
 
     return result;
   }
-
-  /**
-   * Sweep GC — find orphaned artifacts from dead sessions.
-   * System-wide operation: only call from admin-authorized paths or internal
-   * scheduled jobs.  Individual session cleanup is handled by collect().
-   */
-  async sweepOrphans(): Promise<GCSweepResult> {
-    const start = Date.now();
-    const cleaned: GCResult[] = [];
-
-    // 1. Find all session-scoped Valkey keys (non-blocking SCAN)
-    const allSessionKeys = await this.scanKeys('mosaic:session:*');
-
-    // Extract unique session IDs from keys
-    const sessionIds = new Set<string>();
-    for (const key of allSessionKeys) {
-      const match = key.match(/^mosaic:session:([^:]+):/);
-      if (match) sessionIds.add(match[1]!);
-    }
-
-    // 2. For each session ID, collect stale keys
-    for (const sessionId of sessionIds) {
-      const gcResult = await this.collect(sessionId);
-      if (Object.keys(gcResult.cleaned).length > 0) {
-        cleaned.push(gcResult);
-      }
-    }
-
-    return {
-      orphanedSessions: cleaned.length,
-      totalCleaned: cleaned,
-      duration: Date.now() - start,
-    };
-  }
-
-  /**
-   * Full GC — aggressive collection for cold start.
-   * Assumes no sessions survived the restart.
-   */
-  async fullCollect(): Promise<FullGCResult> {
-    const start = Date.now();
-
-    // 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);
-    }
-
-    // 2. NOTE: channel keys are NOT collected on cold start
-    //    (discord/telegram plugins may reconnect and resume)
-
-    // 3. PG: demote stale hot-tier logs older than 24h to warm
-    const hotCutoff = new Date(Date.now() - 24 * 60 * 60 * 1000);
-    const logsDemoted = await this.logService.logs.promoteToWarm(hotCutoff);
-
-    // 4. No summarization job purge API available yet
-    const jobsPurged = 0;
-
-    return {
-      valkeyKeys: sessionKeys.length,
-      logsDemoted,
-      jobsPurged,
-      tempFilesRemoved: 0,
-      duration: Date.now() - start,
-    };
-  }
 }