Method loadFromCache

packages/service-worker/worker/src/data.ts:496–528

(
    req: Request,
    lru: LruList,
  )

  }

  private async loadFromCache(
    req: Request,
    lru: LruList,
  ): Promise<{res: Response; age: number} | null> {
    // Look for a response in the cache. If one exists, return it.
    const cache = await this.cache;
    let res = await cache.match(req, this.config.cacheQueryOptions);
    if (res !== undefined) {
      // A response was found in the cache, but its age is not yet known. Look it up.
      try {
        const ageTable = await this.ageTable;
        const age = this.adapter.time - (await ageTable.read<AgeRecord>(req.url)).age;
        // If the response is young enough, use it.
        if (age <= this.config.maxAge) {
          // Successful match from the cache. Use the response, after marking it as having
          // been accessed.
          lru.accessed(req.url);
          return {res, age};
        }

        // Otherwise, or if there was an error, assume the response is expired, and evict it.
      } catch {
        // Some error getting the age for the response. Assume it's expired.
      }

      lru.remove(req.url);
      await this.clearCacheForUrl(req.url);

      // TODO: avoid duplicate in event of network timeout, maybe.
      await this.syncLru();
    }
    return null;
  }

  /**
   * Operation for caching the response from the server. This has to happen all