优化数据库读写

tests/cache.test.mjs

@@ -83,16 +83,35 @@ const silentLogger = { warn() {} };
   await cache.invalidate('results');
   assert.deepEqual(await cache.remember('results', 'candidate:1', loadResults), { version: 3 });
   assert.equal(resultLoads, 3, '后台手动刷新后应重新生成成绩缓存');
+
+  client.isReady = false;
+  let fallbackLoads = 0;
+  assert.equal(await cache.remember('public', 'runtime-fallback', async () => ++fallbackLoads), 1);
+  assert.equal(await cache.remember('public', 'runtime-fallback', async () => ++fallbackLoads), 1);
+  assert.equal(fallbackLoads, 1, 'Redis 运行中断开后，相同热点读取应由本机缓存合并');
+  client.isReady = true;
   await cache.close();
 }
 
 {
   const cache = await createRedisCache({ env: {}, logger: silentLogger });
   let loads = 0;
-  await cache.remember('public', 'home', async () => ++loads);
-  await cache.remember('public', 'home', async () => ++loads);
-  assert.equal(loads, 2, '未配置 Redis 时应始终回源');
+  assert.equal(await cache.remember('public', 'home', async () => ++loads), 1);
+  assert.equal(await cache.remember('public', 'home', async () => ++loads), 1);
+  assert.equal(loads, 1, '未配置 Redis 时应使用有界本机缓存，避免重复回源');
+  await cache.invalidate('public');
+  assert.equal(await cache.remember('public', 'home', async () => ++loads), 2);
+  assert.equal(loads, 2, '本机缓存应在数据库写入后立即失效');
   assert.equal(cache.status, 'disabled');
+
+  let releaseOld;
+  const oldLoad = cache.remember('public', 'race', () => new Promise(resolve => { releaseOld = () => resolve('old'); }));
+  await cache.invalidate('public');
+  const newLoad = cache.remember('public', 'race', async () => 'new');
+  releaseOld();
+  assert.equal(await oldLoad, 'old');
+  assert.equal(await newLoad, 'new', '失效后不得等待失效前仍在运行的加载');
+  assert.equal(await cache.remember('public', 'race', async () => 'unexpected'), 'new', '旧加载完成后不得覆盖新缓存');
 }
 
 {
@@ -104,6 +123,7 @@ const silentLogger = { warn() {} };
   });
   assert.equal(cache.status, 'unavailable');
   assert.equal(await cache.remember('public', 'home', async () => 'database'), 'database');
+  assert.equal(await cache.remember('public', 'home', async () => 'unexpected'), 'database', 'Redis 故障时本机缓存应继续承接重复读取');
 }
 
 console.log('Redis 缓存测试通过');