Use a singleton for model cache

1 files changed, 54 insertions, 0 deletions

diff --git a/server/models/model-cache.ts b/server/models/model-cache.ts
new file mode 100644
index 000000000..bfa163b6b
--- /dev/null
+++ b/server/models/model-cache.ts
@@ -0,0 +1,54 @@
+import { Model } from 'sequelize-typescript'
+import * as Bluebird from 'bluebird'
+import { logger } from '@server/helpers/logger'
+
+type ModelCacheType =
+  'local-account-name'
+  | 'local-actor-name'
+  | 'local-actor-url'
+
+class ModelCache {
+
+  private static instance: ModelCache
+
+  private readonly localCache: { [id in ModelCacheType]: Map<string, any> } = {
+    'local-account-name': new Map(),
+    'local-actor-name': new Map(),
+    'local-actor-url': new Map()
+  }
+
+  private constructor () {
+  }
+
+  static get Instance () {
+    return this.instance || (this.instance = new this())
+  }
+
+  doCache<T extends Model> (options: {
+    cacheType: ModelCacheType
+    key: string
+    fun: () => Bluebird<T>
+    whitelist?: () => boolean
+  }) {
+    const { cacheType, key, fun, whitelist } = options
+
+    if (whitelist && whitelist() !== true) return fun()
+
+    const cache = this.localCache[cacheType]
+
+    if (cache.has(key)) {
+      logger.debug('Model cache hit for %s -> %s.', cacheType, key)
+      return Bluebird.resolve<T>(cache.get(key))
+    }
+
+    return fun().then(m => {
+      if (!whitelist || whitelist()) cache.set(key, m)
+
+      return m
+    })
+  }
+}
+
+export {
+  ModelCache
+}