Adds schema caching capabilities (5s by default) (#2286)

* Adds schema caching capabilities (off by default)

* Use InMemoryCacheAdapter

* Uses proper adapter to generate a cache

* Fix bugs when running disabled cache

* nits

* nits

* Use options object instead of boolean

* Imrpove concurrency of loadSchema

* Adds testing with SCHEMA_CACHE_ON

* Use CacheController instead of generator

- Makes caching SchemaCache use a generated prefix
- Makes clearing the SchemaCache clear only the cached schema keys
- Enable cache by default (ttl 5s)

src/Controllers/SchemaCache.js

@@ -0,0 +1,68 @@
+const MAIN_SCHEMA = "__MAIN_SCHEMA";
+const SCHEMA_CACHE_PREFIX = "__SCHEMA";
+const ALL_KEYS = "__ALL_KEYS";
+
+import { randomString } from '../cryptoUtils';
+
+export default class SchemaCache {
+  cache: Object;
+
+  constructor(cacheController, ttl = 30) {
+    this.ttl = ttl;
+    if (typeof ttl == 'string') {
+      this.ttl = parseInt(ttl);
+    }
+    this.cache = cacheController;
+    this.prefix = SCHEMA_CACHE_PREFIX+randomString(20);
+  }
+
+  put(key, value) {
+    return this.cache.get(this.prefix+ALL_KEYS).then((allKeys) => {
+      allKeys = allKeys || {};
+      allKeys[key] = true;
+      return Promise.all([this.cache.put(this.prefix+ALL_KEYS, allKeys, this.ttl), this.cache.put(key, value, this.ttl)]);
+    });
+  }
+
+  getAllClasses() {
+    if (!this.ttl) {
+      return Promise.resolve(null);
+    }
+    return this.cache.get(this.prefix+MAIN_SCHEMA);
+  }
+
+  setAllClasses(schema) {
+    if (!this.ttl) {
+      return Promise.resolve(null);
+    }
+    return this.put(this.prefix+MAIN_SCHEMA, schema);
+  }
+
+  setOneSchema(className, schema) {
+    if (!this.ttl) {
+      return Promise.resolve(null);
+    }
+    return this.put(this.prefix+className, schema);
+  }
+
+  getOneSchema(className) {
+    if (!this.ttl) {
+      return Promise.resolve(null);
+    }
+    return this.cache.get(this.prefix+className);
+  }
+
+  clear() {
+    // That clears all caches...
+    let promise = Promise.resolve();
+    return this.cache.get(this.prefix+ALL_KEYS).then((allKeys) => {
+      if (!allKeys) {
+        return;
+      }
+      let promises = Object.keys(allKeys).map((key) => {
+        return this.cache.del(key);
+      });
+      return Promise.all(promises);
+    });
+  }
+}