Improve single schema cache (#7214)

* Initial Commit

* fix flaky test

* temporary set ci timeout

* turn off ci check

* fix postgres tests

* fix tests

* node flaky test

* remove improvements

* Update SchemaPerformance.spec.js

* fix tests

* revert ci

* Create Singleton Object

* properly clear cache testing

* Cleanup

* remove fit

* try PushController.spec

* try push test rewrite

* try push enqueue time

* Increase test timeout

* remove pg server creation test

* xit push tests

* more xit

* remove skipped tests

* Fix conflicts

* reduce ci timeout

* fix push tests

* Revert "fix push tests"

This reverts commit 05aba62f1cbbca7d5d3e80b9444529f59407cb56.

* improve initialization

* fix flaky tests

* xit flaky test

* Update CHANGELOG.md

* enable debug logs

* Update LogsRouter.spec.js

* create initial indexes in series

* lint

* horizontal scaling documentation

* Update Changelog

* change horizontalScaling db option

* Add enableSchemaHooks option

* move enableSchemaHooks to databaseOptions

src/Adapters/Storage/Postgres/PostgresStorageAdapter.js

@@ -4,6 +4,8 @@ import { createClient } from './PostgresClient';
 import Parse from 'parse/node';
 // @flow-disable-next
 import _ from 'lodash';
+// @flow-disable-next
+import { v4 as uuidv4 } from 'uuid';
 import sql from './sql';
 
 const PostgresRelationDoesNotExistError = '42P01';
@@ -794,20 +796,33 @@ const buildWhereClause = ({ schema, query, index, caseInsensitive }): WhereClaus
 
 export class PostgresStorageAdapter implements StorageAdapter {
   canSortOnJoinTables: boolean;
+  enableSchemaHooks: boolean;
 
   // Private
   _collectionPrefix: string;
   _client: any;
+  _onchange: any;
   _pgp: any;
+  _stream: any;
+  _uuid: any;
 
-  constructor({ uri, collectionPrefix = '', databaseOptions }: any) {
+  constructor({ uri, collectionPrefix = '', databaseOptions = {} }: any) {
     this._collectionPrefix = collectionPrefix;
+    this.enableSchemaHooks = !!databaseOptions.enableSchemaHooks;
+    delete databaseOptions.enableSchemaHooks;
+
     const { client, pgp } = createClient(uri, databaseOptions);
     this._client = client;
+    this._onchange = () => {};
     this._pgp = pgp;
+    this._uuid = uuidv4();
     this.canSortOnJoinTables = false;
   }
 
+  watch(callback: () => void): void {
+    this._onchange = callback;
+  }
+
   //Note that analyze=true will run the query, executing INSERTS, DELETES, etc.
   createExplainableQuery(query: string, analyze: boolean = false) {
     if (analyze) {
@@ -818,12 +833,39 @@ export class PostgresStorageAdapter implements StorageAdapter {
   }
 
   handleShutdown() {
+    if (this._stream) {
+      this._stream.done();
+      delete this._stream;
+    }
     if (!this._client) {
       return;
     }
     this._client.$pool.end();
   }
 
+  async _listenToSchema() {
+    if (!this._stream && this.enableSchemaHooks) {
+      this._stream = await this._client.connect({ direct: true });
+      this._stream.client.on('notification', data => {
+        const payload = JSON.parse(data.payload);
+        if (payload.senderId !== this._uuid) {
+          this._onchange();
+        }
+      });
+      await this._stream.none('LISTEN $1~', 'schema.change');
+    }
+  }
+
+  _notifySchemaChange() {
+    if (this._stream) {
+      this._stream
+        .none('NOTIFY $1~, $2', ['schema.change', { senderId: this._uuid }])
+        .catch(error => {
+          console.log('Failed to Notify:', error); // unlikely to ever happen
+        });
+    }
+  }
+
   async _ensureSchemaCollectionExists(conn: any) {
     conn = conn || this._client;
     await conn
@@ -859,6 +901,7 @@ export class PostgresStorageAdapter implements StorageAdapter {
         values
       );
     });
+    this._notifySchemaChange();
   }
 
   async setIndexesWithSchemaFormat(
@@ -920,11 +963,12 @@ export class PostgresStorageAdapter implements StorageAdapter {
         [className, 'schema', 'indexes', JSON.stringify(existingIndexes)]
       );
     });
+    this._notifySchemaChange();
   }
 
   async createClass(className: string, schema: SchemaType, conn: ?any) {
     conn = conn || this._client;
-    return conn
+    const parseSchema = await conn
       .tx('create-class', async t => {
         await this.createTable(className, schema, t);
         await t.none(
@@ -940,6 +984,8 @@ export class PostgresStorageAdapter implements StorageAdapter {
         }
         throw err;
       });
+    this._notifySchemaChange();
+    return parseSchema;
   }
 
   // Just create a table, do not insert in schema
@@ -1073,6 +1119,7 @@ export class PostgresStorageAdapter implements StorageAdapter {
         );
       }
     });
+    this._notifySchemaChange();
   }
 
   // Drops a collection. Resolves with true if it was a Parse Schema (eg. _User, Custom, etc.)
@@ -1085,9 +1132,12 @@ export class PostgresStorageAdapter implements StorageAdapter {
         values: [className],
       },
     ];
-    return this._client
+    const response = await this._client
       .tx(t => t.none(this._pgp.helpers.concat(operations)))
       .then(() => className.indexOf('_Join:') != 0); // resolves with false when _Join table
+
+    this._notifySchemaChange();
+    return response;
   }
 
   // Delete all data known to this adapter. Used for testing.
@@ -1173,6 +1223,7 @@ export class PostgresStorageAdapter implements StorageAdapter {
         await t.none(`ALTER TABLE $1:name DROP COLUMN IF EXISTS ${columns}`, values);
       }
     });
+    this._notifySchemaChange();
   }
 
   // Return a promise for all schemas known to this adapter, in Parse format. In case the
@@ -2237,6 +2288,7 @@ export class PostgresStorageAdapter implements StorageAdapter {
         })
         .then(() => this.schemaUpgrade(schema.className, schema));
     });
+    promises.push(this._listenToSchema());
     return Promise.all(promises)
       .then(() => {
         return this._client.tx('perform-initialization', async t => {