feat(server): add store based on redis@4

Reference: https://github.com/redis/node-redis/blob/master/docs/v3-to-v4.md

Related: #65

Author: darrachequesne

lib/index.ts

@@ -594,4 +594,4 @@ export function instrument(io: Server, opts: Partial<InstrumentOptions>) {
   initStatsEmitter(adminNamespace, options.serverId);
 }
 
-export { InMemoryStore, RedisStore } from "./stores";
+export { InMemoryStore, RedisStore, RedisV4Store } from "./stores";

lib/stores.ts

@@ -70,3 +70,32 @@ export class RedisStore extends Store {
       .exec();
   }
 }
+
+export class RedisV4Store extends Store {
+  private options: RedisStoreOptions;
+
+  constructor(readonly redisClient: any, options?: Partial<RedisStoreOptions>) {
+    super();
+    this.options = Object.assign(
+      {
+        prefix: "socket.io-admin",
+        sessionDuration: 86400,
+      },
+      options
+    );
+  }
+
+  private computeKey(sessionId: string) {
+    return `${this.options.prefix}#${sessionId}`;
+  }
+
+  doesSessionExist(sessionId: string): Promise<boolean> {
+    return this.redisClient.exists(this.computeKey(sessionId));
+  }
+
+  saveSession(sessionId: string) {
+    return this.redisClient.set(this.computeKey(sessionId), "1", {
+      EX: this.options.sessionDuration,
+    });
+  }
+}