run/websockets/redis.js

// Copyright 2021 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// [START cloudrun_websockets_redis]
const REDISHOST = process.env.REDISHOST || 'localhost';
const REDISPORT = process.env.REDISPORT || 6379;

// Instantiate the Redis client
const redisClient = require('redis').createClient({
  url: `redis://${REDISHOST}:${REDISPORT}`,
});

// Connect to the Redis server
(async () => {
  await redisClient.connect();
})();
// [END cloudrun_websockets_redis]

// Insert new messages into the Redis cache
async function addMessageToCache(roomName, msg) {
  // Check for current cache
  let room = await getRoomFromCache(roomName);
  if (room) {
    // Update old room
    room.messages.push(msg);
  } else {
    // Create a new room
    room = {
      room: roomName,
      messages: [msg],
    };
  }
  await redisClient.set(roomName, JSON.stringify(room));
  // Insert message to the database as well
  addMessageToDb(room);
}

// Query Redis for messages for a specific room
// If not in Redis, query the database
async function getRoomFromCache(roomName) {
  if (!(await redisClient.exists(roomName))) {
    const room = getRoomFromDatabase(roomName);
    if (room) {
      await redisClient.set(roomName, JSON.stringify(room));
    }
  }
  return JSON.parse(await redisClient.get(roomName));
}

// In-memory database example -
// Production applications should use a persistent database such as Firestore
const messageDb = [
  {
    room: 'my-room',
    messages: [
      {user: 'Chris', text: 'Hi!'},
      {user: 'Chris', text: 'How are you!?'},
      {user: 'Megan', text: 'Doing well!'},
      {user: 'Chris', text: "That's great"},
    ],
  },
  {
    room: 'new-room',
    messages: [
      {user: 'Chris', text: 'The project is due tomorrow'},
      {user: 'Chris', text: 'I am wrapping up the final pieces'},
      {user: 'Chris', text: 'Are you ready for the presentation'},
      {user: 'Megan', text: 'Of course!'},
    ],
  },
];

// Insert messages into the example database for long term storage
async function addMessageToDb(data) {
  const room = messageDb.find(messages => messages.room === data.room);
  if (room) {
    // Update room in database
    Object.assign(room, data);
  } else {
    // Create new room in database
    messageDb.push(data);
  }
}

// Query the example database for messages for a specific room
function getRoomFromDatabase(roomName) {
  return messageDb.find(messages => messages.room === roomName);
}

module.exports = {
  getRoomFromCache,
  addMessageToCache,
  redisClient,
};