Nodejs operation cache database-Redis

Hi I’m Shendi

Nodejs column
Nodejs operation cache database-Redis

In server-side development, cache database is also indispensable, which can improve program concurrency and facilitate subsequent expansion. Currently, the most commonly used one is Redis.

Install dependencies

Like the previous mysql, the most commonly used dependency of redis is redis

npm install redis

Depend on the corresponding github address: https://github.com/redis/node-redis

This is the official NodeJS connection guide from Redis https://redis.io/docs/clients/nodejs/

For information on the installation and use of Redis, you can read this article: https://sdpro.top/blog/html/article/1023.html

Connection example

The following is the official sample code

import {<!-- --> createClient } from 'redis';

const client = createClient();

client.on('error', err => console.log('Redis Client Error', err));

await client.connect();

await client.set('key', 'value');
const value = await client.get('key');
await client.disconnect();

The above code connects to localhost:6379. To connect to other addresses, use the following format

redis[s]://[[username][:password]@][host][:port][/db-number]

For example

createClient({<!-- -->
  url: 'redis://alice:[email protected]:6380/0'
});

Among them username account, password, host host address, port port, database subscript used by db-number, default 0

For more information refer to the documentation: client configuration guide

To check if the client is connected and ready to send commands, use client.isReady, which returns a boolean value. client.isOpen is also available. This function returns true when the client’s underlying socket is open, and false when it is not open (for example, when the client is still connected or reconnecting after a network error).

The operations of the library are basically asynchronous. If await is used above, then the current function needs to be set to async asynchronous, for example

async function test() {<!-- -->
    await client.connect();
}

Because it is asynchronous, we need to control the error handling ourselves.

Let me mention here, the asynchronous here is all the returned Promise, so you can use the Promise method

Rather than destructuring assignment, I prefer the following approach

var redis = require("redis");
const client = redis.createClient();

client.on('error', err => console.log('Redis Client Error', err));

await client.connect();

await client.set('key', 'value');
const value = await client.get('key');
await client.disconnect();

No need to worry about connections and connection pools

Node_redis manages connections automatically, so there is no need to wait for connections or callbacks. Since both Node.js and Redis are effectively single-threaded, there is no need to use multiple client instances or any pooling mechanism with few exceptions; the most common exceptions are if you use Pub/Sub subscriptions, or use streams or lists To block, you need to have a dedicated client to receive these long-running commands.

For example, if you connect to an incorrect Redis address, you will be reconnected all the time.

Use

The library provides built-in support for all Redis commands out of the box. These commands are exposed using the original Redis command names (HSET, HGETALL, etc.) and a more friendly camelCase version (hSet, hGetAll, etc.):

//Original redis command
await client.HSET('key', 'field', 'value');
await client.HGETALL('key');

// Friendly js command
await client.hSet('key', 'field', 'value');
await client.hGetAll('key');

To specify modifiers for a command, you can use a JavaScript object:

await client.set('key', 'value', {<!-- -->
  EX: 10,
  NX: true
});

The above EX is the expiration time in seconds. When NX is true, it will be set when the key does not exist. For more parameters, please refer to https://sdpro.top/blog/html/article/1023 for more parameters. .html

The retrieved content will be converted into useful structures

await client.hGetAll('key'); // { field1: 'value1', field2: 'value2' }
await client.hVals('key'); // ['value1', 'value2']

The library also supports Buffer:

await client.hSet('key', 'field', Buffer.from('value')); // 'OK'
await client.hGetAll(
  commandOptions({<!-- --> returnBuffers: true }),
  'key'
); // { field: <Buffer 76 61 6c 75 65> }

If you want to run a command that Node Redis doesn’t support (yet!), use .sendCommand():

await client.sendCommand(['SET', 'key', 'value', 'NX']); // 'OK'
await client.sendCommand(['HGETALL', 'key']); // ['key1', 'field1', 'key2', 'field2']

Transaction (Multi/Exec)

Start a transaction by calling .multi() and then chain your commands together. Once done, call .exec() and you will get an array containing your results:

await client.set('another-key', 'another-value');

const [setKeyReply, otherKeyValue] = await client
  .multi()
  .set('key', 'value')
  .get('another-key')
  .exec(); // ['OK', 'another-value']

You can also watch keys by calling .watch(). If any of the monitored keys change, the transaction will be aborted.
To learn more about transactions, check out the Isolated Execution Guide.

Event

The Node Redis client class is a Nodejs EventEmitter that emits an event every time the network status changes:

Name	When it happens	Listening parameters
connect	Start connection with server	No arguments
ready	The client is ready to use	No arguments
end	The connection has been closed (via .quit() or .disconnect()) td>	No arguments
error	An error occurred – usually network Problems, such as “Socket closed unexpectedly”	(error: Error)
reconnecting	The client is trying to reconnect to the server	No arguments
sharded-channel -moved	See here	See here

Supported versions

Version	Whether it is supported
7.0.z
6.2.z
6.0.z
5.0.z
< 5.0	?

Node Redis should work with older versions of Redis, but it has not been fully tested and we cannot provide support.

The windows version of redis I use is currently 3.0.504, and there are no problems for the time being.

Error resolution

Connection error ErrorReply: ERR wrong number of arguments for auth’ command

This error occurred by calling createClient({url: “”}), because redis did not set an account, only a password, and the url user password given above has it, so I searched for the default account of redis. to default… but no account is set, the account number should be left blank

Link settings are solved as follows

redis://:password@localhost:6379

END