Node JS Redis Client Connection Retry

Question

Currently I'm using https://github.com/mranney/node_redis as my node redis client.

client.retry_delay is set to 250ms default.

I tried connecting to redis and once connection was successful, I manually stopped the redis server to see whether client.retry_delay works. But I didn't see it working.

The following log messages are logged on ready & end events on redisClients created using createClient:

[2012-03-30 15:13:05.498] [INFO] Development - Node Application is running on port 8090
[2012-03-30 15:13:08.507] [INFO] Development - Connection Successfully Established to  '127.0.0.1' '6379'
[2012-03-30 15:16:33.886] [FATAL] Development - Connection Terminated to  '127.0.0.1' '6379'

I didn't see Success message again [ready event was not fired] when the server came back live.

Am I missing something? When will be the retry constant used? Is there a work around to find whether a redis server has come up after a failure from node?

Answer 1

I can't reproduce this. Could you try this code, stop your redis server, and check the log output?

var client = require('redis').createClient();

client.on('connect'     , log('connect'));
client.on('ready'       , log('ready'));
client.on('reconnecting', log('reconnecting'));
client.on('error'       , log('error'));
client.on('end'         , log('end'));

function log(type) {
    return function() {
        console.log(type, arguments);
    }
}

Answer 2

Answer @ Feb-2020

const redis = require('redis');
const log = (type, fn) => fn ? () => {
    console.log(`connection ${type}`);
} : console.log(`connection ${type}`);

// Option 1: One connection is enough per application
const client = redis.createClient('6379', "localhost", {
    retry_strategy: (options) => {
        const {error, total_retry_time, attempt} = options;
        if (error && error.code === "ECONNREFUSED") {
            log(error.code); // take actions or throw exception
        }
        if (total_retry_time > 1000 * 15) { //in ms i.e. 15 sec
            log('Retry time exhausted'); // take actions or throw exception
        }
        if (options.attempt > 10) {
            log('10 attempts done'); // take actions or throw exception
        }
        console.log("Attempting connection");
        // reconnect after
        return Math.min(options.attempt * 100, 3000); //in ms
    },
});

client.on('connect', log('connect', true));
client.on('ready', log('ready', true));
client.on('reconnecting', log('reconnecting', true));
client.on('error', log('error', true));
client.on('end', log('end', true));

For complete running example clone node-cheat and run node connect-retry.js.

Answer 3

Adding to the answer above. Small change. The callback provided should be a method name and not execute the method itself. Something like below:

function redisCallbackHandler(message){
    console.log("Redis:"+ message);
}

var redis = require("redis");
var redisclient = redis.createClient();
redisclient.on('connect', redisCallbackHandler);
redisclient.on('ready', redisCallbackHandler);
redisclient.on('reconnecting', redisCallbackHandler);
redisclient.on('error', redisCallbackHandler);
redisclient.on('end', redisCallbackHandler);