Question

We are using node_redis client to access the redis at present. I need to use HAProxy in front of redis slaves which in my case is 3 nos. I installed the HAProxy and configured it to load balance the redis slaves. But when I tried to create connection from the node_redis client to the HAProxy I was not able to create the connection and was getting a error

   Error: Redis reply parser error: Error: Protocol error, got "H" as reply type byte
at HiredisReplyParser.execute (/home/user1/doosra/node-exp/node_modules/redis/lib/parser/hiredis.js:32:31)
at RedisClient.on_data (/home/user1/doosra/node-exp/node_modules/redis/index.js:440:27)
at Socket.<anonymous> (/home/user1/doosra/node-exp/node_modules/redis/index.js:70:14)
at Socket.emit (events.js:67:17)
at TCP.onread (net.js:347:14)

Answer 1

Posting the haproxy configuration would have helped …

The most likely explanation is haproxy is not configured to process generic TCP traffic but HTTP traffic.

Example:

With the following configuration:

global
    daemon
    maxconn 256

defaults
    mode http
    timeout connect 5000ms
    timeout client 50000ms
    timeout server 50000ms

frontend redis
    bind *:1521
    default_backend servers

backend servers
    server R1 127.0.0.1:6379 maxconn 1000

and the following node.js script:

var redis = require('redis')
var redis_client = redis.createClient(1521, 'localhost');
redis_client.get( 'key', function(e,o) {
    console.log("return "+e+o);
});

… we get the same exact error:

Error: Redis reply parser error: Error: Protocol error, got "H" as reply type byte

It is expected, because the Redis protocol parser does not understand HTTP.
To fix it, just alter the haproxy configuration to enforce a generic TCP mode:

    mode http

to be changed into:

    mode tcp

… and now it works fine.