HAProxy with Redis Enterprise

Summary

This is Part 2 of a two-part series on the implementation of a contact center ACD using Redis data structures.  This part is focused on the network configuration.  In particular, I explain the configuration of HAProxy load balancing with VRRP redundancy in a Redis Enterprise environment.  To boot, I explain some of the complexities of doing this inside a Docker container environment.

• Part 1:  Basic ACD with Redis Enterprise
• Part 2:  HAProxy with Redis Enterprise

Network Architecture

Load Balancing Configuration

HAProxy w/Keepalived

Docker Container

Dockerfile and associated Docker compose script below for two instances of HAProxy w/keepalived.  Note the default start-up for the HAProxy container is overridden with a CMD to start keepalived and haproxy.

Keepalived Config

VRRP redundancy of the two HAProxy instances is implemented with keepalived.  Below is the config for the Master instance.  The Backup instance is identical except for the priority.

Web Servers

I'll start with the simplest load-balancing scenario - web farm.

Docker Container

Below is the Dockerfile and associated Docker compose scripting for a 2-server deployment of Python FastAPI.  Note that no IP addresses are assigned and multiple instances are deployed via Docker compose 'replicas'.

HAProxy Config

Below are the front and backend configurations.  Note the use of Docker's DNS server to enable dynamic mapping of the web servers via a HAProxy server template.

Redis Enterprise Components

Redis Enterprise can provide its own load balancing via internal DNS servers.  For those that do not want to use DNS, external load balancing is also supported.  Official Redis documentation on the general configuration of external load balancing is here.  I'm going to go into detail on the specifics of setting this up with the HAProxy load balancer in a Docker environment.

Docker Containers

A three-node cluster is provisioned below.  Note the ports that are opened:

• 8443 - Redis Enterprise Admin Console
• 9443 - Redis Enterprise REST API
• 12000 - The client port configured for the database.

RE Database Configuration

Below is a JSON config that can be used via the RE REST API to create a Redis database.  Note the proxy policy.  "all-nodes" enables a database client connection point on all the Redis nodes.

RE Cluster Configuration

In the start.sh script, this command below is added to configure redirects in the Cluster (per the Redis documentation).

HAProxy Config - RE Admin Console

Redis Enterprise has a web interface for configuration and monitoring (TLS, port 8443).  I configure back-to-back TLS sessions below with a local SSL cert for the front end.  Additionally, I configure 'sticky' sessions via cookies.

HAProxy Config - RE REST API

Redis Enterprise provides a REST API for programmatic configuration and provisioning (TLS, port 9443).  For this scenario, I simply pass the TLS sessions through HAProxy via TCP.

HAProxy Config - RE Database

A Redis Enterprise database can have a configurable client connection port.  In this case, I've configured it to 12000 (TCP).  Note in the backend configuration I've set up a Layer 7 health check that will attempt to create an authenticated Redis client connection, send a Redis PING, and then close that connection.

Source

https://github.com/Redislabs-Solution-Architects/basic-acd

Copyright ©1993-2024 Joey E Whelan, All rights reserved.

Basic ACD with Redis Enterprise

Summary

This post covers a contact ACD implementation I've done utilizing Redis data structures.  The applications are written in Python.  The client interface is implemented as REST API via FastAPI.  An internal Python app (Dispatcher) is used to monitor and administer the ACD data structures in Redis.  Docker containers are used for architectural components.

• Part 1:  Basic ACD with Redis Enterprise
• Part 2:  HAProxy with Redis Enterprise

Application Architecture

Data Structures

Contact, Queue

Contacts are implemented as Redis JSON objects.  Each contact has an associated array of skills necessary to service that contact.  Example:  English language proficiency.

A single queue for all contacts is implemented as a Redis Sorted Set.  The members of the set are the Redis key names of the contacts.  The associated scores are millisecond timestamps of the time the contact entered the queue.  This allows for FIFO queue management  

Agent

Agents are implemented as Redis JSON objects.  Agent meta-data is stored as simple properties.  Agent skills are maintained as arrays.  The redis-py implementation of Redlock is used to ensure mutual exclusion to agent objects.

Agent Availability

Redis Sorted Sets are also used to track Agent availability.  A sorted set is created per skill.  The members of that set are the Redis keys for the agents that are available with the associated skill.  The associated scores are millisecond timestamps of the time the agent became available.  This use of sorted sets allows for multi-skill routing to the longest available agent (LAA).

Operations

Agent Targeting 

Routing of contacts to agents is performed by multiple Dispatcher processes.  Each Dispatcher is running an infinite loop that does the following:

• Pop the oldest contact from the queue
• Perform an intersection of the availability sets for the skills necessary for that contact
• If there are agent(s) available, assign that agent to this contact and set the agent to unavailable.
• If there are no agents available with the necessary skills, put the contact back in the queue

Source

https://github.com/Redislabs-Solution-Architects/basic-acd