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Mizan

Experimental Load Balancer to balance traffic between multiple services and multiple replicas of a service.

Mizan is the Arabic word for Balance, pronounced as /mɪˈzæn/ or /mɪˈzɑːn/.

Features

  • Multiple Balancing Algorithms

    • Round Robin
    • Weighted Round Robin
    • Upcoming: Random, Least Response Time, Least Connections

  • Continuous Health Check

    • Actively checking the health for each replica of each service. Directing traffic only to healthy replicas.

  • Hot Configuration Reloading

    • Reloading configuration without restarting the load balancer with zero downtime.

  • Layer 7 Load Balancing

    • Load balancing based on HTTP request path.

  • Graceful Shutdown

    • Gracefully shutting down the load balancer without dropping any connections.

Usage

Configuration

Mizan uses YAML for configuration.
a sample configuration file for a Round Robin balancer as follows:

strategy: "rr"
max_connections: 1024 
ports:
  - 8080
  - 8081
  - 8082
services: 
  - matcher: "/api/v1"
    name: "test service"
    replicas:
      - url: "http://localhost:9090"
      - url: "http://localhost:9091"
      - url: "http://localhost:9092"

The configuration file is divided into 4 sections:

  • strategy: the load balancing strategy to use. currently only round robin is supported.
  • max_connections: the maximum number of connections to be handled by the load balancer.
  • ports: the ports to listen on.
  • services: the services to be load balanced. each service has the following properties:
    • matcher: the path to match the request against. if the request path starts with this string, the request will be directed to this service.
    • name: the name of the service.
    • replicas: the replicas of the service. each replica has the following properties:
      • url: the url of the replica.
        • metadata: the metadata of the replica, such as weight.

Examples of configuration files can be found in the examples directory.

Running

Mizan can be run using the following command:

go run main.go -config-path <path to config file>

Running Examples

1- There are example services that can served as a backend services and can be run by:

make example-service

2- Run Mizan with the example configurations in ./examples by:

go run main.go -config-path ./examples/config-rr.yml

Now, the server is listening on ports 8080, 8081 and 8082. You can curl these ports from another terminal and mizan will distribute requests to the backend services

3- Since the example services are running in the background, you can kill them with:

make kill-example

Roadmap

  • Multiple Load Balancing Algorithms
  • Continuous Health Check
  • Hot Configuration Reloading without Restarting
  • TLS Support
  • Layer 4 Load Balancing
  • HTTP/2 Support
  • Add OpenTelemtry Instrumentation
  • More comprehensive tests