Balancer

A Balancer accepts incoming traffic and balances it between the Processes of a Service.

Balancer Definition

A Balancer is defined in convox.yml.

balancers:
  custom:
    annotations:
    - test.annotation.org/value=foobar
    service: mqtt
    ports:
      8883: 8883
services:
  mqtt:
    ports:
      - 8883
    whitelist: 192.168.0.0/16

Attributes

Name	Required	Description
annotations	no	A list of annotation keys and values to populate the metadata for the deployed balancer
ports	yes	A map of ports in the format listen:forward where listen is the port that the balancer will listen on and forward is the port that the traffic will be forwarded to on the Service
service	yes	The name of the service that will receive the traffic
whitelist	no	A list of CIDR ranges from which to limit inbound traffic to this balancer

Command Line Interface

Listing Balancers

$ convox balancers
BALANCER  SERVICE  ENDPOINT
custom    mqtt     1.2.3.4

Configuration Examples

Configuring TCP Ports

To configure TCP ports on a balancer, you can use the following example:

balancers:
  custom:
    annotations:
      - test.annotation.org/value=foobar
    service: web
    ports:
      5000: 3001
      5002: 3002
services:
  web:
    domain: ${HOST}
    build: .
    port: 3000
    ports:
      - 3001
      - 3002

Configuring UDP Ports

To configure UDP ports on a balancer, specify the protocol explicitly for UDP ports. The default protocol is TCP, so it does not need to be specified for TCP ports.

balancers:
  custom:
    annotations:
      - test.annotation.org/value=foobar
    service: web
    ports:
      5000:
        protocol: UDP
        port: 3001
      5002:
        protocol: UDP
        port: 3002
services:
  web:
    domain: ${HOST}
    build: .
    port: 3000
    ports:
      - 3001/udp
      - 3002/udp

Important Notes

• A custom balancer can only be configured with multiple TCP or multiple UDP ports and redirects, but you cannot have both TCP and UDP on the same balancer.
• Ports configured using ports: will never be publicly accessible; all connections must go through the load balancer, which is internet-facing.

Difference Between port and ports

• port: Used to define the main port that the service will listen on. This port is exposed via the default ingress and is used for primary traffic, including health checks.
• ports: Used to define additional ports for service-to-service communication within the cluster. These ports can be exposed using a custom balancer for specific protocols like TCP or UDP.

services:
  web:
    domain: ${HOST}
    build: .
    port: 3000
    ports:
      - 3001/udp
      - 3002

By using the ports attribute, you can configure additional ports with specific protocols on both the Kubernetes service and pod levels.

The main port must always be defined, and it will use the default ingress. Health checks go over the port defined as port:.

Example of Configuring an Alternate Health Check Port

You can configure an alternate health check port using the ports attribute.

balancers:
  custom:
    annotations:
      - test.annotation.org/foo=bar
    service: web
    ports:
      5000: 3001
      5002: 3002
services:
  web:
    domain: ${HOST}
    build: .
    port: 3000
    ports:
      - 3001
      - 3002

In this configuration, the main traffic goes through port 3000, while additional service communication uses ports 3001 and 3002.

Ports defined with the ports: attribute will only be accessible within the cluster and through the configured custom balancer.

For more detailed information on configuring load balancers, refer to the Load Balancers documentation page.