Haproxy

Go module for Haproxy

Install package

go get -u github.com/eosswedenorg-go/haproxy@latest

Agent check module

import "github.com/eosswedenorg-go/haproxy/agentcheck"

This module exposes a simple API to deal with HAproxy's auxiliary agent check via TCP Messages.

Read the official documentation for more information about what effect each type of message have on the HAproxy server.

Include the following line in your go file:

Interface

All responses implements this simple interface.

type Response interface {
    // Returns the TCP Message to send back to haproxy.
    String() string
}

Weight Response

func NewWeightResponse(percent int) WeigthResponse

Construct a weight response message, percent should be a value between 0-100 and indicates to HAproxy to set the server's weight proportional to the initial weight when HAproxy first started.

For example: if a server is set to 200 on startup and a message with 75 percent is received from the agent Haproxy will update the server's weight to 150

Max Connections Response

func NewMaxConnResponse(value int) MaxConnResponse

Construct a Max Connections Response. This response tells HAproxy to set max connections of the server to the value specified.

Status Response

func NewStatusResponse(status StatusResponseType) StatusResponse

Constructs a status response. status can be one of the following constants Up, Maint, Ready or Drain

Status Message Response

func NewStatusMessageResponse(status StatusMessageResponseType, msg string) StatusMessageResponse

Constructs a status message response. Same as StatusResponse but with an optinal message msg. To omit the message just pass a empty string.

status can be one of the following constants Down, Failed or Stopped.

Example

package main

import (
    "fmt"
	"log"
	"net"
    "github.com/eosswedenorg-go/haproxy/agentcheck"
)

func onConnection(c net.Conn) {

    // Perform whatever logic is needed to check the status of the server.

    // in this example, we just tell HAproxy that the server is down with some helpful message.
    r := agentcheck.NewStatusMessageResponse(agentcheck.Down, "process is not running")

    // Send the message
    fmt.Fprint(c, r)

    // Shut down the connection.
    c.Close()
}

// TCP Code taken from: https://pkg.go.dev/net#example-Listener
func main() {

	// Listen on TCP port 2000 on localhost
	l, err := net.Listen("tcp", "127.0.0.1:2000")
	if err != nil {
		log.Fatal(err)
	}
	defer l.Close()
	for {
		// Wait for a connection.
		conn, err := l.Accept()
		if err != nil {
			log.Fatal(err)
		}
		// Handle the connection in a new goroutine.
		// The loop then returns to accepting, so that
		// multiple connections may be served concurrently.
		go onConnection(conn)
	}
}

Author

Henrik Hautakoski - Sw/eden - henrik@eossweden.org