GO GELF LOGGER

This package provides an io.Writer that can be used with logging libraries such as zerolog or zap for sending your logs to a GELF-compatible server like Graylog.

This project was inspired by https://github.com/Graylog2/go-gelf.

I was missing the capability of also sending the additional fields, which can be specified in zerolog or zap, as actual additional field with GELF.

This package takes all fields except of "level", "message"/"msg" and "time" and adds them as additional fields in the GELF request.

So you don't need an additional custom extractor or pipline for those fields. An example could be a "request-id" field.

Requirements

Go1.22.0
The timestamp field must be a UNIX timestamp with milliseconds.
The log message must be a JSON string.

Installation

TODO: To install the package, use the following command:

Usage

Below is a basic usage example:

package main

import (
	"crypto/tls"
	"crypto/x509"
	gelflogger "github.com/jame-developer/gelf-logger"
	"github.com/rs/zerolog"
	"io"
	"log"
	"net"
	"os"
)

// Main function with zerolog integration using the MultilevelWriter func.
func main() {
	// Create an array of log writers for the MultilevelWriter and add `os.Stderr` as default.
	logWriters := []io.Writer{os.Stderr}

	// Load our Root CA certificate chain
	caCert, err := os.ReadFile("path to your rootCA certificate chain")
	if err != nil {
		log.Fatal(err)
	}

	caCertPool := x509.NewCertPool()
	caCertPool.AppendCertsFromPEM(caCert)

	// Create the credentials and return it
	config := &tls.Config{
		RootCAs:            caCertPool,
		InsecureSkipVerify: false,
		// Filled other fields as necessary
	}

	graylogLogger, gelfLoggerInitErr := gelflogger.NewLogger("<YOUR_GRAYLOG_SERVER>:12201", true, config)
	
	// Only append the gelf-writer to the logWrites if initialization was successful.
	if gelfLoggerInitErr == nil {

		gelfWriter := gelflogger.GelfWriter{
			Logger: graylogLogger,
		}
		logWriters = append(logWriters, &gelfWriter)
	}

	// Set the time field format to a GELF compatible timestamp format see also https://go2docs.graylog.org/5-0/getting_in_log_data/gelf.html?tocpath=Getting%20in%20Logs%7CLog%20Sources%7CGELF%7C_____0#GELFPayloadSpecification
	zerolog.TimeFieldFormat = zerolog.TimeFormatUnixMs

	// Create the Multilevel writer and create the zero logger.
	multiLevelWriter := zerolog.MultiLevelWriter(logWriters...)
	logger := zerolog.New(multiLevelWriter).With().Timestamp().Logger()

	// Use the created zero logger to log an error message, in case the initialization of the GELF-logger failed
	if gelfLoggerInitErr != nil {
		logger.Error().Err(gelfLoggerInitErr).Msg("Failed to initialize GELF logger.")
	}

	// Log a test message, you should see this message in your console and on the server you specified above.
	logger.Info().Str("custom_field", "custom_value").IPAddr("remoteIP", net.ParseIP("192.168.0.1")).Msg("This is a test log message with zerolog2")
}

Testing

create test certificate files. You can use OpenSSL with the following commands in your test_data folder under project root:

openssl req -newkey rsa:2048 -nodes -keyout testkey.pem -x509 -days 1 -out testcert.pem

To run tests in the terminal, go to the directory where the project is located and type: go test ./...

License

This project is licensed under the terms of MIT license.

Contact

If you have specific questions about this project, you can reach out. I'll get back to you as soon as I can.

# Packages