jourlog

jourlog is a Go package for writing structured logs to systemd-journald and reading logs back using journal filters.

Installation

go get github.com/yskomur/jourlog

Quick start

package main

import (
	"github.com/coreos/go-systemd/v22/journal"
	"github.com/yskomur/jourlog"
)

func main() {
	logger := jourlog.NewJourlog()
	logger.SetLogLevel(journal.PriInfo)
	logger.SetEcho(true)

	logger.Info("application started")
	logger.Error("database unavailable")
}

Read from journal

package main

import (
	"fmt"
	"log"

	"github.com/yskomur/jourlog"
)

func main() {
	reader, err := jourlog.NewJournalReader()
	if err != nil {
		log.Fatal(err)
	}
	defer reader.Close()

	if err := reader.LastHour(); err != nil {
		log.Fatal(err)
	}

	for {
		message, err := reader.Retrieve()
		if err != nil {
			break
		}
		fmt.Println(message)
	}
}

API overview

Logging (JourLog)

• NewJourlog() creates a logger.
• SetLogLevel(...) sets the minimum accepted priority.
• SetEcho(true) mirrors messages to stdout.
• Priority helpers: Emerge, Alert, Critical, Error, Warning, Notice, Info, Debug.

Each log record includes caller metadata fields (CODE_FILE, CODE_LINE, CODE_FUNC) in journald.

Journal reading (JournalReader)

• NewJournalReader() opens a journal reader.
• Time filters: SetSince, SetUntil, LastHour, LastDay, LastWeek, Today.
• Match filters: SetUnit, SetService, SetPriority, SetHostname, SetExecutable, SetMessageFilter, AddFilter.
• Cursor helpers: SeekHead, SeekTail, SeekCursor, GetCursor.
• Limits and state: SetLimit, ResetCounter, ClearFilters.

Documentation

• Package docs: go doc github.com/yskomur/jourlog
• Rendered docs: pkg.go.dev/github.com/yskomur/jourlog

License

See LICENSE.