How to Real-Time Parse Log Files in Go Using the `tail` Package?

How to Read Log Files in Real-Time in Go

To parse log files as they're updated in Go, consider using the tail package from github.com/hpcloud/tail. It provides a convenient way to track changes in a file without repeatedly rereading it.

Implementation:

import (
    "fmt"

    "github.com/hpcloud/tail"
)

func main() {
    // Open the log file for tailing
    t, err := tail.TailFile("/var/log/nginx.log", tail.Config{Follow: true})
    if err != nil {
        panic(err)
    }

    // Process new log lines as they are written
    for line := range t.Lines {
        fmt.Println(line.Text)
    }
}

Handling Truncation and Renaming:

To handle log file truncation and renaming (e.g., due to logrotate):

    t, err := tail.TailFile("/var/log/nginx.log", tail.Config{
        Follow: true,
        ReOpen: true,
    })

    _ = t // Ignore return value for demonstration purposes

The Config.ReOpen option is similar to the -F option of the tail command, which reopens the file if it is renamed or rotated.

Limitations:

Note that while the tail package monitors the file size to detect changes, it does not handle all scenarios, such as file deletion. For more robust handling, consider monitoring the file using a dedicated process (e.g., using inotify) or using a log management system.

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