kubenetworks/kubevpn

package action

import (
    "bufio"
    "io"
    "log"
    "os"

    "github.com/hpcloud/tail"

    "github.com/wencaiwulue/kubevpn/v2/pkg/daemon/rpc"
)

func (svr *Server) Logs(req *rpc.LogRequest, resp rpc.Daemon_LogsServer) error {
    path := GetDaemonLogPath()

    lines, err2 := countLines(path)
    if err2 != nil {
        return err2
    }

    // only show latest N lines
    if req.Lines < 0 {
        lines = -req.Lines
    } else {
        lines -= req.Lines
    }

    config := tail.Config{Follow: req.Follow, ReOpen: false, MustExist: true, Logger: log.New(io.Discard, "", log.LstdFlags)}
    if !req.Follow {
        // FATAL -- cannot set ReOpen without Follow.
        config.ReOpen = false
    }
    file, err := tail.TailFile(path, config)
    if err != nil {
        return err
    }
    defer file.Stop()
    for {
        select {
        case <-resp.Context().Done():
            return nil
        case line, ok := <-file.Lines:
            if !ok {
                return nil
            }
            if line.Err != nil {
                return err
            }

            if lines--; lines >= 0 {
                continue
            }

            err = resp.Send(&rpc.LogResponse{Message: line.Text})
            if err != nil {
                return err
            }
        }
    }
}

func countLines(filename string) (int32, error) {
    file, err := os.Open(filename)
    if err != nil {
        return 0, err
    }
    defer file.Close()

    scanner := bufio.NewScanner(file)
    lineCount := int32(0)

    for scanner.Scan() {
        lineCount++
    }

    if err = scanner.Err(); err != nil {
        return 0, err
    }

    return lineCount, nil
}