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e8786d73bb
Also simplify the code by directly storing the path to the log file in the LogFile structure. Signed-off-by: Rolf Neugebauer <rolf.neugebauer@docker.com>
202 lines
4.7 KiB
Go
202 lines
4.7 KiB
Go
package main
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// Write logs to files and perform rotation.
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import (
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"bufio"
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"errors"
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"flag"
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"fmt"
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"io"
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"log"
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"net"
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"os"
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"path/filepath"
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"strings"
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"time"
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)
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// These must be kept in sync with memlogd:
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const (
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logDump byte = iota
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logFollow
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logDumpFollow
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)
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const mb = 1024 * 1024
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// LogMessage is a message received from memlogd.
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type LogMessage struct {
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Time time.Time // time message was received by memlogd
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Name string // name of the service that wrote the message
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Message string // body of the message
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}
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func (m *LogMessage) String() string {
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return m.Time.Format(time.RFC3339) + " " + m.Name + " " + m.Message
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}
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// ParseLogMessage reconstructs a LogMessage from a line of text which looks like:
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// <timestamp>,<origin>;<body>
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func ParseLogMessage(line string) (*LogMessage, error) {
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bits := strings.SplitN(line, ";", 2)
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if len(bits) != 2 {
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return nil, errors.New("Failed to parse log message: " + line)
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}
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bits2 := strings.Split(bits[0], ",")
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if len(bits2) < 2 {
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// There could be more parameters in future
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return nil, errors.New("Failed to parse log message: " + line)
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}
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Time, err := time.Parse(time.RFC3339, bits2[0])
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if err != nil {
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return nil, err
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}
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return &LogMessage{
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Time: Time,
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Name: bits2[1],
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Message: bits[1],
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}, nil
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}
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// LogFile is where we write LogMessages to
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type LogFile struct {
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File *os.File // active file handle
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Path string // Path to the logfile
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BytesWritten int // total number of bytes written so far
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}
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// NewLogFile creates a new LogFile.
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func NewLogFile(dir, name string) (*LogFile, error) {
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// If the log exists already we want to append to it.
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p := filepath.Join(dir, name+".log")
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f, err := os.OpenFile(p, os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0644)
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if err != nil {
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return nil, err
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}
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fi, err := f.Stat()
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if err != nil {
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return nil, err
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}
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return &LogFile{
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File: f,
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Path: p,
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BytesWritten: int(fi.Size()),
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}, nil
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}
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// Write appends a message to the log file
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func (l *LogFile) Write(m *LogMessage) error {
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s := m.String()
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_, err := io.WriteString(l.File, s)
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if err == nil {
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l.BytesWritten += len(s)
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}
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return err
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}
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// Close a log file
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func (l *LogFile) Close() error {
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return l.File.Close()
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}
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// Rotate closes the current log file, rotates the files and creates an empty log file.
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func (l *LogFile) Rotate(maxLogFiles int) error {
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if err := l.File.Close(); err != nil {
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return err
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}
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for i := maxLogFiles - 1; i >= 0; i-- {
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newerFile := fmt.Sprintf("%s.%d", l.Path, i-1)
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// special case: if index is 0 we omit the suffix i.e. we expect
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// foo foo.1 foo.2 up to foo.<maxLogFiles-1>
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if i == 0 {
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newerFile = l.Path
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}
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olderFile := fmt.Sprintf("%s.%d", l.Path, i)
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// overwrite the olderFile with the newerFile
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err := os.Rename(newerFile, olderFile)
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if os.IsNotExist(err) {
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// the newerFile does not exist
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continue
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}
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if err != nil {
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return err
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}
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}
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f, err := os.Create(l.Path)
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if err != nil {
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return err
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}
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l.File = f
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l.BytesWritten = 0
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return nil
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}
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func main() {
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socketPath := flag.String("socket", "/var/run/memlogdq.sock", "memlogd log query socket")
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logDir := flag.String("log-dir", "/var/log", "Directory containing log files")
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maxLogFiles := flag.Int("max-log-files", 10, "Maximum number of rotated log files before deletion")
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maxLogSize := flag.Int("max-log-size", mb, "Maximum size of a log file before rotation")
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flag.Parse()
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addr := net.UnixAddr{
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Name: *socketPath,
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Net: "unix",
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}
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conn, err := net.DialUnix("unix", nil, &addr)
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if err != nil {
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log.Fatal(err)
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}
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defer conn.Close()
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n, err := conn.Write([]byte{logDumpFollow})
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if err != nil || n < 1 {
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log.Fatalf("Failed to write request to memlogd socket: %v", err)
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}
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// map of service name to active log file
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logs := make(map[string]*LogFile)
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r := bufio.NewReader(conn)
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for {
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line, err := r.ReadString('\n')
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if err == io.EOF {
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return
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}
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if err != nil {
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log.Fatalf("Failed to read from memlogd: %v", err)
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}
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msg, err := ParseLogMessage(line)
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if err != nil {
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log.Println(err)
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continue
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}
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if strings.HasPrefix(msg.Name, "logwrite") {
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// don't log our own output in a loop
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continue
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}
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var logF *LogFile
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var ok bool
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if logF, ok = logs[msg.Name]; !ok {
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logF, err = NewLogFile(*logDir, msg.Name)
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if err != nil {
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log.Printf("Failed to create log file %s: %v", msg.Name, err)
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continue
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}
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logs[msg.Name] = logF
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}
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if err = logF.Write(msg); err != nil {
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log.Printf("Failed to write to log file %s: %v", msg.Name, err)
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if err := logF.Close(); err != nil {
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log.Printf("Failed to close log file %s: %v", msg.Name, err)
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}
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delete(logs, msg.Name)
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continue
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}
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if logF.BytesWritten > *maxLogSize {
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logF.Rotate(*maxLogFiles)
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}
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}
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}
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