Consul is a distributed, highly available, and data center aware solution to connect and configure applications across dynamic, distributed infrastructure.
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package logger
import (
"fmt"
"os"
"path/filepath"
"strconv"
"strings"
"sync"
"time"
"github.com/hashicorp/logutils"
)
var (
now = time.Now
)
//LogFile is used to setup a file based logger that also performs log rotation
type LogFile struct {
// Log level Filter to filter out logs that do not matcch LogLevel criteria
logFilter *logutils.LevelFilter
//Name of the log file
fileName string
//Path to the log file
logPath string
//Duration between each file rotation operation
duration time.Duration
//LastCreated represents the creation time of the latest log
LastCreated time.Time
//FileInfo is the pointer to the current file being written to
FileInfo *os.File
//MaxBytes is the maximum number of desired bytes for a log file
MaxBytes int
//BytesWritten is the number of bytes written in the current log file
BytesWritten int64
// Max rotated files to keep before removing them.
MaxFiles int
//acquire is the mutex utilized to ensure we have no concurrency issues
acquire sync.Mutex
}
func (l *LogFile) fileNamePattern() string {
// Extract the file extension
fileExt := filepath.Ext(l.fileName)
// If we have no file extension we append .log
if fileExt == "" {
fileExt = ".log"
}
// Remove the file extension from the filename
return strings.TrimSuffix(l.fileName, fileExt) + "-%s" + fileExt
}
func (l *LogFile) openNew() error {
fileNamePattern := l.fileNamePattern()
// New file name has the format : filename-timestamp.extension
createTime := now()
newfileName := fmt.Sprintf(fileNamePattern, strconv.FormatInt(createTime.UnixNano(), 10))
newfilePath := filepath.Join(l.logPath, newfileName)
// Try creating a file. We truncate the file because we are the only authority to write the logs
filePointer, err := os.OpenFile(newfilePath, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0640)
if err != nil {
return err
}
l.FileInfo = filePointer
// New file, new bytes tracker, new creation time :)
l.LastCreated = createTime
l.BytesWritten = 0
return nil
}
func (l *LogFile) rotate() error {
// Get the time from the last point of contact
timeElapsed := time.Since(l.LastCreated)
// Rotate if we hit the byte file limit or the time limit
if (l.BytesWritten >= int64(l.MaxBytes) && (l.MaxBytes > 0)) || timeElapsed >= l.duration {
l.FileInfo.Close()
if err := l.pruneFiles(); err != nil {
return err
}
return l.openNew()
}
return nil
}
func (l *LogFile) pruneFiles() error {
if l.MaxFiles == 0 {
return nil
}
pattern := l.fileNamePattern()
//get all the files that match the log file pattern
globExpression := filepath.Join(l.logPath, fmt.Sprintf(pattern, "*"))
matches, err := filepath.Glob(globExpression)
if err != nil {
return err
}
// Prune if there are more files stored than the configured max
stale := len(matches) - l.MaxFiles
for i := 0; i < stale; i++ {
if err := os.Remove(matches[i]); err != nil {
return err
}
}
return nil
}
// Write is used to implement io.Writer
func (l *LogFile) Write(b []byte) (n int, err error) {
// Filter out log entries that do not match log level criteria
if !l.logFilter.Check(b) {
return 0, nil
}
l.acquire.Lock()
defer l.acquire.Unlock()
//Create a new file if we have no file to write to
if l.FileInfo == nil {
if err := l.openNew(); err != nil {
return 0, err
}
}
// Check for the last contact and rotate if necessary
if err := l.rotate(); err != nil {
return 0, err
}
l.BytesWritten += int64(len(b))
return l.FileInfo.Write(b)
}