Add support for logging to a file

command/agent/command.go

@@ -391,28 +391,58 @@ func (c *Command) setupLoggers(config *Config) (*gatedwriter.Writer, *logWriter,
 		return nil, nil, nil
 	}
 
+	// Create a log writer, and wrap a logOutput around it
+	logWriter := NewLogWriter(512)
+	writers := []io.Writer{c.logFilter, logWriter}
+
 	// Check if syslog is enabled
-	var syslog io.Writer
 	if config.EnableSyslog {
 		l, err := gsyslog.NewLogger(gsyslog.LOG_NOTICE, config.SyslogFacility, "nomad")
 		if err != nil {
 			c.Ui.Error(fmt.Sprintf("Syslog setup failed: %v", err))
 			return nil, nil, nil
 		}
-		syslog = &SyslogWrapper{l, c.logFilter}
+		writers = append(writers, &SyslogWrapper{l, c.logFilter})
 	}
 
-	// Create a log writer, and wrap a logOutput around it
-	logWriter := NewLogWriter(512)
-	var logOutput io.Writer
-	if syslog != nil {
-		logOutput = io.MultiWriter(c.logFilter, logWriter, syslog)
-	} else {
-		logOutput = io.MultiWriter(c.logFilter, logWriter)
+	// Check if file logging is enabled
+	if config.LogFile != "" {
+		dir, fileName := filepath.Split(config.LogFile)
+
+		// if a path is provided, but has no filename, then a default is used.
+		if fileName == "" {
+			fileName = "nomad.log"
+		}
+
+		// Try to enter the user specified log rotation duration first
+		var logRotateDuration time.Duration
+		if config.LogRotateDuration != "" {
+			duration, err := time.ParseDuration(config.LogRotateDuration)
+			if err != nil {
+				c.Ui.Error(fmt.Sprintf("Failed to parse log rotation duration: %v", err))
+				return nil, nil, nil
+			}
+			logRotateDuration = duration
+		} else {
+			// Default to 24 hrs if no rotation period is specified
+			logRotateDuration = 24 * time.Hour
+		}
+
+		logFile := &logFile{
+			logFilter: c.logFilter,
+			fileName:  fileName,
+			logPath:   dir,
+			duration:  logRotateDuration,
+			MaxBytes:  config.LogRotateBytes,
+			MaxFiles:  config.LogRotateMaxFiles,
+		}
+
+		writers = append(writers, logFile)
 	}
-	c.logOutput = logOutput
-	log.SetOutput(logOutput)
-	return logGate, logWriter, logOutput
+
+	c.logOutput = io.MultiWriter(writers...)
+	log.SetOutput(c.logOutput)
+	return logGate, logWriter, c.logOutput
 }
 
 // setupAgent is used to start the agent and various interfaces

command/agent/config.go

@@ -57,6 +57,18 @@ type Config struct {
 	// LogJson enables log output in a JSON format
 	LogJson bool `hcl:"log_json"`
 
+	// LogFile enables logging to a file
+	LogFile string `hcl:"log_file"`
+
+	// LogRotateDuration is the time period that logs should be rotated in
+	LogRotateDuration string `hcl:"log_rotate_duration"`
+
+	// LogRotateBytes is the max number of bytes that should be written to a file
+	LogRotateBytes int `hcl:"log_rotate_bytes"`
+
+	// LogRotateMaxFiles is the max number of log files to keep
+	LogRotateMaxFiles int `hcl:"log_rotate_max_files"`
+
 	// BindAddr is the address on which all of nomad's services will
 	// be bound. If not specified, this defaults to 127.0.0.1.
 	BindAddr string `hcl:"bind_addr"`
@@ -898,6 +910,18 @@ func (c *Config) Merge(b *Config) *Config {
 	if b.LogJson {
 		result.LogJson = true
 	}
+	if b.LogFile != "" {
+		result.LogFile = b.LogFile
+	}
+	if b.LogRotateDuration != "" {
+		result.LogRotateDuration = b.LogRotateDuration
+	}
+	if b.LogRotateBytes != 0 {
+		result.LogRotateBytes = b.LogRotateBytes
+	}
+	if b.LogRotateMaxFiles != 0 {
+		result.LogRotateMaxFiles = b.LogRotateMaxFiles
+	}
 	if b.BindAddr != "" {
 		result.BindAddr = b.BindAddr
 	}

command/agent/config_parse_test.go

@@ -19,6 +19,7 @@ var basicConfig = &Config{
 	NodeName:    "my-web",
 	DataDir:     "/tmp/nomad",
 	PluginDir:   "/tmp/nomad-plugins",
+	LogFile:     "/var/log/nomad.log",
 	LogLevel:    "ERR",
 	LogJson:     true,
 	BindAddr:    "192.168.0.1",
@@ -409,14 +410,10 @@ func TestConfig_Parse(t *testing.T) {
 		t.Run(tc.File, func(t *testing.T) {
 			require := require.New(t)
 			path, err := filepath.Abs(filepath.Join("./testdata", tc.File))
-			if err != nil {
-				t.Fatalf("file: %s\n\n%s", tc.File, err)
-			}
+			require.NoError(err)
 
 			actual, err := ParseConfigFile(path)
-			if (err != nil) != tc.Err {
-				t.Fatalf("file: %s\n\n%s", tc.File, err)
-			}
+			require.NoError(err)
 
 			// ParseConfig used to re-merge defaults for these three objects,
 			// despite them already being merged in LoadConfig. The test structs

command/agent/log_file.go

@@ -0,0 +1,146 @@
+package agent
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"sort"
+	"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
+	}
+
+	// Stort the strings as filepath.Glob does not publicly guarantee that files
+	// are sorted, so here we add an extra defensive sort.
+	sort.Strings(matches)
+
+	// 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) (int, 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
+	}
+
+	n, err := l.FileInfo.Write(b)
+	l.BytesWritten += int64(n)
+	return n, err
+}