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@dsymonds @robpike
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// Go support for leveled logs, analogous to https://code.google.com/p/google-glog/
//
// Copyright 2013 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// File I/O for logs.
package glog
import (
"errors"
"flag"
"fmt"
"os"
"os/user"
"path/filepath"
"strings"
"sync"
"time"
)
// MaxSize is the maximum size of a log file in bytes.
var MaxSize uint64 = 1024 * 1024 * 1800
// logDirs lists the candidate directories for new log files.
var logDirs []string
// If non-empty, overrides the choice of directory in which to write logs.
// See createLogDirs for the full list of possible destinations.
var logDir = flag.String("log_dir", "", "If non-empty, write log files in this directory")
func createLogDirs() {
if *logDir != "" {
logDirs = append(logDirs, *logDir)
}
logDirs = append(logDirs, os.TempDir())
}
var (
pid = os.Getpid()
program = filepath.Base(os.Args[0])
host = "unknownhost"
userName = "unknownuser"
)
func init() {
h, err := os.Hostname()
if err == nil {
host = shortHostname(h)
}
current, err := user.Current()
if err == nil {
userName = current.Username
}
// Sanitize userName since it may contain filepath separators on Windows.
userName = strings.Replace(userName, `\`, "_", -1)
}
// shortHostname returns its argument, truncating at the first period.
// For instance, given "www.google.com" it returns "www".
func shortHostname(hostname string) string {
if i := strings.Index(hostname, "."); i >= 0 {
return hostname[:i]
}
return hostname
}
// logName returns a new log file name containing tag, with start time t, and
// the name for the symlink for tag.
func logName(tag string, t time.Time) (name, link string) {
name = fmt.Sprintf("%s.%s.%s.log.%s.%04d%02d%02d-%02d%02d%02d.%d",
program,
host,
userName,
tag,
t.Year(),
t.Month(),
t.Day(),
t.Hour(),
t.Minute(),
t.Second(),
pid)
return name, program + "." + tag
}
var onceLogDirs sync.Once
// create creates a new log file and returns the file and its filename, which
// contains tag ("INFO", "FATAL", etc.) and t. If the file is created
// successfully, create also attempts to update the symlink for that tag, ignoring
// errors.
func create(tag string, t time.Time) (f *os.File, filename string, err error) {
onceLogDirs.Do(createLogDirs)
if len(logDirs) == 0 {
return nil, "", errors.New("log: no log dirs")
}
name, link := logName(tag, t)
var lastErr error
for _, dir := range logDirs {
fname := filepath.Join(dir, name)
f, err := os.Create(fname)
if err == nil {
symlink := filepath.Join(dir, link)
os.Remove(symlink) // ignore err
os.Symlink(name, symlink) // ignore err
return f, fname, nil
}
lastErr = err
}
return nil, "", fmt.Errorf("log: cannot create log: %v", lastErr)
}
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