github.com/cellofellow/gopkg@v0.0.0-20140722061823-eec0544a62ad/glog/glog_file.go (about)

     1  // Go support for leveled logs, analogous to https://code.google.com/p/google-glog/
     2  //
     3  // Copyright 2013 Google Inc. All Rights Reserved.
     4  //
     5  // Licensed under the Apache License, Version 2.0 (the "License");
     6  // you may not use this file except in compliance with the License.
     7  // You may obtain a copy of the License at
     8  //
     9  //     http://www.apache.org/licenses/LICENSE-2.0
    10  //
    11  // Unless required by applicable law or agreed to in writing, software
    12  // distributed under the License is distributed on an "AS IS" BASIS,
    13  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14  // See the License for the specific language governing permissions and
    15  // limitations under the License.
    16  
    17  // File I/O for logs.
    18  
    19  package glog
    20  
    21  import (
    22  	"errors"
    23  	"flag"
    24  	"fmt"
    25  	"os"
    26  	"os/user"
    27  	"path/filepath"
    28  	"strings"
    29  	"sync"
    30  	"time"
    31  )
    32  
    33  // MaxSize is the maximum size of a log file in bytes.
    34  var MaxSize uint64 = 1024 * 1024 * 1800
    35  
    36  // logDirs lists the candidate directories for new log files.
    37  var logDirs []string
    38  
    39  // If non-empty, overrides the choice of directory in which to write logs.
    40  // See createLogDirs for the full list of possible destinations.
    41  var logDir = flag.String("log_dir", "", "If non-empty, write log files in this directory")
    42  
    43  func createLogDirs() {
    44  	if *logDir != "" {
    45  		logDirs = append(logDirs, *logDir)
    46  	}
    47  	logDirs = append(logDirs, os.TempDir())
    48  }
    49  
    50  var (
    51  	pid      = os.Getpid()
    52  	program  = filepath.Base(os.Args[0])
    53  	host     = "unknownhost"
    54  	userName = "unknownuser"
    55  )
    56  
    57  func init() {
    58  	h, err := os.Hostname()
    59  	if err == nil {
    60  		host = shortHostname(h)
    61  	}
    62  
    63  	current, err := user.Current()
    64  	if err == nil {
    65  		userName = current.Username
    66  	}
    67  
    68  	// Sanitize userName since it may contain filepath separators on Windows.
    69  	userName = strings.Replace(userName, `\`, "_", -1)
    70  }
    71  
    72  // shortHostname returns its argument, truncating at the first period.
    73  // For instance, given "www.google.com" it returns "www".
    74  func shortHostname(hostname string) string {
    75  	if i := strings.Index(hostname, "."); i >= 0 {
    76  		return hostname[:i]
    77  	}
    78  	return hostname
    79  }
    80  
    81  // logName returns a new log file name containing tag, with start time t, and
    82  // the name for the symlink for tag.
    83  func logName(tag string, t time.Time) (name, link string) {
    84  	name = fmt.Sprintf("%s.%s.%s.log.%s.%04d%02d%02d-%02d%02d%02d.%d",
    85  		program,
    86  		host,
    87  		userName,
    88  		tag,
    89  		t.Year(),
    90  		t.Month(),
    91  		t.Day(),
    92  		t.Hour(),
    93  		t.Minute(),
    94  		t.Second(),
    95  		pid)
    96  	return name, program + "." + tag
    97  }
    98  
    99  var onceLogDirs sync.Once
   100  
   101  // create creates a new log file and returns the file and its filename, which
   102  // contains tag ("INFO", "FATAL", etc.) and t.  If the file is created
   103  // successfully, create also attempts to update the symlink for that tag, ignoring
   104  // errors.
   105  func create(tag string, t time.Time) (f *os.File, filename string, err error) {
   106  	onceLogDirs.Do(createLogDirs)
   107  	if len(logDirs) == 0 {
   108  		return nil, "", errors.New("log: no log dirs")
   109  	}
   110  	name, link := logName(tag, t)
   111  	var lastErr error
   112  	for _, dir := range logDirs {
   113  		fname := filepath.Join(dir, name)
   114  		f, err := os.Create(fname)
   115  		if err == nil {
   116  			symlink := filepath.Join(dir, link)
   117  			os.Remove(symlink)        // ignore err
   118  			os.Symlink(name, symlink) // ignore err
   119  			return f, fname, nil
   120  		}
   121  		lastErr = err
   122  	}
   123  	return nil, "", fmt.Errorf("log: cannot create log: %v", lastErr)
   124  }