gopkg.in/ubuntu-core/snappy.v0@v0.0.0-20210902073436-25a8614f10a6/logger/logger.go (about)

     1  // -*- Mode: Go; indent-tabs-mode: t -*-
     2  
     3  /*
     4   * Copyright (C) 2014,2015,2017 Canonical Ltd
     5   *
     6   * This program is free software: you can redistribute it and/or modify
     7   * it under the terms of the GNU General Public License version 3 as
     8   * published by the Free Software Foundation.
     9   *
    10   * This program is distributed in the hope that it will be useful,
    11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
    12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    13   * GNU General Public License for more details.
    14   *
    15   * You should have received a copy of the GNU General Public License
    16   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
    17   *
    18   */
    19  
    20  package logger
    21  
    22  import (
    23  	"bytes"
    24  	"fmt"
    25  	"io"
    26  	"log"
    27  	"os"
    28  	"sync"
    29  
    30  	"github.com/snapcore/snapd/osutil"
    31  )
    32  
    33  // A Logger is a fairly minimal logging tool.
    34  type Logger interface {
    35  	// Notice is for messages that the user should see
    36  	Notice(msg string)
    37  	// Debug is for messages that the user should be able to find if they're debugging something
    38  	Debug(msg string)
    39  }
    40  
    41  const (
    42  	// DefaultFlags are passed to the default console log.Logger
    43  	DefaultFlags = log.Ldate | log.Ltime | log.Lmicroseconds | log.Lshortfile
    44  )
    45  
    46  type nullLogger struct{}
    47  
    48  func (nullLogger) Notice(string) {}
    49  func (nullLogger) Debug(string)  {}
    50  
    51  // NullLogger is a logger that does nothing
    52  var NullLogger = nullLogger{}
    53  
    54  var (
    55  	logger Logger = NullLogger
    56  	lock   sync.Mutex
    57  )
    58  
    59  // Panicf notifies the user and then panics
    60  func Panicf(format string, v ...interface{}) {
    61  	msg := fmt.Sprintf(format, v...)
    62  
    63  	lock.Lock()
    64  	defer lock.Unlock()
    65  
    66  	logger.Notice("PANIC " + msg)
    67  	panic(msg)
    68  }
    69  
    70  // Noticef notifies the user of something
    71  func Noticef(format string, v ...interface{}) {
    72  	msg := fmt.Sprintf(format, v...)
    73  
    74  	lock.Lock()
    75  	defer lock.Unlock()
    76  
    77  	logger.Notice(msg)
    78  }
    79  
    80  // Debugf records something in the debug log
    81  func Debugf(format string, v ...interface{}) {
    82  	msg := fmt.Sprintf(format, v...)
    83  
    84  	lock.Lock()
    85  	defer lock.Unlock()
    86  
    87  	logger.Debug(msg)
    88  }
    89  
    90  // MockLogger replaces the exiting logger with a buffer and returns
    91  // the log buffer and a restore function.
    92  func MockLogger() (buf *bytes.Buffer, restore func()) {
    93  	buf = &bytes.Buffer{}
    94  	oldLogger := logger
    95  	l, err := New(buf, DefaultFlags)
    96  	if err != nil {
    97  		panic(err)
    98  	}
    99  	SetLogger(l)
   100  	return buf, func() {
   101  		SetLogger(oldLogger)
   102  	}
   103  }
   104  
   105  // WithLoggerLock invokes f with the global logger lock, useful for
   106  // tests involving goroutines with MockLogger.
   107  func WithLoggerLock(f func()) {
   108  	lock.Lock()
   109  	defer lock.Unlock()
   110  
   111  	f()
   112  }
   113  
   114  // SetLogger sets the global logger to the given one
   115  func SetLogger(l Logger) {
   116  	lock.Lock()
   117  	defer lock.Unlock()
   118  
   119  	logger = l
   120  }
   121  
   122  type Log struct {
   123  	log *log.Logger
   124  
   125  	debug bool
   126  }
   127  
   128  // Debug only prints if SNAPD_DEBUG is set
   129  func (l *Log) Debug(msg string) {
   130  	if l.debug || osutil.GetenvBool("SNAPD_DEBUG") {
   131  		l.log.Output(3, "DEBUG: "+msg)
   132  	}
   133  }
   134  
   135  // Notice alerts the user about something, as well as putting it syslog
   136  func (l *Log) Notice(msg string) {
   137  	l.log.Output(3, msg)
   138  }
   139  
   140  // New creates a log.Logger using the given io.Writer and flag.
   141  func New(w io.Writer, flag int) (Logger, error) {
   142  	logger := &Log{
   143  		log:   log.New(w, "", flag),
   144  		debug: debugEnabledOnKernelCmdline(),
   145  	}
   146  	return logger, nil
   147  }
   148  
   149  // SimpleSetup creates the default (console) logger
   150  func SimpleSetup() error {
   151  	flags := log.Lshortfile
   152  	if term := os.Getenv("TERM"); term != "" {
   153  		// snapd is probably not running under systemd
   154  		flags = DefaultFlags
   155  	}
   156  	l, err := New(os.Stderr, flags)
   157  	if err == nil {
   158  		SetLogger(l)
   159  	}
   160  	return err
   161  }
   162  
   163  // used to force testing of the kernel command line parsing
   164  var procCmdlineUseDefaultMockInTests = true
   165  
   166  // TODO: consider generalizing this to snapdenv and having it used by
   167  // other places that consider SNAPD_DEBUG
   168  func debugEnabledOnKernelCmdline() bool {
   169  	// if this is called during tests, always ignore it so we don't have to mock
   170  	// the /proc/cmdline for every test that ends up using a logger
   171  	if osutil.IsTestBinary() && procCmdlineUseDefaultMockInTests {
   172  		return false
   173  	}
   174  	m, _ := osutil.KernelCommandLineKeyValues("snapd.debug")
   175  	return m["snapd.debug"] == "1"
   176  }