Source Code for Module ganeti.utils.log

  1  # 
  2  # 
  3   
  4  # Copyright (C) 2006, 2007, 2010, 2011 Google Inc. 
  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 as published by 
  8  # the Free Software Foundation; either version 2 of the License, or 
  9  # (at your option) any later version. 
 10  # 
 11  # This program is distributed in the hope that it will be useful, but 
 12  # WITHOUT ANY WARRANTY; without even the implied warranty of 
 13  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU 
 14  # General Public License for more details. 
 15  # 
 16  # You should have received a copy of the GNU General Public License 
 17  # along with this program; if not, write to the Free Software 
 18  # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 
 19  # 02110-1301, USA. 
 20   
 21  """Utility functions for logging. 
 22   
 23  """ 
 24   
 25  import os.path 
 26  import logging 
 27  import logging.handlers 
 28   
 29  from ganeti import constants 
 30  from ganeti import compat 
 31   
 32   
 33 -class _ReopenableLogHandler(logging.handlers.BaseRotatingHandler): 
 34    """Log handler with ability to reopen log file on request. 
 35   
 36    In combination with a SIGHUP handler this class can reopen the log file on 
 37    user request. 
 38   
 39    """ 
 40 -  def __init__(self, filename): 
 41      """Initializes this class. 
 42   
 43      @type filename: string 
 44      @param filename: Path to logfile 
 45   
 46      """ 
 47      logging.handlers.BaseRotatingHandler.__init__(self, filename, "a") 
 48   
 49      assert self.encoding is None, "Encoding not supported for logging" 
 50      assert not hasattr(self, "_reopen"), "Base class has '_reopen' attribute" 
 51   
 52      self._reopen = False 
 53   
 54 -  def shouldRollover(self, _): # pylint: disable-msg=C0103 
 55      """Determine whether log file should be reopened. 
 56   
 57      """ 
 58      return self._reopen or not self.stream 
 59   
 60 -  def doRollover(self): # pylint: disable-msg=C0103 
 61      """Reopens the log file. 
 62   
 63      """ 
 64      if self.stream: 
 65        self.stream.flush() 
 66        self.stream.close() 
 67        self.stream = None 
 68   
 69      # Reopen file 
 70      # TODO: Handle errors? 
 71      self.stream = open(self.baseFilename, "a") 
 72   
 73      # Don't reopen on the next message 
 74      self._reopen = False 
 75   
 76 -  def RequestReopen(self): 
 77      """Register a request to reopen the file. 
 78   
 79      The file will be reopened before writing the next log record. 
 80   
 81      """ 
 82      self._reopen = True 
 83   
 84   
 85 -def _LogErrorsToConsole(base): 
 86    """Create wrapper class writing errors to console. 
 87   
 88    This needs to be in a function for unittesting. 
 89   
 90    """ 
 91    class wrapped(base): # pylint: disable-msg=C0103 
 92      """Log handler that doesn't fallback to stderr. 
 93   
 94      When an error occurs while writing on the logfile, logging.FileHandler 
 95      tries to log on stderr. This doesn't work in Ganeti since stderr is 
 96      redirected to a logfile. This class avoids failures by reporting errors to 
 97      /dev/console. 
 98   
 99      """ 
100      def __init__(self, console, *args, **kwargs): 
101        """Initializes this class. 
102   
103        @type console: file-like object or None 
104        @param console: Open file-like object for console 
105   
106        """ 
107        base.__init__(self, *args, **kwargs) 
108        assert not hasattr(self, "_console") 
109        self._console = console 
110   
111      def handleError(self, record): # pylint: disable-msg=C0103 
112        """Handle errors which occur during an emit() call. 
113   
114        Try to handle errors with FileHandler method, if it fails write to 
115        /dev/console. 
116   
117        """ 
118        try: 
119          base.handleError(record) 
120        except Exception: # pylint: disable-msg=W0703 
121          if self._console: 
122            try: 
123              # Ignore warning about "self.format", pylint: disable-msg=E1101 
124              self._console.write("Cannot log message:\n%s\n" % 
125                                  self.format(record)) 
126            except Exception: # pylint: disable-msg=W0703 
127              # Log handler tried everything it could, now just give up 
128              pass 
129   
130    return wrapped 
131   
132   
133  #: Custom log handler for writing to console with a reopenable handler 
134  _LogHandler = _LogErrorsToConsole(_ReopenableLogHandler) 
135   
136   
137 -def _GetLogFormatter(program, multithreaded, debug, syslog): 
138    """Build log formatter. 
139   
140    @param program: Program name 
141    @param multithreaded: Whether to add thread name to log messages 
142    @param debug: Whether to enable debug messages 
143    @param syslog: Whether the formatter will be used for syslog 
144   
145    """ 
146    parts = [] 
147   
148    if syslog: 
149      parts.append(program + "[%(process)d]:") 
150    else: 
151      parts.append("%(asctime)s: " + program + " pid=%(process)d") 
152   
153    if multithreaded: 
154      if syslog: 
155        parts.append(" (%(threadName)s)") 
156      else: 
157        parts.append("/%(threadName)s") 
158   
159    # Add debug info for non-syslog loggers 
160    if debug and not syslog: 
161      parts.append(" %(module)s:%(lineno)s") 
162   
163    # Ses, we do want the textual level, as remote syslog will probably lose the 
164    # error level, and it's easier to grep for it. 
165    parts.append(" %(levelname)s %(message)s") 
166   
167    return logging.Formatter("".join(parts)) 
168   
169   
170 -def _ReopenLogFiles(handlers): 
171    """Wrapper for reopening all log handler's files in a sequence. 
172   
173    """ 
174    for handler in handlers: 
175      handler.RequestReopen() 
176   
177   
178 -def SetupLogging(logfile, program, debug=0, stderr_logging=False, 
179                   multithreaded=False, syslog=constants.SYSLOG_USAGE, 
180                   console_logging=False, root_logger=None): 
181    """Configures the logging module. 
182   
183    @type logfile: str 
184    @param logfile: the filename to which we should log 
185    @type program: str 
186    @param program: the name under which we should log messages 
187    @type debug: integer 
188    @param debug: if greater than zero, enable debug messages, otherwise 
189        only those at C{INFO} and above level 
190    @type stderr_logging: boolean 
191    @param stderr_logging: whether we should also log to the standard error 
192    @type multithreaded: boolean 
193    @param multithreaded: if True, will add the thread name to the log file 
194    @type syslog: string 
195    @param syslog: one of 'no', 'yes', 'only': 
196        - if no, syslog is not used 
197        - if yes, syslog is used (in addition to file-logging) 
198        - if only, only syslog is used 
199    @type console_logging: boolean 
200    @param console_logging: if True, will use a FileHandler which falls back to 
201        the system console if logging fails 
202    @type root_logger: logging.Logger 
203    @param root_logger: Root logger to use (for unittests) 
204    @raise EnvironmentError: if we can't open the log file and 
205        syslog/stderr logging is disabled 
206    @rtype: callable 
207    @return: Function reopening all open log files when called 
208   
209    """ 
210    progname = os.path.basename(program) 
211   
212    formatter = _GetLogFormatter(progname, multithreaded, debug, False) 
213    syslog_fmt = _GetLogFormatter(progname, multithreaded, debug, True) 
214   
215    reopen_handlers = [] 
216   
217    if root_logger is None: 
218      root_logger = logging.getLogger("") 
219    root_logger.setLevel(logging.NOTSET) 
220   
221    # Remove all previously setup handlers 
222    for handler in root_logger.handlers: 
223      handler.close() 
224      root_logger.removeHandler(handler) 
225   
226    if stderr_logging: 
227      stderr_handler = logging.StreamHandler() 
228      stderr_handler.setFormatter(formatter) 
229      if debug: 
230        stderr_handler.setLevel(logging.NOTSET) 
231      else: 
232        stderr_handler.setLevel(logging.CRITICAL) 
233      root_logger.addHandler(stderr_handler) 
234   
235    if syslog in (constants.SYSLOG_YES, constants.SYSLOG_ONLY): 
236      facility = logging.handlers.SysLogHandler.LOG_DAEMON 
237      syslog_handler = logging.handlers.SysLogHandler(constants.SYSLOG_SOCKET, 
238                                                      facility) 
239      syslog_handler.setFormatter(syslog_fmt) 
240      # Never enable debug over syslog 
241      syslog_handler.setLevel(logging.INFO) 
242      root_logger.addHandler(syslog_handler) 
243   
244    if syslog != constants.SYSLOG_ONLY: 
245      # this can fail, if the logging directories are not setup or we have 
246      # a permisssion problem; in this case, it's best to log but ignore 
247      # the error if stderr_logging is True, and if false we re-raise the 
248      # exception since otherwise we could run but without any logs at all 
249      try: 
250        if console_logging: 
251          logfile_handler = _LogHandler(open(constants.DEV_CONSOLE, "a"), 
252                                        logfile) 
253        else: 
254          logfile_handler = _ReopenableLogHandler(logfile) 
255   
256        logfile_handler.setFormatter(formatter) 
257        if debug: 
258          logfile_handler.setLevel(logging.DEBUG) 
259        else: 
260          logfile_handler.setLevel(logging.INFO) 
261        root_logger.addHandler(logfile_handler) 
262        reopen_handlers.append(logfile_handler) 
263      except EnvironmentError: 
264        if stderr_logging or syslog == constants.SYSLOG_YES: 
265          logging.exception("Failed to enable logging to file '%s'", logfile) 
266        else: 
267          # we need to re-raise the exception 
268          raise 
269   
270    return compat.partial(_ReopenLogFiles, reopen_handlers) 
271