utils.log: Restrict I/O error handling coverage
[ganeti-github.git] / lib / utils / log.py
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 logging
26 import logging.handlers
27
28 from ganeti import constants
29
30
31 class _ReopenableLogHandler(logging.handlers.BaseRotatingHandler):
32 """Log handler with ability to reopen log file on request.
33
34 In combination with a SIGHUP handler this class can reopen the log file on
35 user request.
36
37 """
38 def __init__(self, filename):
39 """Initializes this class.
40
41 @type filename: string
42 @param filename: Path to logfile
43
44 """
45 logging.handlers.BaseRotatingHandler.__init__(self, filename, "a")
46
47 assert self.encoding is None, "Encoding not supported for logging"
48 assert not hasattr(self, "_reopen"), "Base class has '_reopen' attribute"
49
50 self._reopen = False
51
52 def shouldRollover(self, _): # pylint: disable-msg=C0103
53 """Determine whether log file should be reopened.
54
55 """
56 return self._reopen or not self.stream
57
58 def doRollover(self): # pylint: disable-msg=C0103
59 """Reopens the log file.
60
61 """
62 if self.stream:
63 self.stream.flush()
64 self.stream.close()
65 self.stream = None
66
67 # Reopen file
68 # TODO: Handle errors?
69 self.stream = open(self.baseFilename, "a")
70
71 def RequestReopen(self):
72 """Register a request to reopen the file.
73
74 The file will be reopened before writing the next log record.
75
76 """
77 self._reopen = True
78
79
80 def _LogErrorsToConsole(base):
81 """Create wrapper class writing errors to console.
82
83 This needs to be in a function for unittesting.
84
85 """
86 class wrapped(base): # pylint: disable-msg=C0103
87 """Log handler that doesn't fallback to stderr.
88
89 When an error occurs while writing on the logfile, logging.FileHandler
90 tries to log on stderr. This doesn't work in Ganeti since stderr is
91 redirected to a logfile. This class avoids failures by reporting errors to
92 /dev/console.
93
94 """
95 def __init__(self, console, *args, **kwargs):
96 """Initializes this class.
97
98 @type console: file-like object or None
99 @param console: Open file-like object for console
100
101 """
102 base.__init__(self, *args, **kwargs)
103 assert not hasattr(self, "_console")
104 self._console = console
105
106 def handleError(self, record): # pylint: disable-msg=C0103
107 """Handle errors which occur during an emit() call.
108
109 Try to handle errors with FileHandler method, if it fails write to
110 /dev/console.
111
112 """
113 try:
114 base.handleError(record)
115 except Exception: # pylint: disable-msg=W0703
116 if self._console:
117 try:
118 # Ignore warning about "self.format", pylint: disable-msg=E1101
119 self._console.write("Cannot log message:\n%s\n" %
120 self.format(record))
121 except Exception: # pylint: disable-msg=W0703
122 # Log handler tried everything it could, now just give up
123 pass
124
125 return wrapped
126
127
128 #: Custom log handler for writing to console with a reopenable handler
129 _LogHandler = _LogErrorsToConsole(_ReopenableLogHandler)
130
131
132 def _GetLogFormatter(program, multithreaded, debug, syslog):
133 """Build log formatter.
134
135 @param program: Program name
136 @param multithreaded: Whether to add thread name to log messages
137 @param debug: Whether to enable debug messages
138 @param syslog: Whether the formatter will be used for syslog
139
140 """
141 parts = []
142
143 if syslog:
144 parts.append(program + "[%(process)d]:")
145 else:
146 parts.append("%(asctime)s: " + program + " pid=%(process)d")
147
148 if multithreaded:
149 if syslog:
150 parts.append(" (%(threadName)s)")
151 else:
152 parts.append("/%(threadName)s")
153
154 # Add debug info for non-syslog loggers
155 if debug and not syslog:
156 parts.append(" %(module)s:%(lineno)s")
157
158 # Ses, we do want the textual level, as remote syslog will probably lose the
159 # error level, and it's easier to grep for it.
160 parts.append(" %(levelname)s %(message)s")
161
162 return logging.Formatter("".join(parts))
163
164
165 def SetupLogging(logfile, debug=0, stderr_logging=False, program="",
166 multithreaded=False, syslog=constants.SYSLOG_USAGE,
167 console_logging=False):
168 """Configures the logging module.
169
170 @type logfile: str
171 @param logfile: the filename to which we should log
172 @type debug: integer
173 @param debug: if greater than zero, enable debug messages, otherwise
174 only those at C{INFO} and above level
175 @type stderr_logging: boolean
176 @param stderr_logging: whether we should also log to the standard error
177 @type program: str
178 @param program: the name under which we should log messages
179 @type multithreaded: boolean
180 @param multithreaded: if True, will add the thread name to the log file
181 @type syslog: string
182 @param syslog: one of 'no', 'yes', 'only':
183 - if no, syslog is not used
184 - if yes, syslog is used (in addition to file-logging)
185 - if only, only syslog is used
186 @type console_logging: boolean
187 @param console_logging: if True, will use a FileHandler which falls back to
188 the system console if logging fails
189 @raise EnvironmentError: if we can't open the log file and
190 syslog/stderr logging is disabled
191
192 """
193 formatter = _GetLogFormatter(program, multithreaded, debug, False)
194 syslog_fmt = _GetLogFormatter(program, multithreaded, debug, True)
195
196 root_logger = logging.getLogger("")
197 root_logger.setLevel(logging.NOTSET)
198
199 # Remove all previously setup handlers
200 for handler in root_logger.handlers:
201 handler.close()
202 root_logger.removeHandler(handler)
203
204 if stderr_logging:
205 stderr_handler = logging.StreamHandler()
206 stderr_handler.setFormatter(formatter)
207 if debug:
208 stderr_handler.setLevel(logging.NOTSET)
209 else:
210 stderr_handler.setLevel(logging.CRITICAL)
211 root_logger.addHandler(stderr_handler)
212
213 if syslog in (constants.SYSLOG_YES, constants.SYSLOG_ONLY):
214 facility = logging.handlers.SysLogHandler.LOG_DAEMON
215 syslog_handler = logging.handlers.SysLogHandler(constants.SYSLOG_SOCKET,
216 facility)
217 syslog_handler.setFormatter(syslog_fmt)
218 # Never enable debug over syslog
219 syslog_handler.setLevel(logging.INFO)
220 root_logger.addHandler(syslog_handler)
221
222 if syslog != constants.SYSLOG_ONLY:
223 # this can fail, if the logging directories are not setup or we have
224 # a permisssion problem; in this case, it's best to log but ignore
225 # the error if stderr_logging is True, and if false we re-raise the
226 # exception since otherwise we could run but without any logs at all
227 try:
228 if console_logging:
229 logfile_handler = _LogHandler(open(constants.DEV_CONSOLE, "a"), logfile)
230 else:
231 logfile_handler = _ReopenableLogHandler(logfile)
232 except EnvironmentError:
233 if stderr_logging or syslog == constants.SYSLOG_YES:
234 logging.exception("Failed to enable logging to file '%s'", logfile)
235 else:
236 # we need to re-raise the exception
237 raise
238
239 logfile_handler.setFormatter(formatter)
240 if debug:
241 logfile_handler.setLevel(logging.DEBUG)
242 else:
243 logfile_handler.setLevel(logging.INFO)
244 root_logger.addHandler(logfile_handler)