utils.SetupLogging: Return function to reopen log file

This function can be used from a SIGHUP handler to reopen log files.
Initial, simple unittests are included.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: René Nussbaumer <rn@google.com>

lib/utils/log.py

@@ -27,6 +27,7 @@ import logging
 import logging.handlers
 
 from ganeti import constants
+from ganeti import compat
 
 
 class _ReopenableLogHandler(logging.handlers.BaseRotatingHandler):
@@ -163,9 +164,17 @@ def _GetLogFormatter(program, multithreaded, debug, syslog):
   return logging.Formatter("".join(parts))
 
 
+def _ReopenLogFiles(handlers):
+  """Wrapper for reopening all log handler's files in a sequence.
+
+  """
+  for handler in handlers:
+    handler.RequestReopen()
+
+
 def SetupLogging(logfile, program, debug=0, stderr_logging=False,
                  multithreaded=False, syslog=constants.SYSLOG_USAGE,
-                 console_logging=False):
+                 console_logging=False, root_logger=None):
   """Configures the logging module.
 
   @type logfile: str
@@ -187,6 +196,8 @@ def SetupLogging(logfile, program, debug=0, stderr_logging=False,
   @type console_logging: boolean
   @param console_logging: if True, will use a FileHandler which falls back to
       the system console if logging fails
+  @type root_logger: logging.Logger
+  @param root_logger: Root logger to use (for unittests)
   @raise EnvironmentError: if we can't open the log file and
       syslog/stderr logging is disabled
 
@@ -196,7 +207,10 @@ def SetupLogging(logfile, program, debug=0, stderr_logging=False,
   formatter = _GetLogFormatter(progname, multithreaded, debug, False)
   syslog_fmt = _GetLogFormatter(progname, multithreaded, debug, True)
 
-  root_logger = logging.getLogger("")
+  reopen_handlers = []
+
+  if root_logger is None:
+    root_logger = logging.getLogger("")
   root_logger.setLevel(logging.NOTSET)
 
   # Remove all previously setup handlers
@@ -245,3 +259,7 @@ def SetupLogging(logfile, program, debug=0, stderr_logging=False,
     else:
       logfile_handler.setLevel(logging.INFO)
     root_logger.addHandler(logfile_handler)
+
+    reopen_handlers.append(logfile_handler)
+
+  return compat.partial(_ReopenLogFiles, reopen_handlers)

test/ganeti.utils.log_unittest.py

@@ -25,6 +25,7 @@ import os
 import unittest
 import logging
 import tempfile
+import shutil
 
 from ganeti import constants
 from ganeti import errors
@@ -133,5 +134,59 @@ class TestLogHandler(unittest.TestCase):
       raise Exception
 
 
+class TestSetupLogging(unittest.TestCase):
+  def setUp(self):
+    self.tmpdir = tempfile.mkdtemp()
+
+  def tearDown(self):
+    shutil.rmtree(self.tmpdir)
+
+  def testSimple(self):
+    logfile = utils.PathJoin(self.tmpdir, "basic.log")
+    logger = logging.Logger("TestLogger")
+    self.assertTrue(callable(utils.SetupLogging(logfile, "test",
+                                                console_logging=False,
+                                                syslog=constants.SYSLOG_NO,
+                                                stderr_logging=False,
+                                                multithreaded=False,
+                                                root_logger=logger)))
+    self.assertEqual(utils.ReadFile(logfile), "")
+    logger.error("This is a test")
+
+    # Ensure SetupLogging used custom logger
+    logging.error("This message should not show up in the test log file")
+
+    self.assertTrue(utils.ReadFile(logfile).endswith("This is a test\n"))
+
+  def testReopen(self):
+    logfile = utils.PathJoin(self.tmpdir, "reopen.log")
+    logfile2 = utils.PathJoin(self.tmpdir, "reopen.log.OLD")
+    logger = logging.Logger("TestLogger")
+    reopen_fn = utils.SetupLogging(logfile, "test",
+                                   console_logging=False,
+                                   syslog=constants.SYSLOG_NO,
+                                   stderr_logging=False,
+                                   multithreaded=False,
+                                   root_logger=logger)
+    self.assertTrue(callable(reopen_fn))
+
+    self.assertEqual(utils.ReadFile(logfile), "")
+    logger.error("This is a test")
+    self.assertTrue(utils.ReadFile(logfile).endswith("This is a test\n"))
+
+    os.rename(logfile, logfile2)
+    assert not os.path.exists(logfile)
+
+    # Notify logger to reopen on the next message
+    reopen_fn()
+    assert not os.path.exists(logfile)
+
+    # Provoke actual reopen
+    logger.error("First message")
+
+    self.assertTrue(utils.ReadFile(logfile).endswith("First message\n"))
+    self.assertTrue(utils.ReadFile(logfile2).endswith("This is a test\n"))
+
+
 if __name__ == "__main__":
   testutils.GanetiTestProgram()