Make support for copytruncate log rotation the default.

We print a warning if copytruncate is disabled and the log file shrinks.
Also added a --no-copytruncate flag for kicks.

README.md

@@ -20,9 +20,11 @@ From the command line:
       -o OFFSET_FILE, --offset-file=OFFSET_FILE
                             File to which offset data is written (default:
                             <logfile>.offset).
-      -p, --paranoid        Update the offset file every time we read a line 
+      -p, --paranoid        Update the offset file every time we read a line
                             (as opposed to only when we reach the end of the
                             file).
+      --no-copytruncate     Don't support copytruncate-style log rotation.
+                            Instead, if the log file shrinks, print a warning.
 
 In your code:
 

README.txt

@@ -1,7 +1,7 @@
 pygtail
 =======
 
-A python "port" of `logcheck's logtail2 <http://logcheck.org>`_.
+A python "port" of `logcheck's logtail2 <http://logcheck.org>`__.
 
 Pygtail reads log file lines that have not been read. It will even
 handle log files that have been rotated.
@@ -22,13 +22,15 @@ From the command line:
       -o OFFSET_FILE, --offset-file=OFFSET_FILE
                             File to which offset data is written (default:
                             <logfile>.offset).
-      -p, --paranoid        Update the offset file every time we read a line 
+      -p, --paranoid        Update the offset file every time we read a line
                             (as opposed to only when we reach the end of the
                             file).
+      --no-copytruncate     Don't support copytruncate-style log rotation.
+                            Instead, if the log file shrinks, print a warning.
 
 In your code:
 
-::
+.. code:: python
 
     from pygtail import Pygtail
 
@@ -42,3 +44,11 @@ Pygtail does not handle rotated logs that have been compressed. You
 should configure your log rotation script so that the most recently
 rotated log is left uncompressed (``logrotated``, for example, has a
 ``delaycompress`` option that does just that).
+
+Build status
+------------
+
+|Build Status|
+
+.. |Build Status| image:: https://secure.travis-ci.org/bgreenlee/pygtail.png
+   :target: http://travis-ci.org/bgreenlee/pygtail

debian/changelog

@@ -1,3 +1,11 @@
+pygtail (0.4.0) lucid; urgency=low
+
+  * Make support for copytruncate log rotation the default.
+  * Add --no-copytruncate commandline switch.
+  * Print warning if copytruncate is disabled and the log file shrinks
+
+ -- Brad Greenlee <[email protected]>  Fri, 9 May 2014 17:31:00 -0700
+
 pygtail (0.3.0) lucid; urgency=low
 
   * Add support for copytruncate style logrotation (contributed by https://github.com/atward)

pygtail/core.py

@@ -29,14 +29,20 @@
 import string
 from optparse import OptionParser
 
-__version__ = '0.3.0'
+__version__ = '0.4.0'
 
 
 class Pygtail(object):
     """
     Creates an iterable object that returns only unread lines.
+
+    Keyword arguments:
+    offset_file   File to which offset data is written (default: <logfile>.offset).
+    paranoid      Update the offset file every time we read a line (as opposed to
+                  only when we reach the end of the file (default: False)
+    copytruncate  Support copytruncate-style log rotation (default: True)
     """
-    def __init__(self, filename, offset_file=None, paranoid=False, copytruncate=False):
+    def __init__(self, filename, offset_file=None, paranoid=False, copytruncate=True):
         self.filename = filename
         self.paranoid = paranoid
         self.copytruncate = copytruncate
@@ -146,9 +152,18 @@ def _determine_rotated_logfile(self):
         if rotated_filename and exists(rotated_filename):
             if stat(rotated_filename).st_ino == self._offset_file_inode:
                 return rotated_filename
-            elif self.copytruncate and \
-                    stat(self.filename).st_ino == self._offset_file_inode:
-                return rotated_filename
+
+            # if the inode hasn't changed, then the file shrank; this is expected with copytruncate,
+            # otherwise print a warning
+            if stat(self.filename).st_ino == self._offset_file_inode:
+                if self.copytruncate:
+                    return rotated_filename
+                else:
+                    sys.stderr.write(
+                        "[pygtail] [WARN] file size of %s shrank, and copytruncate support is "
+                        "disabled (expected at least %d bytes, was %d bytes).\n" %
+                        (self.filename, self._offset, stat(self.filename).st_size))
+
         return None
 
     def _check_rotated_filename_candidates(self):
@@ -192,6 +207,9 @@ def main():
     cmdline.add_option("--paranoid", "-p", action="store_true",
         help="Update the offset file every time we read a line (as opposed to"
              " only when we reach the end of the file).")
+    cmdline.add_option("--no-copytruncate", action="store_true",
+        help="Don't support copytruncate-style log rotation. Instead, if the log file"
+             " shrinks, print a warning.")
 
     options, args = cmdline.parse_args()
 
@@ -200,7 +218,9 @@ def main():
 
     pygtail = Pygtail(args[0],
                       offset_file=options.offset_file,
-                      paranoid=options.paranoid)
+                      paranoid=options.paranoid,
+                      copytruncate=not options.no_copytruncate)
+
     for line in pygtail:
         sys.stdout.write(line)
 

pygtail/test/test_pygtail.py

@@ -1,4 +1,5 @@
 import os
+import sys
 import unittest
 import shutil
 import tempfile
@@ -71,8 +72,9 @@ def test_copytruncate_off_smaller(self):
         self.copytruncate()
         new_lines = "4\n5\n"
         self.append(new_lines)
-        pygtail = Pygtail(self.logfile.name)
+        pygtail = Pygtail(self.logfile.name, copytruncate=False)
         self.assertEqual(pygtail.read(), None)
+        self.assertRegexpMatches(sys.stderr.getvalue(), r".*?\bWARN\b.*?\bshrank\b.*")
 
     def test_copytruncate_on_smaller(self):
         self.test_readlines()
@@ -99,7 +101,7 @@ def test_copytruncate_larger_on(self):
 
 
 def main():
-    unittest.main()
+    unittest.main(buffer=True)
 
 
 if __name__ == "__main__":