From f65f63ef8d43adbec08450e4ca7e77e7ba0629f5 Mon Sep 17 00:00:00 2001
From: Iustin Pop <iustin@google.com>
Date: Tue, 20 Jan 2009 11:18:20 +0000
Subject: [PATCH] Add a TailFile function
This patch adds a tail file function, to be used for parsing and returning in
the job log OS installation failures.
Reviewed-by: ultrotter
---
lib/utils.py | 26 ++++++++++++++++++++
test/ganeti.utils_unittest.py | 46 ++++++++++++++++++++++++++++++++++-
2 files changed, 71 insertions(+), 1 deletion(-)
diff --git a/lib/utils.py b/lib/utils.py
index 6a6679c3f..8a4087a42 100644
--- a/lib/utils.py
+++ b/lib/utils.py
@@ -1713,6 +1713,32 @@ def SetupLogging(logfile, debug=False, stderr_logging=False, program=""):
raise
+def TailFile(fname, lines=20):
+ """Return the last lines from a file.
+
+ @note: this function will only read and parse the last 4KB of
+ the file; if the lines are very long, it could be that less
+ than the requested number of lines are returned
+
+ @param fname: the file name
+ @type lines: int
+ @param lines: the (maximum) number of lines to return
+
+ """
+ fd = open(fname, "r")
+ try:
+ fd.seek(0, 2)
+ pos = fd.tell()
+ pos = max(0, pos-4096)
+ fd.seek(pos, 0)
+ raw_data = fd.read()
+ finally:
+ fd.close()
+
+ rows = raw_data.splitlines()
+ return rows[-lines:]
+
+
def LockedMethod(fn):
"""Synchronized object access decorator.
diff --git a/test/ganeti.utils_unittest.py b/test/ganeti.utils_unittest.py
index 133d68765..423f5fa0b 100755
--- a/test/ganeti.utils_unittest.py
+++ b/test/ganeti.utils_unittest.py
@@ -42,7 +42,9 @@ from ganeti.utils import IsProcessAlive, RunCmd, \
RemoveFile, CheckDict, MatchNameComponent, FormatUnit, \
ParseUnit, AddAuthorizedKey, RemoveAuthorizedKey, \
ShellQuote, ShellQuoteArgs, TcpPing, ListVisibleFiles, \
- SetEtcHostsEntry, RemoveEtcHostsEntry, FirstFree, OwnIpAddress
+ SetEtcHostsEntry, RemoveEtcHostsEntry, FirstFree, OwnIpAddress, \
+ TailFile
+
from ganeti.errors import LockError, UnitParseError, GenericError, \
ProgrammerError
@@ -772,6 +774,48 @@ class TestFirstFree(unittest.TestCase):
self.failUnlessRaises(AssertionError, FirstFree, [0, 3, 4, 6], base=3)
+class TestTailFile(testutils.GanetiTestCase):
+ """Test case for the TailFile function"""
+
+ def testEmpty(self):
+ fname = self._CreateTempFile()
+ self.failUnlessEqual(TailFile(fname), [])
+ self.failUnlessEqual(TailFile(fname, lines=25), [])
+
+ def testAllLines(self):
+ data = ["test %d" % i for i in range(30)]
+ for i in range(30):
+ fname = self._CreateTempFile()
+ fd = open(fname, "w")
+ fd.write("\n".join(data[:i]))
+ if i > 0:
+ fd.write("\n")
+ fd.close()
+ self.failUnlessEqual(TailFile(fname, lines=i), data[:i])
+
+ def testPartialLines(self):
+ data = ["test %d" % i for i in range(30)]
+ fname = self._CreateTempFile()
+ fd = open(fname, "w")
+ fd.write("\n".join(data))
+ fd.write("\n")
+ fd.close()
+ for i in range(1, 30):
+ self.failUnlessEqual(TailFile(fname, lines=i), data[-i:])
+
+ def testBigFile(self):
+ data = ["test %d" % i for i in range(30)]
+ fname = self._CreateTempFile()
+ fd = open(fname, "w")
+ fd.write("X" * 1048576)
+ fd.write("\n")
+ fd.write("\n".join(data))
+ fd.write("\n")
+ fd.close()
+ for i in range(1, 30):
+ self.failUnlessEqual(TailFile(fname, lines=i), data[-i:])
+
+
class TestFileLock(unittest.TestCase):
"""Test case for the FileLock class"""
--
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