From 2635bb04740bc5b90a5f955ba29c7569b9d55b45 Mon Sep 17 00:00:00 2001
From: Michael Hanselmann <hansmi@google.com>
Date: Thu, 5 Jan 2012 21:22:45 +0100
Subject: [PATCH] Move helper class from watcher to utils.io
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βFileStatHelperβ can be used together with βReadFileβ to a file's status
while it's opened. This avoids certain race conditions.
Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>
---
lib/utils/io.py | 19 +++++++++++++++++++
lib/watcher/__init__.py | 19 +------------------
2 files changed, 20 insertions(+), 18 deletions(-)
diff --git a/lib/utils/io.py b/lib/utils/io.py
index 8c785f7d7..ed55f92d6 100644
--- a/lib/utils/io.py
+++ b/lib/utils/io.py
@@ -72,6 +72,25 @@ def ErrnoOrStr(err):
return detail
+class FileStatHelper:
+ """Helper to store file handle's C{fstat}.
+
+ Useful in combination with L{ReadFile}'s C{preread} parameter.
+
+ """
+ def __init__(self):
+ """Initializes this class.
+
+ """
+ self.st = None
+
+ def __call__(self, fh):
+ """Calls C{fstat} on file handle.
+
+ """
+ self.st = os.fstat(fh.fileno())
+
+
def ReadFile(file_name, size=-1, preread=None):
"""Reads a file.
diff --git a/lib/watcher/__init__.py b/lib/watcher/__init__.py
index 915dea031..0325cce15 100644
--- a/lib/watcher/__init__.py
+++ b/lib/watcher/__init__.py
@@ -410,23 +410,6 @@ def _UpdateInstanceStatus(filename, instances):
for inst in instances])
-class _StatCb:
- """Helper to store file handle's C{fstat}.
-
- """
- def __init__(self):
- """Initializes this class.
-
- """
- self.st = None
-
- def __call__(self, fh):
- """Calls C{fstat} on file handle.
-
- """
- self.st = os.fstat(fh.fileno())
-
-
def _ReadInstanceStatus(filename):
"""Reads an instance status file.
@@ -440,7 +423,7 @@ def _ReadInstanceStatus(filename):
"""
logging.debug("Reading per-group instance status from '%s'", filename)
- statcb = _StatCb()
+ statcb = utils.FileStatHelper()
try:
content = utils.ReadFile(filename, preread=statcb)
except EnvironmentError, err:
--
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