From: Christian Heller <c.heller@plomlompom.de>
Date: Sun, 22 Feb 2015 10:50:03 +0000 (+0100)
Subject: Server/py: Improve atomicity of record(), description of its strategy.
X-Git-Tag: tce~503
X-Git-Url: https://plomlompom.com/repos/%7B%7Bprefix%7D%7D/static/%7B%7Byoutube_prefix%7D%7D%7B%7Bvideo_id%7D%7D?a=commitdiff_plain;h=1b641d2c660fa003e73db970cbbbc935345a495d;p=plomrogue

Server/py: Improve atomicity of record(), description of its strategy.
---

diff --git a/plomrogue-server.py b/plomrogue-server.py
index 47390a4..c9cc20e 100755
--- a/plomrogue-server.py
+++ b/plomrogue-server.py
@@ -78,8 +78,10 @@ def obey(cmd, io_db, prefix):
 
 
 def record(cmd, io_db):
-    """Append cmd string plus newline to file at path_recordfile."""
-    # Doesn't yet replace old record() fully.
+    """Append cmd string plus newline to file at path_recordfile. (Atomic.)"""
+    # This misses some optimizations from the original record(), namely only
+    # finishing the atomic write with flush() and fsync() every 15 seconds
+    # unless explicitely forced. Implement as needed.
     path_tmp = io_db["path_record"] + io_db["tmp_suffix"]
     if os.access(io_db["path_record"], os.F_OK):
         shutil.copyfile(io_db["path_record"], path_tmp)
@@ -88,6 +90,8 @@ def record(cmd, io_db):
     file.flush()
     os.fsync(file.fileno())
     file.close()
+    if os.access(io_db["path_record"], os.F_OK):
+        os.remove(io_db["path_record"])
     os.rename(path_tmp, io_db["path_record"])