Server/py: Add atomic writing to record().

[plomrogue] / plomrogue-server.py

diff --git a/plomrogue-server.py b/plomrogue-server.py
index e5b7c0e68bc3a0067384e15b6dd50d55cf1161fe..47390a4dffdb14056a7975404810688c485b64b6 100755 (executable)
--- a/plomrogue-server.py
+++ b/plomrogue-server.py
@@ -2,6 +2,7 @@ import argparse
 import errno
 import os
 import shlex
+import shutil
 import time
 
 
@@ -21,6 +22,7 @@ def setup_server_io(io_db):
     io_db["path_record"] = "record"
     io_db["path_save"] = "save"
     io_db["path_worldconf"] = "confserver/world"
+    io_db["tmp_suffix"] = "_tmp"
     io_db["teststring"] = str(os.getpid()) + " " + str(time.time())
     os.makedirs(io_dir, exist_ok=True)
     io_db["file_out"] = open(io_db["path_out"], "w")
@@ -43,9 +45,9 @@ def cleanup_server_io(io_db):
     helper("file_worldstate", "path_worldstate")
 
 
-def detect_atomic_leftover(path):
-    """Raise explained SystemExit if file is found at path + "_tmp"."""
-    path_tmp = path + "_tmp"
+def detect_atomic_leftover(path, tmp_suffix):
+    """Raise explained SystemExit if file is found at path + tmp_suffix."""
+    path_tmp = path + tmp_suffix
     msg = "Found file '" + path_tmp + "' that may be a leftover from an " \
           "aborted previous attempt to write '" + path + "'. Aborting until " \
           "the matter is resolved by removing it from its current path."
@@ -70,17 +72,23 @@ def obey(cmd, io_db, prefix):
         raise SystemExit("received QUIT command")
     elif "MAKE_WORLD" == tokens[0] and 2 == len(tokens):
         print("I would generate a new world now, if only I knew how.")
-        record(cmd, io_db["path_record"])
+        record(cmd, io_db)
     else:
         print("Invalid command/argument, or bad number of tokens.")
 
 
-def record(cmd, path_recordfile):
+def record(cmd, io_db):
     """Append cmd string plus newline to file at path_recordfile."""
     # Doesn't yet replace old record() fully.
-    file = open(path_recordfile, "a")
+    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)
+    file = open(path_tmp, "a")
     file.write(cmd + "\n")
+    file.flush()
+    os.fsync(file.fileno())
     file.close()
+    os.rename(path_tmp, io_db["path_record"])
 
 
 def obey_lines_in_file(path, name):
@@ -92,6 +100,7 @@ def obey_lines_in_file(path, name):
         line_n = line_n + 1
     file.close()
 
+
 io_db = {}
 try:
     parser = argparse.ArgumentParser()
@@ -99,8 +108,8 @@ try:
                         action='store')
     setup_server_io(io_db)
     # print("DUMMY: Run game.")
-    detect_atomic_leftover(io_db["path_save"])
-    detect_atomic_leftover(io_db["path_record"])
+    detect_atomic_leftover(io_db["path_save"], io_db["tmp_suffix"])
+    detect_atomic_leftover(io_db["path_record"], io_db["tmp_suffix"])
     opts, unknown = parser.parse_known_args()
     if None != opts.replay:
         if opts.replay < 1: