Server/py: Improve handling of parallel server instances conflict.

[plomrogue] / plomrogue-server.py

diff --git a/plomrogue-server.py b/plomrogue-server.py
index 5018304e6a0af417d5e0d450162bb918a16ad498..a921e93558fe3cd7993aa4757bc8dc4d3a36193a 100755 (executable)
--- a/plomrogue-server.py
+++ b/plomrogue-server.py
@@ -28,6 +28,7 @@ def setup_server_io(io_db):
     os.makedirs(io_dir, exist_ok=True)
     io_db["file_out"] = open(io_db["path_out"], "w")
     io_db["file_out"].write(io_db["teststring"] + "\n")
+    io_db["file_out"].flush()
     if os.access(io_db["path_in"], os.F_OK):
         os.remove(io_db["path_in"])
     io_db["file_in"] = open(io_db["path_in"], "w")
@@ -38,11 +39,12 @@ def setup_server_io(io_db):
 
 
 def cleanup_server_io(io_db):
-    """Close and remove all files open in IO files DB."""
+    """Close and (if io_db["kicked_by_rival"] false) remove files in io_db."""
     def helper(file_key, path_key):
         if file_key in io_db:
             io_db[file_key].close()
-            os.remove(io_db[path_key])
+            if not io_db["kicked_by_rival"]:
+                os.remove(io_db[path_key])
     helper("file_out", "path_out")
     helper("file_in", "path_in")
     helper("file_worldstate", "path_worldstate")
@@ -98,7 +100,7 @@ def record(cmd, io_db):
     os.rename(path_tmp, io_db["path_record"])
 
 
-def obey_lines_in_file(path, name, break_test = None):
+def obey_lines_in_file(path, name, break_test=None):
     """Call obey() on each line of path's file, use name in input prefix.
 
     If break_test function is set, only read the file until it returns True.
@@ -120,7 +122,6 @@ def make_turn_tester(turn_to_compare, world_db):
     return turn_tester
 
 
-
 def parse_command_line_arguments():
     """Return settings values read from command line arguments."""
     parser = argparse.ArgumentParser()
@@ -130,6 +131,24 @@ def parse_command_line_arguments():
     return opts
 
 
+def server_test(io_db):
+    """Ensure valid server out file belonging to current process.
+
+    On failure, set io_db["kicked_by_rival"] and raise SystemExit.
+    """
+    if not os.access(io_db["path_out"], os.F_OK):
+        raise SystemExit("Server output file has disappeared.")
+    file = open(io_db["path_out"], "r")
+    test = file.readline().rstrip("\n")
+    file.close()
+    if test != io_db["teststring"]:
+        io_db["kicked_by_rival"] = True
+        msg = "Server test string in server output file does not match. This" \
+              " indicates that the current server process has been " \
+              "superseded by another one."
+        raise SystemExit(msg)
+
+
 io_db = {}
 world_db = {}
 try:
@@ -156,6 +175,8 @@ try:
                 raise SystemExit(msg)
             obey_lines_in_file(io_db["path_worldconf"], "world config ")
             obey("MAKE_WORLD " + str(int(time.time())), io_db, "in file")
+        while 1:
+            server_test(io_db)
         # print("DUMMY: Run io_loop().")
 except SystemExit as exit:
     print("ABORTING: " + exit.args[0])