0001777: Multiple instances of DF can run simultaneously in same folder, resulting in save corruption

(0006241)
Footkerchief (manager)
2010-05-05 22:25
edited on: 2010-05-05 22:27

Most likely because they're sharing the "current" folder. That was probably the motivation for this old bug entry:

# 000020 □ [technical] (http://www.bay12forums.com/smf/index.php?topic=21812.0 [^]) stop multiple copies of the program from being open

(0009985)
shibdib (reporter)
2010-07-11 17:17

confirmed still in 0.31.10

(0020942)
zombiejustice (reporter)
2012-03-01 06:04

This doesn't seem like high priority: you're doing something OUTSIDE the game, that you know will break the game. Should this be closed as 'working as intended'?

(0020943)
Footkerchief (manager)
2012-03-01 07:08

As I mentioned in the first note, this was in the old bug list that Toady used to maintain (dev_bugs.html).

(0020947)
thvaz (reporter)
2012-03-01 09:00

If he never got around to fix it, maybe he doesn't know how? He may need some help then.

I have little experience as a programmer, but this doesn't sound like something that would demand a lot of time.

(0020948)
Xotano (reporter)
2012-03-01 09:02

well you would think people would refrain from opening multiple game windows.

(0023994)
Brilliand (reporter)
2013-06-06 15:11

Multiple instances of DF being able to load the same save is a good thing. However, it should probably balk at overwriting a save that doesn't match the one it loaded (say, store a version number somewhere). If that happens, it could maybe offer to save in a different folder.

That's getting pretty far away from the "permanent death" ideal, but I don't like permanent death anyway. :p

(0036522)
alexchandel (reporter)
2017-05-11 13:16

I recently had to run two DF instances at once, so I'm glad it's possible.

Assuming you don't attempt to save, and kill both processes with killall/SIGTERM, is there any possible way DF can corrupt any of its files?

As far as behavior, the only change that could be added is: locking on a lock-file in the region folder when saving, so that another process doesn't try to simultaneously save and corrupt the files.

(0036537)
lethosor (manager)
2017-05-17 14:21

If you don't save, as far as I know, the only files that will be touched are those in data/save/current, which is cleared periodically.

However, I would still recommend not doing what you did, because DF could be confused if it tries to read files from data/save/current and gets files from another save, or if it fails to read files that the other DF process deleted already.

As for your locking suggestion, that wouldn't prevent corruption, because if data/save/current contains files from two different saves, they'll still be copied into the wrong region folder(s).

Issue History
Date Modified	Username	Field	Change
2010-05-05 22:17	The Architect	New Issue
2010-05-05 22:25	Footkerchief	Note Added: 0006241
2010-05-05 22:27	Footkerchief	Note Edited: 0006241	View Revisions
2010-06-29 07:38	Footkerchief	Category	Technical => Technical -- General
2010-07-11 16:50	Footkerchief	Relationship added	has duplicate 0002641
2010-07-11 16:50	Footkerchief	Summary	Saving simultaneously with two DF programs causes file corruption => Multiple instances of DF can run simultaneously in same folder, resulting in save corruption
2010-07-11 17:17	shibdib	Note Added: 0009985
2012-03-01 02:14	Knight Otu	Relationship added	has duplicate 0005518
2012-03-01 06:04	zombiejustice	Note Added: 0020942
2012-03-01 07:08	Footkerchief	Note Added: 0020943
2012-03-01 09:00	thvaz	Note Added: 0020947
2012-03-01 09:02	Xotano	Note Added: 0020948
2012-09-20 08:04	Footkerchief	Relationship added	has duplicate 0006204
2013-06-06 15:11	Brilliand	Note Added: 0023994
2014-01-20 19:06	Footkerchief	Relationship deleted	has duplicate 0006204
2017-05-11 13:16	alexchandel	Note Added: 0036522
2017-05-17 14:21	lethosor	Note Added: 0036537

Notes
(0006241) Footkerchief (manager) 2010-05-05 22:25 edited on: 2010-05-05 22:27	Most likely because they're sharing the "current" folder. That was probably the motivation for this old bug entry: # 000020 □ [technical] (http://www.bay12forums.com/smf/index.php?topic=21812.0 [^]) stop multiple copies of the program from being open

(0009985) shibdib (reporter) 2010-07-11 17:17	confirmed still in 0.31.10

(0020942) zombiejustice (reporter) 2012-03-01 06:04	This doesn't seem like high priority: you're doing something OUTSIDE the game, that you know will break the game. Should this be closed as 'working as intended'?

(0020943) Footkerchief (manager) 2012-03-01 07:08	As I mentioned in the first note, this was in the old bug list that Toady used to maintain (dev_bugs.html).

(0020947) thvaz (reporter) 2012-03-01 09:00	If he never got around to fix it, maybe he doesn't know how? He may need some help then. I have little experience as a programmer, but this doesn't sound like something that would demand a lot of time.

(0020948) Xotano (reporter) 2012-03-01 09:02	well you would think people would refrain from opening multiple game windows.

(0023994) Brilliand (reporter) 2013-06-06 15:11	Multiple instances of DF being able to load the same save is a good thing. However, it should probably balk at overwriting a save that doesn't match the one it loaded (say, store a version number somewhere). If that happens, it could maybe offer to save in a different folder. That's getting pretty far away from the "permanent death" ideal, but I don't like permanent death anyway. :p

(0036522) alexchandel (reporter) 2017-05-11 13:16	I recently had to run two DF instances at once, so I'm glad it's possible. Assuming you don't attempt to save, and kill both processes with killall/SIGTERM, is there any possible way DF can corrupt any of its files? As far as behavior, the only change that could be added is: locking on a lock-file in the region folder when saving, so that another process doesn't try to simultaneously save and corrupt the files.

(0036537) lethosor (manager) 2017-05-17 14:21	If you don't save, as far as I know, the only files that will be touched are those in data/save/current, which is cleared periodically. However, I would still recommend not doing what you did, because DF could be confused if it tries to read files from data/save/current and gets files from another save, or if it fails to read files that the other DF process deleted already. As for your locking suggestion, that wouldn't prevent corruption, because if data/save/current contains files from two different saves, they'll still be copied into the wrong region folder(s).