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60 lines
3.0 KiB
Markdown
60 lines
3.0 KiB
Markdown
# Debugging / reporting desyncs
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As desyncs are hard to make reproducible OpenTTD has the ability to log all
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actions done by clients so we can replay the whole game in an effort to make
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desyncs better reproducible. You need to turn this ability on. When turned
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on an automatic savegame will be made once the map has been constructed in
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the 'save/autosave' directory, see OpenTTD directories to know where to find
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this directory. Furthermore the log file 'commands-out.log' will be created
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and all actions will be written to there.
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To enable the desync debugging you need to set the debug level for 'desync'
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to at least 1. You do this by starting OpenTTD with '`-d desync=<level>`' as
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parameter or by typing '`debug_level desync=<level>`' in OpenTTD's internal
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console.
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The desync debug levels are:
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- 0: nothing.
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- 1: dumping of commands to 'commands-out.log'.
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- 2: same as 1 plus checking vehicle caches and dumping that too.
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- 3: same as 2 plus monthly saves in autosave.
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- 4 and higher: same as 3
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Restarting OpenTTD will overwrite 'commands-out.log'. OpenTTD will not remove
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the savegames (dmp_cmds_*.sav) made by the desync debugging system, so you
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have to occasionally remove them yourself!
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The naming format of the desync savegames is as follows:
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dmp_cmds_XXXXXXXX_YYYYYYYY.sav. The XXXXXXXX is the hexadecimal representation
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of the generation seed of the game and YYYYYYYY is the hexadecimal
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representation of the date of the game. This sorts the savegames by game and
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then by date making it easier to find the right savegames.
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When a desync has occurred with the desync debugging turned on you should file
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a bug report with the following files attached:
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- commands-out.log as it contains all the commands that were done
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- the last saved savegame (search for the last line beginning with
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'save: dmp_cmds_' in commands-out.log). We use this savegame to check
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whether we can quickly reproduce the desync. Otherwise we will need …
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- the first saved savegame (search for the first line beginning with 'save'
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where the first part, up to the last underscore '_', is the same). We need
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this savegame to be able to reproduce the bug when the last savegame is not
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old enough. If you loaded a scenario or savegame you need to attach that.
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- optionally you can attach the savegames from around 50%, 75%, 85%, 90% and
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95% of the game's progression. We can use these savegames to speed up the
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reproduction of the desync, but we should be able to reproduce these
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savegames based on the first savegame and commands-out.log.
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- in case you use any NewGRFs you should attach the ones you used unless
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we can easily find them ourselves via bananas or when they are in the
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#openttdcoop pack.
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Do NOT remove the dmp_cmds savegames of a desync you have reported until the
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desync has been fixed; if you, by accident, send us the wrong savegames we
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will not be able to reproduce the desync and thus will be unable to fix it.
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## More information
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You can find more theory on the causes and debugging of desyncs in the
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[desync documentation](./desync.md).
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