Fix windows dataloss issue#1134
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jarifibrahim merged 3 commits intomasterfrom Dec 6, 2019
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Windows doesn't allow memory mapping a file to a size greater than the file's actual size. To circumvent this, we increase the file size by truncating it. https://github.com/dgraph-io/badger/blob/f5b63211d7f3e2f5f8b698893313b2a54e4df7de/y/mmap_windows.go#L41-L48 When badger would re-open, we try to replay this "truncated" file. Since this truncated file consists of all zeros, the replay would return the last offset as `zero` and then we would truncate the original file to size `zero`. The replay function would return `zero` as the last valid offset which was wrong. The last valid offset is start offset plus the forward movements of the file offset. So instead of https://github.com/dgraph-io/badger/blob/f5b63211d7f3e2f5f8b698893313b2a54e4df7de/value.go#L433 ```go var validEndOff uint32 // notice we're starting from zero, not the start point. ``` we should be doing ```go var validEndOff uint32 = offset ``` Fixes - #1126 (cherry picked from commit 969a8e8)
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I see that this issue has been resolved, but currently I am encountering the same phenomenon on Windows 10 Golang 1.21.0. When the program interrupts abnormally and fails to close properly, the vlog size becomes 1kb and prompts "Value log truncate required to run DB. This might result in data loss" @jarifibrahim |
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Windows doesn't allow memory mapping a file to a size greater than the file's actual size. To circumvent this, we increase the file size by truncating it.
badger/y/mmap_windows.go
Lines 41 to 48 in f5b6321
When badger would re-open, we try to replay this "truncated" file. Since this truncated file consists of all zeros, the replay would return the last offset as
zeroand then we would truncate the original file to sizezero.The replay function would return
zeroas the last valid offset which was wrong. The last valid offset is start offset plus the forward movements of the file offset.So instead of
badger/value.go
Line 433 in f5b6321
we should be doing
Fixes - #1126
This change is