Lost cache in some condition

[teoking]

I found an issue: you created a new cache and just then the app is crashed, the cache will be lost.

I check the journal file and found that: the new cache you just created is marked with "DIRTY", and even if I called commit, there's no "CLEAN" followed that "DIRTY", at this time, if the app crashes, the cache leaves "DIRTY" but not "CLEAN" which it should be. Then you launch the app again, the "DIRTY" cache with no "CLEAN" followed will be deleted, and you lost the cache.

This scenario cannot covered by android test cases.

I found this may be caused by the journal is opened by BufferedWriter which has a 8K buffer internally. So the latest "CLEAN" state is actually in the buffer but not in disk when the crash happens.

Add the following line in completeEdit method seems can solve this: journalWriter.flush();

[swankjesse]

This is a policy decision in the API. You can manually call flush() in your own code if you'd like to flush the journal after every write. DiskLruCache doesn't do this by default because it wants to minimize the number of slow disk writes it makes.

[swankjesse]

That said, this does need to be documented!

[teoking]

I see your point. I'd like not flush journal after every write, only after write "CLEAN" or "DIRTY", while not flush after write "READ"(not worth to do). Back to my case, my app is an android app which may be closed or interrupted unpredictably, and I has only one chance to create a cache(after a video is downloaded) and use it elsewhere. If someone has the similar case with me, I suggest flush after every commit immediately.

[lexer]

@swankjesse could you suggest where it is better to flush DiskLruCache for Android apps to prevent loosing of image cache after app close or crash?

[swankjesse]

Calling flush after committing an edit would work.

[lexer]

Thanks!

[kroikie]

Thank you so much for this, flush works!