Fixed how blob storage PutBlob errors are handled in content.Manager #117
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In order to guarantee that all index entries have corresponding pack blobs, we must ensure that `content.Manager.Flush` will not succeed unless all pending writes have completed. Added test that simulates various patterns of PutBlock failures and ensures that data remains durable despite those, assuming all calls to `WriteContent()` and `Flush()` are retried.
julio-lopez
approved these changes
Sep 27, 2019
| @@ -152,6 +153,16 @@ func (bm *Manager) addToPackUnlocked(ctx context.Context, contentID ID, data []b | |||
| bm.cond.Wait() | |||
| } | |||
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| // see if we have any packs that have failed previously | |||
| // retry writing them now. | |||
| fp := append([]*pendingPackInfo(nil), bm.failedPacks...) | |||
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There is a subtle "dependency" here on the implementation of .writePackAndAddToIndex(...).
Would it make sense to add a comment here explaining why the slice needs to be copied, namely that bm.failedPacks is modified inside bm.writePackAndAddToIndex ?
| return errors.Wrap(err, "error writing previously failed pack") | ||
| } | ||
| } | ||
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Not related to this change, but "surprising" if you will. Is the assumption (expected semantics here) that when bm.flushPackIndexesLocked(ctx) returns an error below, it should not release the lock?
For what I can tell from the calling paths into addToPackUnlocked(), both from WriteContent and RewriteContent, this is unexpected.
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you're right, clearly forgot that one
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In order to guarantee that all index entries have corresponding
pack blobs, we must ensure that
content.Manager.Flushwillnot succeed unless all pending writes have completed.
Added test that simulates various patterns of PutBlock failures and
ensures that data remains durable despite those, assuming all calls
to
WriteContent()andFlush()are retried.