While early PoCs had download resumption working, we didn't have tests
and had not verified the behavior. With this test suite, we now are able
to show that download resumption is properly supported in the content
store. In particular, there was a bug where resuming a download would
not issue the writes to the correct offset in the file. A Seek was added
to ensure we are writing from the current ingest offset.
In this investigation, it was also discovered that using the OS/Disk
created time on files was skewed from the monotonic clock in Go's
runtime. The startedat values are now taken from the Go runtime and
written to a separate file.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
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