This way provide both Time and TimeNano in the event. For the display of
the JSONMessage, use either, but prefer TimeNano Proving only TimeNano
would break Subscribers that are using the `Time` field, so both are set
for backwards compatibility.
The events logging uses nano formatting, but only provides a Unix()
time, therefor ordering may get lost in the output. Example:
```
2015-09-15T14:18:51.000000000-04:00 ee46febd64ac629f7de9cd8bf58582e6f263d97ff46896adc5b508db804682da: (from busybox) resize
2015-09-15T14:18:51.000000000-04:00 a78c9149b1c0474502a117efaa814541926c2ae6ec3c76607e1c931b84c3a44b: (from busybox) resize
```
By having a field just for Nano time, when set, the marshalling back to
`time.Unix(sec int64, nsec int64)` has zeros exactly where it needs to.
This does not break any existing use of jsonmessage.JSONMessage, but now
allows for use of `UnixNano()` and get event formatting that has
distinguishable order. Example:
```
2015-09-15T15:37:23.810295632-04:00 6adcf8ed9f5f5ec059a915466cd1cde86a18b4a085fc3af405e9cc9fecbbbbaf: (from busybox) resize
2015-09-15T15:37:23.810412202-04:00 6b7c5bfdc3f902096f5a91e628f21bd4b56e32590c5b4b97044aafc005ddcb0d: (from busybox) resize
```
Including tests for TimeNano and updated event API reference doc.
Signed-off-by: Vincent Batts <vbatts@redhat.com>
The practice of buffering to a tempfile during a pushing contributes massively
to slow V2 push performance perception. The protocol was actually designed to
avoid precalculation, supporting cut-through data push. This means we can
assemble the layer, calculate its digest and push to the remote endpoint, all
at the same time.
This should increase performance massively on systems with slow disks or IO
bottlenecks.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
