Use layer digest in the description of DiffID by coolljt0725 · Pull Request #328 · opencontainers/image-spec

coolljt0725 · 2016-09-19T11:40:04Z

Signed-off-by: Lei Jitang leijitang@huawei.com

manifest digest means the digest of manifest, I think this is wrong.

wking · 2016-09-19T17:30:21Z

config.md

 	A layer DiffID is a SHA256 digest over the layer's uncompressed tar archive and serialized in the descriptor digest format, e.g., <code>sha256:a9561eb1b190625c9adb5a9513e72c4dedafc1cb2d4c5236c9a6957ec7dfd5a9</code>.
 	Layers must be packed and unpacked reproducibly to avoid changing the layer ID, for example by using tar-split to save the tar headers.
-	NOTE: the DiffID is different than the digest in the manifest list because the manifest digest is taken over the gzipped layer for <code>application/vnd.oci.image.layer.tar+gzip</code> types.
+	NOTE: the DiffID is different than the digest in the manifest list because the digest in the manifest is taken over the gzipped layer for <code>application/vnd.oci.image.layer.tar+gzip</code> types.


+1 to avoiding “manifest digest”. But to make it extra clear that we're comparing with layer digests, how about a separate paragraph:

The DiffID is different than the layer digest in the <a href="manifest.md#image-manifest-property-descriptions">manifest's <code>layers</code></a> because the layer digest is taken over the blob regardless of compression, while the DiffID is taken after removing any compression. For an <code>application/vnd.oci.image.layer.tar+gzip</code> layer.md, the layer digest is taken over the <code>application/vnd.oci.image.layer.tar+gzip</code> content, while the DiffID is take over the <code>application/vnd.oci.image.layer.tar</code> content.

Although that gets into defining a +gzip suffix (more on that in #316).

@wking You suggestion make it much more clear, but the application/vnd.oci.image.layer.tar is not explicit define at the moment.

Mentioning manifests here is the real problem. We should probably just say this is the content of the uncompressed layer tar.

wking · 2016-09-20T08:37:01Z

On Mon, Sep 19, 2016 at 07:35:57PM -0700, Lei Jitang wrote:

NOTE: the DiffID is different than the digest in the manifest list because the manifest digest is taken over the gzipped layer for application/vnd.oci.image.layer.tar+gzip types.

NOTE: the DiffID is different than the digest in the manifest list because the digest in the manifest is taken over the gzipped layer for application/vnd.oci.image.layer.tar+gzip types.

@wking You suggestion make it much more clear, but the
application/vnd.oci.image.layer.tar is not explicit define at the
moment.

So we wait until #316 or similar lands with a definition of the +gzip
suffix? I'll work up a PR for the suffix.

vbatts · 2016-09-21T19:57:01Z

On 20/09/16 01:37 -0700, W. Trevor King wrote:

So we wait until #316 or similar lands with a definition of the +gzip
suffix? I'll work up a PR for the suffix.

This change does not require waiting on the +gzip wording. That is one
of the ways that removing it here causes confusion.

vbatts · 2016-09-21T19:59:42Z

This LGTM though perhaps it could go a step further to word that "the digest in the manifest is taken over the entire object" or " ... opaque blob"? So it is not so specific to just gzipped layers?

wking · 2016-09-21T20:13:34Z

On Wed, Sep 21, 2016 at 12:57:02PM -0700, Vincent Batts wrote:

On 20/09/16 01:37 -0700, W. Trevor King wrote:

So we wait until #316 or similar lands with a definition of the
+gzip suffix? I'll work up a PR for the suffix.

This change does not require waiting on the +gzip wording. That is
one of the ways that removing it here causes confusion.

With the suffix defined, we could use the wording I've proposed in
1. @coolljt0725 liked that wording, but (correctly) pointed out
that it only makes sense once application/vnd.oci.image.layer.tar has
been defined 2. With the +gzip PR (#332), both
application/vnd.oci.image.layer.tar and
application/vnd.oci.image.layer.tar+gzip will be defined, and we can
use the wording from 1.

stevvooe · 2016-09-21T23:53:39Z

config.md

 	A layer DiffID is a SHA256 digest over the layer's uncompressed tar archive and serialized in the descriptor digest format, e.g., <code>sha256:a9561eb1b190625c9adb5a9513e72c4dedafc1cb2d4c5236c9a6957ec7dfd5a9</code>.
 	Layers must be packed and unpacked reproducibly to avoid changing the layer ID, for example by using tar-split to save the tar headers.
-	NOTE: the DiffID is different than the digest in the manifest list because the manifest digest is taken over the gzipped layer for <code>application/vnd.oci.image.layer.tar+gzip</code> types.
+	NOTE: the DiffID is different than the digest in the manifest list because the digest in the manifest is taken over the gzipped layer for <code>application/vnd.oci.image.layer.tar+gzip</code> types.


Mentioning manifests here is the real problem. We should probably just say this is the content of the uncompressed layer tar.

coolljt0725 · 2016-09-22T03:24:57Z

updated
@vbatts @stevvooe

vbatts · 2016-09-22T19:31:12Z

config.md

 	A layer DiffID is a SHA256 digest over the layer's uncompressed tar archive and serialized in the descriptor digest format, e.g., <code>sha256:a9561eb1b190625c9adb5a9513e72c4dedafc1cb2d4c5236c9a6957ec7dfd5a9</code>.
 	Layers must be packed and unpacked reproducibly to avoid changing the layer ID, for example by using tar-split to save the tar headers.
-	NOTE: the DiffID is different than the digest in the manifest list because the manifest digest is taken over the gzipped layer for <code>application/vnd.oci.image.layer.tar+gzip</code> types.
+	NOTE: the DiffID is different than the layer digest because the digest is taken over the content of the uncompressted layer tar for <code>application/vnd.oci.image.layer.tar+gzip</code> types.


uncompressed

@vbatts fixed, thx

coolljt0725 · 2016-09-28T01:41:42Z

@vbatts @stevvooe rebased after #333

vbatts · 2016-10-06T18:03:28Z

LGTM

vbatts · 2016-10-19T13:29:17Z

the needs another LGTM

stevvooe · 2016-10-19T22:11:27Z

config.md

 Layers must be packed and unpacked reproducibly to avoid changing the layer DiffID, for example by using tar-split to save the tar headers.

-NOTE: the DiffID is different than the digest in the manifest list because the manifest digest is taken over the gzipped layer for `application/vnd.oci.image.layer.v1.tar+gzip` types.
+NOTE: the DiffID is different than the layer digest because the layer digest is taken over the content of the gzipped layer for `application/vnd.oci.image.layer.v1.tar+gzip` types.


NOTE: the DiffID is different than the layer digest because it is taken over the uncompressed content of the gzipped layer for application/vnd.oci.image.layer.v1.tar+gzip types.

Your suggested language points out the DiffID being over the uncompressed content. @coolljt0725's current wording points out the layer digest being over the (raw) gzipped content. Both of these are important for understanding the difference, and while the uncompressed-ness of DiffID is mentioned in the previous paragraph, I think it's worth talking about both of them in this note. I have wording for that in my earlier suggestion. Until something like #332 or #388 lands, we could just use “over the uncompressed content” instead of “over the application/vnd.oci.image.layer.v1.tar content”.

coolljt0725 · 2016-10-20T01:28:14Z

@stevvooe updated

Signed-off-by: Lei Jitang <leijitang@huawei.com>

stevvooe · 2016-10-21T18:33:34Z

LGTM

coolljt0725 · 2016-10-24T02:18:00Z

ping @vbatts needs re-LGTM after rebasing

vbatts · 2016-10-24T13:14:55Z

LGTM

wking reviewed Sep 19, 2016

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wking mentioned this pull request Sep 20, 2016

media-types: Define '+gzip' structured syntax suffix #332

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stevvooe requested changes Sep 21, 2016

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coolljt0725 force-pushed the digest branch from d6633bf to f06fef7 Compare September 22, 2016 03:22

coolljt0725 changed the title ~~Replace 'manifest digest' with 'the digest in manifest'~~ Use layer digest in the description of DiffID Sep 22, 2016

vbatts reviewed Sep 22, 2016

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coolljt0725 force-pushed the digest branch 2 times, most recently from 3b5a4b2 to a319777 Compare September 28, 2016 01:39

coolljt0725 force-pushed the digest branch from a319777 to f7b5cb5 Compare October 3, 2016 12:58

stevvooe reviewed Oct 19, 2016

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coolljt0725 force-pushed the digest branch from f7b5cb5 to 5fb15b3 Compare October 20, 2016 01:27

coolljt0725 force-pushed the digest branch from 5fb15b3 to ffcaa5e Compare October 20, 2016 01:31

Use layer digest in the description of DiffID

ffcaa5e

Signed-off-by: Lei Jitang <leijitang@huawei.com>

stevvooe approved these changes Oct 21, 2016

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vbatts merged commit 48e3743 into opencontainers:master Oct 24, 2016

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