19088: Document S3 properties-as-metadata feature.

Arvados-DCO-1.1-Signed-off-by: Tom Clegg <tom@curii.com>

diff --git a/doc/api/keep-s3.html.textile.liquid b/doc/api/keep-s3.html.textile.liquid
index bee91516bc12fc61e87a51b603361372ad64e358..2e0c90ef47617e7aabc1d01928c4d7496842654d 100644 (file)
--- a/doc/api/keep-s3.html.textile.liquid
+++ b/doc/api/keep-s3.html.textile.liquid
@@ -70,6 +70,22 @@ h4. GetBucketVersioning
 
 Bucket versioning is presently not supported, so this will always respond that bucket versioning is not enabled.
 
 
 Bucket versioning is presently not supported, so this will always respond that bucket versioning is not enabled.
 

+h3. Accessing collection/project properties as metadata
+
+GetObject, HeadObject, and HeadBucket return Arvados object properties as S3 metadata headers, e.g., @X-Amz-Meta-Foo: bar@.
+
+If the requested path indicates a file or directory placeholder inside a collection, or the top level of a collection, GetObject and HeadObject return the collection properties.
+
+If the requested path indicates a directory placeholder corresponding to a project, GetObject and HeadObject return the properties of the project.
+
+HeadBucket returns the properties of the collection or project corresponding to the bucket name.
+
+Non-string property values are returned in a JSON representation, e.g., @["foo","bar"]@.
+
+As in Amazon S3, property values containing non-ASCII characters are returned in BASE64-encoded form as described in RFC 2047, e.g., @=?UTF-8?b?4pu1?=@.
+
+It is not possible to modify collection or project properties using the S3 API.
+

 h3. Authorization mechanisms
 
 Keep-web accepts AWS Signature Version 4 (AWS4-HMAC-SHA256) as well as the older V2 AWS signature.
 h3. Authorization mechanisms
 
 Keep-web accepts AWS Signature Version 4 (AWS4-HMAC-SHA256) as well as the older V2 AWS signature.