ECS 3.6.2 Data Access Guide

Appending data to an object

You can use ECS extensions to the EMC Atmos protocol to append data to an object.

There may be cases where you need to append to an object, but determining the exact byte offset is not efficient or useful. For this scenario, ECS provides the ability to atomically append data to the object without specifying an offset (the correct offset is returned to you in the response).

A Range header with the special value bytes=-1- is used to append data to an object. In this way, the object can be extended without knowing the existing object size. The format is: Range: bytes=-1-

A sample request showing appending to an existing object using a Range value of bytes=-1- is shown in the following example. Here the value and cat is sent in the request.

PUT /rest/namespace/myObject HTTP/1.1
Content-Length: 8
Range: bytes=-1-
ACCEPT: application/json,application/xml,text/html,application/octet-stream
Date: Mon, 17 Jun 2013 20:46:01 -0000
x-emc-date: Mon, 17 Jun 2013 20:46:01 -0000
x-emc-namespace: emc
x-emc-uid: fa4e31a68d3e4929bec2f964d4cac3de/wuser1@sanity.local
x-emc-signature: ZpW9KjRb5+YFdSzZjwufZUqkExc=
Content-Type: application/octet-stream
Accept-Encoding: gzip, deflate, compress

and cat 

HTTP/1.1 200 OK
x-emc-mtime: 1431626712933
Date: Mon, 17 Jun 2013 20:46:01 GMT
x-emc-policy: default
x-emc-utf8: true
x-emc-request-id: 0af9ed8d:14cc314a9bc:112f6:9
x-emc-delta: 8
x-emc-append-offset: 24
Content-Length: 0
Server: Jetty(7.6.4.v20120524)

The offset position at which the data was appended is returned in the x-emc-append-offset header.

When the object is retrieved, and cat has been appended, and you can see the full value: The quick green fox jumps over the lazy dog and cat.