The ReST API allows you to poll for the status of
certain operations by performing a GET on various
elements. Rather than re-downloading and re-parsing
the full status at each polling interval, your ReST
client may use the
changes-since parameter to
check for changes since a previous request. The
changes-since time is
specified as an ISO 8601 dateTime (2011-01-24T17:08Z). The
form for the timestamp is CCYY-MM-DDThh:mm:ss. An
optional time zone may be written in by appending the
form ±hh:mm which describes the timezone as an
offset from UTC. When the timezone is not specified
(2011-01-24T17:08), the UTC timezone will be assumed.
If nothing has changed since the
changes-since time, an
empty list will be returned. If data has changed, only
the items changed since the specified time will be
returned in the response. For example, performing a
GET against
https://api.servers.openstack.org/v2/224532/servers?changes-since=2011-01-24T17:08Z
would list all servers that have changed since Mon, 24
Jan 2011 17:08:00 UTC.
To allow clients to keep track of changes, the
changes-since filter displays items that have been
recently deleted. Both images
and servers contain a DELETED status that
indicates that the resource has been removed.
Implementations are not required to keep track of
deleted resources indefinitely, so sending a changes
since time in the distant past may miss deletions.
