Ali Beyad 743217a430 Enhances get snapshots API to allow retrieving repository index only (#24477)
Currently, the get snapshots API (e.g. /_snapshot/{repositoryName}/_all)
provides information about snapshots in the repository, including the
snapshot state, number of shards snapshotted, failures, etc.  In order
to provide information about each snapshot in the repository, the call
must read the snapshot metadata blob (`snap-{snapshot_uuid}.dat`) for
every snapshot.  In cloud-based repositories, this can be expensive,
both from a cost and performance perspective.  Sometimes, all the user
wants is to retrieve all the names/uuids of each snapshot, and the
indices that went into each snapshot, without any of the other status
information about the snapshot.  This minimal information can be
retrieved from the repository index blob (`index-N`) without needing to
read each snapshot metadata blob.

This commit enhances the get snapshots API with an optional `verbose`
parameter.  If `verbose` is set to false on the request, then the get
snapshots API will only retrieve the minimal information about each
snapshot (the name, uuid, and indices in the snapshot), and only read
this information from the repository index blob, thereby giving users
the option to retrieve the snapshots in a repository in a more
cost-effective and efficient manner.

Closes #24288
2017-05-10 15:48:40 -04:00
..