This change adds a new cluster state that waits for the replication of a shard to finish before starting snapshotting process. Because this change adds a new snapshot state, an pre-1.2.0 nodes will not be able to join the 1.2.0 cluster that is currently running snapshot/restore operation.
Closes#5531
Fixes#4701. Changes behavior of the snapshot operation. The operation now fails if not all primary shards are available at the beginning of the snapshot operation. The restore operation no longer tries to restore indices with shards that failed or were missing during snapshot operation.
* `ignore_unavailable` - Controls whether to ignore if any specified indices are unavailable, this includes indices that don't exist or closed indices. Either `true` or `false` can be specified.
* `allow_no_indices` - Controls whether to fail if a wildcard indices expressions results into no concrete indices. Either `true` or `false` can be specified. For example if the wildcard expression `foo*` is specified and no indices are available that start with `foo` then depending on this setting the request will fail. This setting is also applicable when `_all`, `*` or no index has been specified.
* `expand_wildcards` - Controls to what kind of concrete indices wildcard indices expression expand to. If `open` is specified then the wildcard expression if expanded to only open indices and if `closed` is specified then the wildcard expression if expanded only to closed indices. Also both values (`open,closed`) can be specified to expand to all indices.
Closes to #4436
Igor Motov
Clinton Gormley
Peter Dyson
David Pilato
Costin Leau
Martijn van Groningen