The shard preference _primary, _replica and its variants were useful
for the asynchronous replication. However, with the current impl, they
are no longer useful and should be removed.
Closes#26335
This commit clarifies the preference docs regarding the explanation of
how operations are routed by default. In particular, the previous use of
"shard replicas" was confusing as it could imply an operation would only
be routed to replicas by default.
Relates #23794
The shards preference on a search request enables specifying a list of
shards to hit, and then a secondary preference (e.g., "_primary") can be
added. Today, the separator between the shards list and the secondary
preference is ';'. Unfortunately, this is also a valid separtor for URL
query parameters. This means that a preference like "_shards:0;_primary"
will be parsed into two URL parameters: "_shards:0" and "_primary". With
the recent change to strict URL parsing, the second parameter will be
rejected, "_primary" is not a valid URL parameter on a search
request. This means that this feature has never worked (unless the ';'
is escaped, but no one does that because our docs do not that, and there
was no indication from Elasticsearch that this did not work). This
commit changes the separator to '|'.
Relates #20786
This commit removes the search preference _only_node as the same
functionality can be obtained by using the search preference
_only_nodes. This commit also adds a test that ensures that _only_nodes
will continue to support specifying node IDs.
Relates #18875
The search preference _prefer_node allows specifying a single node to
prefer when routing a request. This functionality can be enhanced by
permitting multiple nodes to be preferred. This commit replaces the
search preference _prefer_node with the search preference _prefer_nodes
which supplants the former by specifying a single node and otherwise
adds functionality.
Relates #18872
Just like specifying `?preference=_primary`, this adds the ability to
specify `?preference=_replica` or `?preference=_replica_first` on
requests that support it.
Resolves#12222
Nhat
Glen Smith
Clinton Gormley
Jason Tedor
Isabel Drost-Fromm
Lee Hinman
Nirmal Chidambaram