Updates the cross-cluster search (CCS) documentation to note how
cluster-level settings are applied.
When `ccs_minimize_roundtrips` is `true`, each cluster applies its own
cluster-level settings to the request.
When `ccs_minimize_roundtrips` is `false`, cluster-level settings for
the local cluster is used. This includes shard limit settings, such as
`action.search.shard_count.limit`, `pre_filter_shard_size`, and
`max_concurrent_shard_requests`. If these limits are set too low, the
request could be rejected.
This commit clarifies how the gateway selection works when configuring
remote clusters for CCR or CCS. Specifically, it clarifies compatibility
between different versions which is a very common question.
`SearchShardIterator` inherits its `compareTo` implementation from `PlainShardIterator`. That is good in most of the cases, as such comparisons are based on the shard id which is unique, even when searching against indices with same names across multiple clusters (thanks to the index uuid being different). In case though the same cluster is registered multiple times with different aliases, the shard id is exactly the same, hence remote results will be returned before local ones with same shard id objects. That is because remote iterators are added before local ones, and we use a stable sorting method in `GroupShardIterators` constructor.
This PR enhances `compareTo` for `SearchShardIterator` to tie break on cluster alias and introduces consistent `equals` and `hashcode` methods. This allows to remove a TODO in `SearchResponseMerger` which otherwise has to handle this special case specifically. Also, while at it I added missing tests around equals/hashcode and compareTo and expanded existing ones.
With #37000 we made sure that fnial reduction is automatically disabled
whenever a localClusterAlias is provided with a SearchRequest.
While working on #37838, we found a scenario where we do need to set a
localClusterAlias yet we would like to perform a final reduction in the
remote cluster: when searching on a single remote cluster.
Relates to #32125
This commit adds support for a separate finalReduce flag to
SearchRequest and makes use of it in TransportSearchAction in case we
are searching against a single remote cluster.
This also makes sure that num_reduce_phases is correct when searching
against a single remote cluster: it makes little sense to return
`num_reduce_phases` set to `2`, which looks especially weird in case
the search was performed against a single remote shard. We should
perform one reduction phase only in this case and `num_reduce_phases`
should reflect that.
* line length
With #37566 we have introduced the ability to merge multiple search responses into one. That makes it possible to expose a new way of executing cross-cluster search requests, that makes CCS much faster whenever there is network latency between the CCS coordinating node and the remote clusters. The coordinating node can now send a single search request to each remote cluster, which gets reduced by each one of them. from + size results are requested to each cluster, and the reduce phase in each cluster is non final (meaning that buckets are not pruned and pipeline aggs are not executed). The CCS coordinating node performs an additional, final reduction, which produces one search response out of the multiple responses received from the different clusters.
This new execution path will be activated by default for any CCS request unless a scroll is provided or inner hits are requested as part of field collapsing. The search API accepts now a new parameter called ccs_minimize_roundtrips that allows to opt-out of the default behaviour.
Relates to #32125
This commit changes the format of the `hits.total` in the search response to be an object with
a `value` and a `relation`. The `value` indicates the number of hits that match the query and the
`relation` indicates whether the number is accurate (in which case the relation is equals to `eq`)
or a lower bound of the total (in which case it is equals to `gte`).
This change also adds a parameter called `rest_total_hits_as_int` that can be used in the
search APIs to opt out from this change (retrieve the total hits as a number in the rest response).
Note that currently all search responses are accurate (`track_total_hits: true`) or they don't contain
`hits.total` (`track_total_hits: true`). We'll add a way to get a lower bound of the total hits in a
follow up (to allow numbers to be passed to `track_total_hits`).
Relates #33028
With remote clusters taking on a larger role, we have make the
infrastructure more generic than being tied to cross-cluster search
(CCS). We want to refer to the remote clusters configuration in the
cross-cluster replication (CCR) docs. Yet, these docs are still tied to
CCS. This commit extracts the remote clusters docs from CCS (with some
wording changes to make them more general) so that we can refer to them
in the CCR docs.
With features like CCR building on the CCS infrastructure, the settings
prefix search.remote makes less sense as the namespace for these remote
cluster settings than does a more general namespace like
cluster.remote. This commit replaces these settings with cluster.remote
with a fallback to the deprecated settings search.remote.
Allowing `_doc` as a type will enable users to make the transition to 7.0
smoother since the index APIs will be `PUT index/_doc/id` and `POST index/_doc`.
This also moves most of the documentation to `_doc` as a type name.
Closes#27750Closes#27751
Today Cross Cluster Search requires at least one node in each remote cluster to be up once the cross cluster search is run. Otherwise the whole search request fails despite some of the data (either local and/or remote) is available. This happens when performing the _search/shards calls to find out which remote shards the query has to be executed on. This scenario is different from shard failures that may happen later on when the query is actually executed, in case e.g. remote shards are missing, which is not going to fail the whole request but rather yield partial results, and the _shards section in the response will indicate that.
This commit introduces a boolean setting per cluster called search.remote.$cluster_alias.skip_if_disconnected, set to false by default, which allows to skip certain clusters if they are down when trying to reach them through a cross cluster search requests. By default all clusters are mandatory.
Scroll requests support such setting too when they are first initiated (first search request with scroll parameter), but subsequent scroll rounds (_search/scroll endpoint) will fail if some of the remote clusters went down meanwhile.
The search API response contains now a new _clusters section, similar to the _shards section, that gets returned whenever one or more clusters were disconnected and got skipped:
"_clusters" : {
"total" : 3,
"successful" : 2,
"skipped" : 1
}
Such section won't be part of the response if no clusters have been skipped.
The per cluster skip_unavailable setting value has also been added to the output of the remote/info API.
Adds CONSOLE to cross-cluster-search docs but skips them for testing
because we don't have a second cluster set up. This gets us the
`VIEW IN CONSOLE` and `COPY AS CURL` links and makes sure that they
are valid yaml (not json, technically) but doesn't get testing.
Which is better than we had before.
Adds CONSOLE to the dynamic templates docs and ingest-node docs.
The ingest-node docs contain a *ton* of non-console snippets. We
might want to convert them to full examples later, but that can be
a separate thing.
Relates to #18160
Today either all nodes in the cluster connect to remote clusters of only nodes
that have remote clusters configured in their node config. To allow global remote
cluster configuration but restrict connections to a set of nodes in the cluster
this change adds a new setting `search.remote.connect` (defaults to `true`) to allow
to disable remote cluster connections on a per node basis.
Instead of `search.remote.seeds.${clustername}` we now specify the seeds as:
`search.remote.${clustername}.seeds` which is a real list setting compared to an unvalidated
group setting before.
James Rodewig
Luca Cavanna
Lisa Cawley
Jim Ferenczi
Jason Tedor
Ryan Ernst
Simon Willnauer
Adrien Grand
javanna
Clinton Gormley
Nik Everett