Cumulative 7.x backport

docs/reference/search.asciidoc

@@ -154,12 +154,11 @@ configure a soft limit, you can update the `action.search.shard_count.limit`
 cluster setting in order to reject search requests that hit too many shards.
 
 The request parameter `max_concurrent_shard_requests` can be used to control the
-maximum number of concurrent shard requests the search API will execute for the
-request. This parameter should be used to protect a single request from
+maximum number of concurrent shard requests the search API will execute per node
+for the request. This parameter should be used to protect a single request from
 overloading a cluster (e.g., a default request will hit all indices in a cluster
 which could cause shard request rejections if the number of shards per node is
-high). This default is based on the number of data nodes in the cluster but at
-most `256`.
+high). This default value is `5`.
 
 --
 

docs/reference/search/multi-search.asciidoc

@@ -85,15 +85,16 @@ The msearch's `max_concurrent_searches` request parameter can be used to control
 the maximum number of concurrent searches the multi search api will execute.
 This default is based on the number of data nodes and the default search thread pool size.
 
-The request parameter `max_concurrent_shard_requests` can be used to control the
-maximum number of concurrent shard requests the each sub search request will execute.
-This parameter should be used to protect a single request from overloading a cluster
-(e.g., a default request will hit all indices in a cluster which could cause shard request rejections
-if the number of shards per node is high). This default is based on the number of
-data nodes in the cluster but at most `256`.In certain scenarios parallelism isn't achieved through
-concurrent request such that this protection will result in poor performance. For
-instance in an environment where only a very low number of concurrent search requests are expected
-it might help to increase this value to a higher number.
+The request parameter `max_concurrent_shard_requests` can be used to control
+the maximum number of concurrent shard requests that each sub search request
+will execute per node. This parameter should be used to protect a single
+request from overloading a cluster (e.g., a default request will hit all
+indices in a cluster which could cause shard request rejections if the number
+of shards per node is high). This default value is `5`.In certain scenarios
+parallelism isn't achieved through concurrent request such that this protection
+will result in poor performance. For instance in an environment where only a
+very low number of concurrent search requests are expected it might help to
+increase this value to a higher number.
 
 [float]
 [[msearch-security]]

docs/reference/search/suggesters/phrase-suggest.asciidoc

@@ -267,7 +267,10 @@ POST _search
 
 The `phrase` suggester supports multiple smoothing models to balance
 weight between infrequent grams (grams (shingles) are not existing in
-the index) and frequent grams (appear at least once in the index).
+the index) and frequent grams (appear at least once in the index). The
+smoothing model can be selected by setting the `smoothing` parameter
+to one of the following options. Each smoothing model supports specific
+properties that can be configured.
 
 [horizontal]
 `stupid_backoff`::
@@ -288,6 +291,28 @@ the index) and frequent grams (appear at least once in the index).
     All parameters (`trigram_lambda`, `bigram_lambda`, `unigram_lambda`)
     must be supplied.
 
+[source,js]
+--------------------------------------------------
+POST _search
+{
+  "suggest": {
+    "text" : "obel prize",
+    "simple_phrase" : {
+      "phrase" : {
+        "field" : "title.trigram",
+        "size" : 1,
+        "smoothing" : {
+          "laplace" : {
+            "alpha" : 0.7
+          }
+        }
+      }
+    }
+  }
+}
+--------------------------------------------------
+// CONSOLE
+
 ==== Candidate Generators
 
 The `phrase` suggester uses candidate generators to produce a list of

rest-api-spec/src/main/resources/rest-api-spec/api/msearch.json

@@ -43,8 +43,8 @@
         },
         "max_concurrent_shard_requests" : {
           "type" : "number",
-          "description" : "The number of concurrent shard requests each sub search executes concurrently. This value should be used to limit the impact of the search on the cluster in order to limit the number of concurrent shard requests",
-          "default" : "The default grows with the number of nodes in the cluster but is at most 256."
+          "description" : "The number of concurrent shard requests each sub search executes concurrently per node. This value should be used to limit the impact of the search on the cluster in order to limit the number of concurrent shard requests",
+          "default" : 5
         },
         "rest_total_hits_as_int" : {
           "type" : "boolean",

rest-api-spec/src/main/resources/rest-api-spec/api/search.json

@@ -192,7 +192,7 @@
         "max_concurrent_shard_requests" : {
           "type" : "number",
           "description" : "The number of concurrent shard requests per node this search executes concurrently. This value should be used to limit the impact of the search on the cluster in order to limit the number of concurrent shard requests",
-          "default" : "The default is 5."
+          "default" : 5
         },
         "pre_filter_shard_size" : {
           "type" : "number",

server/src/main/java/org/elasticsearch/action/search/SearchRequest.java

@@ -135,9 +135,10 @@ public SearchRequest(String[] indices, SearchSourceBuilder source) {
     }
 
     /**
-     * Creates a new search request by providing the search request to copy all fields from, the indices to search against, the alias of
-     * the cluster where it will be executed, as well as the start time in milliseconds from the epoch time and whether the reduction
-     * should be final or not. Used when a {@link SearchRequest} is created and executed as part of a cross-cluster search request
+     * Creates a new sub-search request starting from the original search request that is provided.
+     * For internal use only, allows to fork a search request into multiple search requests that will be executed independently.
+     * Such requests will not be finally reduced, so that their results can be merged together in one response at completion.
+     * Used when a {@link SearchRequest} is created and executed as part of a cross-cluster search request
      * performing reduction on each cluster in order to minimize network round-trips between the coordinating node and the remote clusters.
      *
      * @param originalSearchRequest the original search request
@@ -146,8 +147,8 @@ public SearchRequest(String[] indices, SearchSourceBuilder source) {
      * @param absoluteStartMillis the absolute start time to be used on the remote clusters to ensure that the same value is used
      * @param finalReduce whether the reduction should be final or not
      */
-    static SearchRequest crossClusterSearch(SearchRequest originalSearchRequest, String[] indices,
-                                            String clusterAlias, long absoluteStartMillis, boolean finalReduce) {
+    static SearchRequest subSearchRequest(SearchRequest originalSearchRequest, String[] indices,
+                                          String clusterAlias, long absoluteStartMillis, boolean finalReduce) {
         Objects.requireNonNull(originalSearchRequest, "search request must not be null");
         validateIndices(indices);
         Objects.requireNonNull(clusterAlias, "cluster alias must not be null");
@@ -300,15 +301,15 @@ boolean isFinalReduce() {
     /**
      * Returns the current time in milliseconds from the time epoch, to be used for the execution of this search request. Used to
      * ensure that the same value, determined by the coordinating node, is used on all nodes involved in the execution of the search
-     * request. When created through {@link #crossClusterSearch(SearchRequest, String[], String, long, boolean)}, this method returns
+     * request. When created through {@link #subSearchRequest(SearchRequest, String[], String, long, boolean)}, this method returns
      * the provided current time, otherwise it will return {@link System#currentTimeMillis()}.
      */
     long getOrCreateAbsoluteStartMillis() {
         return absoluteStartMillis == DEFAULT_ABSOLUTE_START_MILLIS ? System.currentTimeMillis() : absoluteStartMillis;
     }
 
     /**
-     * Returns the provided <code>absoluteStartMillis</code> when created through {@link #crossClusterSearch} and
+     * Returns the provided <code>absoluteStartMillis</code> when created through {@link #subSearchRequest} and
      * -1 otherwise.
      */
     long getAbsoluteStartMillis() {