add doc

Signed-off-by: Peng Huo <[email protected]>

docs/user/admin/settings.rst

@@ -347,3 +347,39 @@ SQL query::
       }
     }
 
+plugins.query.executionengine.spark.session.limit
+===================================================
+
+Description
+-----------
+
+Each datasource can have maximum 100 sessions running in parallel by default. You can increase limit by this setting.
+
+1. The default value is 100.
+2. This setting is node scope.
+3. This setting can be updated dynamically.
+
+You can update the setting with a new value like this.
+
+SQL query::
+
+    sh$ curl -sS -H 'Content-Type: application/json' -X PUT localhost:9200/_plugins/_query/settings \
+    ... -d '{"transient":{"plugins.query.executionengine.spark.session.limit":200}}'
+    {
+      "acknowledged": true,
+      "persistent": {},
+      "transient": {
+        "plugins": {
+          "query": {
+            "executionengine": {
+              "spark": {
+                "session": {
+                  "limit": "200"
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+