Support batch ingestion in bulk API (#12457)

modules/ingest-common/src/yamlRestTest/resources/rest-api-spec/test/ingest/70_bulk.yml

@@ -244,6 +244,7 @@ teardown:
       reason: "Added in 2.14.0"
 
   - do:
+      catch: bad_request
       bulk:
         refresh: true
         batch_size: -1
@@ -253,17 +254,3 @@ teardown:
           - '{"text": "text1"}'
           - '{"index": {"_index": "test_index", "_id": "test_id2"}}'
           - '{"text": "text2"}'
-
-  - match: { errors: false }
-
-  - do:
-      get:
-        index: test_index
-        id: test_id1
-  - match: { _source: { "text": "text1", "field1": "value1" } }
-
-  - do:
-      get:
-        index: test_index
-        id: test_id2
-  - match: { _source: { "text": "text2", "field1": "value1" } }

server/src/main/java/org/opensearch/action/bulk/BulkRequest.java

@@ -357,11 +357,10 @@ public final BulkRequest timeout(TimeValue timeout) {
      * @return {@link BulkRequest}
      */
     public BulkRequest batchSize(int size) {
-        if (size > 1) {
-            this.batchSize = size;
-        } else {
-            this.batchSize = 1;
+        if (size < 1) {
+            throw new IllegalArgumentException("batch_size must be larger than 0");
         }
+        this.batchSize = size;
         return this;
     }