Avoid sending bulk requests larger than bulk_limit_bytes

Send a smaller bulk request if adding another item would
go over bulk limit

ee/changelogs/unreleased/211597-elasticsearch-indexer-failed-with-error-code-413-request-entity.yml

+---
+title: Reduce 413 errors when making bulk indexing requests to Elasticsearch
+merge_request: 31653
+author:
+type: fixed

ee/lib/gitlab/elastic/bulk_indexer.rb

@@ -35,10 +35,12 @@ module Gitlab
         else
           delete(ref)
         end
+
+        self
       end
 
       def flush
-        maybe_send_bulk(force: true).failures
+        send_bulk.failures
       end
 
       private
@@ -56,8 +58,6 @@ module Gitlab
         op = build_op(ref, proxy)
 
         submit({ index: op }, proxy.as_indexed_json)
-
-        maybe_send_bulk
       end
 
       def delete(ref)
@@ -65,8 +65,6 @@ module Gitlab
         op = build_op(ref, proxy)
 
         submit(delete: op)
-
-        maybe_send_bulk
       end
 
       def build_op(ref, proxy)
@@ -86,17 +84,27 @@ module Gitlab
       end
 
       def submit(*hashes)
-        hashes.each do |hash|
-          text = hash.to_json
+        jsons = hashes.map(&:to_json)
+        bytesize = calculate_bytesize(jsons)
+
+        send_bulk if will_exceed_bulk_limit?(bytesize)
 
-          body.push(text)
-          @body_size_bytes += text.bytesize + 2 # Account for newlines
+        body.concat(jsons)
+        @body_size_bytes += bytesize
+      end
+
+      def calculate_bytesize(jsons)
+        jsons.reduce(0) do |sum, json|
+          sum + json.bytesize + 2 # Account for newlines
         end
       end
 
-      def maybe_send_bulk(force: false)
+      def will_exceed_bulk_limit?(bytesize)
+        body_size_bytes + bytesize > bulk_limit_bytes
+      end
+
+      def send_bulk
         return self if body.empty?
-        return self if body_size_bytes < bulk_limit_bytes && !force
 
         failed_refs = try_send_bulk
 

ee/spec/lib/gitlab/elastic/bulk_indexer_spec.rb

@@ -31,16 +31,31 @@ describe Gitlab::Elastic::BulkIndexer, :elastic do
       indexer.process(issue_as_ref)
     end
 
-    it 'sends a bulk request if the max bulk request size is reached' do
+    it 'sends the action and source in the same request' do
       set_bulk_limit(indexer, 1)
+      indexer.process(issue_as_ref)
+      allow(es_client).to receive(:bulk).and_return({})
+
+      indexer.process(issue_as_ref)
 
       expect(es_client)
-        .to receive(:bulk)
+        .to have_received(:bulk)
         .with(body: [kind_of(String), kind_of(String)])
-        .and_return({})
+      expect(indexer.failures).to be_empty
+    end
 
+    it 'sends a bulk request before adding an item that exceeds the bulk limit' do
+      bulk_limit_bytes = (issue_as_json_with_times.to_json.bytesize * 1.5).to_i
+      set_bulk_limit(indexer, bulk_limit_bytes)
       indexer.process(issue_as_ref)
+      allow(es_client).to receive(:bulk).and_return({})
 
+      indexer.process(issue_as_ref)
+
+      expect(es_client).to have_received(:bulk) do |args|
+        body_bytesize = args[:body].map(&:bytesize).reduce(:+)
+        expect(body_bytesize).to be <= bulk_limit_bytes
+      end
       expect(indexer.failures).to be_empty
     end
   end