SpringBoot - elasticsearch bulkrequest - synchronization of add&flush controller

Question

I use high-level rest client to connect to elasticsearch 6.5 from spring boot application.

I want to create a controller with methods to add commands to bulk request and a method to flush (actually execute) the bulk request operation.

I coded it like this:
BulkRequest bean - note the singleton scope

@Bean
public BulkRequest bulkRequest() {
  return new BulkRequest();
}

Bulk Controller

@RestController
@RequestMapping("/bulk")
public class BulkController {

    @Autowired
    private BulkRequest bulkRequest;

    @Autowired
    RestHighLevelClient client;

    @PostMapping
    public void index(@RequestBody String o) {
        bulkRequest.add(new IndexRequest(config.INDEX, config.TYPE).source(o, XContentType.JSON));
    }

    @PostMapping(path = "/flush")
    public String flush() throws Exception {
        BulkResponse bulkResponse = client.bulk(bulkRequest, RequestOptions.DEFAULT);

        if(bulkResponse.hasFailures()) {
          return bulkResponse.buildFailureMessage();
        }
        else {
          return "All operations in the bulk request proceeded successfully!";
        }
    }

Now the questions:
- is the bulkRequest.add method synchronized over the scope of the BulkRequest bean (in this case singleton) ?

- how to start a new BulkRequest after the BulkController.flush method is called ? Do I need to instance a new bean of the BulkRequest and somehow push it to the bean environment ?

- what would need to change in the case of BulkRequest bean having the @session scope ?

Answer 1

I found a similar question - here on StackOverflow - unfortunately, I forgot to save a link, so I will just interpret here in this response.

I used AtomicReference as a bean type a reinitialized BulkRequest object in the flush method. Then I added synchronization over BulkRequest.add calls since it uses List in the background.

Note that this solution is kind of dirty and was described as so in the referenced answer - but it WORKS for me..

Code:
Bean

    @Bean
    public AtomicReference<BulkRequest> bulkRequest() {
      return new AtomicReference<BulkRequest>(new BulkRequest());
    }

Controller:

        @Autowired
        private AtomicReference<BulkRequest> bulkRequest;

        @PostMapping
        public void index(@RequestBody String o) {
            synchronized (bulkRequest.get()) {
                bulkRequest.get().add(new IndexRequest(config.INDEX, config.TYPE).source(o, XContentType.JSON));
            }
        }

        @DeleteMapping(path="/{id}")
        public void delete(@PathVariable String id) {
            synchronized (bulkRequest.get()) {
                bulkRequest.get().add(new DeleteRequest(config.INDEX, config.TYPE, id));
            }
        }

        @PutMapping(path="/{id}")
        public void update(@PathVariable String id, @RequestBody String o) {
            synchronized (bulkRequest.get()) {
                bulkRequest.get().add(new UpdateRequest(config.INDEX, config.TYPE, id).doc(o, XContentType.JSON));
            }
        }

 @PostMapping(path = "/flush")
    public String flush() throws Exception {
        synchronized (bulkRequest.get()) {
            String result = bulkService.flush(bulkRequest);

            bulkRequest.set(new BulkRequest());

            return result;
        }
    }

BulkService

@Service
public class BulkService {

    @Autowired
    private RestHighLevelClient client;

    public String flush( AtomicReference<BulkRequest> bulkRequest) throws Exception {

        BulkResponse bulkResponse = client.bulk(bulkRequest.get(), RequestOptions.DEFAULT);

        if(bulkResponse.hasFailures()) {
            return bulkResponse.buildFailureMessage();
        }
        else {
            return "All operations in the bulk request proceeded successfully!";
        }
    }
}