@Override
        public CompletableFuture<?> acceptBatch(List<ApiMessageAndVersion> recordBatch) {
            ControllerWriteEvent<Void> batchEvent = new ControllerWriteEvent<>(
                "ZK Migration Batch",
                new MigrationWriteOperation(recordBatch), eventFlags);
            queue.append(batchEvent);
            return batchEvent.future;
        }
Append records to the Raft log. They will be written out asynchronously.

@param log                   The log4j logger.
@param result                The controller result we are writing out.
@param maxRecordsPerBatch    The maximum number of records to allow in a batch.
@param appender              The callback to invoke for each batch. The arguments are last
                             write offset, record list, and the return result is the new
                             last write offset.
@return                      The final offset that was returned from the Raft layer.
metadata/src/main/java/org/apache/kafka/controller/QuorumController.java