频繁出现409， version conflict

bulk upsert操作日志中，频繁出现409，类似 current version[2] is different than the one provided [1]或是already exists这样， 贴两个吧，哪位老铁给个思路，感谢
```
{
"update": {
"_index": "",
"_type": "test",
"_id": "188656244",
"error": {
"reason": "[test][188656244]: version conflict, current version [3] is different than the one provided [2]",
"index_uuid": "7B0eai0wQa-xiulTFkkKRw",
"index": "",
"shard": "3",
"type": "version_conflict_engine_exception"
},
"status": 409
}
}
```
```

{
"update": {
"_index": "",
"_type": "test",
"_id": "188658596",
"error": {
"reason": "[test][188658596]: version conflict, document already exists (current version [1])",
"index_uuid": "7B0eai0wQa-xiulTFkkKRw",
"index": "",
"shard": "0",
"type": "version_conflict_engine_exception"
},
"status": 409
}
}

```