官网解释：

When Elasticsearch rejects a request, it stops the operation and returns an error with a 429 response code. Rejected requests are commonly caused by:

• A depleted thread pool. A depleted search or write thread pool returns a TOO_MANY_REQUESTS error message.
• A circuit breaker error.
• High indexing pressure that exceeds the indexing_pressure.memory.limit.

一般是由于磁盘空间不足引起

解决办法：

1、释放空间（可以删除索引或者修改索引生命周期）

2、扩展硬盘

3、在kibana的开发工具执行，立即恢复读写功能

PUT _all/_settings
{
  "index.blocks.read_only_allow_delete": null
}