ES：一次分片设计问题导致的故障

### 现象：

1. 单节点CPU持续高

2.写入骤降

3.线程池队列积压，但没有reject

4.使用方没有记录日志

### 排查

1.ES监控

只能看到相应的结果指标，无法反应出原因。

2.ES日志：大量日志打印相关异常（routate等调用栈）

core.appender.OutputStreamManager.writeToDestination(OutputStreamManager.java:263)
at org.apache.logging.log4j.core.appender.FileManager.writeToDestination

3.查询CPU的使用，GET _nodes/hot_threads

35.3% (176.7ms out of 500ms) cpu usage by thread 'elasticsearch[xxxxx-es-hot2-13][write][T#10]'10/10 snapshots sharing following 179 elementsapp//org.elasticsearch.action.support.replication.TransportReplicationAction$AsyncPrimaryAction.runWithPrimaryShardReference(TransportReplicationAction.java:433)app//org.elasticsearch.action.support.replication.TransportReplicationAction$AsyncPrimaryAction.lambda$doRun$0(TransportReplicationAction.java:374)app//org.elasticsearch.action.support.replication.TransportReplicationAction$AsyncPrimaryAction$$Lambda$3657/0x0000000800d2f440.accept(Unknown Source)app//org.elasticsearch.action.ActionListener$1.onResponse(ActionListener.java:61)app//org.elasticsearch.index.shard.IndexShard.lambda$wrapPrimaryOperationPermitListener$14(IndexShard.java:2588)app//org.elasticsearch.index.shard.IndexShard$$Lambda$3659/0x0000000800d2fc40.accept(Unknown Source)app//org.elasticsearch.action.ActionListener$1.onResponse(ActionListener.java:61)app//org.elasticsearch.index.shard.IndexShardOperationPermits.acquire(IndexShardOperationPermits.java:273)app//org.elasticsearch.index.shard.IndexShardOperationPermits.acquire(IndexShardOperationPermits.java:240)app//org.elasticsearch.index.shard.IndexShard.acquirePrimaryOperationPermit(IndexShard.java:2563)app//org.elasticsearch.action.support.replication.TransportReplicationAction.acquirePrimaryOperationPermit(TransportReplicationAction.java:996)app//org.elasticsearch.action.support.replication.TransportReplicationAction$AsyncPrimaryAction.doRun(TransportReplicationAction.java:370)....35.0% (174.7ms out of 500ms) cpu usage by thread 'elasticsearch[xxxxxx-es-hot2-13][write][T#5]'5/10 snapshots sharing following 216 elementsapp//org.apache.logging.log4j.core.layout.TextEncoderHelper.encodeChunkedText(TextEncoderHelper.java:146)app//org.apache.logging.log4j.core.layout.TextEncoderHelper.encodeText(TextEncoderHelper.java:58)app//org.apache.logging.log4j.core.layout.StringBuilderEncoder.encode(StringBuilderEncoder.java:68)app//org.apache.logging.log4j.core.layout.StringBuilderEncoder.encode(StringBuilderEncoder.java:32)app//org.apache.logging.log4j.core.layout.PatternLayout.encode(PatternLayout.java:220)app//org.apache.logging.log4j.core.layout.PatternLayout.encode(PatternLayout.java:58)app//org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.directEncodeEvent(AbstractOutputStreamAppender.java:177)app//org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.tryAppend(AbstractOutputStreamAppender.java:170)app//org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.append(AbstractOutputStreamAppender.java:161)app//org.apache.logging.log4j.core.config.AppenderControl.tryCallAppender(AppenderControl.java:156)app//org.apache.logging.log4j.core.config.AppenderControl.callAppender0(AppenderControl.java:129)app//org.apache.logging.log4j.core.config.AppenderControl.callAppenderPreventRecursion(AppenderControl.java:120)app//org.apache.logging.log4j.core.config.AppenderControl.callAppender(AppenderControl.java:84)

“CPU高” 和写入、日志打印相关，无法获取更详细的信息，且由于瞬时抓取，也并不非常精准。

4.火焰图

大致确认和日志相关。

5. 根据以往经验，可能和单分片doc数量限制相关

6.继续搜索日志，确认是单分片超过限制

2023-08-21 02:31:10,215 elasticsearch[xxxx-es-hot2-13][write][T#1] ERROR Recovering from StringBuilderEncoder.encode('[2023-08-21T02:31:10,201][DEBUG][o.e.a.b.TransportShardBulkAction] [xxxxx-es-hot2-13][cp0001001_2023_08][0] failed to execute bulk item (index) index {[xxxxx001_2023_08][event_xxx][xxxxxxxxx], source[{"id":"9f61ef55-0334-4363-9bcf-xxxx","rowkey":"xxxxxxd83ce110","column01":"1007922682","datachangelasttime":1692584511322,"column19":"xxx","column20":"80,295",xxx.......}]}
2023-08-21T02:31:10.237858677Z java.lang.IllegalArgumentException: number of documents in the index cannot exceed 2147483519