Getting warning : monitoring execution failed, Exception when closing export bulk

[saranyu]

Detail Error
[2019-05-10T10:04:44,304][WARN ][o.e.x.m.MonitoringService] [ip-172-30-3-238] monitoring execution failed
org.elasticsearch.xpack.monitoring.exporter.ExportException: Exception when closing export bulk
at org.elasticsearch.xpack.monitoring.exporter.ExportBulk$1$1.(ExportBulk.java:95) ~[x-pack-monitoring-7.0.0.jar:7.0.0]
at org.elasticsearch.xpack.monitoring.exporter.ExportBulk$1.onFailure(ExportBulk.java:93) [x
at org.elasticsearch.action.bulk.TransportBulkAction$BulkOperation.doRun(TransportBulkAction.java:434) [elasticsearch-7.0.0.jar:7.0.0]
at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:37) [elasticsearch-7.0.0.jar:7.0.0]
at org.elasticsearch.action.bulk.TransportBulkAction.executeBulk(TransportBulkAction.java:547) [elasticsearch-7.0.0.jar:7.0.0]
at org.elasticsearch.action.bulk.TransportBulkAction.doExecute(TransportBulkAction.java:253) [elasticsearch-7.0.0.jar:7.0.0]
at org.elasticsearch.action.bulk.TransportBulkAction.lambda$processBulkIndexIngestRequest$4(TransportBulkAction.java:601) [elasticsearch-7.0.0.jar:7.0.0]
at org.elasticsearch.ingest.IngestService$4.doRun(IngestService.java:419) [elasticsearch-7.0.0.jar:7.0.0]
at org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingAbstractRunnable.doRun(ThreadContext.java:751) [elasticsearch-7.0.0.jar:7.0.0]
at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:37) [elasticsearch-7.0.0.jar:7.0.0]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]
at java.lang.Thread.run(Thread.java:835) [?:?]
Caused by: org.elasticsearch.xpack.monitoring.exporter.ExportException: failed to flush export bulks
at org.elasticsearch.xpack.monitoring.exporte