Search unavailable after upgrade

[Trinh X_ Nguyen]

Hi, We have done an upgrade on out Bitbucket data server from 7.17.1 to 7.21.0 but after upgrade we are unable to do search in Bitbucket and The Atlassian ElasticSearch service will not start

This is the error from event viewer regarding ElasticSearch "The Atlassian Bitbucket Elasticsearch 7.10.2 (AtlassianBitbucketElasticsearch) service terminated unexpectedly. "

The service gives this error when trying to start: "Windows could not start the Atlassian Bitbucket Elasticsearch 7.10.2 (AtlassianBitbucketElasticsearch) service on Local Computer. Error 1067: The process terminated unecpectedly 

Do we need do upgrade the ElasticSearch or what can we test to make search work again?