In 7.14.0, ES-Hadoop began preventing access to Elasticsearch clusters that did not include an
X-elastic-productheader in responses in order to ensure that ES-Hadoop was working with an Elasticsearch cluster that it was compatible with. See #1672 for more information about this. However if the case of the
X-elastic-productheader name sent from Elasticsearch is changed (for example if it is lower-cased) by an intermediary between Elasticsearch and ES-Hadoop (for example, the http proxy for cloud.elastic.co), then ES-Hadoop ignores the header and will reject the response as not being from a valid Elasticsearch cluster.
We have fixed this issue in ES-Hadoop 7.14.2 and later versions. For more details,see #1745.