elasticsearch Bad Request during ConnectionConfiguration create

I am getting the following when connecting to a elastic search instance
Runner: Spark

code
{{ ConnectionConfiguration connectionConfiguration = ConnectionConfiguration.create(new String[] {"http://elasticsearch:9200"},"bigindex_write","bigindex");
}}
Error
{{FATAL: Connection to elasticsearch elasticsearch:9200 failedNov 01, 2017 1:13:15 PM .listener.Kafka2Elastic main
SEVERE: FATAL: Connection to elasticsearch elasticsearch:9200 failed
org.elasticsearch.client.ResponseException: GET http://elasticsearch:9200/: HTTP/1.1 400 Bad Request
{"error":{"root_cause":[{"type":"illegal_argument_exception","reason":"empty headers are not allowed []"}],"type":"illegal_argument_exception","reason":"empty headers are not allowed []"},"status":400}
at org.elasticsearch.client.RestClient$1.completed(RestClient.java:310)
at org.elasticsearch.client.RestClient$1.completed(RestClient.java:299)
at org.apache.http.concurrent.BasicFuture.completed(BasicFuture.java:119)
at org.apache.http.impl.nio.client.DefaultClientExchangeHandlerImpl.responseCompleted(DefaultClientExchangeHandlerImpl.java:177)
at org.apache.http.nio.protocol.HttpAsyncRequestExecutor.processResponse(HttpAsyncRequestExecutor.java:436)
at org.apache.http.nio.protocol.HttpAsyncRequestExecutor.inputReady(HttpAsyncRequestExecutor.java:326)
at org.apache.http.impl.nio.DefaultNHttpClientConnection.consumeInput(DefaultNHttpClientConnection.java:265)
at org.apache.http.impl.nio.client.InternalIODispatch.onInputReady(InternalIODispatch.java:81)
at org.apache.http.impl.nio.client.InternalIODispatch.onInputReady(InternalIODispatch.java:39)
at org.apache.http.impl.nio.reactor.AbstractIODispatch.inputReady(AbstractIODispatch.java:114)
at org.apache.http.impl.nio.reactor.BaseIOReactor.readable(BaseIOReactor.java:162)
at org.apache.http.impl.nio.reactor.AbstractIOReactor.processEvent(AbstractIOReactor.java:337)
at org.apache.http.impl.nio.reactor.AbstractIOReactor.processEvents(AbstractIOReactor.java:315)
at org.apache.http.impl.nio.reactor.AbstractIOReactor.execute(AbstractIOReactor.java:276)
at org.apache.http.impl.nio.reactor.BaseIOReactor.execute(BaseIOReactor.java:104)
at org.apache.http.impl.nio.reactor.AbstractMultiworkerIOReactor$Worker.run(AbstractMultiworkerIOReactor.java:588)
at java.lang.Thread.run(Thread.java:748)
}}

Imported from Jira [BEAM-3132](https://issues.apache.org/jira/browse/BEAM-3132). Original Jira may contain additional context.
Reported by: orjan.lundberg@gmail.com.

Start by reproducing the ConnectionConfiguration.create call against the Elasticsearch URL and review the Elasticsearch client request shown in the stack trace. Determine why the request receives the empty-headers 400 response; done means the connection succeeds without that error, with a focused regression test if the relevant test location can be identified.

Written by the indexing model from the issue text.