aws-athena-query-federation: [BUG] Elasticsearch Connector does not work with VPC

Describe the bug When using the connector with cluster inside of a vpc, the connector does not work.

Any request made to elasticsearch itself will fail to sign with a message like:

java.lang.RuntimeException: com.amazonaws.services.lambda.invoke.LambdaFunctionException: Error processing request to list indices: Unable to calculate a request signature: null

Full stack trace of which:

Error processing request to list indices: Unable to calculate a request signature: null: java.lang.RuntimeException
java.lang.RuntimeException: Error processing request to list indices: Unable to calculate a request signature: null
	at com.amazonaws.connectors.athena.elasticsearch.ElasticsearchMetadataHandler.doListTables(ElasticsearchMetadataHandler.java:211)
	at com.amazonaws.athena.connector.lambda.handlers.MetadataHandler.doHandleRequest(MetadataHandler.java:243)
	at com.amazonaws.athena.connector.lambda.handlers.CompositeHandler.handleRequest(CompositeHandler.java:132)
	at com.amazonaws.athena.connector.lambda.handlers.CompositeHandler.handleRequest(CompositeHandler.java:100)
Caused by: java.lang.RuntimeException: Unable to calculate a request signature: null
	at org.elasticsearch.client.RestClient.extractAndWrapCause(RestClient.java:812)
	at org.elasticsearch.client.RestClient.performRequest(RestClient.java:225)
	at org.elasticsearch.client.RestClient.performRequest(RestClient.java:212)
	at org.elasticsearch.client.RestHighLevelClient.internalPerformRequest(RestHighLevelClient.java:1433)
	at org.elasticsearch.client.RestHighLevelClient.performRequest(RestHighLevelClient.java:1403)
	at org.elasticsearch.client.RestHighLevelClient.performRequestAndParseEntity(RestHighLevelClient.java:1373)
	at org.elasticsearch.client.IndicesClient.getAlias(IndicesClient.java:986)
	at com.amazonaws.connectors.athena.elasticsearch.AwsRestHighLevelClient.getAliases(AwsRestHighLevelClient.java:82)
	at com.amazonaws.connectors.athena.elasticsearch.ElasticsearchMetadataHandler.doListTables(ElasticsearchMetadataHandler.java:196)
	... 3 more
Caused by: com.amazonaws.SdkClientException: Unable to calculate a request signature: null
	at com.amazonaws.auth.AbstractAWSSigner.sign(AbstractAWSSigner.java:109)
	at com.amazonaws.auth.AWS4Signer.newSigningKey(AWS4Signer.java:641)
	at com.amazonaws.auth.AWS4Signer.deriveSigningKey(AWS4Signer.java:404)
	at com.amazonaws.auth.AWS4Signer.sign(AWS4Signer.java:253)
	at com.amazonaws.connectors.athena.elasticsearch.AWSRequestSigningApacheInterceptor.process(AWSRequestSigningApacheInterceptor.java:128)
	at org.apache.http.protocol.ImmutableHttpProcessor.process(ImmutableHttpProcessor.java:133)
	at org.apache.http.impl.nio.client.MainClientExec.prepareRequest(MainClientExec.java:520)
	at org.apache.http.impl.nio.client.MainClientExec.prepare(MainClientExec.java:146)
	at org.apache.http.impl.nio.client.DefaultClientExchangeHandlerImpl.start(DefaultClientExchangeHandlerImpl.java:128)
	at org.apache.http.impl.nio.client.InternalHttpAsyncClient.execute(InternalHttpAsyncClient.java:141)
	at org.elasticsearch.client.RestClient.performRequest(RestClient.java:221)
	... 10 more
Caused by: java.lang.NullPointerException
	at com.amazonaws.auth.AbstractAWSSigner.sign(AbstractAWSSigner.java:104)
	... 20 more

The reason being is because a cluster within a vpc does not have an endpoint, but endpoints. My pull request shows what I mean:

https://github.com/awslabs/aws-athena-query-federation/pull/339

I’m not sure what other problems are caused by having a domain within the VPC. Getting this project to run is not trivial. The setup, install, and publish instructions are invalid for my dev environment (Mac) and even for a fresh AmazonLinux2 EC2. The ./tools/prepare_dev_env.sh script throws several errors (on linux. i know it’s not compatible with mac), and running mvn clean install in the elasticsearch project throws this error (on mac and linux):

[ERROR] Failed to execute goal on project athena-elasticsearch: Could not resolve dependencies for project com.amazonaws:athena-elasticsearch:jar:1.0: Failed to collect dependencies at com.amazonaws:aws-athena-federation-sdk:jar:2020.51.1: Failed to read artifact descriptor for com.amazonaws:aws-athena-federation-sdk:jar:2020.51.1: Could not find artifact com.amazonaws:aws-athena-query-federation:pom:1.0 in central (https://repo.maven.apache.org/maven2) -> [Help 1]