in flink-connector-elasticsearch-base/src/main/java/org/apache/flink/connector/elasticsearch/sink/ElasticsearchSinkBuilderBase.java [387:398]
private NetworkClientConfig buildNetworkClientConfig() {
checkArgument(!hosts.isEmpty(), "Hosts cannot be empty.");
return new NetworkClientConfig(
username,
password,
connectionPathPrefix,
connectionRequestTimeout,
connectionTimeout,
socketTimeout,
sslContextSupplier,
hostnameVerifierSupplier);
}