Using composer 1.10
Deprecation Notice: Class Elasticsearch\Endpoints\Ingest\Pipeline\ProcessorGrok located in ./elasticsearch/elasticsearch/src/Elasticsearch/Endpoints/Ingest/ProcessorGrok.php does not comply with psr-4 autoloading standard. It will not autoload anymore in Composer v2.0. in phar:///usr/local/bin/composer/src/Composer/Autoload/ClassMapGenerator.php:185
Originally upstream as https://github.com/elastic/elasticsearch-php/issues/1006, already fixed in 6.5.0, we're on 6.0.1