2017-10-26 08:32:58,251 ERROR: org.graylog2.periodical.IndexRotationThread - Couldn't point deflector to a new index
org.graylog2.indexer.ElasticsearchException: Unable to create index template graylog-internal
Compressor detection can only be called on some xcontent bytes or compressed xcontent bytes
This seems to be the culprit.
Try disabling compression for the Elasticsearch HTTP connection in Graylog:
(This can be done with the GRAYLOG_ELASTICSEARCH_COMPRESSION_ENABLED
environment variable in the Docker image).