4.2

• We added Change Data Capture (CDC) support for PostgreSQL and MySql. New
  connectors use Debezium to provide a high-level API for processing the
  stream of changes from relational databases. A new map sink can be used to
  automatically keep the map in-sync with changes from the database.
• We added new source and sink connectors for Elasticsearch 5, 6 and 7
  with support for slicing and co-located reading for maximum read performance
  and extended Elasticsearch's client retry mechanism for reliable writing.
• We improved JSON support through a new file source which can read JSON files
  directly and also added built-in Jet methods for parsing and mapping JSON strings.
• We introduced .relabance() operator which can be used for distributing items
  across the cluster.
• We made some improvements to Jet startup scripts:
  • You can now use the PROMETHEUS_PORT to start Jet with prometheus metrics enabled.
  • You can use the jvm.options file to edit the startup JVM parameters.
  • You can now use the JET_MODULES environment variable to add modules when using docker
    or jet-start script.
• We did several rounds of improvements to the documentation:
  • Improvements to Docker and Kubernetes instructions
  • New guidance on Garbage Collector choice and settings
  • New and improved tutorials for CDC
  • New documentation for Python module and early results support in windowing