Better shutdown handling in Logstash core and its plugins. Previously, the shutdown handling was through an injected exception which made it non-deterministic. The change introduces cleaner APIs in the core to signal a shutdown event which can be used by the plugins (#3210)
Upgrade to JrJackson version 0.3.5 which fixes numerous bugs and also provides performance boost for JSON handling (#3702)
Better defaults: Out of the box, the default value of the filter_workers (-w) setting will be set to half of the CPU cores of the machine. Increasing the workers provides parallelism in filter execution which is crucial when doing heavier processing like complex grok patterns or the useragent filter. You can still override the default by passing -w flag when starting Logstash (#3870)
Improved default security configuration for SSL/TLS. Default is now TLS1.2 (#3955)
Added obsolete setting which will cause a configuration error if a config marked obsolete is used. The purpose of :obsolete is to help inform users when a setting has been completely removed. The lifecycle of a plugin setting is now 4 phases: available, deprecated, obsolete, deleted. (#3977)
Obsolete config settings (which were already deprecated): debug, format, charset, message_format. Logstash will not start if you use these settings.
Obsolete config settings (which were already deprecated): type, tags, exclude_tags. Logstash will not start if you use these settings.