New Features

• HTTP POST event handler can now be configured to automatically retry on network and HTTP errors. [server-side][http-api] [#2619]
• It is now possible to configure a file transfer service to emit debugging events for the low-level protocol used. [http][ftp][ftps][sftp][scp][server-side] [#2697]
• The Python Extension event handler now handles events on multiple CPUs. In previous versions all events were handled by a single CPU. [#5262]
• A new destination path action named single-file was added to transfer multiple source files as a single destination file. [client-side] [#4054]
• You can now disable the overwriting rule for a transfer destination. In this way, the file is uploaded right away, without doing any extra requests on the server. [client-side] [#4054]
• Debian 9 is now a supported platform. [#3353]

Defect Fixes

• When changing the current folder in FTP, the SFTPPlus server now only checks that the path is a folder and that path traversal is allowed. It no longer tries to see if the operating system allows listing content. Asking the operating system to list content for every target directory could have caused performance issues. [server-side][ftp][ftps] [#2111]
• You can now use a local directory with a large number of files (more than 10.000), as the source for a transfer. [client-side] [#1319]
• The local filesystem source location no longer stops to monitor the source on I/O errors. It will log an error and retry to get the content again after changes_poll_interval seconds. [client-side] [#3350]
• The SysV and OpenRC init scripts now work when executed as root user. This was a defect introduced in 3.42.0. [#3353]

Deprecations and Removals

• The Python Extension event handler no longer takes a parent argument. The events are no longer handled in separate threads. Instead, they are added to a queue to be executed on a dedicate CPU. [#5262]
• Support for Ubuntu 16.04 on ARM64 was removed. [#3353]
• Support for Debian 8 was removed. [#3353]

You can check the full release notes here.