Bootstrap now accepts any member of an InnoDB cluster and automatically finds and reconnects to a writable primary. (Bug #25489509)

Configuring MySQL Router with sockets would create a socket that was only accessible by the MySQL Router user. (Bug #27179456, Bug #88667)

The apt purge process did not remove the /var/{lib,log,run}/mysqlrouter directories. (Bug #26955232)

Router assumed that a resulting socket from accept()ing a socket would be always blocking. On Solaris and Windows this assumption is not valid, and this resulted in broken connections with large result sets. (Bug #26834769)

Defining a [logger] section in the configuration file was invalid because the logging mechanism is not a plugin as of Router 2.1. [logger] was used in MySQL Router 2.0, but now logging definitions are defined under the [DEFAULT] section. To provide backward compatibility, [logger] section support was added. (Bug #26441587)

The maximum number of concurrent client connections was increased from about 500 to over 5000, a limit now dependent on the operation system. To achieve this, select() based fd event calls were replaced by poll() (or WSAPoll() on Windows). (Bug #22661705, Bug #80260)