Flex 6.0 - After upgrading, the containers cannot go online or offline

Problem

After upgrading to Flex 6.0, under some circumstances, it is not possible to start or stop containers. There is an error message that a task is already in progress (even when there is no task running for that instance).

Error Message

"Operation cannot be performed. A task is already in progress for instance xxxxxxx. Retry after the task is completed."

Cause

Flex 6.0 introduced stricter validation rules around host names - both the hostname of the instances and the entries in the hosts files on the individual instances.

If the hostname of the instance or entries in the /etc/hosts on the instance contain an underscore "_", then this issue can occur. Using underscores in hostnames is not RFC1123 compliant.

Solution

The resolution is to remove all instance configuration entries which have an underscore in them - ideally before updating to Flex 6.0.

if that is not possible, then applying Flex 6.0.20 to the system will revert to the previous validation rules and allow the instances to run.

This will not allow new instances to be created which have underscores in the hostname.

If after following the above, the instance still reports the problem, then please contact support referring to this article for further assistance.