Can I have a backup on the same machine?
If your answer is yes then this is exactly what I tried while following very closely your various user guides but I am getting this error:
"Dual active detected, local saved state STANDALONE and peer saved state STANDALONE."
When I try to start the primary broker.
Yes, it's possible to run both brokers in an FT pair on a single machine, though we'd advise against this in production since you have no backup if the machine fails.
The dual active error indicates that both brokers had previously entered the 'Active' state. This can happen if all the replication connections between the Primary and Backup fail, resulting in both brokers thinking the other has failed. (We strongly recommend configuring multiple replication connection using redundant networks to help avoid this).
It could also happen as a result of mismanagement in cases where an administrator manually forces brokers to activate. In general you should try to avoid activating brokers manually. Instead start both the Primary and Backup and allow them to sort out between themselves which one should become Active and which one Standby.
To recover from the dual active scenario you'll need to reinitialize the storage of one of the brokers*. This can be done using the Sonic Management Console's 'Manage' view: the container hosting the broker needs to be running while the broker itself should be stopped; right-click the broker and select Initialize Storage -> All -> Recreate. Then launch the brokers again.
(*this risks some message loss, but it sounds like you're only experimenting with the brokers at this stage so it shouldn't be an issue)
Thanks Paul your suggested solution fixed the issue, and yes, just like you correctly guessed, this isn't about a mission-critical or production environment, it's on my own sandbox (there is a minor issue in one of our env and I need to show that the problem is not related to Sonic).
Thanks again,
Aziz