I am using istio 1.4.3, this is installed using helm and I have 3 ingress and 1 egress GW in the istio-system namespace. Is there any steps to upgrade from istio 1.4.3 to istio 1.5 using the istioctl while keeping all my GWs.
My understanding is that the upgrade story for helm installs of 1.4 to 1.5 is bleak. In 1.6, the idea of a canary install of Istio exists. You should be able to orchestrate setting up a second control plane, build new gateways with the same configuration, and cut over traffic to the new gateways using DNS.
It’s a massive undertaking but theoretically it’s possible.
Have a look at the istioctl manifest migrate command. It will give you a starting point for a manifest that would work with 1.5 istioctl installation.
It’s also work considering 1.4 to 1.6 via canary upgrade: https://istio.io/latest/docs/setup/upgrade/#upgrading-from-1-4
Although it’s not officially recommended, it’s low risk because you don’t remove the older version so rollback is easy.