Day 51: Cloud pattern: Rolling-update deployment
Rolling update deployment is the process of progressively upgrading version of service instances. Example: automatically upgrade 1 instance every 30 seconds.
Database schema migration must be done before rolling update and be compatible with the inital release.
Sometime, we can keep 2 releases running at the same time (90% nodes on v1 and 10% node on v1.1). Monitoring could show failures before general availibility of v1.1. In that case, using a load-balancer with sticky routing may be necessary (a user always requesting the same instance).