I'm working with a project that has scalability issues due to cache management and full resource management.
I decide to use Apache Ignite as my caching layer but I don't want to up the separate cluster for that. Can we use my spring application as a cluster node, and there are several other instances together that make the ignite cluster, and also The same application act as ignite client. It will use my unused JVM.
Yes, you can do that.
You need to configure Static IP Finder to only use 127.0.0.1 host, use the same localHost/localAddress, use some custom discovery port to avoid interference with any other clusters. You can also try implementing no-op Discovery, but I don't think it is worth the hassle.
An Ignite node can do everything that client node can, so you never need to spawn a separate client if you already possess a (server) node.
As for Spring integration, you can use IgniteSpringBean or just manage Ignite lifecycle on its own.