Importance of a discovery service in a service mesh

In a service mesh, where there are many services interacting with one another, there is an important aspect of discovery service. The job of a discovery service is to keep track of all the available hosts for the respective services. This information about the active live instances of any service can happen if we have some common code running on the individual service instances. This individual code or a sidecar (we can call it) interacts with the discovery service and get it informed about the individual service node statuses on the cloud. There is an option to create your own discovery service and sidecar or use one available open source, but without a discovery service, the service mesh becomes very difficult to manage.