I am a noob in Solr and zookeeper and trying to learn by myself. I understood that zookeeper is a file structure that manages solr cluster and prevents race condition using locks. I didn’t understand what is upconfig and downconfig and when we do that. It would be of great help if someone can give me a clear picture on it. Thanks in advance!
A better and more general description of Zookeeper is an application that provides centralised configuration for distributed systems. So in Solr Cloud, you can have multiple Solr instances across multiple servers acting together as a single cloud. However, if you want to update a collection's configuration, you don't want to have to go to each server and update them all individually. You want only one version of the config which is then used by any collection that needs it. Hence the conf commands.
upconfig uploads a configuration to ZooKeeper, which then ensures that all collections using that configuration (throughout the Cloud, on all the servers) have that specific config. So you only need to upload it once, on one server.
downconfig lets you fetch a configuration from Zookeeper.