On 1/11/2022 7:01 PM, Ashwin Ramesh wrote:
1. Does the local node/core download the config (schema etc.) & solr.xml from ZK? If so, where would the files exist? (I can't seem to locate it in my local running instance).
The files are not downloaded. Solr pulls them from zookeeper and uses them directly. I really doubt that the files obtained are ever saved to the local disk.
2. When I issue a RELOAD command, what does SolrCloud and the underlying nodes in a collection actually do?
If you issue a RELOAD with the collections API, Solr will ask each shard replica in the collection to reload.
If you issue a RELOAD with CoreAdmin on a single core, I am actually not sure whether Solr would magnify that to the rest of the cores in the collection. Hopefully it won't. I do not have access to a SolrCloud install to try this. FYI: Using the CoreAdmin API for ANYTHING is strongly discouraged when Solr is in cloud mode.
3. If we change the solr.xml file and upload the new version to the root directory of the ZK path for the given cluster, will a RELOAD command update the configuration for all running nodes?
The solr.xml file contains configuration for the node as a whole. Reloading will not make changes take effect. After changing solr.xml in ZK you will need to completely restart each Solr instance connected to that zookeeper ensemble. When it starts, it check for the existence of solr.xml in ZK. If it finds it there, it will pull solr.xml from zookeeper to configure itself. If it doesn't find solr.xml in zookeeper then it will look for it in the solr home. I'm fairly sure that if it's not found in either location, the Solr versions I have used will not start. If that's still the case, I think it's a bug.
Thanks, Shawn
