@rbiswas, You may have read this but there's some good info here in what they describe as a "real world" production configuration using the new cross-data-center replication: https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=62687462 Since this feature only came out in 6.0 which was released less than 2 months ago, there's probably been limited production use. ALSO....Not a best practice, but since way before Solr Cloud existed, we used a brute force method of cross-data-center replication for stand-by Solrs with the magic of rsync. You can reliably use rsync to copy indexes as they are being updated, but there's a bit of scripting required. I have only done this in non-cloud environments, but I'm pretty sure it can be done in cloud as well. It is crude, but it worked for years and uses some of the great features of linux. Example script, run in crontab from the DR site nodes: #step 1 - create a backup first, assuming your current copy is good. cp -rl ${data_dir} ${data_dir}.BAK #step 2 - Now copy from the primary site status=1 while [ $status != 0 ]; do rsync -a --delete ${primary_site_node}:${data_dir} ${data_dir} status=$? done echo "COPY COMPLETE!" That script will create local backup (instantly via hard-links, not soft links) and then copies [only] new files and deletes files from DR that are have been deleted from Primary/remote. If files disappear during the rsync copy, it will copy again until nothing changes during the rsync. This can be run from crontab, but it does need a bit of bullet-proofing. Simple. Crude. It works. ... View more

@David Lam I believe that would be pretty straight forward. 1) Write your SOAP client 2) Integrate it a custom class which extends UpdaterequestFactory in the processAdd(AddUpdateCommand) method. 3) Create your updateRequestProcessorChain in the solrconfig.xml 4) Add the chain to a requestHandler Look at the example here for the ConditionalCopyProcessorFactory but just make your SOAP call instead.: https://wiki.apache.org/solr/UpdateRequestProcessor In the processAdd, since you have access to the SolrInputDocument, you can get any field's value and you can also add a new field or child document, which is just another SolrInputDocument. Be aware that by doing this you could add a bottleneck to your update pipeline if the web service is slow or down and you could also add additional stress on the Solr server, which perhaps is also serving queries. It just depends on your load and other factors. Alternatively, you could annotate the SolrDocuments in your ingest pipeline, before they are sent to Solr to push the load elsewhere. If you have no control over the ingest pipeline, you may have to do it in the update request chain anyway. ... View more