I seem to have discovered something unusual about the SOLR master/slave replication and the core version numbers.
We have a simple 1 master 1 slave replication setup with multiple cores. We have a monitoring script that checks /solr/admin/cores endpoint on both the master and the slave and compares the number of documents and the version number. This has been working fine for about half a year.
Recently we're seeing that sometimes the master's version number is a few numbers higher that the slave's, but the replication status shows that it's up to date.
I know that replication checks another endpoint /solr/?replication?command=indexversion, gives the same version number on both the slave and the master.
We've seen this happening on two different projects. One of them uses solr 4.10.3 and another 5.4.1.
Has anyone seen this kind of behaviour? Is this just a SOLR issue or a symptom of something going wrong? Or should I just change the monitoring to check the other endpoint?
Anyone know what the difference between the two version numbers in SOLR are?