Generation number's role in SOLR replication

Question

I set up a replication master and a replication salve for SOLR and it doesn't do anything. My suspicion is the generation number. The master has 232 while the slave has 241. If somebody can confirm my suspicion, that would be great and I also would like to know how to resolve this issue if so?

Answer 1

I can't confirm it but I can deny it. :)

From this post, here is how it works:

It look at the index version AND the index generation. If both slave's version and generation are the same as on master, nothing gets replicated. if the master's generation is greater than on slave, the slave fetches the delta files only (even if the partial merge was done on the master) and put the new files from master to the same index folder on slave (either index or index., see further explanation). However, if the master's index generation is equals or less than one on slave, the slave does the full replication by fetching all files of the master's index and place them into a separate folder on slave (index.). Then, if the fetch is successfull, the slave updates (or creates) the index.properties file and puts there the name of the "current" index folder. The "old" index. folder(s) will be kept in 1.4.x - which was treated as a bug - see SOLR-2156 (and this was fixed in 3.1). After this, the slave does commit or reload core depending whether the config files were replicated. There is another bug in 1.4.x that fails replication if the slave need to do the full replication AND the config files were changed - also fixed in 3.1 (see SOLR-1983).

plus there is another bug still opened about the index generation id: http://lucene.472066.n3.nabble.com/replication-problems-with-solr4-1-td4039647.html

Now to answer your question in one line, the replication always occur (full pr partial) if the version (or replication) numbers are different from master to slave.