On Thu, Aug 9, 2012 at 5:39 PM, Bing Hua <bh...@cornell.edu> wrote: > I'm a bit confused with the purpose of Transaction Logs (Update Logs) in > Solr. > > My understanding is, update request comes in, first the new item is put in > RAM buffer as well as T-Log. After a soft commit happens, the new item > becomes searchable but not hard committed in stable storage. Configuring > soft commit interval to 1 sec achieves NRT. > > Then what exactly T-Log is doing in this scenario?
It serves realtime-get... when even 1 second isn't acceptable (i.e. you need to be guaranteed of getting the latest version of a document): http://searchhub.org/dev/2011/09/07/realtime-get/ and also allows for a peer to ask "give me the list of the last update events you know about". You can also "kill -9" the server and solr will automatically recover from the log. > what circumstances is it being cleared? A new log file is created every time a hard commit is done, and old log files are removed if newer log files contain enough entries to satisfy the needs of what I call "peersync" in solr cloud (currently ~100 updates IIRC). It's cleared after a hard commit and after there are enough entries in other log files to satisfy the lookback requirements of what I call "peersync" in SolrCloud (currently ~100 updates IIRC). -Yonik http://lucidimagination.com
