How to maintain lucene indexes in azure cloud-app

Question

I just started playing with the Azure Library for Lucene.NET (http://code.msdn.microsoft.com/AzureDirectory). Until now, I was using my own custom code for writing lucene indexes on the azure blob. So, I was copying the blob to localstorage of the azure web/worker role and reading/writing docs to the index. I was using my custom locking mechanism to make sure we dont have clashes between reads and writes to the blob. I am hoping Azure Library would take care of these issues for me.

However, while trying out the test app, I tweaked the code to use compound-file option, and that created a new file everytime I wrote to the index. Now, my question is, if I have to maintain the index - i.e keep a snapshot of the index file and use it if the main index gets corrupt, then how do I go about doing this. Should I keep a backup of all the .cfs files that are created or handling only the latest one is fine. Are there api calls to clean up the blob to keep the latest file after each write to the index?

Thanks Kapil

Answer 1

After i answered this, we ended up changing our search infrastructure and used Windows Azure Drive. We had a Worker Role, which would mount a VHD using the Block Storage, and host the Lucene.NET Index on it. The code checked to make sure the VHD was mounted first and that the index directory existed. If the worker role fell over, the VHD would automatically dismount after 60 seconds, and a second worker role could pick it up.

We have since changed our infrastructure again and moved to Amazon with a Solr instance for search, but the VHD option worked well during development. it could have worked well in Test and Production, but Requirements meant we needed to move to EC2.

Answer 2

i am using AzureDirectory for Full Text indexing on Azure, and i am getting some odd results also... but hopefully this answer will be of some use to you...

firstly, the compound-file option: from what i am reading and figuring out, the compound file is a single large file with all the index data inside. the alliterative to this is having lots of smaller files (configured using the SetMaxMergeDocs(int) function of IndexWriter) written to storage. the problem with this is once you get to lots of files (i foolishly set this to about 5000) it takes an age to download the indexes (On the Azure server it takes about a minute,, of my dev box... well its been running for 20 min now and still not finished...).

as for backing up indexes, i have not come up against this yet, but given we have about 5 million records currently, and that will grow, i am wondering about this also. if you are using a single compounded file, maybe downloading the files to a worker role, zipping them and uploading them with todays date would work... if you have a smaller set of documents, you might get away with re-indexing the data if something goes wrong... but again, depends on the number....