# Lock index when not using drb server?

**URL:** <https://www.ruby-forum.com/t/lock-index-when-not-using-drb-server/127411>\
**Category:** Ferret\
**Created:** [January 28, 2008, 11:54pm UTC](https://www.ruby-forum.com/t/lock-index-when-not-using-drb-server/127411 "2008-01-28T23:54:56Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![johnnybutler7](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/8491ac/32.png) [@johnnybutler7](https://www.ruby-forum.com/u/johnnybutler7)\
**Post date:** [January 28, 2008, 11:54pm UTC](https://www.ruby-forum.com/t/lock-index-when-not-using-drb-server/127411/1 "2008-01-28T23:54:56Z")

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We all know that using ferret/aaf without the drb server is not  
thread-safe-- but why not? Would it be so hard to sacrifice  
performance by using a simple locking system?

Very often I run into a situation where I want to quickly stage a  
project, and I want to use a few mongrels but don’t want to configure  
every last piece of the system, including the drb server. It would be  
nice if I didn’t have to worry about index corruption.

Just a thought.

John

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<div class="post-metadata">

**Author:** ![johnnybutler7](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/8491ac/32.png) [@johnnybutler7](https://www.ruby-forum.com/u/johnnybutler7)\
**Post date:** [January 29, 2008, 12:46am UTC](https://www.ruby-forum.com/t/lock-index-when-not-using-drb-server/127411/2 "2008-01-29T00:46:03Z")

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Please anyone correct me if I’m wrong.

I think it’s because the thread safety is implemented at the class  
level. Which means it’s ok to share a single instance of IndexWriter  
across many threads. But when you have a multi-process model going  
(Rails), you effectively have many different programs accessing the  
same index files, thus running into file locking issues.

Implementing a shared locking mechanism that’s fast enough not to get  
in the way of performance (in a really bad way) is a subject for a lot  
of research. The first idea that springs to my mind is using a  
tempfile based one. Solves the problem, but you can kiss goodbye to  
fast indexing. (e.g.: if File.exists? ‘foo’ # index is locked, wait a  
bit and try again)

One other solution is to have a common daemon that all processes share  
and handle file locking in memory, and that’s precisely what the DRb  
server is. Perhaps a quickie would be to tie the DRb server to a  
thread that runs along with Rails. This would make it transparent.

I think I’ll risk it and reply later with a hack.