generate hash on ruby

Question

On production server:

"KYK_iphone3.jpg".hash.abs%1000
=> 908

But on staging server:

"KYK_iphone3.jpg".hash.abs%1000
=> 740

The two hashes do not match. Can you please give me your ideas on what to do in this situation?

Answer 1

Ruby's default hashing is not guaranteed to be consistent across implementations. You should use a standardized hashing algorithm such as MD5, SHA1 or similar, if you require consistent hashes.

EDIT: On further investigation, it turns out it is not even consistent across different processes:

$ irb
> "abc".hash
 => 3669021835949727595
> exit 
$ irb
> "abc".hash
 => 2091809102525897616

It appears this might be an intended security feature inherited from Perl to protect against algorithmic complexity attacks.