I had a better description of this, but it was on the old Lighthouse which is now closed.

Sinatra 1.0 leaks memory when the cache is enabled on 1.8.6 due to the hash within array bug, eventually eating all the memory on the system.

Example:

irb(main):006:0> example = { [{:key => 'val'}] => 'ok' }
=> {[{:key=>"val"}]=>"ok"}
irb(main):007:0> example[{:key => 'val'}]
=> nil

This works on 1.8.7 and doesn't on 1.8.6. Sinatra essentially does this for caching, so it just keeps missing and re-storing, and the hash builds up with duplicate entries.

Here's a reworked Tile::Cache#fetch that makes the test pass. It's not pretty, might be a bit verbose, but it seems to work.

def fetch(*key)
 cached_template = nil
 if RUBY_VERSION == '1.8.6'
   @cache.keys.each do |k|
     if k == key
       @cache[k] ||= yield
       cached_template = @cache[k]
     end
   end
   if cached_template.nil?
     @cache[key] = yield
     cached_template = @cache[key]
   end
 else
   @cache[key] ||= yield
   cached_template = @cache[key]
 end
 cached_template
end

Finally, here is a test for reproduction: http://github.com/kyledrake/tilt/commit/76672520040c4e4501f85a83194d7dcc562ff2dd