Cookie data size exceeds 4K - But its 'only' 1100 bytes encrypted

Question

I have a Sinatra app using Rack::Session::Cookie

use Rack::Session::Cookie, :key => 'my.key',
                           :path => '/',
                           :expire_after => 3600, # In seconds
                           :secret => 'something'

I have one place in the session where I set the data, and I do a dump of the session, which is about 600 bytes right before the erb call

  puts "session is #{session.inspect}" ==> 400 bytes of text

Then I get

Warning! Rack::Session::Cookie data size exceeds 4K.
Warning! Rack::Session::Cookie failed to save session. Content dropped.

Funny thing is, it all seems to be working, in that everything I set on the session comes back to me on the next hit. The session size as reported in the Safari development window is 1195 bytes, and it all looks encrypted, etc.

Any ideas on how this could be happening? It appears that the message is spurious, but looking at the Rack:Session code - it appears that something is being dumped...

Answer 1

Fred is right. session.inspect is not going to show you the exact size of the cookie string length. You could use tcpdump to get a better idea of its size;

tcpdump -s 1500 -A host and port

Then make the request and check out the actual ascii dump of the cookie data.

lal00 is likely onto the real underlying issue