[chef] Re: RE: Re: Memcached on a separate node?

[Three Tee < >]

While the line of code that you highlighted does indeed exclude the local 
host from the search, the subsequent lines add the local host to the results 
if it has the memcache role and no other memcache nodes are returned by the 
search. This means that the application cookbook as written supports two 
scenarios when generating memcache.yml:
1. A single rails server with a local memcache
2. Any number of rails servers that use any number of external memcache 
servers (with no overlap between the two groups of servers)

The "right" way to architect your rails cache is probably a topic for another 
email, but if you require overlap between the rails and memcache servers, 
you'll probably want to eschew the application cookbook's memcache.yml 
generation altogether and add some of your own code to the before_deploy 
callback that generates the memcache.yml file to your spec. 

Hope this helps!

On Dec 4, 2012, at 4:23 PM, Warren Bain 
<
 >
 wrote:

> Noah,
> 
> Perhaps I didn't explain myself very well or I don't understand your reply 
> :)
> 
> The cookbook looks for a node that has whatever the role is called and 
> which isn't this node i.e. has to be a different node to the app server.  
> See here:
> 
> https://github.com/opscode-cookbooks/application_ruby/blob/master/providers/memcached.rb#L28
> 
> Wazza
> ________________________________________
> From: Noah Kantrowitz 
> 
 
> Sent: Wednesday, 5 December 2012 10:07 AM
> To: 
> 
 
> Subject: [chef] Re: Memcached on a separate node?
> 
> You just have to give it a role, there is no reason that role can't be 
> "www" or some such :-)
> 
> --Noah
> 
> On Dec 4, 2012, at 2:54 PM, Warren Bain wrote:
> 
>> We are using the application cookbook to do Rails deployments.
>> 
>> I'm wondering about the logic around memcached which requires a separate 
>> node that is not the app node to be set up as a memcached master.  I'm not 
>> expert in this area at all but the common wisdom from our Rails developers 
>> is that memcached should be on the app server, not a separate vm which 
>> would seem to defeat the purpose.  In particular we are doing deployments 
>> across availability zones so the network costs is higher than on a same 
>> physical host vm.
>> 
>> Can someone in OpsCode explain why separate memcached node is the model?
>> 
>> Regards,
>> Wazza