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

[Noah Kantrowitz < >]

The way the application cookbook was built is to allow customizing those 
kinds of things very closely. You can just copy that LWRP (the 
application_ruby_memcache one) into a cookbook of your own and customize it, 
and then in the main application do end block refer to myapp_memcache 
instead. Nice and modular :)

--Noah

On Dec 4, 2012, at 5:36 PM, Three Tee wrote:

> 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