load balancer on complete_unicorn_nginx_postgresql

[Thimios Dimopulos]

Hi all,

I am using the latest stable rubber version and the default complete_unicorn_nginx_postgresql template. I understand that there is no haproxy anymore in this template.

Does this mean that nginx is the load balancer on this template?

I started with one instance with roles web, app, web_tools and one instance with role: db:primary=true. When I added another instance of role app, it seems not to be receiving any requests (I monitor all app instances on newrelic).

Do I need to add the haproxy role in order to be able to add more app instances to the cluster? Is there another point I am maybe completely missing?

Thanks a lot,

Thimios

[Gordon McNaughton]

Hi Thimios,

Not sure my experience translates 100% (I'm using passenger instead of unicorn), but I dropped haproxy in favor of an ELB (Amazon Elastic Load Balancer).  It's straightforward to set up, though instances have to be added manually.

The setup looks like this:

• one [web_tools] instance
  
• one [db:primary=true] instance
  
• multiple [web,app] instances (see https://groups.google.com/d/msg/rubber-ec2/6-04XSnEPo4/zJDGAlxXX64J for why they need both roles)
• one AWS ELB that has all [web,app] instances in its pool (you have to add them to the pool manually, unless you script it)
  
• CNAME for www.mydomain.com points to the ELB
  

Requests hit the ELB, which forwards them to nginx on a [web,app] instance.  nginx passes the request to passenger on the same instance.

This is not ideal -- the web and app tiers are running on the same instances -- but it seems to work!

Hope that helps,
-G

[Thimios Dimopulos]

Hi Gordon,

thanks a lot for your reply. I would prefer to avoid setting up ELB and rather follow the standard rubber way if it provides a load balancer. It is unclear to me how to do a simple multiinstance setup.

I am using the complete_unicorn_nginx_postgresql template and I would like to have one instance running the database and two instances running the app. 

What roles should I give to them to have that simple setup? Do I need to additionally vulanize with the haproxy template in order to have a load balancer? 

Does anyone have such a setup running and could recommend the appropriate roles?

thanks a lot!

Thimios

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[Gabriel Cebrian]

Hi Thimios,

I am stuck on this just like you. I actually added web: [haproxy] to my rubber-complete file and deployed a web role box but I cannot get the web box to work.

Any ideas on this is appreciated.

Gabriel

[Thimios Dimopulos]

I decided not not use haproxy but elb. I created:

* ALIAS=db01 ROLES="db:primary=true" cap rubber:create

* ALIAS=app01,app02 ROLES=web,app cap rubber:create

I created an ELB and added the two instances manually to it