_README.md

How do you logically model data centers?

For example, I have 6 types of web servers, and 8 datacenters. Each webserver has a config file that has to point to an IP that is unique per datacenter.

Asked question here, and IRC. Haven't found a good solution yet. http://serverfault.com/questions/700860/can-chef-have-different-databags-in-different-datacenters

OptionA.md

Option A

#################

Pros: flat 2 layer design Cons: Boat load of nearly identical roles. (could be hundreds)

Environments

- Production : web: 0.12.0, elastic search:0.3.13
- Stage:          web: 1.0.0,  elasticsearch: 0.3.14

Roles ( 9 datacenters/regions * 6 web servers = 54 web server roles)

- us-east1-web-base
- us-east1-web-netsage
- us-east1-web-mailproc
- us-east1-web-fast
- eu-north1-web-base
- eu-north1-web-netsage
- eu-north1-web-mailproc
- aws-west1-web-base
- aws-west1-web-netsage
- aws-west1-web-mailproc
- aws-west1-web-fast

Cookbooks

- web-base
- web-netsage
- web-mailproc
- web-fast

OptionB.md

Option B

#########################

Pros: Far less roles, uses two types of roles. You apply both a datacenter role and a web server type role. No real need for wrapper cookbooks. Need to be careful that when you apply two types of roles, they don't overlap settings. Last one applied will win. Make sure datacenter roles are 'overrides' Cons: Be careful you don't duplicate settings between _datacenter and _web override roles. Last one will win.

Databags

- web
 - production
   -web-version = 2.0.0
   -web-version-beta = 2.2.0
   -web-version-previous = 1.0.0
 - stage
   -web-version = 3.0.0

Environments

- Production
- Stage

Roles The roles that start with an underscore are override roles for the special snowflakes. They have a variable that tells the cookbook to look at a special databag (e.g web-version-beta databag and web-version-previous databag).

- _us-east1      #Uses override level attributes
- _eu-north1    #Uses override level attributes
- _aws-west1    #Uses override level attributes
- _azure-south1    #Uses override level attributes
- _web-beta        #Overrides pool of web-base servers 
- _web-previous  #Override pool of web-base servers
- web-base
- web-netsage
- web-mailproc
- web-fast

Cookbooks

- web-base
- web-netsage
- web-mailproc
- web-fast

OptionC.md

Option C

#########################

Pros: Simple Roles Cons: Extreme amount of wrapper cookbooks

Databags ???

Environments

- Production
- Stage

Roles

- _us-east1
- _eu-north1
- _aws-west1
- _azure-south1
- web-base
- web-netsage
- web-mailproc
- web-fast
- previous_release 

WrapperCookbooks

- web-base-us-east1
- web-base-eu-north1
- web-base-aws-west1
- web-base-azure-south1
- web-netsage-us-east1
- web-netsage-us-north1
- web-netsage-aws-west1
- web-netsage-azure-south1
- web-mailproc-us-east1
- web-mailproc-us-north1
- web-mailproc-aws-west1
- web-mailproc-azure-south1
- web-fast-us-east1
- web-fast-us-north1
- web-fast-aws-west1
- web-fast-azure-south1

Cookbooks

• nd-web

OptionD.md

Option D

#########################

Pros: Cons:

Databags ???

Environments

- Production
- Stage

Roles

- _us-east1
- _eu-north1
- _aws-west1
- _azure-south1
- web-base
- web-netsage
- web-mailproc
- web-fast
- previous_release 

WrapperCookbooks

Cookbooks

• nd-web

OptionE.md

Option E

###################

Somehow use wrapper cookbooks?

You could do: Base web server wrappers Role wrappers Environment wrappers

That makes for a lot of wrapper cookbooks, that I"m not sure are needed, since roles can do that anyway.

Finally figured out the best solution for us by using a combination of roles. Will blog about it here: http://spuder.github.io/2015/chef-datacenter-pattern/