* Overview

Swift is part of Openstack, and provides a distributed blob storage. This barclamp installs swift.
Swift includes the following components:
 - Proxy node- provides the API to the cluster, including authentication.
 - Storage nodes - provide storage for clsuter.

* Roles
The following node roles are definied in this cookbook:
 - Storage node - configures a node to be used as a storage node
 - Proxy node - configures a node to be a proxy. each proxy node will have a memcached server installed. all proxy nodes are updated with all the memcached severs' addresses (listening on the internal IP addresses)
 - Proxy node with account management - same as proxy node, but allows account_management.
 - ring-compute-node - computes and update the ring file (contains information about what partitions are stored where). The ring file distributed to other cluster members via rsync (rsyncd configured on this node, other nodes configured to sync periodically)


* General comments

 The cookbook is designed to be useful in many different environments without requiring changes to the recpies themselvs. This is achieved by using attributes which provide expressions evaluated at recpie execution time. For example:

default[:swift][:admin_ip_expr] = "node[:ipaddress]" 
default[:swift][:storage_ip_expr] = "node[:ipaddress]"


Instructs the recipes to look at the ipaddress attribute set on the node for use for both the admin and storage networks. In environments where more copmlex address allocation is present, these expressions can be modified (even to function calls).


as a more complex example:

# expression to find a hash of possible disks to be used.
default[:swift][:disk_enum_expr]= 'node[:block_device]'
# expression accepting a k,v pair for evaluation. if expression returns true, then the disk will be used.
# by default, use any sdX or hdX that is not the first one (which will hold the OS).
default[:swift][:disk_test_expr]= 'k =~/sd[^a]/ or k=~/hd[^a]/'      

The first attribute provides a source for a list of possible disks to use. In this case, it's the ohai disk list. The second attribute is a test against the found disk - if the expression is true, the disk is ''claimed'' by swift (partitioned and formatted). The comment describes the sample expression. 


Look in the attributes\default.rb for the full set of expressions provided.
Look in data_bags/crowbar/bc-default-swift.json for some additional examples