Add erasure code policy support to swift

This patch is version 1 (not tested) of adding erasure code support
to swift. It adds the following:

  - Add policy_type, ec_type, ec_num_data_fragments,
    ec_num_parity_fragments and ec_object_segment_size to the
    policy definition.

  - Update the ring.contents.j2 to set replica count for the ring
    to ec_num_parity_fragments + ec_object_segment_size, if using
    the erasure code policy_type.

  - Adds extra EC options to swift.conf for EC policies.

I may have missed something and again this hasn't been tested yet.

NOTE: EC in Swift is strictly _BETA_ and shouldn't be run in
      production, however, we do need to test it!

Change-Id: If2069a95e6ea92e34fb329cb6e0027188f15f0bb

templates/ring.contents.j2

@@ -22,7 +22,11 @@
 {### Lets get the min_part_hours, part_power and repl_number vals #}
 {% set min_part_hours = item.min_part_hours | default(swift.min_part_hours | default(swift_default_min_part_hours)) %}
 {% set part_power = item.part_power | default(swift.part_power) %}
+{% if (item.policy_type is defined) and (item.policy_type == "erasure_coding") %}
+{%   set repl_number = item.ec_num_data_fragments + item.ec_num_parity_fragments %}
+{% else %}
 {%   set repl_number = item.repl_number | default(swift.repl_number | default(swift_default_replication_number)) %}
+{% endif %}
 {### Create the builder dict #}
 {% set builder = {} %}
 {### This is a hacky way of updating the builder dict #}

templates/swift.conf.j2

@@ -4,16 +4,31 @@
 swift_hash_path_suffix = {{ swift_hash_path_suffix }}
 swift_hash_path_prefix = {{ swift_hash_path_prefix }}
 
+
 # Storage Policies
 {% for policy in swift.storage_policies %}
+{% set swift_policy_type = policy.policy.policy_type|default('replication') %}
+
 [storage-policy:{{ policy.policy.index }}]
 name = {{ policy.policy.name }}
+policy_type = {{ swift_policy_type }}
+
+{% if swift_policy_type == 'erasure_coding' %}
+ec_type = {{ policy.policy.ec_type }}
+ec_num_data_fragments = {{ policy.policy.ec_num_data_fragments }}
+ec_num_parity_fragments = {{ policy.policy.ec_num_parity_fragments }}
+ec_object_segment_size = {{ policy.policy.ec_object_segment_size }}
+{% endif %}
+
 {% if policy.policy.deprecated is defined %}
 deprecated = {{ policy.policy.deprecated }}
 {% endif %}
+
 {% if policy.policy.default is defined %}
 default = {{ policy.policy.default }}
 {% endif %}
 
 {% endfor %}
+
+
 [swift-constraints]