Merge "Add additional documentation on extra spec operations."

doc/source/devref/capabilities_and_extra_specs.rst

@@ -37,8 +37,45 @@ enabled by default), the scheduler will only create a share on a backend
 that reports capabilities that match the share type's un-scoped extra-spec
 keys.
 
-Refer to the CapabilitiesFilter for matching operators.  For example, to
-match a boolean capability the extra-spec value would be '<is> True'.
+The CapabilitiesFilter uses the following for matching operators:
+
+* No operator
+  This defaults to doing a python ==. Additionally it will match boolean values.
+
+* **<=, >=, ==, !=**
+
+  This does a float conversion and then uses the python operators as expected.
+
+* **<in>** 
+
+  This either chooses a host that has partially matching string in the capability
+  or chooses a host if it matches any value in a list. For example, if "<in> sse4" 
+  is used, it will match a host that reports capability of "sse4_1" or "sse4_2".
+
+* **<or>**
+
+  This chooses a host that has one of the items specified. If the first word in 
+  the string is <or>, another <or> and value pair can be concatenated. Examples 
+  are "<or> 3", "<or> 3 <or> 5", and "<or> 1 <or> 3 <or> 7". This is for 
+  string values only. 
+
+* **<is>**
+
+  This chooses a host that matches a boolean capability. An example extra-spec value 
+  would be "<is> True".
+
+* **=**
+
+  This does a float conversion and chooses a host that has equal to or greater 
+  than the resource specified. This operator behaves this way for historical
+  reasons.
+
+* **s==, s!=, s>=, s>, s<=, s<**
+
+  The "s" indicates it is a string comparison. These choose a host that satisfies 
+  the comparison of strings in capability and specification. For example, 
+  if "capabilities:replication_type s== dr", a host that reports replication_type of 
+  "dr" will be chosen.
 
 For vendor-specific capabilities (which need to be visible to the
 CapabilityFilter), it is recommended to use the vendor prefix followed