Added metadata.Vars as quick access to Property like attributes

src/lib/Bcfg2/Server/Plugins/Vars.py

@@ -0,0 +1,116 @@
+"""
+  Support for metadata.Vars
+  these contain arbitrary strings for faster generation of templates
+"""
+
+import copy
+import os
+import sys
+
+import lxml
+
+import Bcfg2.Server.Plugin
+from Bcfg2.Server.Cache import Cache
+from Bcfg2.Server.Plugin import PluginExecutionError
+
+HAS_JSON = False
+try:
+    import json
+    HAS_JSON = True
+except ImportError:
+    pass
+
+
+class VarsFile(Bcfg2.Server.Plugin.StructFile):
+    """ representation of Vars vars.xml.
+    Manages caching and handles file events. """
+
+    def __init__(self, name, core, should_monitor=False):
+        Bcfg2.Server.Plugin.StructFile.__init__(self, name,
+                                                should_monitor=should_monitor)
+        self.name = name
+        self.core = core
+        # even though we are a connector plugin, keep a local cache
+        self.cache = Cache("Vars")
+
+    __init__.__doc__ = Bcfg2.Server.Plugin.StructFile.__init__.__doc__
+
+    def Index(self):
+        Bcfg2.Server.Plugin.StructFile.Index(self)
+        self.cache.clear()
+        self.core.metadata_cache.expire()
+
+    Index.__doc__ = Bcfg2.Server.Plugin.StructFile.Index.__doc__
+
+    def get_vars(self, metadata):
+        """ gets all var tags from the vars.xml """
+        if metadata.hostname in self.cache:
+            self.debug_log("Vars: Found cached vars for %s." %
+                           metadata.hostname)
+            return copy.copy(self.cache[metadata.hostname])
+        rv = dict()
+        for el in self.XMLMatch(metadata).xpath("//var"):
+            if 'name' not in el.attrib:
+                # if we have a correct schema, this should not happen
+                raise Bcfg2.Server.Plugin.PluginExecutionError(
+                    "Vars: Invalid structure of vars.xml. "
+                    "Missing name attribute for variable.")
+            if HAS_JSON and el.get('type') == "json":
+                rv[el.get('name')] = json.loads(el.text)
+            else:
+                rv[el.get('name')] = el.text
+        self.cache[metadata.hostname] = copy.copy(rv)
+
+        return rv
+
+    def validate_data(self):
+        """ ensure that the data in this object validates against the
+        XML schema for the vars file (if a schema exists) """
+        schemafile = self.name.replace(".xml", ".xsd")
+        if os.path.exists(schemafile):
+            try:
+                schema = lxml.etree.XMLSchema(file=schemafile)
+            except lxml.etree.XMLSchemaParseError:
+                err = sys.exc_info()[1]
+                raise PluginExecutionError(
+                    "Failed to process schema for %s: "
+                    "%s" % (self.name, err))
+        else:
+            # no schema exists
+            return True
+
+        if not schema.validate(self.xdata):
+            raise PluginExecutionError(
+                "Data for %s fails to validate; run "
+                "bcfg2-lint for more details" % self.name)
+
+
+class Vars(Bcfg2.Server.Plugin.Plugin,
+           Bcfg2.Server.Plugin.Connector):
+    """ The vars plugins adds additional info to the metadata object
+    based on entries in the vars.xml. Data can even be serialized
+    with json if desired.
+    """
+
+    def __init__(self, core):
+        Bcfg2.Server.Plugin.Plugin.__init__(self, core)
+        Bcfg2.Server.Plugin.Connector.__init__(self)
+        self.vars_file = VarsFile(os.path.join(self.data, 'vars.xml'),
+                                  core,
+                                  should_monitor=True)
+
+    __init__.__doc__ = Bcfg2.Server.Plugin.Plugin.__init__.__doc__
+
+    def get_additional_data(self, metadata):
+        self.debug_log("Vars: Getting vars for %s" % metadata.hostname)
+        return self.vars_file.get_vars(metadata)
+
+    get_additional_data.__doc__ = \
+        Bcfg2.Server.Plugin.Connector.get_additional_data.__doc__
+
+    def set_debug(self, debug):
+        rv = Bcfg2.Server.Plugin.Plugin.set_debug(self, debug)
+        self.vars_file.set_debug(debug)
+        return rv
+
+    set_debug.__doc__ = Bcfg2.Server.Plugin.Plugin.set_debug.__doc__