add the part-handler plugin

If a part of a multipart file is 'text/part-handler' then it is 
expected to be python code that implements 2 methods

- list_types()
  list the types that this part-handler supports, return
  a list.  ie: return(['text/plain'])

- handle_parts(data,ctype,filename,payload)
  this method will be called:
     once, when loaded, with ctype == '__begin__'
     once per part
     once, at the end, with ctype == '__end__'

   - ctype is the content type ('text/plain')
   - filename is the filename portion of the mime data
   - payload is the content of the part
   - data is currently the cloud object, but this could change

doc/examples/part-handler.txt

@@ -0,0 +1,12 @@
+#part-handler
+# vi: syntax=python ts=4
+
+def list_types():
+    return(["text/plain", "text/go-cubs-go"])
+
+def handle_part(data,ctype,filename,payload):
+    if ctype == "__end__" or ctype == "__begin__": return
+
+    print "==== received ctype=%s filename=%s ====" % (ctype,filename)
+    print payload
+    print "==== end ctype=%s filename=%s" % (ctype, filename)

ec2init/UserDataHandler.py

@@ -8,7 +8,8 @@ starts_with_mappings={
     '#include' : 'text/x-include-url',
     '#!' : 'text/x-shellscript',
     '#cloud-config' : 'text/cloud-config',
-    '#upstart-job'  : 'text/upstart-job'
+    '#upstart-job'  : 'text/upstart-job',
+    '#part-handler' : 'text/part-handler'
 }
 
 # if 'str' is compressed return decompressed otherwise return it

ec2init/__init__.py

@@ -30,6 +30,7 @@ import yaml
 
 datadir = '/var/lib/cloud/data'
 semdir = '/var/lib/cloud/sem'
+pluginsdir = datadir + '/plugins'
 cachedir = datadir + '/cache'
 userdata_raw = datadir + '/user-data.txt'
 userdata = datadir + '/user-data.txt.i'
@@ -228,13 +229,37 @@ class EC2Init:
             func(data,"__end__",None,None)
 
     def handle_handler(self,data,ctype,filename,payload):
-        if ctype == "__begin__" or ctype == "__end__": return
+        if ctype == "__end__": return
+        if ctype == "__begin__" :
+            self.handlercount = 0
+            return
+
+        # add the path to the plugins dir to the top of our list for import
+        if self.handlercount == 0:
+            sys.path.insert(0,pluginsdir)
+
+        self.handlercount=self.handlercount+1
+
+        # write content to pluginsdir
+        modname  = 'part-handler-%03d' % self.handlercount
+        modfname = modname + ".py"
+        util.write_file("%s/%s" % (pluginsdir,modfname), payload, 0600)
+
+        try:
+            mod = __import__(modname)
+            lister = getattr(mod, "list_types")
+            handler = getattr(mod, "handle_part")
+        except:
+            import traceback
+            traceback.print_exc(file=sys.stderr)
+            return
 
-        # - do something to include the handler, ie, eval it or something
         # - call it with '__begin__'
+        handler(data, "__begin__", None, None)
+
         # - add it self.part_handlers
-        # self.part_handlers['new_type']=handler
-        print "Do not know what to do with a handler yet, sorry"
+        for mtype in lister():
+            self.part_handlers[mtype]=handler
 
     def handle_user_script(self,data,ctype,filename,payload):
         if ctype == "__end__": return

tools/write-mime-multipart

@@ -24,7 +24,8 @@ starts_with_mappings={
     '#include' : 'text/x-include-url',
     '#!' : 'text/x-shellscript',
     '#cloud-config' : 'text/cloud-config',
-    '#upstart-job'  : 'text/upstart-job'
+    '#upstart-job'  : 'text/upstart-job',
+    '#part-handler' : 'text/part-handler'
 }
 
 def get_type(fname,deftype):