Implement query for instances

Queries don't create jobs and are more efficient. Log messages
are not yet stored anywhere.

Reviewed-by: iustinp

daemons/ganeti-masterd

@@ -227,9 +227,25 @@ class ClientOps:
       (job_ids, fields) = args
       return queue.QueryJobs(job_ids, fields)
 
+    elif method == luxi.REQ_QUERY_INSTANCES:
+      (names, fields) = args
+      op = opcodes.OpQueryInstances(names=names, output_fields=fields)
+      return self._Query(op)
+
     else:
       raise ValueError("Invalid operation")
 
+  def _DummyLog(self, *args):
+    pass
+
+  def _Query(self, op):
+    """Runs the specified opcode and returns the result.
+
+    """
+    proc = mcpu.Processor(self.server.context)
+    # TODO: Where should log messages go?
+    return proc.ExecOpCode(op, self._DummyLog)
+
 
 class GanetiContext(object):
   """Context common to all ganeti threads.

lib/luxi.py

@@ -47,6 +47,7 @@ REQ_SUBMIT_JOB = "SubmitJob"
 REQ_CANCEL_JOB = "CancelJob"
 REQ_ARCHIVE_JOB = "ArchiveJob"
 REQ_QUERY_JOBS = "QueryJobs"
+REQ_QUERY_INSTANCES = "QueryInstances"
 
 DEF_CTMO = 10
 DEF_RWTO = 60
@@ -288,4 +289,7 @@ class Client(object):
   def QueryJobs(self, job_ids, fields):
     return self.CallMethod(REQ_QUERY_JOBS, (job_ids, fields))
 
+  def QueryInstances(self, names, fields):
+    return self.CallMethod(REQ_QUERY_INSTANCES, (names, fields))
+
 # TODO: class Server(object)