Jobs: Fixes job initialize/finalize

Previously initialize and finalize were being called for each iteration
of each workload at the start/end of the run which is incorrect
behaviour. To prevent this, each iteration of a workload now shares a
single instance of the workload combined with the 'once_per_instance' decorator
to ensure that the methods are only invoked once per set of workload
runs.

wa/framework/job.py

@@ -6,6 +6,8 @@ from wa.framework.configuration.core import Status
 
 class Job(object):
 
+    _workload_cache = {}
+
     @property
     def id(self):
         return self.spec.id
@@ -40,11 +42,15 @@ class Job(object):
 
     def load(self, target, loader=pluginloader):
         self.logger.info('Loading job {}'.format(self.id))
-        self.workload = loader.get_workload(self.spec.workload_name,
-                                            target,
-                                            **self.spec.workload_parameters)
-        self.workload.init_resources(self.context)
-        self.workload.validate()
+        if self.iteration == 1:
+            self.workload = loader.get_workload(self.spec.workload_name,
+                                                target,
+                                                **self.spec.workload_parameters)
+            self.workload.init_resources(self.context)
+            self.workload.validate()
+            self._workload_cache[self.id] = self.workload
+        else:
+            self.workload = self._workload_cache[self.id]
 
     def initialize(self, context):
         self.logger.info('Initializing job {}'.format(self.id))

wa/framework/workload.py

@@ -24,7 +24,7 @@ from wa.framework.resource import (ApkFile, JarFile, ReventFile, NO_ONE,
 from wa.framework.exception import WorkloadError
 from wa.utils.types import ParameterDict
 from wa.utils.revent import ReventRecorder
-from wa.utils.exec_control import once
+from wa.utils.exec_control import once_per_instance
 
 from devlib.utils.android import ApkInfo
 from devlib.exception import TargetError
@@ -161,6 +161,7 @@ class ApkWorkload(Workload):
     def init_resources(self, context):
         pass
 
+    @once_per_instance
     def initialize(self, context):
         self.apk.initialize(context)
 
@@ -177,7 +178,7 @@ class ApkWorkload(Workload):
     def teardown(self, context):
         self.apk.teardown()
 
-    @once
+    @once_per_instance
     def finalize(self, context):
         pass
 
@@ -192,6 +193,7 @@ class ApkUIWorkload(ApkWorkload):
         super(ApkUIWorkload, self).init_resources(context)
         self.gui.init_resources(context.resolver)
 
+    @once_per_instance
     def initialize(self, context):
         super(ApkUIWorkload, self).initialize(context)
 
@@ -212,7 +214,7 @@ class ApkUIWorkload(ApkWorkload):
         self.gui.teardown()
         super(ApkUIWorkload, self).teardown(context)
 
-    @once
+    @once_per_instance
     def finalize(self, context):
         super(ApkUIWorkload, self).finalize(context)
         self.gui.remove()