Create the workflow context in the Popper cache dir

Earlier the Kubernetes runner used to create the workflow context tar file in the workspace. To prevent that, the context tar file is now created in `$POPPER_CACHE_DIR/kubernetes` directory. Also, the workflow context file is appended with the workflow id so that we can later build the feature of resuing a workflow context tar file.


Co-authored-by: Vivek Ramanathan <vivek@Viveks-MBP.attlocal.net>

src/popper/runner_kubernetes.py

@@ -132,10 +132,17 @@ def _copy_ctx(self):
         """Tar up the workspace context and copy the tar file into
         the PersistentVolume in the Pod.
         """
+        source_dir = os.path.join(self._config.cache_dir, "kubernetes")
+        if not os.path.exists(source_dir):
+            os.makedirs(source_dir)
+
+        target_file = "ctx_" + str(self._config.wid) + ".tar.gz"
+        source_file = os.path.join(source_dir, target_file)
+        destination_file = "/workspace/" + target_file
+
         files = os.listdir(self._config.workspace_dir)
-        with tarfile.open(
-            os.path.join(self._config.workspace_dir, "ctx.tar.gz"), mode="w:gz"
-        ) as archive:
+
+        with tarfile.open(source_file, mode="w:gz") as archive:
             for f in files:
                 archive.add(f)
 
@@ -152,9 +159,6 @@ def _copy_ctx(self):
             _preload_content=False,
         )
 
-        source_file = os.path.join(self._config.workspace_dir, "ctx.tar.gz")
-        destination_file = "/workspace/ctx.tar.gz"
-
         with open(source_file, "rb") as image_file:
             encoded_string = base64.b64encode(image_file.read())
 
@@ -177,7 +181,7 @@ def _copy_ctx(self):
         response.close()
 
         # extract the archive inside the pod
-        exec_command = ["tar", "-zxvf", "/workspace/ctx.tar.gz"]
+        exec_command = ["tar", "-zxvf", destination_file]
         response = stream(
             self._kclient.connect_get_namespaced_pod_exec,
             self._init_pod_name,