config: use centrally configured k8s namespace

* In order to be able to deploy REANA in different Kubernetes
  namespaces we use the centrally configured variable from
  REANA-Commons which represents it. This configuration happens
  at deployment time and can be different than the namespace
  in which the REANA infrastructure pods run
  (closes reanahub/reana#274 reanahub/reana#268).

CHANGES.rst

@@ -11,6 +11,7 @@ Version master (UNRELEASED)
 - Improves error reporting on Docker image related failures.
 - Prefixes user workflows with the configured REANA prefix.
 - Switches CVMFS to be read-only mount.
+- Instantiates jobs in the configured runtime namespace.
 - Enables running tests locally on MacOS.
 - Adds Black formatter support.
 

reana_job_controller/job_monitor.py

@@ -14,6 +14,7 @@
 import traceback
 
 from kubernetes import client, watch
+from reana_commons.config import REANA_RUNTIME_KUBERNETES_NAMESPACE
 from reana_commons.k8s.api_client import (
     current_k8s_batchv1_api_client,
     current_k8s_corev1_api_client,
@@ -202,10 +203,6 @@ def get_job_logs(self, job_pod):
         """Get job pod's containers' logs."""
         try:
             pod_logs = ""
-            # job_pod = current_k8s_corev1_api_client.read_namespaced_pod(
-            #     namespace='default',
-            #     name=job_pod.metadata.name)
-            # we probably don't need this call again... FIXME
             container_statuses = job_pod.status.container_statuses + (
                 job_pod.status.init_container_statuses or []
             )
@@ -214,7 +211,7 @@ def get_job_logs(self, job_pod):
             for container in container_statuses:
                 if container.state.terminated:
                     container_log = current_k8s_corev1_api_client.read_namespaced_pod_log(
-                        namespace="default",
+                        namespace=REANA_RUNTIME_KUBERNETES_NAMESPACE,
                         name=job_pod.metadata.name,
                         container=container.name,
                     )
@@ -244,7 +241,7 @@ def watch_jobs(self, job_db, app=None):
                 w = watch.Watch()
                 for event in w.stream(
                     current_k8s_corev1_api_client.list_namespaced_pod,
-                    namespace="default",
+                    namespace=REANA_RUNTIME_KUBERNETES_NAMESPACE,
                     label_selector="job-name",
                 ):
                     logging.info("New Pod event received: {0}".format(event["type"]))

reana_job_controller/kubernetes_job_manager.py

@@ -22,8 +22,8 @@
     CVMFS_REPOSITORIES,
     K8S_CERN_EOS_AVAILABLE,
     K8S_CERN_EOS_MOUNT_CONFIGURATION,
-    K8S_DEFAULT_NAMESPACE,
     REANA_COMPONENT_PREFIX,
+    REANA_RUNTIME_KUBERNETES_NAMESPACE,
     WORKFLOW_RUNTIME_USER_GID,
     WORKFLOW_RUNTIME_USER_UID,
 )
@@ -112,7 +112,8 @@ def execute(self):
         self.job = {
             "kind": "Job",
             "apiVersion": "batch/v1",
-            "metadata": {"name": backend_job_id, "namespace": K8S_DEFAULT_NAMESPACE},
+            "metadata": {"name": backend_job_id,
+                         "namespace": REANA_RUNTIME_KUBERNETES_NAMESPACE},
             "spec": {
                 "backoffLimit": KubernetesJobManager.MAX_NUM_JOB_RESTARTS,
                 "autoSelector": True,
@@ -194,7 +195,7 @@ def _submit(self):
         """Submit job and return its backend id."""
         try:
             api_response = current_k8s_batchv1_api_client.create_namespaced_job(
-                namespace=K8S_DEFAULT_NAMESPACE, body=self.job
+                namespace=REANA_RUNTIME_KUBERNETES_NAMESPACE, body=self.job
             )
             return self.job["metadata"]["name"]
         except ApiException as e:
@@ -214,7 +215,7 @@ def stop(backend_job_id, asynchronous=True):
             propagation_policy = "Background" if asynchronous else "Foreground"
             delete_options = V1DeleteOptions(propagation_policy=propagation_policy)
             current_k8s_batchv1_api_client.delete_namespaced_job(
-                backend_job_id, K8S_DEFAULT_NAMESPACE, body=delete_options
+                backend_job_id, REANA_RUNTIME_KUBERNETES_NAMESPACE, body=delete_options
             )
         except ApiException as e:
             logging.error(