add MAX_JOBS to configure the number of concurrent jobs

docker/Dockerfile

@@ -20,6 +20,7 @@ EXPOSE 4567
 ENV	PORT="4567"	\
 	ENV=""		\
 	REGISTRY=""	\
+	MAX_JOBS="4"	\
 	DATASTORE_PATH="/data/{ENV}/rails/rw/datastore/"	\
 	SANDBOX_PATH="/data/{ENV}/ssh/cache/sandbox/"		\
 	DOCKER_HOST="unix:///run/docker.sock"			\

docker/controller.py

@@ -739,8 +739,8 @@ EOF
 
 
 class JobManager(Manager):
-    def __init__(self, ctrl, nb_threads=NB_JOB_TASKS):
-        super().__init__(nb_threads)
+    def __init__(self, ctrl, nb_jobs=NB_JOB_TASKS):
+        super().__init__(nb_jobs)
         self.ctrl = ctrl
 
     def _run_job(self, job_id, ver_id):
@@ -1036,7 +1036,8 @@ class ImageManager:
 
 class DockerController:
     def __init__(self, sandbox_host, swarm_host, mysql_host,
-            port, registry, env, datastore_path, sandbox_path):
+            port, registry, env, datastore_path, sandbox_path,
+            max_jobs):
 
         self.sandbox = docker.Client(sandbox_host)
         self.swarm   = self.sandbox if sandbox_host == swarm_host else docker.Client(swarm_host)
@@ -1053,7 +1054,7 @@ class DockerController:
 
         self.image_manager   = ImageManager(self)
         self.sandbox_manager = SandboxManager(self)
-        self.job_manager     = JobManager(self)
+        self.job_manager     = JobManager(self, max_jobs)
 
         self.registry       = registry
         self.env            = env

docker/test_controller.py

@@ -154,6 +154,7 @@ class ControllerTestCase(unittest.TestCase):
                 env          = ENV,
                 datastore_path = "/data/dev/cache/test/datastore",
                 sandbox_path   = "/data/dev/ssh/cache/sandbox",
+                max_jobs     = 4,
                 )
 
     @classmethod