container backend pluggability (#405)

Makes it possible (in principle; reality TBD) for a plugin to override the default Docker Swarm container backend

WDL/CLI.py

@@ -626,9 +626,6 @@ def file_found(fn):
 
         rerun_sh = f"pushd {shellquote(os.getcwd())} && miniwdl {' '.join(shellquote(t) for t in sys.argv[1:])}; popd"
 
-        # initialize local Docker Swarm
-        runtime.task.SwarmContainer.global_init(cfg, logger)
-
         # run & log any errors
         cleanup.enter_context(runtime._statusbar.enable(set_status))
         cache = cleanup.enter_context(runtime.cache.CallCache(cfg, logger))
@@ -1214,9 +1211,6 @@ def scan(x):
             sys.exit(0)
         logger.notice(_("starting downloads", uri=uri))
 
-        # initialize Docker Swarm
-        runtime.task.SwarmContainer.global_init(cfg, logger)
-
         # cheesy trick: provide the list of URIs as File inputs to a dummy workflow, causing the
         # runtime to download & cache them
         localizer_wdl = """

WDL/runtime/config.py

@@ -302,6 +302,13 @@ def _parse_list(v: str) -> List[Any]:
     ],
     "task": [],
     "workflow": [],
+    "container_backend": [
+        importlib_metadata.EntryPoint(
+            group="miniwdl.plugin.container_backend",
+            name="docker_swarm",
+            value="WDL.runtime.task_container:SwarmContainer",
+        )
+    ],
 }
 
 

WDL/runtime/config_templates/default.cfg

@@ -22,6 +22,8 @@
 # 0 = default to host `nproc`.
 # -@
 call_concurrency = 0
+# container backend (pluggable)
+container_backend = docker_swarm
 
 
 [docker_swarm]