Replace django-background-tasks with huey (#657)

* Replace django-background-tasks with huey

* Add command for migrating tasks

* Add custom admin view

* fix dockerfile

* fix tests

* fix tests in CI

* fix task tests

* implement retries

* improve config

* workaround to avoid running singlefile tasks in parallel

* properly kill single-file sub-processes

* use period task for HTML snapshots

* clear task lock when starting task consumer

* remove obsolete cleanup task command

siteroot/settings/base.py

@@ -42,7 +42,7 @@ INSTALLED_APPS = [
     "widget_tweaks",
     "rest_framework",
     "rest_framework.authtoken",
-    "background_task",
+    "huey.contrib.djhuey",
     "mozilla_django_oidc",
 ]
 
@@ -173,13 +173,27 @@ LD_DISABLE_BACKGROUND_TASKS = os.getenv("LD_DISABLE_BACKGROUND_TASKS", False) in
     "1",
 )
 
-# django-background-tasks
-MAX_ATTEMPTS = 5
-# How many tasks will run in parallel
-# We want to keep this low to prevent SQLite lock errors and in general not to consume too much resources on smaller
-# specced systems like Raspberries. Should be OK as tasks are not time critical.
-BACKGROUND_TASK_RUN_ASYNC = True
-BACKGROUND_TASK_ASYNC_THREADS = 2
+# Huey task queue
+HUEY = {
+    "huey_class": "huey.SqliteHuey",
+    "filename": os.path.join(BASE_DIR, "data", "tasks.sqlite3"),
+    "immediate": False,
+    "results": False,
+    "store_none": False,
+    "utc": True,
+    "consumer": {
+        "workers": 2,
+        "worker_type": "thread",
+        "initial_delay": 5,
+        "backoff": 1.15,
+        "max_delay": 10,
+        "scheduler_interval": 10,
+        "periodic": True,
+        "check_worker_health": True,
+        "health_check_interval": 10,
+    },
+}
+
 
 # Enable OICD support if configured
 LD_ENABLE_OIDC = os.getenv("LD_ENABLE_OIDC", False) in (True, "True", "1")