Repository: pulp/pulpcore

Issue:
PulpImport can overload the task-queue
**Version**
main

**Describe the bug**
PulpImport dispatches a task-per-repository. For large imports, with large repositories, this means that Pulp can't do anything else until the import is finished or nearly so, as all workers are busy importing repositories.

It would be good to teach the import-process to arrange to not use up more than, say, 25% of the available workers.



Discussion:
Also we could introduce a setting for the import task that would make the % value configurable.

I am adding a prio-list to this issue since this problem impairs some of our customer's environment.

Resolving patch:
diff --git a/pulpcore/app/settings.py b/pulpcore/app/settings.py
--- a/pulpcore/app/settings.py
+++ b/pulpcore/app/settings.py
@@ -296,6 +296,10 @@
 
 DEFAULT_AUTO_FIELD = "django.db.models.AutoField"
 
+# What percentage of available-workers will pulpimport use at a time, max
+# By default, use all available workers.
+IMPORT_WORKERS_PERCENT = 100
+
 # HERE STARTS DYNACONF EXTENSION LOAD (Keep at the very bottom of settings.py)
 # Read more at https://dynaconf.readthedocs.io/en/latest/guides/django.html
 import dynaconf  # noqa
diff --git a/pulpcore/app/tasks/importer.py b/pulpcore/app/tasks/importer.py
--- a/pulpcore/app/tasks/importer.py
+++ b/pulpcore/app/tasks/importer.py
@@ -8,6 +8,7 @@
 from gettext import gettext as _
 from logging import getLogger
 
+from django.conf import settings
 from django.core.files.storage import default_storage
 from django.db.models import F
 from naya.json import stream_array, tokenize
@@ -28,6 +29,7 @@
     Repository,
     Task,
     TaskGroup,
+    Worker,
 )
 from pulpcore.app.modelresource import (
     ArtifactResource,
@@ -482,6 +484,18 @@ def validate_and_assemble(toc_filename):
                             default_storage.save(base_path, f)
 
         # Now import repositories, in parallel.
+
+        # We want to be able to limit the number of available-workers that import will consume,
+        # so that pulp can continue to work while doing an import. We accomplish this by creating
+        # a reserved-resource string for each repo-import-task based on that repo's index in
+        # the dispatch loop, mod number-of-workers-to-consume.
+        #
+        # By default (setting is not-set), import will continue to use 100% of the available
+        # workers.
+        import_workers_percent = int(settings.get("IMPORT_WORKERS_PERCENT", 100))
+        total_workers = Worker.objects.online_workers().count()
+        import_workers = max(1, int(total_workers * (import_workers_percent / 100.0)))
+
         with open(os.path.join(temp_dir, REPO_FILE), "r") as repo_data_file:
             data = json.load(repo_data_file)
             gpr = GroupProgressReport(
@@ -493,7 +507,10 @@ def validate_and_assemble(toc_filename):
             )
             gpr.save()
 
-            for src_repo in data:
+            for index, src_repo in enumerate(data):
+                # pulpcore-worker limiter
+                worker_rsrc = f"import-worker-{index % import_workers}"
+                exclusive_resources = [worker_rsrc]
                 try:
                     dest_repo = _destination_repo(importer, src_repo["name"])
                 except Repository.DoesNotExist:
@@ -503,6 +520,8 @@ def validate_and_assemble(toc_filename):
                         )
                     )
                     continue
+                else:
+                    exclusive_resources.append(dest_repo)
 
                 dispatch(
                     import_repository_version,


Test patch: