Loosened import version-restriction to x.y instead of x.y.z.

closes #2269

CHANGES/2269.bugfix

@@ -0,0 +1 @@
+Loosened the version-restrictions on PulpImport to only require X.Y matching.

docs/workflows/import-export.rst

@@ -37,22 +37,6 @@ In order to minimize space utilization, import/export operates on sets of
 :term:`Artifacts<Artifact>` only once per-export, rather than once for each
 :term:`Repository` being exported.
 
-.. note::
-
-    Export will not operate on :term:`RepositoryVersions<RepositoryVersion>` that have
-    been synchronized using ``policy=on_demand``. :term:`Artifacts<Artifact>` must actually
-    exist in order to be exported - this is, after all the only way for the Downstream Pulp
-    instance to gain access to them!
-
-.. note::
-
-    Import and Export strictly control which directories may be read from/written to via
-    the settings options ``ALLOWED_IMPORT_PATHS`` and ``ALLOWED_EXPORT_PATHS``.
-    These default to empty, if not explicitly set attempts to import or export will fail
-    with a validation error like
-
-        ``"Path '/tmp/exports/' is not an allowed export path"``
-
 Definitions
 ^^^^^^^^^^^
 Upstream
@@ -87,6 +71,55 @@ Import order
     ModelResources be imported in order. Plugins are responsible for specifying the
     import-order of the ModelResources they own
 
+Assumptions
+^^^^^^^^^^^
+
+The import/export workflow operates on a set of assumptions. Violating them will result
+in error-messages as described below.
+
+On-Demand content not supported
+-------------------------------
+
+Export will not operate on :term:`RepositoryVersions<RepositoryVersion>` that have
+been synchronized using ``policy=on_demand`` or ``policy=streamed``. :term:`Artifacts<Artifact>`
+must actually exist in order to be exported - this is, after
+all the only way for the Downstream Pulp instance to gain access to them!
+
+If a repository is specified for export that utilized on-demand/streamed syncing, the
+export will fail with a RuntimeError:
+
+    ``Remote artifacts cannot be exported.``
+
+Export/Import Directories must be explicitly allowed
+----------------------------------------------------
+
+Import and Export strictly control which directories may be read from/written to via
+the settings options ``ALLOWED_IMPORT_PATHS`` and ``ALLOWED_EXPORT_PATHS``.
+These default to empty - if they not explicitly set, attempts to import or export will fail
+with a validation error like
+
+    ``"Path '/tmp/exports/' is not an allowed export path"``
+
+Installed plugins must match
+----------------------------
+
+A Downstream must support the complete set of plugins present in a given export. If the
+export includes plugins that are not installed in the Downstream, an import attempt will
+fail with a validation error like
+
+    ``Export uses pulp_rpm which is not installed.``
+
+Version-compatibility required
+------------------------------
+
+The export-to-import workflow is built on the assumption that the Upstream and
+Downstream instances are running "compatible" versions of pulpcore and plugins. In this
+context, "compatible" is defined as **"share the same X.Y version"**.  If this is not the
+case, an import attempt will fail with a validation error like
+
+    ``Export version 3.14.15 of pulpcore incompatible with installed version 3.16.3.``
+
+
 Exporting
 ^^^^^^^^^
 

pulpcore/app/tasks/importer.py

@@ -91,7 +91,12 @@ def _import_file(fpath, resource_class, retry=False):
 
 
 def _check_versions(version_json):
-    """Compare the export version_json to the installed components."""
+    """
+    Compare the export version_json to the installed components.
+
+    An upstream whose db-metadata doesn't match the downstream won't import successfully; check
+    for compatibility and raise a ValidationError if incompatible versions are found.
+    """
     error_messages = []
     for component in version_json:
         try:
@@ -101,10 +106,13 @@ def _check_versions(version_json):
                 _("Export uses {} which is not installed.").format(component["component"])
             )
         else:
-            if version != component["version"]:
+            # Check that versions are compatible. Currently, "compatible" is defined as "same X.Y".
+            # Versions are strings that generally look like "X.Y.Z" or "X.Y.Z.dev"; we check that
+            # first two places are the same.
+            if version.split(".")[:2] != component["version"].split(".")[:2]:
                 error_messages.append(
                     _(
-                        "Export version {export_ver} of {component} does not match "
+                        "Export version {export_ver} of {component} incompatible with "
                         "installed version {ver}."
                     ).format(
                         export_ver=component["version"],
@@ -113,8 +121,8 @@ def _check_versions(version_json):
                     )
                 )
 
-        if error_messages:
-            raise ValidationError((" ".join(error_messages)))
+    if error_messages:
+        raise ValidationError((" ".join(error_messages)))
 
 
 def import_repository_version(importer_pk, destination_repo_pk, source_repo_name, tar_path):

pulpcore/tests/unit/test_import_checks.py

@@ -0,0 +1,28 @@
+from unittest.mock import patch
+
+from django.test import TestCase
+from rest_framework.serializers import ValidationError
+
+from pulpcore.app.tasks.importer import _check_versions
+
+
+class TestObject:
+    version = "1.2.3"  # Every component is vers 1.2.3
+
+
+class TestCheckVersions(TestCase):
+    @patch("pulpcore.app.tasks.importer.get_distribution", return_value=TestObject())
+    def test_vers_check(self, mock_get_distribution):
+        export_json = [{"component": "xyz", "version": "1.2.3"}]
+        _check_versions(export_json)
+
+        export_json = [{"component": "xy", "version": "1.2"}]
+        _check_versions(export_json)
+
+        export_json = [{"component": "x_noty_z", "version": "1.4.3"}]
+        with self.assertRaises(ValidationError):
+            _check_versions(export_json)
+
+        export_json = [{"component": "notx_y_z", "version": "2.2.3"}]
+        with self.assertRaises(ValidationError):
+            _check_versions(export_json)