Clients: Return information on download exception rucio#5250

The different download functions in the `DownloadClient` return lists containing
the files and the states of the corresponding downloads. These states also
include failed states.

If an unknown exception is thrown in the `_download_item` method, the
corresponding file, which should be downloaded, is not present in the output
list. This leads to two problems; both can be solved by adding the file with the
download status `FAILED` to the output list:

- The number of files in the input queue and output queue is different, which
  throws an error. This is easily resolved by setting the file download status
  to `FAILED`. An error is later thrown.

- The client does not print the summary in case there is no items in the output
  queue. By adding the file to the output queue this problem is resolved.

lib/rucio/client/downloadclient.py

@@ -424,6 +424,8 @@ def _download_worker(self, input_queue, output_queue, trace_custom_fields, trace
             except Exception as error:
                 logger(logging.ERROR, '%sFailed to download item' % log_prefix)
                 logger(logging.DEBUG, error)
+                item["clientState"] = "FAILED"
+                output_queue.put(item)
 
     @staticmethod
     def _compute_actual_transfer_timeout(item):

lib/rucio/tests/test_clients.py

@@ -16,6 +16,7 @@
 from __future__ import print_function
 
 import unittest
+from unittest.mock import patch
 from datetime import datetime, timedelta
 
 try:
@@ -33,9 +34,13 @@
 
 from rucio.client.baseclient import BaseClient
 from rucio.client.client import Client
+from rucio.client.downloadclient import DownloadClient
 from rucio.common.config import config_get, config_get_bool
 from rucio.common.exception import CannotAuthenticate, ClientProtocolNotSupported, RucioException
-from rucio.common.utils import get_tmp_dir
+from rucio.common.types import InternalAccount, InternalScope
+from rucio.common.utils import get_tmp_dir, generate_uuid as uuid
+from rucio.core.rse import get_rse_id
+from rucio.core.replica import add_replica
 from rucio.tests.common import get_long_vo
 
 
@@ -195,3 +200,26 @@ def test_ping(self):
         client = Client(account='root', ca_cert=self.cacert, auth_type='userpass', creds=creds, **self.vo)
 
         print(client.ping())
+
+
+class TestDownloadClient(unittest.TestCase):
+    def setUp(self):
+        if config_get_bool('common', 'multi_vo', raise_exception=False, default=False):
+            self.vo = {'vo': get_long_vo()}
+        else:
+            self.vo = {}
+
+    def test_download_exception_return_information(self):
+        scope = InternalScope('mock', **self.vo)
+        root = InternalAccount('root', **self.vo)
+        client = Client(account='root', ca_cert={}, auth_type='userpass', creds={}, **self.vo)
+        download_client = DownloadClient(client=client)
+
+        _file = 'file_%s' % uuid()
+        add_replica(rse_id=get_rse_id(rse="MOCK", **self.vo), scope=scope, name=_file, bytes_=1, account=root)
+
+        with patch('rucio.client.downloadclient.DownloadClient._download_item', side_effect=Exception()):
+            res = download_client.download_dids([{"did": "mock:" + _file}], deactivate_file_download_exceptions=True)
+
+        assert len(res) == 1
+        assert res[0]["clientState"] == "FAILED"