workflows: retry arxiv pdf download

* Retries the download of a PDF from arXiv if what we get is
  not a PDF. In fact, in that case it's probably the splash
  page that is being served while the PDF is being generated.

Signed-off-by: Samuele Kaplun <[email protected]>

inspirehep/modules/workflows/errors.py

@@ -0,0 +1,30 @@
+# -*- coding: utf-8 -*-
+#
+# This file is part of INSPIRE.
+# Copyright (C) 2014-2017 CERN.
+#
+# INSPIRE is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# INSPIRE is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with INSPIRE. If not, see <http://www.gnu.org/licenses/>.
+#
+# In applying this license, CERN does not waive the privileges and immunities
+# granted to it by virtue of its status as an Intergovernmental Organization
+# or submit itself to any jurisdiction.
+
+from __future__ import absolute_import, division, print_function
+
+from invenio_workflows.errors import WorkflowsError
+
+
+class DownloadError(WorkflowsError):
+
+    """Error representing a failed download in a workflow."""

inspirehep/modules/workflows/tasks/arxiv.py

@@ -28,6 +28,7 @@
 import re
 from functools import wraps
 
+import backoff
 from flask import current_app
 from lxml.etree import XMLSyntaxError
 from six import BytesIO
@@ -45,6 +46,7 @@
 from plotextractor.converter import untar
 from plotextractor.errors import InvalidTarball, NoTexFilesFound
 
+from ..errors import DownloadError
 from ..utils import download_file_to_workflow, with_debug_logging
 
 
@@ -56,6 +58,7 @@
 
 
 @with_debug_logging
+@backoff.on_exception(backoff.expo, DownloadError, base=4, max_tries=5)
 def arxiv_fulltext_download(obj, eng):
     """Perform the fulltext download step for arXiv records.
 
@@ -70,8 +73,14 @@ def arxiv_fulltext_download(obj, eng):
         url=current_app.config['ARXIV_PDF_URL'].format(arxiv_id=arxiv_id),
     )
 
-    if pdf:
+    if pdf and pdf.get_version().mimetype == 'application/pdf':
         obj.log.info('PDF retrieved from arXiv for %s', arxiv_id)
+    elif pdf:
+        # We need to delete the failed download as otherwise it would
+        # create a new version instead of replacing the previous one.
+        del obj.files[filename]
+        pdf.delete()
+        raise DownloadError()
     else:
         obj.log.error('Cannot retrieve PDF from arXiv for %s', arxiv_id)
 

tests/unit/helpers/mocks.py

@@ -67,13 +67,42 @@ def __contains__(self, item):
         return item in self.data
 
     def __setitem__(self, key, value):
-        self.data[key] = {'key': key}
+        self.data[key] = MockFileObject(key=key)
+
+    def __delitem__(self, key):
+        del self.data[key]
 
     @property
     def keys(self):
         return self.data.keys()
 
 
+class MockFileObject(object):
+    def __init__(self, key):
+        self.obj = {'key': key}
+
+    def __eq__(self, other):
+        return self.obj['key'] == other.obj['key']
+
+    def __getitem__(self, key):
+        return self.obj[key]
+
+    def __setitem__(self, key, value):
+        self.obj[key] = value
+
+    def delete(self):
+        pass
+
+    def get_version(self):
+        return MockObjectVersion()
+
+
+class MockObjectVersion(object):
+    @property
+    def mimetype(self):
+        return 'application/pdf'
+
+
 class MockLog(object):
     def __init__(self):
         self._debug = StringIO()

tests/unit/workflows/test_workflows_utils.py

@@ -30,7 +30,7 @@
 
 from inspirehep.modules.workflows.utils import download_file_to_workflow
 
-from mocks import MockFiles, MockObj
+from mocks import MockFiles, MockFileObject, MockObj
 
 
 def test_download_file_to_workflow_retries_on_protocol_error():
@@ -50,7 +50,7 @@ def test_download_file_to_workflow_retries_on_protocol_error():
 
         obj = MockObj(data, extra_data, files=files)
 
-        expected = {'key': '1605.03844.pdf'}
+        expected = MockFileObject(key='1605.03844.pdf')
         result = download_file_to_workflow(
             obj, '1605.03844.pdf', 'http://export.arxiv.org/pdf/1605.03844')