Add implementation of S3Cache

setup.py

@@ -42,6 +42,7 @@ def get_git_sha():
     zip_safe=False,
     scripts=['superset/bin/superset'],
     install_requires=[
+        'boto3==1.4.4',
         'celery==3.1.23',
         'cryptography==1.5.3',
         'flask-appbuilder==1.8.1',

superset/assets/version_info.json

@@ -1 +1 @@
-{"GIT_SHA": "2d08e240285288b71df98747ddd4b6cca3220c5a", "version": "0.15.2"}
+{"GIT_SHA": "1e94498d9d548cbea6466a45dafa3b919c65bd1f", "version": "0.15.4"}

superset/results_backends.py

@@ -7,28 +7,123 @@
 from __future__ import print_function
 from __future__ import unicode_literals
 
+import cPickle
+import logging
+import StringIO
+
+import boto3
 from werkzeug.contrib.cache import BaseCache
 
+from superset import app
+
+config = app.config
+
 
 class S3Cache(BaseCache):
 
-    """S3 cache"""
+    """S3 cache implementation.
+
+    Adapted from examples in
+    https://github.com/pallets/werkzeug/blob/master/werkzeug/contrib/cache.py.
+
+    Timeout parameters are ignored as S3 doesn't support key-level expiration.
+    To expire keys, set up an expiration policy as described in
+    https://aws.amazon.com/blogs/aws/amazon-s3-object-expiration/.
+    """
 
     def __init__(self, default_timeout=300):
         self.default_timeout = default_timeout
 
+        self.s3_client = boto3.client('s3')
+
+        self.bucket = config.get('S3_CACHE_BUCKET')
+        self.key_prefix = config.get('S3_CACHE_KEY_PREFIX')
+
     def get(self, key):
-        return None
+        """Look up key in the cache and return the value for it.
+
+        :param key: the key to be looked up.
+        :returns: The value if it exists and is readable, else ``None``.
+        """
+        if not self._key_exists(key):
+            return None
+        else:
+            value_file = StringIO.StringIO()
+
+            try:
+                self.s3_client.download_fileobj(
+                    self.bucket,
+                    self._full_s3_key(key),
+                    value_file
+                )
+            except Exception as e:
+                logging.warn('Exception while trying to get %s: %s', key, e)
+                return None
+            else:
+                value_file.seek(0)
+                return cPickle.load(value_file)
 
     def delete(self, key):
-        return True
+        """Delete `key` from the cache.
+
+        :param key: the key to delete.
+        :returns: Whether the key existed and has been deleted.
+        :rtype: boolean
+        """
+        if not self._key_exists(key):
+            return False
+        else:
+            try:
+                self.s3_client.delete_objects(
+                    Bucket=self.bucket,
+                    Delete={
+                        'Objects': [
+                            {
+                                'Key': self._full_s3_key(key)
+                            }
+                        ]
+                    }
+                )
+            except Exception as e:
+                logging.warn('Exception while trying to delete %s: %s', key, e)
+                return False
+            else:
+                return True
 
     def set(self, key, value, timeout=None):
-        return True
+        """Add a new key/value to the cache.
+
+        If the key already exists, the existing value is overwritten.
+
+        :param key: the key to set
+        :param value: the value for the key
+        :param timeout: the cache timeout for the key in seconds (if not
+                        specified, it uses the default timeout). A timeout of
+                        0 idicates that the cache never expires.
+        :returns: ``True`` if key has been updated, ``False`` for backend
+                  errors. Pickling errors, however, will raise a subclass of
+                  ``pickle.PickleError``.
+        :rtype: boolean
+        """
+        value_file = StringIO.StringIO()
+        cPickle.dump(value, value_file)
+
+        try:
+            value_file.seek(0)
+            self.s3_client.upload_fileobj(
+                value_file,
+                self.bucket,
+                self._full_s3_key(key)
+            )
+        except Exception as e:
+            logging.warn('Exception while trying to set %s: %s', key, e)
+            return False
+        else:
+            return True
 
     def add(self, key, value, timeout=None):
-        """Works like :meth:`set` but does not overwrite the values of already
-        existing keys.
+        """Works like :meth:`set` but does not overwrite existing values.
+
         :param key: the key to set
         :param value: the value for the key
         :param timeout: the cache timeout for the key in seconds (if not
@@ -38,12 +133,33 @@ def add(self, key, value, timeout=None):
                   existing keys.
         :rtype: boolean
         """
-        return True
+        if self._key_exists(key):
+            return False
+        else:
+            return self.set(key, value, timeout=timeout)
 
     def clear(self):
-        """Clears the cache.  Keep in mind that not all caches support
-        completely clearing the cache.
+        """Clears the cache.
+
+        Keep in mind that not all caches support completely clearing the cache.
         :returns: Whether the cache has been cleared.
         :rtype: boolean
         """
-        return True
+        return False
+
+    def _full_s3_key(self, key):
+        """Convert a cache key to a full S3 key, including the key prefix."""
+        return '%s%s' % (self.key_prefix, key)
+
+    def _key_exists(self, key):
+        """Determine whether the given key exists in the bucket."""
+        try:
+            self.s3_client.head_object(
+                Bucket=self.bucket,
+                Key=self._full_s3_key(key)
+            )
+        except Exception:
+            # head_object throws an exception when object doesn't exist
+            return False
+        else:
+            return True

tests/results_backends_tests.py

@@ -0,0 +1,121 @@
+import cPickle
+
+import mock
+
+from superset import app, results_backends
+from .base_tests import SupersetTestCase
+
+app.config['S3_CACHE_BUCKET'] = 'test-bucket'
+app.config['S3_CACHE_KEY_PREFIX'] = 'test-prefix/'
+
+
+class ResultsBackendsTests(SupersetTestCase):
+    requires_examples = False
+
+    @mock.patch('boto3.client')
+    def setUp(self, mock_boto3_client):
+        self.mock_boto3_client = mock_boto3_client
+        self.mock_s3_client = mock.MagicMock()
+
+        self.mock_boto3_client.return_value = self.mock_s3_client
+
+        self.s3_cache = results_backends.S3Cache()
+        self.s3_cache._key_exists = ResultsBackendsTests._mock_key_exists
+
+    @staticmethod
+    def _mock_download_fileobj(bucket, key, value_file):
+        value_file.write(cPickle.dumps('%s:%s' % (bucket, key)))
+
+    @staticmethod
+    def _mock_key_exists(key):
+        return key == 'test-key'
+
+    def test_s3_cache_initilization(self):
+        self.mock_boto3_client.assert_called_with('s3')
+
+    def test_s3_cache_set(self):
+        result = self.s3_cache.set('test-key', 'test-value')
+
+        self.assertTrue(result)
+        self.mock_s3_client.upload_fileobj.assert_called_once()
+
+        call_args = self.mock_s3_client.upload_fileobj.call_args_list[0][0]
+
+        self.assertEquals(cPickle.loads(call_args[0].getvalue()), 'test-value')
+        self.assertEquals(call_args[1], 'test-bucket')
+        self.assertEquals(call_args[2], 'test-prefix/test-key')
+
+    def test_s3_cache_set_exception(self):
+        self.mock_s3_client.upload_fileobj.side_effect = Exception('Something bad happened!')
+        result = self.s3_cache.set('test-key', 'test-value')
+
+        self.assertFalse(result)
+        self.mock_s3_client.upload_fileobj.assert_called_once()
+
+    def test_s3_cache_get_exists(self):
+        self.mock_s3_client.download_fileobj.side_effect = (
+            ResultsBackendsTests._mock_download_fileobj)
+        result = self.s3_cache.get('test-key')
+
+        self.assertEquals(result, 'test-bucket:test-prefix/test-key')
+        self.mock_s3_client.download_fileobj.assert_called_once()
+
+    def test_s3_cache_get_does_not_exist(self):
+        result = self.s3_cache.get('test-key2')
+
+        self.assertEquals(result, None)
+        self.assertFalse(self.mock_s3_client.download_fileobj.called)
+
+    def test_s3_cache_get_s3_exception(self):
+        self.mock_s3_client.download_fileobj.side_effect = Exception('Something bad happened')
+        result = self.s3_cache.get('test-key')
+
+        self.assertEquals(result, None)
+        self.mock_s3_client.download_fileobj.assert_called_once()
+
+    def test_s3_cache_delete_exists(self):
+        result = self.s3_cache.delete('test-key')
+
+        self.assertTrue(result)
+        self.mock_s3_client.delete_objects.assert_called_once_with(
+            Bucket='test-bucket',
+            Delete={'Objects': [{'Key': 'test-prefix/test-key'}]}
+        )
+
+    def test_s3_cache_delete_does_not_exist(self):
+        result = self.s3_cache.delete('test-key2')
+
+        self.assertFalse(result)
+        self.assertFalse(self.mock_s3_client.delete_objects.called)
+
+    def test_s3_cache_delete_exception(self):
+        self.mock_s3_client.delete_objects.side_effect = Exception('Something bad happened')
+        result = self.s3_cache.delete('test-key')
+
+        self.assertFalse(result)
+        self.mock_s3_client.delete_objects.assert_called_once()
+
+    def test_s3_cache_add_exists(self):
+        result = self.s3_cache.add('test-key', 'test-value')
+
+        self.assertFalse(result)
+        self.assertFalse(self.mock_s3_client.upload_fileobj.called)
+
+    def test_s3_cache_add_does_not_exist(self):
+        result = self.s3_cache.add('test-key2', 'test-value')
+
+        self.assertTrue(result)
+        self.mock_s3_client.upload_fileobj.assert_called_once()
+
+        call_args = self.mock_s3_client.upload_fileobj.call_args_list[0][0]
+
+        self.assertEquals(cPickle.loads(call_args[0].getvalue()), 'test-value')
+        self.assertEquals(call_args[1], 'test-bucket')
+        self.assertEquals(call_args[2], 'test-prefix/test-key2')
+
+    def test_s3_cache_add_exception(self):
+        self.mock_s3_client.upload_fileobj.side_effect = Exception('Something bad happened')
+        result = self.s3_cache.add('test-key2', 'test-value')
+
+        self.assertFalse(result)
+        self.mock_s3_client.upload_fileobj.assert_called_once()