Added cloud storage utility to toolkit

Author: leela

requirements.txt

@@ -3,3 +3,4 @@ psycopg2-binary
 pandas
 pyYAML
 click
+boto3

setup.py

@@ -19,7 +19,7 @@ def get_version():
 
 __version__ = get_version()
 
-install_requires = ['web.py', 'psycopg2-binary', 'pandas', 'pyYAML', 'click']
+install_requires = ['web.py', 'psycopg2-binary', 'pandas', 'pyYAML', 'click', 'boto3']
 extras_require = {
     'all': ['requests']
 }

toolkit/__init__.py

@@ -7,3 +7,4 @@
 from .dateutil import relative_date, truncate_date # noqa
 from .signals import Signal # noqa
 from .fileformat import FileFormat # noqa
+from .storage import StoragePath # noqa

toolkit/storage.py

@@ -0,0 +1,118 @@
+"""Storage utility to work with S3, GCS and minio.
+
+HOW TO USE:
+* Make sure that credentials are configured the way boto3 expects
+* You need to do extra setup to use this module with GCS
+    - Generate GCS HMAC credentials and set them as aws crentials.
+    - Please make sure that endpoint url is set to 'https://storage.googleapis.com'
+"""
+import boto3
+import botocore
+
+s3 = boto3.resource("s3")
+
+class StoragePath:
+    """The StoragePath class provides a pathlib.Path like interface for
+    storage.
+    USAGE:
+        root = StoragePath(bucket_name, "alpha")
+        path = root.join("datasets", "customer-master", "template.csv")
+        text = path.read_text()
+
+    TODO: Add delete and list directoy methods.
+    """
+    def __init__(self, bucket: str, path: str):
+        self.bucket = bucket
+        self.path = path
+
+    @property
+    def _object(self):
+        return s3.Object(bucket_name=self.bucket, key=self.path)
+
+    def exists(self):
+        """Tells the storage path exists or not.
+
+        Checks if the path exists or not by getting objects metadata.
+        """
+        obj = self._object
+        try:
+            obj.metadata
+            return True
+        except botocore.exceptions.ClientError as e:
+            if e.response['Error']['Code'] == "404":
+                return False
+            raise
+
+    def delete(self):
+        """Deletes the storage path file.
+        """
+        obj = self._object
+        obj.delete()
+
+    def download(self, local_path):
+        """Download the contents of storage file to the local_path file.
+        """
+        obj = self._object
+        obj.download_file(local_path)
+
+    def upload(self, local_path):
+        """Uploads the file from local_path to storage path.
+        """
+        obj = self._object
+        obj.upload_file(local_path)
+
+    def read_text(self):
+        """Read the contents of a path
+        """
+        obj = self._object
+        return obj.get()['Body'].read()
+
+    def _get_presigned_url(self, client_method, expires=600, content_type=None):
+        """Returns a presigned URL for upload or download.
+        The client_method should be one of get_object or put_object.
+        """
+        params = {
+            'Bucket': self.bucket,
+            'Key': self.path,
+        }
+        if content_type:
+            params['ContentType'] = content_type
+
+        return s3.meta.client.generate_presigned_url(client_method,
+            Params=params,
+            ExpiresIn=expires
+        )
+
+    def get_presigned_url_for_download(self, expires=3600):
+        """Returns a presigned URL for upload.
+
+        The default expiry is one hour (3600 seconds).
+        """
+        return self._get_presigned_url(client_method='get_object', expires=expires)
+
+    def get_presigned_url_for_upload(self, expires=600, content_type="text/csv"):
+        """Returns a presigned URL for upload.
+
+        The default expiry is 10 minutes (600 seconds).
+        """
+        return self._get_presigned_url(client_method='put_object', expires=expires, content_type=content_type)
+
+    def read_dataframe(self):
+        """TODO: Support csv and parq.
+        """
+        pass
+
+    def copy_to(self, dest_path):
+        """Copy the file to destination path within the bucket.
+        """
+        pass
+
+    def join(self, *parts):
+        """Combine the storage path with one or more parts and returns a new path.
+        """
+        path = "/".join([self.path] + list(parts))
+        return StoragePath(self.bucket, path)
+
+    def __repr__(self):
+        return f'<StoragePath {self.path}>'
+