From cddf139bbca5d8f8c8fb941b1b7a3e09f8ffa8f8 Mon Sep 17 00:00:00 2001
From: Steve Pulec <spulec@gmail.com>
Date: Tue, 3 Nov 2015 09:37:02 -0500
Subject: [PATCH] Add ability to create EBS volumes from snapshots. Closes
 #447.

---
 moto/ec2/models.py                         | 11 ++++++++---
 moto/ec2/responses/elastic_block_store.py  | 19 ++++++++++++++-----
 tests/test_ec2/test_elastic_block_store.py | 17 +++++++++++++++++
 3 files changed, 39 insertions(+), 8 deletions(-)

diff --git a/moto/ec2/models.py b/moto/ec2/models.py
index 0a2c3ffb7..446561d33 100644
--- a/moto/ec2/models.py
+++ b/moto/ec2/models.py
@@ -1388,12 +1388,13 @@ class VolumeAttachment(object):
 
 
 class Volume(TaggedEC2Resource):
-    def __init__(self, ec2_backend, volume_id, size, zone):
+    def __init__(self, ec2_backend, volume_id, size, zone, snapshot_id=None):
         self.id = volume_id
         self.size = size
         self.zone = zone
         self.create_time = utc_date_and_time()
         self.attachment = None
+        self.snapshot_id = snapshot_id
         self.ec2_backend = ec2_backend
 
     @classmethod
@@ -1436,10 +1437,14 @@ class EBSBackend(object):
         self.snapshots = {}
         super(EBSBackend, self).__init__()
 
-    def create_volume(self, size, zone_name):
+    def create_volume(self, size, zone_name, snapshot_id=None):
         volume_id = random_volume_id()
         zone = self.get_zone_by_name(zone_name)
-        volume = Volume(self, volume_id, size, zone)
+        if snapshot_id:
+            snapshot = self.get_snapshot(snapshot_id)
+            if size is None:
+                size = snapshot.volume.size
+        volume = Volume(self, volume_id, size, zone, snapshot_id)
         self.volumes[volume_id] = volume
         return volume
 
diff --git a/moto/ec2/responses/elastic_block_store.py b/moto/ec2/responses/elastic_block_store.py
index 876766b2f..5adb4c7d0 100644
--- a/moto/ec2/responses/elastic_block_store.py
+++ b/moto/ec2/responses/elastic_block_store.py
@@ -25,9 +25,10 @@ class ElasticBlockStore(BaseResponse):
         return template.render(snapshot=snapshot)
 
     def create_volume(self):
-        size = self.querystring.get('Size')[0]
-        zone = self.querystring.get('AvailabilityZone')[0]
-        volume = self.ec2_backend.create_volume(size, zone)
+        size = self._get_param('Size')
+        zone = self._get_param('AvailabilityZone')
+        snapshot_id = self._get_param('SnapshotId')
+        volume = self.ec2_backend.create_volume(size, zone, snapshot_id)
         template = self.response_template(CREATE_VOLUME_RESPONSE)
         return template.render(volume=volume)
 
@@ -110,7 +111,11 @@ CREATE_VOLUME_RESPONSE = """<CreateVolumeResponse xmlns="http://ec2.amazonaws.co
   <requestId>59dbff89-35bd-4eac-99ed-be587EXAMPLE</requestId>
   <volumeId>{{ volume.id }}</volumeId>
   <size>{{ volume.size }}</size>
-  <snapshotId/>
+  {% if volume.snapshot_id %}
+    <snapshotId>{{ volume.snapshot_id }}</snapshotId>
+  {% else %}
+    <snapshotId/>
+  {% endif %}
   <availabilityZone>{{ volume.zone.name }}</availabilityZone>
   <status>creating</status>
   <createTime>{{ volume.create_time}}</createTime>
@@ -124,7 +129,11 @@ DESCRIBE_VOLUMES_RESPONSE = """<DescribeVolumesResponse xmlns="http://ec2.amazon
           <item>
              <volumeId>{{ volume.id }}</volumeId>
              <size>{{ volume.size }}</size>
-             <snapshotId/>
+             {% if volume.snapshot_id %}
+               <snapshotId>{{ volume.snapshot_id }}</snapshotId>
+             {% else %}
+               <snapshotId/>
+             {% endif %}
              <availabilityZone>{{ volume.zone.name }}</availabilityZone>
              <status>{{ volume.status }}</status>
              <createTime>{{ volume.create_time}}</createTime>
diff --git a/tests/test_ec2/test_elastic_block_store.py b/tests/test_ec2/test_elastic_block_store.py
index b2308fe04..06b55841e 100644
--- a/tests/test_ec2/test_elastic_block_store.py
+++ b/tests/test_ec2/test_elastic_block_store.py
@@ -33,6 +33,7 @@ def test_create_and_delete_volume():
     cm.exception.status.should.equal(400)
     cm.exception.request_id.should_not.be.none
 
+
 @mock_ec2
 def test_filter_volume_by_id():
     conn = boto.connect_ec2('the_key', 'the_secret')
@@ -116,6 +117,7 @@ def test_create_snapshot():
     cm.exception.status.should.equal(400)
     cm.exception.request_id.should_not.be.none
 
+
 @mock_ec2
 def test_filter_snapshot_by_id():
     conn = boto.connect_ec2('the_key', 'the_secret')
@@ -136,6 +138,7 @@ def test_filter_snapshot_by_id():
         s.volume_id.should.be.within([volume2.id, volume3.id])
         s.region.name.should.equal(conn.region.name)
 
+
 @mock_ec2
 def test_snapshot_attribute():
     conn = boto.connect_ec2('the_key', 'the_secret')
@@ -217,6 +220,20 @@ def test_snapshot_attribute():
                                                     user_ids=['user']).should.throw(NotImplementedError)
 
 
+@mock_ec2
+def test_create_volume_from_snapshot():
+    conn = boto.connect_ec2('the_key', 'the_secret')
+    volume = conn.create_volume(80, "us-east-1a")
+
+    snapshot = volume.create_snapshot('a test snapshot')
+    snapshot.update()
+    snapshot.status.should.equal('completed')
+
+    new_volume = snapshot.create_volume('us-east-1a')
+    new_volume.size.should.equal(80)
+    new_volume.snapshot_id.should.equal(snapshot.id)
+
+
 @mock_ec2
 def test_modify_attribute_blockDeviceMapping():
     """