Prevent deleted devices from being recreated

This addresses issue:

 #3

In that it prevents a device to ever get re-created, as this is not
allowed by OTA Connect. This seems like a bug in OTA Connect, but
was easiest to fix here. Additionally, we think this addresses
a bug we had in production:

 advancedtelematic/ota-device-registry#89

Signed-off-by: Andy Doan <andy@foundries.io>

docker_run.sh

@@ -3,6 +3,9 @@
 # if FLASK_DEBUG is defined, we'll run via flask with dynamic reloading of
 # code changes to disk. This is helpful for debugging something already in k8s
 
+echo "Adding deleted hack DB table"
+python3 -c "from ota_api.deleted_hack import migrate; migrate()"
+
 if [ -z "$FLASK_DEBUG" ] ; then
 	exec /usr/bin/gunicorn -n ota-api -w4 -b 0.0.0.0:8000 $FLASK_APP:app
 fi

ota_api/deleted_hack.py

@@ -0,0 +1,60 @@
+# Copyright (C) 2019 Foundries.io
+# Author: Andy Doan <andy@foundries.io>
+import contextlib
+import os
+
+from pymysql import Connect
+
+DB = os.environ.get('DEVICE_REGISTRY_DB', 'device_registry')
+DBHOST = os.environ.get('DEVICE_REGISTRY_DBHOST', 'mysql')
+DBUSER = os.environ.get('DEVICE_REGISTRY_DBUSER', 'device_registry')
+DBPASS = os.environ.get('DEVICE_REGISTRY_DBPASS', 'device_registry')
+
+
+@contextlib.contextmanager
+def db_cursor(commit=False):
+    con = None
+    try:
+        con = Connect(host=DBHOST, user=DBUSER, password=DBPASS, db=DB)
+        with con.cursor() as cur:
+            yield cur
+        if commit:
+            con.commit()
+    finally:
+        if con:
+            con.close()
+
+
+def migrate():
+    stmt = '''
+        CREATE TABLE IF NOT EXISTS OtaApiDeleted (
+            uuid CHAR(36) NOT NULL,
+            PRIMARY KEY (uuid)
+        );
+    '''
+    with db_cursor() as c:
+        c.execute(stmt)
+
+
+def device_mark_deleted(device_uuid):
+    '''Mark a device as deleted so that it won't ever be allowed to be added
+       again.'''
+    stmt = 'INSERT INTO OtaApiDeleted (uuid) VALUES (%s)'
+    with db_cursor(commit=True) as c:
+        c.execute(stmt, device_uuid)
+
+
+def device_is_deleted(device_uuid):
+    '''Check to see if this device was deleted. We can't allow it to be
+       re-added and OTA connect will. Letting a device through will cause
+       something like:
+         https://github.com/advancedtelematic/ota-device-registry/issues/89
+    '''
+    stmt = '''SELECT uuid
+              FROM OtaApiDeleted
+              WHERE uuid = %s
+           '''
+    with db_cursor() as c:
+        c.execute(stmt, device_uuid)
+        for r in c:
+            return True

ota_api/ota_user.py

@@ -4,6 +4,7 @@
 
 from flask import abort, jsonify, make_response, request
 
+from ota_api.deleted_hack import device_is_deleted, device_mark_deleted
 from ota_api.ota_ce import OTACommunityEditionAPI
 
 VALID_DEVICE_CHAR = set(string.ascii_letters + string.digits + '-' + '_' + '/')
@@ -99,8 +100,12 @@ def device_rename(self, name, new_name):
     def device_delete(self, name):
         api, d = self._get(name)
         api.device_delete(d)
+        device_mark_deleted(d['uuid'])
 
     def device_create(self, name, uuid, client_pem):
+        if device_is_deleted(uuid):
+            message = 'A device with this uuid has been deleted.'
+            abort(make_response(jsonify(message=message), 400))
         api = OTACommunityEditionAPI('default')
         api.device_create(name, uuid, client_pem)