Add DynamoDB backend

fastapi_cache/backends/dynamodb.py

@@ -0,0 +1,88 @@
+import datetime
+
+from typing import Tuple
+from aiobotocore.session import get_session
+
+from fastapi_cache.backends import Backend
+
+
+class DynamoBackend(Backend):
+    """
+    Amazon DynamoDB backend provider
+
+    This backend requires an existing table within your AWS environment to be passed during
+    backend init. If ttl is going to be used, this needs to be manually enabled on the table
+    using the `ttl` key. Dynamo will take care of deleting outdated objects, but this is not
+    instant so don't be alarmed when they linger around for a bit.
+
+    As with all AWS clients, credentials will be taken from the environment. Check the AWS SDK
+    for more information.
+    """
+
+    def __init__(self, table_name, region=None):
+        self.session = get_session()
+        self.client = None # Needs async init
+        self.table_name = table_name
+        self.region = region
+
+    async def init(self):
+        self.client = await self.session.create_client('dynamodb', region_name=self.region).__aenter__()
+
+    async def close(self):
+        self.client = await self.client.__aexit__(None, None, None)
+
+    async def get_with_ttl(self, key: str) -> Tuple[int, str]:
+        response = await self.client.get_item(
+            TableName=self.table_name,
+            Key={
+                "key": {
+                    "S": key
+                }
+            }
+        )
+
+        if "Item" in response:
+            value = response["Item"].get("value", {}).get("S")
+            ttl = response["Item"].get("ttl", {}).get("N")
+
+            if not ttl:
+                return -1, value
+
+            # It's only eventually consistent so we need to check ourselves
+            expire = int(ttl) - int(datetime.datetime.now().timestamp())
+            if expire > 0:
+                return expire, value
+
+        return 0, None
+
+    async def get(self, key) -> str:
+        response = await self.client.get_item(
+            TableName=self.table_name,
+            Key={
+                "key": {
+                    "S": key
+                }
+            }
+        )
+        if "Item" in response:
+            return response["Item"].get("value", {}).get("S")
+
+    async def set(self, key: str, value: str, expire: int = None):
+        ttl = { "ttl": { "N": str(int((datetime.datetime.now() + datetime.timedelta(seconds=expire)).timestamp())) } } if expire else {}
+
+        response = await self.client.put_item(
+            TableName=self.table_name,
+            Item={**{
+                "key": {
+                    "S": key
+                },
+                "value": {
+                    "S": value
+                },
+            }, **ttl
+            }
+        )
+
+    async def clear(self, namespace: str = None, key: str = None) -> int:
+        raise NotImplementedError
+