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90 lines
3.3 KiB
Python
90 lines
3.3 KiB
Python
# Copyright 2023 Declan Teevan
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import pickle
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import logging
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from typing import Type, List
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import redis.asyncio as redis
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from comment_service.models.service import CommentRepository, Comment, CommentCreate, CommentUpdate
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class ServiceRedisRepository(CommentRepository):
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"""The Redis repository is responsible for caching
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requests to help reduce the amount of database calls,
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allowing for faster data access.
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If the Redis repository does not have the data cached,
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or does not cache data for that request, then the call is
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passed downstream to the database repository.
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Attributes:
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_conn (redis.asyncio.redis.Redis): The Redis connection.
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_repo (CommentRepository): The next downstream repository (the DB repo).
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"""
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def __init__(self, redis_conn: redis.Redis, downstream_repo: Type[CommentRepository]) -> None:
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self._conn = redis_conn
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self._repo = downstream_repo
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async def _purge_cached_comments(self, post_id: str) -> None:
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try:
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self._conn.delete(post_id)
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except Exception:
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pass
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async def get_comment(self, comment_id: int) -> Comment:
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return await self._repo.get_comment(comment_id)
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async def get_post_comments(self, post_id: str) -> List[Comment]:
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post_id = post_id.lower()
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failure = False
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try:
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# check for a cached version of the post comments
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response = await self._conn.get(post_id)
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if response is not None:
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comments = pickle.loads(response)
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assert type(comments) == list
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return comments
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except Exception as e:
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failure = True
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logging.error("Redis Repo: error whilst getting post comments", e)
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pass
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comments = await self._repo.get_post_comments(post_id)
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if failure is False:
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# cache the retrieved comments
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try:
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await self._conn.set(post_id, pickle.dumps(comments), ex=120) # TTL: 2 minutes
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except Exception:
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logging.error("Redis Repo: error whilst caching post comments", e)
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pass
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return comments
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async def create_comment(self, data: CommentCreate) -> Comment:
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comment = await self._repo.create_comment(data)
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await self._purge_cached_comments(comment.post_id)
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return comment
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async def update_comment(self, comment_id: int, data: CommentUpdate) -> Comment:
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comment = await self._repo.update_comment(comment_id, data)
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await self._purge_cached_comments(comment.post_id)
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return comment
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async def delete_comment(self, comment_id: int) -> None:
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# todo: purge cache of comments on post (instead of waiting for TTL expiry)
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await self._repo.delete_comment(comment_id) |