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https://git.victorphan.net/basketballcantho/ten-project.git
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76 lines
2.2 KiB
Python
76 lines
2.2 KiB
Python
"""
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Redis helper — returns a connected client or None when Redis is unavailable.
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Key namespace design (prevents cross-file / cross-user data leakage):
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ann:{pdf_id}:{page_number}:{user_id}
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Every segment is mandatory, so:
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- User A opening file 1 never touches User A's data on file 2
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- User A opening file 1 never touches User B's data on file 1
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- Data for page 3 never affects page 7
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TTL: 24 h — temp entry expires automatically if the user never returns.
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On permanent save the entry is deleted immediately.
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"""
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import logging
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import os
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from typing import Optional
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import redis as redis_lib
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logger = logging.getLogger(__name__)
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_client: Optional[redis_lib.Redis] = None
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_warned = False # log the "unavailable" warning only once
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def get_redis() -> Optional[redis_lib.Redis]:
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"""Return a live Redis client, or None if Redis is unreachable."""
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global _client, _warned
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if _client is not None:
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try:
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_client.ping()
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return _client
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except Exception:
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_client = None # connection dropped — try to reconnect below
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url = os.getenv("REDIS_URL", "redis://localhost:6379/0")
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try:
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r: redis_lib.Redis = redis_lib.from_url(
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url,
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decode_responses=True,
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socket_connect_timeout=2,
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socket_timeout=2,
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)
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r.ping()
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_client = r
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_warned = False
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logger.info("Redis connected: %s", url)
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return _client
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except Exception as exc:
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if not _warned:
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logger.warning(
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"Redis unavailable (%s) — temp annotation cache disabled. "
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"Set REDIS_URL or start a local Redis instance to enable it.",
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exc,
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)
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_warned = True
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return None
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# Key helpers — centralised so there's one place to change the format.
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ANN_TTL = 86_400 # 24 hours
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def ann_temp_key(pdf_id: int, page_number: int, user_id: int) -> str:
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"""Fully-namespaced Redis key for one user's unsaved canvas on one PDF page."""
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return f"ann:{pdf_id}:{page_number}:{user_id}"
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def ann_temp_page_pattern(pdf_id: int, page_number: int) -> str:
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"""Glob pattern to list all users' temp entries for a given page."""
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return f"ann:{pdf_id}:{page_number}:*"
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