Django Redis Caching Skill

Implements Redis caching with django-cacheops for the DTX Django backend.

Quick Reference

Cacheops Configuration

All models use 1-hour cache timeout (configured in settings.py):

CACHEOPS = {
    "app.tournament": {"ops": "all", "timeout": 60 * 60},
    "app.team": {"ops": "all", "timeout": 60 * 60},
    "app.customuser": {"ops": "all", "timeout": 60 * 60},
    "app.draft": {"ops": "all", "timeout": 60 * 60},
    "app.game": {"ops": "all", "timeout": 60 * 60},
    "app.draftround": {"ops": "all", "timeout": 60 * 60},
}

View Caching Pattern

from cacheops import cached_as

def list(self, request, *args, **kwargs):
    cache_key = f"model_list:{request.get_full_path()}"

    @cached_as(Model1, Model2, extra=cache_key, timeout=60 * 60)
    def get_data():
        queryset = self.filter_queryset(self.get_queryset())
        serializer = self.get_serializer(queryset, many=True)
        return serializer.data

    return Response(get_data())

Cache Invalidation Pattern

Preferred: invalidate_after_commit — use inside transactions, signal handlers, or anywhere writes may be deferred:

from app.cache_utils import invalidate_after_commit

with transaction.atomic():
    user.nickname = "New"
    user.save()
    invalidate_after_commit(tournament, org_user, org_user.organization)

Direct invalidate_obj — safe only OUTSIDE transactions (e.g., after M2M .add()/.remove()):

from cacheops import invalidate_obj

org.admins.add(user)       # M2M auto-commits
invalidate_obj(org)        # Safe — data already committed

When to use which:

Context	Use
Inside transaction.atomic()	invalidate_after_commit()
Inside @transaction.atomic decorator	invalidate_after_commit()
Inside signal handlers (post_save, etc.)	invalidate_after_commit()
After .save() / M2M ops outside transactions	Direct invalidate_obj() is safe
After .update() / .bulk_create()	invalidate_after_commit() (defensive)

DTX Model Cache Dependencies

When modifying data, invalidate these related caches:

Changed Model	Also Invalidate
DraftRound	Tournament, Draft, Team
Draft	Tournament
Team	Tournament (if tournament-scoped)
Game	Tournament, Team
CustomUser	Team (if member changes)

Key Principles

1. Invalidate on Write: Always invalidate related caches after mutations
2. Use invalidate_after_commit: Default to deferred invalidation in transactions — see app/cache_utils.py
3. Monitor Dependencies: Use @cached_as(Model1, Model2, ...) to auto-invalidate
4. Use Specific Keys: Include request path or pk in cache keys
5. Keep Fresh for Detail: Use keep_fresh=True for single-object retrieval

Detailed References

• Cacheops Patterns - Decorator usage, cache keys
• Invalidation Strategies - When and how to invalidate
• Model Dependencies - DTX model relationships

Common Operations

Disable Cache for Management Commands

DISABLE_CACHE=true python manage.py <command>

Manual Cache Invalidation

from cacheops import invalidate_all, invalidate_model, invalidate_obj

# Nuclear option - invalidate everything
invalidate_all()

# Invalidate all instances of a model
invalidate_model(Tournament)

# Invalidate specific instance
invalidate_obj(tournament)

Check if Cache is Working

from django.core.cache import cache
cache.set('test_key', 'test_value', 30)
print(cache.get('test_key'))  # Should print 'test_value'

Timeout Guidelines

Data Type	Timeout	Reason
Static data	60 * 60 (1h)	Rarely changes
Tournament state	60 * 10 (10m)	Changes during events
Draft rounds	60 * 10 (10m)	Active during drafts
Discord guild members (discord_members_<guild_id>)	60 * 60 (1h)	Admin-search-driven refreshes; daily avatar task reads from this same cache. See "Discord Member Cache" below.
Other external API short-burst caches	15-60s	Per-request burst dedup only

Discord Member Cache

Single Redis cache for guild members shared by two consumer patterns — admin-driven and scheduled. Don't add a parallel cache for the same data; extend the timeout or call refresh_discord_members instead.

Cache: discord_members_<guild_id> — full paginated member list per guild, 1-hour TTL (constant: DISCORD_MEMBER_CACHE_TTL_S in backend/discordbot/services/users.py).

Populated by:

• discordbot.services.users.get_discord_members_data(guild_id) — on cache miss, paginates GET /guilds/{id}/members?limit=1000 via the after cursor until the guild is exhausted, then writes the full list back at TTL.
• discordbot.services.users.refresh_discord_members(request) — POST endpoint admins hit when they need to add a user who joined Discord recently. 5-min per-org cooldown. Force-clears + repaves the cache.

Consumed by:

• search_discord_members — admin-search-by-name on org pages
• get_organization_discord_members — full org-member list
• get_discord_voice_channel_activity — voice-channel staffing
• app.tasks.avatar_refresh.refresh_avatars_batched — daily Celery beat. Reads the cache, builds a discord_id → avatar_hash map, posts diffed rows to the internal endpoint POST /api/internal/users/avatars/bulk-update/ (defined in user/internal/avatar.py). The endpoint performs bulk_update(batch_size=500) + invalidate_model(CustomUser) server-side — the worker never touches the ORM. Daily cadence works because admin searches keep the cache current within the day.

Why no separate avatar cache? Avatars are stored on User.avatar (DB column), not in Redis. The "avatar cache" IS the DB column; the daily Celery task is what refreshes it from the live guild member list. No third cache needed.

When you'd add a NEW cache key for guild members: never. Use get_discord_members_data. If a caller needs different semantics (e.g. force-refresh), use the refresh_discord_members endpoint or cache.delete(...) the existing key — don't fork.

Bulk-update + cacheops invariant

When a process writes thousands of rows via Model.objects.bulk_update(...), post_save doesn't fire and cacheops won't auto-invalidate. Pair bulk_update with one invalidate_model(Model) call after the batched write — N per-row invalidate_obj() calls would defeat the whole point of batching.

For Celery workers and the Discord bot, the bulk_update itself must live behind an internal HTTP endpoint (/api/internal/...) because workers don't touch the ORM. Reference impl: user/internal/avatar.py::bulk_update_user_avatars — bulk_update(batch_size=500) + invalidate_model(CustomUser) in a single request body. Mirror this shape (validate payload first, then one bulk_update, then one invalidate_model) for similar batched-write paths in other domains.