Frappe Cache & Locking

Decision Tree

What caching pattern do you need?
│
├─ Cache a function result automatically?
│  ├─ Pure function (same args → same result) → @redis_cache
│  └─ Need custom key/TTL → manual get_value/set_value
│
├─ Cache a document?
│  ├─ Read-only access → frappe.get_cached_doc()
│  └─ Need to invalidate → frappe.clear_document_cache()
│
├─ Cache structured data (multiple fields)?
│  └─ Redis hash → hset/hget/hgetall
│
├─ Per-request cache (avoid repeated DB calls in one request)?
│  └─ frappe.local.cache dict
│
├─ Prevent concurrent execution?
│  └─ Distributed lock → frappe.lock("resource_name")
│
└─ Invalidate cache?
   ├─ Single key → delete_value(key)
   ├─ Pattern → delete_keys("prefix*")
   └─ All site cache → frappe.clear_cache()

String Operations

Set and Get

# Set a value (persists until evicted or deleted)
frappe.cache.set_value("exchange_rate_USD", 1.08)

# Set with TTL (expires after N seconds)
frappe.cache.set_value("exchange_rate_USD", 1.08, expires_in_sec=3600)

# Get value (returns None if missing)
rate = frappe.cache.get_value("exchange_rate_USD")

# Get with generator (calls function on cache miss, stores result)
rate = frappe.cache.get_value(
    "exchange_rate_USD",
    generator=lambda: fetch_exchange_rate("USD"),
)

User-Scoped Values

# Store per-user preference
frappe.cache.set_value("dashboard_layout", "compact", user="[email protected]")

# Retrieve for specific user
layout = frappe.cache.get_value("dashboard_layout", user="[email protected]")

Delete

# Single key
frappe.cache.delete_value("exchange_rate_USD")

# Multiple keys
frappe.cache.delete_value(["exchange_rate_USD", "exchange_rate_EUR"])

# Pattern-based deletion (wildcard)
frappe.cache.delete_keys("exchange_rate*")

Hash Operations

Use hashes to group related fields under a single key.

# Set hash fields
frappe.cache.hset("config|notifications", "email_enabled", True)
frappe.cache.hset("config|notifications", "sms_enabled", False)
frappe.cache.hset("config|notifications", "max_retries", 3)

# Get single field
email_on = frappe.cache.hget("config|notifications", "email_enabled")

# Get all fields as dict
config = frappe.cache.hgetall("config|notifications")
# {"email_enabled": True, "sms_enabled": False, "max_retries": 3}

# Delete field
frappe.cache.hdel("config|notifications", "sms_enabled")

# Check existence
exists = frappe.cache.hexists("config|notifications", "email_enabled")

Hash with Generator

# hget with generator — calls function on miss
value = frappe.cache.hget(
    "user|permissions",
    "[email protected]",
    generator=lambda: compute_permissions("[email protected]"),
)

@redis_cache Decorator

Automatically cache function return values based on arguments.

from frappe.utils.caching import redis_cache

@redis_cache
def get_item_price(item_code, price_list):
    """Expensive query — cached automatically."""
    return frappe.db.get_value("Item Price",
        {"item_code": item_code, "price_list": price_list},
        "price_list_rate",
    )

# First call — hits database, stores in Redis
price = get_item_price("ITEM-001", "Standard Selling")

# Second call — returns from cache
price = get_item_price("ITEM-001", "Standard Selling")

# Clear all cached results for this function
get_item_price.clear_cache()

With TTL

@redis_cache(ttl=300)  # expires after 5 minutes
def get_exchange_rate(from_currency, to_currency):
    return fetch_rate_from_api(from_currency, to_currency)

Rules for @redis_cache:

• ALWAYS ensure arguments are hashable (strings, numbers, tuples). NEVER pass dicts or lists as arguments.
• ALWAYS call .clear_cache() when underlying data changes.
• NEVER use on functions with side effects — the function will NOT execute on cache hits.

frappe.local.cache: Request-Scoped Cache

frappe.local.cache is a plain Python dict that lives for the duration of a single HTTP request. It is NOT stored in Redis.

def get_user_settings():
    """Avoid repeated DB calls within a single request."""
    if "user_settings" not in frappe.local.cache:
        frappe.local.cache["user_settings"] = frappe.get_doc(
            "User Settings", frappe.session.user
        )
    return frappe.local.cache["user_settings"]

Use frappe.local.cache when:

• The same data is needed multiple times in one request
• The data does NOT need to persist across requests
• You want zero Redis overhead

Document Caching

# Get cached document (read-only, no permission check)
settings = frappe.get_cached_doc("System Settings")
item = frappe.get_cached_doc("Item", "ITEM-001")

# Invalidate when document changes
frappe.clear_document_cache("Item", "ITEM-001")

# Cached single value
val = frappe.db.get_value("Item", "ITEM-001", "item_name", cache=True)

NEVER modify a document returned by frappe.get_cached_doc() — it returns a shared reference. Modifications corrupt the cache for all subsequent reads.

Distributed Locking

Prevent concurrent execution of critical sections using Redis-based locks.

# Context manager (recommended)
with frappe.lock("process_payroll"):
    # Only one worker executes this block at a time
    process_all_salary_slips()
    # Lock auto-released on exit

# Manual lock/unlock
frappe.lock("inventory_sync")