django-elastipymemcache

Overview

django-elastipymemcache is a Django cache backend for Amazon ElastiCache (memcached) clusters. It is built on top of pymemcache and connects to all cluster nodes via ElastiCache Auto Discovery.

Originally forked from django-elasticache, this implementation adds:

• Thread-safe topology updates (atomic swaps)
• Auto discovery for scaling events
• Connection pooling (data nodes & config endpoint)
• Optional TLS connectivity
• Compatibility with Django’s cache interface

Requirements

• Python >= 3.10
• Django >= 4.2
• pymemcache >= 4.0.0

Installation

Get it from PyPI:

python3 -m pip install django-elastipymemcache

Usage

Basic

CACHES = {
    "default": {
        "BACKEND": "django_elastipymemcache.backend.ElastiPymemcache",
        "LOCATION": "[configuration-endpoint]:11211",
        "OPTIONS": {
            "ignore_exc": True,
        },
    }
}

Connection Pooling

CACHES = {
    "default": {
        "BACKEND": "django_elastipymemcache.backend.ElastiPymemcache",
        "LOCATION": "[configuration-endpoint]:11211",
        "OPTIONS": {
            # Enable pooling for both config endpoint and data nodes
            "use_pooling": True,
            "max_pool_size": 50,
            "pool_idle_timeout": 30,
            "connect_timeout": 0.3,
            "timeout": 0.5,
            "ignore_exc": True,
        },
    }
}

Auto Discovery (with pooling)

CACHES = {
    "default": {
        "BACKEND": "django_elastipymemcache.backend.ElastiPymemcache",
        "LOCATION": "[configuration-endpoint]:11211",
        "OPTIONS": {
            "use_pooling": True,
            "discovery_interval": 60.0,
            "discovery_retry_delay": 2.0,
            "ignore_exc": True,
        },
    }
}

Options

The backend accepts a combination of ElastiPymemcache-specific options and pymemcache client options. For the complete list of pymemcache options, see: https://pymemcache.readthedocs.io/

ElastiPymemcache-specific options

Option	Type	Default	Description
discovery_interval	float	0.0	Periodic auto-discovery interval in seconds. Set 0.0 to disable.
discovery_retry_delay	float	0.0	Delay (seconds) before retrying discovery after failure.
use_vpc_ip_address	bool	True	Prefer VPC private IPs over DNS hostnames (recommended on AWS).

Notes

• According to the official Amazon ElastiCache documentation, auto-discovery must be enabled to support vertical scaling. https://docs.aws.amazon.com/AmazonElastiCache/latest/dg/Scaling-self-designed.mem-heading.html
• Auto-discovery also runs on demand when the ring is empty, even if discovery_interval is 0.0. This helps recover after scale events.
• If you use TLS, pass the appropriate tls_context through OPTIONS (this is a pymemcache option) and ensure your ElastiCache cluster supports TLS.

Notice

Datadog ddtrace & pymemcache instrumentation (temporary workaround)

When using ddtrace with Django or other frameworks, enabling the pymemcache integration may trigger runtime errors such as:

ValueError: wrapper has not been initialized

This issue occurs due to wrapt interfering with class initialization order inside ddtrace’s pymemcache integration. Until Datadog releases a fix, disable the pymemcache tracer.

Environment variable

DD_TRACE_PYMEMCACHE_ENABLED=false

Code-level patch

patch_all(pymemcache=False)