Redis

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Last edited: Dec 12, 2024

Overview

This topic explains how to use the SDK Redis integration as a persistent feature store.

Many of our server-side SDKs support Redis. The available options are slightly different in each language, but you can always specify the following:

The Redis host address, which defaults to localhost:6379
A prefix string to add to all keys used by the store, to avoid collisions in case the database is also being used for some other purpose
The length of time that recently read or updated data should be cached in memory

Supported Redis configurations

The LaunchDarkly SDKs use third-party open-source libraries to connect to Redis. Not all of these have the same level of support for advanced Redis configurations. Specifically, most of the SDKs and the Relay Proxy do not support connecting to a Redis cluster or using Redis Sentinel for service discovery.

To learn more, read the documentation for the individual SDKs below, or their Redis integration add-on libraries for SDKs that do not have this integration built in.

How the SDKs store data in Redis

The Redis integrations for all LaunchDarkly server-side SDKs use the same conventions, so that SDK instances and Relay Proxy instances sharing a single Redis store can interoperate correctly.

The storage schema is as follows:

There is always a "prefix" string that provides a namespace for the overall data set. If you do not specify a prefix in your configuration, it is launchdarkly. If you are using a persistent store integration, it must be the client-side ID for the environment.
For each type of data that the SDK can store, there is a hash whose key is PREFIX:TYPE. PREFIX is the configured prefix string. TYPE denotes the type of data such as features and segments.
Within each hash, there is one field per data item. For instance, the hash PREFIX:features has one field per feature flag. The field name is the unique key of the item, such as the flag key for a feature flag, and the value is a serialized representation of that item, in a format that is determined by the SDK.
An additional key, PREFIX:$inited, is created with an arbitrary value when the SDK stores a full set of feature flag data. This allows a new SDK instance to check whether there is already a valid data set that was stored earlier.
The SDK may use additional keys starting with the PREFIX string, so you should not assume that the TYPE values mentioned above and $inited are the only possible keys. The SDK never adds, modifies, or removes any keys in Redis other than ones starting with the PREFIX, so it is safe to share a Redis instance that is also being used for other purposes.

Server-side SDKs

In the following examples, the Redis feature store is set to use a host address of my-redis:6379, a prefix string of "my-key-prefix", and a cache TTL of 15 or 30 seconds, depending on the SDK.

Using a persistent store for segments requires a specific key prefix

If you are using a persistent store integration, the value of the key prefix for the persistent store must be the client-side ID of your environment.

Your environment's client-side ID is available in the Environments list for your project. To learn more about key types, read Keys.

This feature is available in the following server-side SDKs:

.NET (server-side)
C++ (server-side)
Erlang
Go
Haskell
Java
Lua
Node.js (server-side)
PHP
Python
Ruby

.NET (server-side)

Expand .NET (server-side) code sample

To use Redis with the .NET SDK you must install an additional package named LaunchDarkly.ServerSdk.Redis.

To learn more, read dotnet-server-sdk-redis.

C++ (server-side)

Expand C++ (server-side) code sample

The C++ integration is part of the main SDK distribution, but is disabled by default in order to avoid bringing in unnecessary dependencies (redis++, a wrapper for hiredis).

To ensure the integration header and library are available for your build, set the CMake option LD_BUILD_REDIS_SUPPORT=ON.

Erlang

The Erlang integration is part of the main SDK distribution.

Expand Erlang code sample

Go

Expand Go code sample

The Go integration is in github.com/launchdarkly/go-server-sdk-redis for 5.0.0 or higher of the SDK. In earlier SDK versions, it is in the main SDK distribution as the subpackage redis.

To learn more, read go-server-sdk-redis-redigo.

Haskell

Expand Haskell code sample

To use Redis with the Haskell SDK, you must install an additional package.

If you are working with version 4.0 of the Haskell SDK, use launchdarkly-server-sdk-redis-hedis, which is in a separate repository. It is compatible with version 4.0 and higher of the Haskell SDK.

If you are working with versions 3.x and earlier, use launchdarkly-server-sdk-redis.

Java

Expand Java code sample

You must install the additional package com.launchdarkly.launchdarkly-java-server-sdk-redis-store.

To learn more, read java-server-sdk-redis.

Lua

Expand Lua code sample

When you use Redis for storing data, you also need to include launchdarkly_server_sdk_redis:

Node.js (server-side)

Expand Node.js (server-side) code sample

In version 8.0.0 and higher of the Node.js SDK, you must install the additional package @launchdarkly/node-server-sdk-redis. In versions 6.0.0-7.x of the Node.js SDK, you must install the additional package launchdarkly-node-server-sdk-redis.

In version 3.0 and higher of the Node.js SDK Redis integration, the ioredis package is used for Redis operations. In versions 2.x of the Node.js SDK Redis integration, the redis package is used for Redis operations.

PHP

Expand PHP code sample

There are two Redis integrations for the PHP SDK. One uses the Predis package, which can be used in any PHP environment. The other uses the more efficient phpredis extension, which must be installed in PHP itself.

In version 4.0 and higher of the PHP SDK, you must add a package to your application's Composer dependencies to use one of these two integrations:

For the Predis integration, add launchdarkly/server-sdk-redis-predis.
For the phpredis integration, add launchdarkly/server-sdk-redis-phpredis.

In versions 3.x and earlier, the Redis integrations are built into the main SDK package, but you must add a package dependency for predis/predis if you are using Predis.

To use the Predis integration:

To use the phpredis integration:

To learn more, read php-server-sdk-redis-predis or php-server-sdk-redis-phpredis.

Python

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The Python integration is part of the main SDK distribution, but you must also install the package redis.

Ruby

Expand Ruby code sample

The Ruby integration is part of the main SDK distribution, but you must also install the gems redis and connection_pool.