Consul

Overview

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

How the SDKs store data in Consul

The Consul integrations for all LaunchDarkly server-side SDKs use the same conventions, so that SDK instances and Relay Proxy instances sharing a single Consul 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.
• For each data item that the SDK can store, such as a feature flag, there is a Consul key-value pair where the key is PREFIX/TYPE/KEY. PREFIX is the configured prefix string. TYPE denotes the type of data such as features and segments. KEY is the unique key of the item. For example, a KEY could be the flag key for a feature flag. 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. But the SDK never adds, modifies, or removes any keys in Consul other than ones starting with the PREFIX, so it is safe to share a Consul instance that is also being used for other purposes.

Server-side SDKs

In the following examples, the Consul feature store is set to use a host address of my-consul:8100, a prefix string of "my-key-prefix", and a cache TTL of 30 seconds.

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

• .NET (server-side)
• Go
• Java
• Node.js (server-side)
• PHP
• Python
• Ruby

.NET (server-side)

Go

Java

Node.js (server-side)

PHP

Python

Ruby