> ## Documentation Index
> Fetch the complete documentation index at: https://launchdarkly.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Consul

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

> [!WARNING]
>
> **Data size limit in Consul**
>
> Consul does not support storing values greater than 512KB. Using Consul as a persistent feature store does not work if the JSON representation of any feature flag or segment exceeds that size. To learn more about these limitations, read [Consul's documentation](https://www.consul.io/docs/troubleshoot/faq#q-what-is-the-per-key-value-size-limitation-for-consul-s-key-value-store).
>
> <View title="Developer">
>   To view the JSON representations of all flags and segments, query `https://sdk.launchdarkly.com/sdk/latest-all`, or `https://sdk.launchdarkly.com/sdk/poll` if using [data saving mode](/docs/sdk/features/data-saving-mode), with your SDK key in the `Authorization` header.
> </View>
>
> <View title="Federal docs">
>   To view the JSON representations of all flags and segments, query `https://sdk.launchdarkly.us/sdk/latest-all`, or `https://sdk.launchdarkly.us/sdk/poll` if using [data saving mode](/docs/sdk/features/data-saving-mode), with your SDK key in the `Authorization` header.
> </View>
>
> <View title="EU docs">
>   To view the JSON representations of all flags and segments, query `https://sdk.eu.launchdarkly.com/sdk/latest-all`, or `https://sdk.eu.launchdarkly.com/sdk/poll` if using [data saving mode](/docs/sdk/features/data-saving-mode), with your SDK key in the `Authorization` header.
> </View>

## 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)](#net-server-side)
* [Go](#go)
* [Java](#java)
* [Node.js (server-side)](#node-js-server-side)
* [PHP](#php)
* [Python](#python)
* [Ruby](#ruby)

### .NET (server-side)

> **Expand .NET (server-side) code sample**
>
> If using the .NET SDK, you must install the additional package [`LaunchDarkly.ServerSdk.Consul`](https://github.com/launchdarkly/dotnet-server-sdk-consul).
>
> ```csharp title="C#" lines wrap theme={null}
> using LaunchDarkly.Sdk.Server;
> using LaunchDarkly.Sdk.Server.Integrations;
> var config = Configuration.Builder(sdkKey)
>     .DataStore(
>         Components.PersistentDataStore(
>             LaunchDarkly.Sdk.Server.Integrations.Consul.DataStore().Address("http://my-consul:8100")
>         ).CacheSeconds(30)
>     )
>     .Build();
> var client = new LdClient(config);
> ```
>
> To learn more, read [`dotnet-server-sdk-consul`](https://github.com/launchdarkly/dotnet-server-sdk-consul).

### Go

> **Expand Go code sample**
>
> The Go integration is in [`github.com/launchdarkly/go-server-sdk-consul`](https://github.com/launchdarkly/go-server-sdk-consul) for version 5.0.0 or higher of the SDK. In versions 4.5.0 and higher, but below 5.0.0, it is in the main SDK distribution as the subpackage `ldconsul`.
>
> ```go title="Go SDK v6+" lines wrap theme={null}
> import (
>     "time"
>
>     ld "github.com/launchdarkly/go-server-sdk/v6"
>     "github.com/launchdarkly/go-server-sdk/v6/ldcomponents"
>     ldconsul "github.com/launchdarkly/go-server-sdk-consul"
> )
>
> var config ld.Config
> config.DataStore = ldcomponents.PersistentDataStore(
>     ldconsul.DataStore().
>         Address("http://my-consul:8100").
>         Prefix("my-key-prefix"),
> ).CacheSeconds(30)
> client, _ := ld.MakeCustomClient(sdkKey, config, 5*time.Second)
> ```
>
> To learn more, read [`go-server-sdk-consul`](https://pkg.go.dev/github.com/launchdarkly/go-server-sdk-consul).

### Java

> **Expand Java code sample**
>
> If using the Java SDK, you must install the additional package [`com.launchdarkly.launchdarkly-java-server-sdk-consul-store`](https://github.com/launchdarkly/java-server-sdk-consul).
>
> ```java title="Java" lines wrap theme={null}
> import com.launchdarkly.sdk.server.*;
> import com.launchdarkly.sdk.server.integrations.*;
>
> LDConfig config = new LDConfig.Builder()
>   .dataStore(
>     Components.persistentDataStore(
>       Consul.dataStore().url(new URL("http://my-consul:8100"))
>         .prefix("my-key-prefix")
>     ).cacheSeconds(30)
>   )
>   .build();
> LDClient client = new LDClient(sdkKey, config);
> ```
>
> To learn more, read [`java-server-sdk-consul`](https://github.com/launchdarkly/java-server-sdk-consul).

### Node.js (server-side)

> **Expand Node.js (server-side) code sample**
>
> If using the Node.js SDK you must install the additional package [`launchdarkly-node-server-consul`](https://github.com/launchdarkly/node-server-sdk-consul).
>
> > [!NOTE]
> >
> > **SDK version compatibility**
> >
> > The Node.js (server-side) SDK v8.0 does not include Consul support. If you have questions or want to request this, [start a Support ticket](https://support.launchdarkly.com/hc/en-us/requests/new).
>
> ```js title="Node.js SDK v8.x+ (JavaScript)" expandable lines wrap theme={null}
> const ld = require('launchdarkly-node-server-sdk');
> const ConsulFeatureStore = require('launchdarkly-node-server-sdk-consul');
>
> const store = ConsulFeatureStore({
>   consulOptions: {
>     host: 'your-consul',
>     port:  8100
>   },
>   prefix: 'your-key-prefix',
>   cacheTTL: 30
> });
>
> const options = {
>   featureStore: store
> };
> const client = ld.init('YOUR_SDK_KEY', options);
> ```
>
> ```ts title="Node.js SDK v8.x+ (TypeScript)" expandable lines wrap theme={null}
> import * as ld from 'launchdarkly-node-server-sdk';
> import ConsulFeatureStore from 'launchdarkly-node-server-sdk-consul';
>
> const store = ConsulFeatureStore({
>   consulOptions: {
>     host: 'your-consul',
>     port: 8100,
>   },
>   prefix: 'your-key-prefix',
>   cacheTTL: 30,
> });
>
> const options: ld.LDOptions = {
>   featureStore: store,
> };
>
> const client = ld.init('YOUR_SDK_KEY', options);
> ```

### PHP

> **Expand PHP code sample**
>
> In version 4.0 and higher of the PHP SDK, you must add the package `launchdarkly/server-sdk-consul` to your application's Composer dependencies to use the Consul integration.
>
> In versions 3.x and earlier, the Consul integration is built into the main SDK package, but you must add a package dependency for `aws/sensiolabs/consul-php-sdk`.
>
> To use the Consul integration:
>
> ```php title="PHP" lines wrap theme={null}
> $fr = LaunchDarkly\Integrations\Consul::featureRequester([
>     'consul_uri' => 'http://my-consul:8100',
>     'consul_prefix' => 'my-key-prefix'
> ]);
> $client = new LaunchDarkly\LDClient("YOUR_SDK_KEY", [
>     'feature_requester' => $fr
> ]);
> ```
>
> To learn more, read [`php-server-sdk-consul`](https://github.com/launchdarkly/php-server-sdk-consul).

### Python

> **Expand Python code sample**
>
> The Python integration is part of the main SDK distribution as of version 6.8.1, but you must also install the package `python-consul`. Python 3.3 and 3.4 are not supported.
>
> ```python title="Python" lines wrap theme={null}
> import ldclient
> from ldclient.config import Config
> from ldclient.feature_store import CacheConfig
> from ldclient.integrations import Consul
>
> store = Consul.new_feature_store(host='my-consul', port=8100,
>     prefix='my-key-prefix', caching=CacheConfig(expiration=30))
>
> config = Config(feature_store=store)
> ldclient.set_config(config)
> ```

### Ruby

> **Expand Ruby code sample**
>
> The Ruby integration is part of the main SDK distribution as of version 5.1.1, but you must also install the gem `diplomat`.
>
> ```ruby title="Ruby" lines wrap theme={null}
> require 'ldclient-rb'
>
> store = LaunchDarkly::Integrations::Consul.new_feature_store(
>   { url: 'http://my-consul:8100', prefix: 'my-key-prefix', expiration: 30 })
>
> config = LaunchDarkly::Config.new(
>   feature_store: store
> )
> client = LaunchDarkly::LDClient.new(sdk_key, config)
> ```