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https://docs.geteppo.com
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### Start Eppo SDK server and get instance

Source: https://docs.geteppo.com/sdks/server-sdks/elixir/quickstart

Use the EppoSdk.Server module to avoid re-initializing the SDK for each request. This example starts the server and retrieves the current client instance.

```elixir
config = %EppoSdk.Client.Config{  
  api_key: api_key,  
  assignment_logger: EppoSdk.AssignmentLogger,  
  is_graceful_mode: true,  
  poll_interval_seconds: 30,  
  poll_jitter_seconds: 3  
}  
  
{:ok, _pid} = EppoSdk.Server.start_link(config)  
client = EppoSdk.Server.get_instance()  

```

--------------------------------

### Install Eppo Go SDK with go get

Source: https://docs.geteppo.com/sdks/server-sdks/go/quickstart

Install the Eppo Go SDK using go get. Run this command in your Go module directory.

```bash
go get github.com/Eppo-exp/golang-sdk/v6  

```

--------------------------------

### Basic SDK Initialization with EppoClient::init

Source: https://docs.geteppo.com/sdks/server-sdks/php/initialization

Initializes the Eppo PHP SDK by providing your SDK key. Requires the Composer autoloader and an existing SDK key. This is the minimal setup to start using the SDK.

```php
use Eppo\EppoClient;  
  
require __DIR__ . '/vendor/autoload.php';  
  
$eppoClient = EppoClient::init("<your_sdk_key>");  
```

--------------------------------

### Install Eppo JavaScript SDK with Bun

Source: https://docs.geteppo.com/sdks/client-sdks/javascript/quickstart

Install the @eppo/js-client-sdk package using Bun.

```bash
bun add @eppo/js-client-sdk  
```

--------------------------------

### Install the Python SDK with pip

Source: https://docs.geteppo.com/quick-starts/sdk-integration/creating-a-flag

Install the Eppo Python SDK using pip.

```bash
pip install eppo-server-sdk  
```

--------------------------------

### Install Eppo JavaScript SDK with NPM

Source: https://docs.geteppo.com/sdks/client-sdks/javascript/quickstart

Install the @eppo/js-client-sdk package using NPM.

```bash
npm install @eppo/js-client-sdk  
```

--------------------------------

### Install the Node SDK with NPM

Source: https://docs.geteppo.com/quick-starts/sdk-integration/creating-a-flag

Install the Eppo Node SDK using NPM for server-side applications.

```bash
npm install @eppo/node-client-sdk  
```

--------------------------------

### Install Eppo Ruby SDK with gem

Source: https://docs.geteppo.com/sdks/server-sdks/ruby/quickstart

Install the eppo-server-sdk gem using the gem command.

```bash
gem install eppo-server-sdk  
```

--------------------------------

### Install Eppo Node.js SDK with yarn

Source: https://docs.geteppo.com/sdks/client-sdks/javascript/nextjs-setup

Run this command to install the @eppo/node-server-sdk package for server-rendered components.

```bash
yarn add @eppo/node-server-sdk  

```

--------------------------------

### Install Eppo PHP SDK with Composer

Source: https://docs.geteppo.com/sdks/server-sdks/php/quickstart

Install the Eppo PHP SDK using Composer. Run this command in your project directory.

```bash
composer require eppo/php-sdk  

```

--------------------------------

### Initialize the Eppo .NET SDK

Source: https://docs.geteppo.com/sdks/server-sdks/dotnet/initialization

Basic initialization requires only an SDK key. Create an SDK key first if you don't already have one. The example shows constructing an EppoClientConfig with the key and passing it to EppoClient.Init.

```csharp
var eppoClientConfig = new EppoClientConfig("<SDK_KEY>", null);  
var eppoClient = EppoClient.Init(eppoClientConfig);  
```

--------------------------------

### Get Switchback Assignment with Eppo SDK

Source: https://docs.geteppo.com/switchback-quickstart

Use this snippet to fetch an assignment for a switchback experiment. Ensure the randomization unit (for example, `city`) is included in the `subject_attributes` object when getting an assignment and is logged to a column in the assignments table in your data warehouse.

```javascript
const client = EppoSdk.getInstance();  

const variant = client.getAssignment(...);
```

--------------------------------

### Get experiment assignment with getStringAssignment

Source: https://docs.geteppo.com/sdks/client-sdks/android/quickstart

Retrieve an experiment assignment using getStringAssignment and handle the variation with a switch statement. The example uses the experiment key 'recommendation-algo' and a default variation of 'control'.

```java
String variation = eppoClient.getStringAssignment(  
    "recommendation-algo",    // Experiment key  
    userId,                   // Subject identifier  
    attributes,              // Targeting attributes  
    "control"                // Default variation  
);  
  
switch (variation) {  
    case "variant-a":  
        showRecommendationAlgoA();  
        break;  
    case "variant-b":  
        showRecommendationAlgoB();  
        break;  
    default:  
        showDefaultRecommendations();  
}  
```

--------------------------------

### Initialize server SDK with init

Source: https://docs.geteppo.com/sdks/architecture/deployment-modes

On server spin up, initialize the Eppo server SDK with an API key and assignment logger.

```javascript
await EppoSdk.init({  
  apiKey: "<SDK_KEY>",  
  assignmentLogger,  
});  
```

--------------------------------

### Make a feature flag assignment

Source: https://docs.geteppo.com/sdks/server-sdks/php/quickstart

Get a string assignment for a feature flag. Provide subject attributes, subject key, and a default value. The example checks if the assignment is not 'control' to apply special logic.

```php
$subjectAttributes = [ 'tier' => 2 ];  
$assignment = $eppoClient->getStringAssignment('experimentalBackground', 'user123', $subjectAttributes, 'control');  
  
if ($assignment !== 'control') {  
    // do something special  
} else {  
  // Show the default treatment  
}  

```

--------------------------------

### Run the Next.js app

Source: https://docs.geteppo.com/sdks/client-sdks/javascript/nextjs-setup

Navigate into the project directory and start the development server. The local URL output (e.g., http://localhost:3000) is shown in the terminal.

```bash
cd react-sdk-walkthrough  
yarn dev  
```

--------------------------------

### Send email with Eppo assignment and Sendgrid

Source: https://docs.geteppo.com/guides/marketing/sendgrid

Node.js example using @sendgrid/mail and @eppo/node-server-sdk. Initializes Eppo, gets a JSON assignment for the user, and sends an email with the template_id and dynamic_template_data from the variation. Includes targeting attributes and default value.

```javascript
import sgMail from "@sendgrid/mail";  
  
import { init } from "@eppo/node-server-sdk";  
import * as EppoSdk from "@eppo/node-server-sdk";  
  
// Eppo startup  
await init({  
    apiKey: '<EPPO_SDK_KEY>',  
  });  
  
const eppoClient = EppoSdk.getInstance();  
  
// Sendgrid setup  
sgMail.setApiKey('<SENDGRID_API_KEY>')  
  
// User's email  
const recipient_email  
  
// User attributes used for targeting conditions, replace with your own values if needed  
const attributes = {}  
  
// Default value for the SDK to return if no conditions are met, replace with your own values  
const default_value = {  
  template_id: "<DEFAULT_TEMPLATE_ID>",  
  promo_code: "<DEFAULT_PROMO_CODE>"  
}  
  
// Loop through list to send email  
const variation = eppoClient.getJSONAssignment(  
  "<FLAG-KEY>",  
  recipient_email,  
  attributes,  
  default_value  
);  
    
const msg = {  
  to: recipient_email,   
  from: '<SG-FROM-SENDER>',   
  template_id: variation.template_id,  
  dynamic_template_data: {  
    promo: variation.promo_code  
  }  
}  
  
sgMail  
  .send(msg)  
  .then(() => {  
    console.log('Email sent')  
  })  
  .catch((error) => {  
    console.error(error)  
  })  
};  
```

--------------------------------

### Basic SDK initialization with eppoclient.InitClient

Source: https://docs.geteppo.com/sdks/server-sdks/go/initialization

Initializes the Eppo Go SDK with a minimal Config containing only the SdkKey. The InitClient function returns a client and an error; handle the error to avoid disrupting the application.

```go
import (  
    "github.com/Eppo-exp/golang-sdk/v6/eppoclient"  
)  
  
config := eppoclient.Config{  
    SdkKey: "<SDK-KEY>",  
}  
client, err := eppoclient.InitClient(config)  
if err != nil {  
    log.Fatal("Failed to initialize Eppo client:", err)  
}  

```

--------------------------------

### Get JSON assignment with Eppo.getJSONAssignment

Source: https://docs.geteppo.com/sdks/client-sdks/dart/assignments

Use Eppo.getJSONAssignment to retrieve a JSON flag value with a default assignment. The returned map can be used to update campaign fields, and the example shows how to safely cast and provide fallback values for optional fields.

```dart
final defaultAssignment = {  
  'hero': false,  
  'heroImage': 'placeholder.png',  
  'heroTitle': 'Placeholder Hero Title',  
  'heroDescription': 'Placeholder Hero Description'  
};  
  
final campaignJson = Eppo.getJSONAssignment(  
  'flag-key-123',  
  defaultAssignment  
);  
  
if (campaignJson != null) {  
  campaign.hero = true;  
  campaign.heroImage = campaignJson['heroImage'] as String?;  
  campaign.heroTitle = campaignJson['heroTitle'] as String? ?? '';  
  campaign.heroDescription = campaignJson['heroDescription'] as String? ?? '';  
}  
  
// Use the campaign settings in your component  
renderHero(campaign.heroImage, campaign.heroTitle, campaign.heroDescription);  

```

--------------------------------

### Initialize the Eppo Java SDK with EppoClient.builder().buildAndInit()

Source: https://docs.geteppo.com/sdks/server-sdks/java/quickstart

Initializes the Eppo Java SDK with your SDK key. Create an SDK key first if you don't already have one.

```java
EppoClient eppoClient = EppoClient.builder(sdkKey).buildAndInit();  
```

--------------------------------

### Query bandit for actions

Source: https://docs.geteppo.com/sdks/server-sdks/php/quickstart

Instead of simple assignments, query the bandit for actions. The bandit considers subject context and action contexts. This example shows the same SegmentLogger implementation as in the bandit setup, but the surrounding text indicates it is used for querying actions.

```php
<?php  
  
use Eppo\Logger\AssignmentEvent;  
use Eppo\Logger\BanditActionEvent;  
use Eppo\Logger\IBanditLogger;  
  
class SegmentLogger implements IBanditLogger  
{  
    public function logAssignment(AssignmentEvent $assignmentEvent): void  
    {  
        Segment::track([  
            'event' => 'Flag Assignment for ' . $assignmentEvent->featureFlag,  
            'userId' => $assignmentEvent->subject,  
            'properties' => $assignmentEvent->toArray()  
        ]);  
    }  
  
    public function logBanditAction(BanditActionEvent $banditActionEvent): void  
    {  
        Segment::track([  
            'event' => 'Bandit Action Selected',  
            'userId' => $banditActionEvent->subjectKey,  
            'properties' => $banditActionEvent->toArray()  
        ]);  
    }  
}  

```

--------------------------------

### Set up bandit loggers

Source: https://docs.geteppo.com/sdks/server-sdks/php/quickstart

Setting up a bandit requires two loggers: an assignment logger (same as experiments) and a bandit logger for recording bandit-specific events. This example implements IBanditLogger with both logAssignment and logBanditAction methods.

```php
use Eppo\Logger\AssignmentEvent;  
use Eppo\Logger\BanditActionEvent;  
use Eppo\Logger\IBanditLogger;  
  
class SegmentLogger implements IBanditLogger  
{  
    public function logAssignment(AssignmentEvent $assignmentEvent): void  
    {  
        Segment::track([  
            'event' => 'Flag Assignment for ' . $assignmentEvent->featureFlag,  
            'userId' => $assignmentEvent->subject,  
            'properties' => $assignmentEvent->toArray()  
        ]);  
    }  
  
    public function logBanditAction(BanditActionEvent $banditActionEvent): void  
    {  
        Segment::track([  
            'event' => 'Bandit Action Selected',  
            'userId' => $banditActionEvent->subjectKey,  
            'properties' => $banditActionEvent->toArray()  
        ]);  
    }  
}  

```

--------------------------------

### Get string assignment with Eppo JS SDK

Source: https://docs.geteppo.com/sdks

Evaluates a flag using the getStringAssignment method. Pass the flag key, subject key (e.g., user ID), optional targeting attributes, and a default value. The example uses 'show-new-feature' flag and 'control' default.

```JavaScript
import * as EppoSdk from "@eppo/js-client-sdk";

const eppoClient = EppoSdk.getInstance();

const variation = eppoClient.getStringAssignment(
  'show-new-feature',  // flag key
  user.id,  // subject key
  {}, // optional subject attributes for targeting
  'control' // default value
);
```

--------------------------------

### Serve precomputed configuration via script tag with window object

Source: https://docs.geteppo.com/sdks/client-sdks/javascript/precomputed-assignments

Exposes the configuration globally on the window object. Simple but exposes the configuration globally.

```html
<script>  
  window.__EPPO_CONFIG__ = JSON.stringify({  
    precomputedConfiguration: /* configuration from server */  
  });  
</script>  
```

--------------------------------

### Integer and Numeric Assignments with @eppo/js-client-sdk

Source: https://docs.geteppo.com/sdks/client-sdks/javascript/assignments

Shows how to get integer and numeric assignment values from the Eppo SDK. The example uses getIntegerAssignment and getNumericAssignment with a flag key, subject key, subject attributes, and a default assignment of 0. The returned values drive business logic such as rendering an item list or item price.

```javascript
import * as EppoSdk from "@eppo/js-client-sdk";
  
const client = EppoSdk.getInstance();  
const flagKey = "flag-key-123";  
const subjectKey = getUserId() || "user-123";  
const defaultAssignment = 0;  
const subjectAttributes = {  
  "country": "US",  
  "age": 30,  
  "isReturningUser": true  
};  
// example of getting an integer assignment  
const numberOfItems = client.getIntegerAssignment(  
  flagKey,  
  subjectKey,  
  subjectAttributes,  
  defaultAssignment  
);  
  
// example of getting a numeric assignment  
const price = client.getNumericAssignment(  
  flagKey,  
  subjectKey,  
  subjectAttributes,  
  defaultAssignment  
);  
  
// use the assignment to drive business logic  
<ItemList items={numberOfItems} />  
  
// use the assignment to drive business logic  
<Item price={price}/>  
  
```
```

--------------------------------

### Install eppo_metrics_sync and set environment variables

Source: https://docs.geteppo.com/data-management/certified-metrics/dbt-models

Installs the eppo_metrics_sync package and sets the EPPO_API_KEY and EPPO_SYNC_TAG environment variables required for syncing. Requires an Eppo API key with read/write Certified Metrics access, created under Admin >> API Keys.

```bash
python3 -m pip install eppo_metrics_sync  
export EPPO_API_KEY=<your API key>  
export EPPO_SYNC_TAG=local_dev_sync  
```

--------------------------------

### String Assignment with @eppo/js-client-sdk

Source: https://docs.geteppo.com/sdks/client-sdks/javascript/assignments

Retrieves a string assignment for a subject using the Eppo JavaScript client SDK. The example gets the client instance, then calls getAssignment with a flag key, subject key, default assignment, and subject attributes. String flags are the most common type and support A/B/n tests and advanced targeting.

```javascript
import * as EppoSdk from "@eppo/js-client-sdk";

const client = EppoSdk.getInstance();

const flagKey = "flag-key-123";
const subjectKey = getUserId() || "user-123";
const defaultAssignment = "version-a";
const subjectAttributes = {
  // ...
};
```

--------------------------------

### Python: Use variationKey from JSON parent flag assignment details

Source: https://docs.geteppo.com/feature-flagging/concepts/dependent-flags

For JSON parent flags, the assignment function returns the JSON value, not the variation key. Use the parent flag's `variationKey` from assignment details as `variation_served`. The example shows getting JSON assignment details and passing the variation key to a dependent flag.

```python
parent = client.get_json_assignment_details(  
  "parent-json-flag",  
  "<SUBJECT-KEY>",  
  {},  
  {},  # default JSON value  
)  
  
variation = client.get_string_assignment(  
  "<DEPENDENT-FLAG-KEY>",  
  "<SUBJECT-KEY>",  
  {  
    "dependent_flag": "parent-json-flag",  
    "variation_served": parent.evaluation_details["variationKey"],  # e.g. "exclude"  
  },  
  "<DEFAULT-VALUE>",  
)  
```
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