Spring Boot Toggle Feature using Togglz

• Feature toggle is a design pattern used to hide, enable or disable a feature during runtime.
  
• For example, during the deployment, a developer can disable the feature in the code which is released to production and enable it later in the next iterations when its 100% ready or enable the feature for testing to limited set of users , profiles or certain geographic location.

• It gives the power to reduce risk, iterate quicker, and gain more control and allows you to decouple feature rollout from code deployment.

• This separation allows you unprecedented control on who sees what and when, independent of release.

• Feature flagging is a core component of continuous delivery that empowers software organizations to release quickly and reliably.

• While there are many ways to achieve this but in this blog we will see how this can be done in Spring Boot microservice using Togglz library

• The Togglz library provides an implementation of the Feature Toggles design pattern.

• To demonstrate this feature we will build the following use case
  
  • Expose a Product API , which will return product information
  • When the festive period is on , then enable the feature to show discounted price
  • Add the code for new product but enable it only when its ready

• To use Togglz library include the following dependency in pom.xml file

<dependency>
    <groupId>org.togglz</groupId>
    <artifactId>togglz-spring-boot-starter</artifactId>
    <version>${togglz.version}</version>
</dependency>

• Togglz library also comes with a user interface and to enable it , add the below dependency

<dependency>
    <groupId>org.togglz</groupId>
    <artifactId>togglz-console</artifactId>
    <version>${togglz.version}</version>
</dependency>

• The main interaction with the Togglz library is done using the FeatureManager class, which is injectable and configured automatically.

public enum ProductFeatureFlag implements Feature {

    @EnabledByDefault
    @Label("Additional information about a book")
    ADDITIONAL_INFORMATION,

    @Label("Price during festive period")
    FESTIVE_DISCOUNT,
}

• The other way to define the feature toggle is defining it in the application.properties file and accessing with new NamedFeature(“NAME”)

togglz.features.NEW_PRODUCT.enabled=true
togglz.feature-enums=com.raj.nola.togglz.config.ProductFeatureFlag

• When ADDITIONAL_INFORMATION flag is active then we need to show additional info and when FESTIVE DISCOUNT is active then the discounted price should be shown

@GetMapping
@RequestMapping("/product")
public ResponseEntity<JsonNode> getProduct() {

    ObjectNode product = objectMapper.createObjectNode();
    product.put("productID", "NB101");
    product.put("productName", "NoteBook");
    product.put("price", 5.00);
    product.put("description", "Good Note Book");
    product.put("availabileFrom", "30-Jan-2020");

    if (featureManager.isActive(ProductFeatureFlag.ADDITIONAL_INFORMATION)) {
        product.put("additionalInfo", "8\" x 10-1/2\", college-ruled notebooks fit more writing per page than wide-ruled sheets; each notebook provides 70 double-sided sheets with red margin lines");
    }

    if (featureManager.isActive(ProductFeatureFlag.FESTIVE_DISCOUNT)) {
        product.put("price", 4.00);
    }
    return ResponseEntity.ok(product);
}

When NEW_PRODUCT flag is active then the new endpoint should be shown, this is configured using application.properties

togglz.features.NEW_PRODUCT.enabled

@GetMapping
@RequestMapping("/productV2")
public ResponseEntity<JsonNode> getBookWishlist() {

    if (featureManager.isActive(new NamedFeature("NEW_PRODUCT"))) {

        ObjectNode product = objectMapper.createObjectNode();
        product.put("productID", "NB102");
        product.put("productName", "B5 Spiral Notebook Lined");
        product.put("price", 10.00);
        product.put("description", "Spiral Ruled Journal");
        product.put("availabileFrom", "1-Feb-2020");
        product.put("additionalInfo", "B5 Size: 26cm x 18cm / 10.3\" x 7.2\", 70 sheets (140 pages) per notebook");

        return ResponseEntity.ok(product);
    }

• So what we have is a Product API , with additional information feature ON by default.
• Price for Festive discount disabled and controlled by Feature Flag
• A New V2 API of Product controlled by Feature Flag but disabled

• Togglz library also comes with a web UI and its configured to run on the same part in which service is running . This is defined in application.properties

togglz.console.enabled=true
togglz.console.path=/togglz-console
togglz.console.secured=false
togglz.console.use-management-port=false

• With this if you start the service and hit – http://localhost:8080/togglz-console/index, you will see one feature enabled and rest 2 disabled.

• API by default will return following output

• If you turn on festive discount feature and hit the API , you will notice the new price is shown now.

• As the NEW Product API is not enabled, when you hit the API you will not get any response.

• Once the flag is turned on , and then if you hit the endpoint again. It will return a response.

• If you click on Actions for the feature, it will help you set an Activation strategy for the API like enabled it on a certain date or only for a certain user

• Using the default configuration, Togglz manages the state of a feature toggle with an in-memory based solution.

• There are out-of-the-box integrations for feature state management with a JDBC data source and MongoDB for maintaining the state.

• Click on this link for details on Togglz Library
• Source code for the example shared: https://github.com/rajeshsgr/togglz-dem

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