Golang SDK

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This package is a server-side SDK for applications written in Golang for the Tailslide feature flag framework.

Visit the https://github.com/tailslide-io repository or see Tailslide’s case study page for more information.

Installation

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Install the Tailslide npm package with go get github.com/tailslide-io/tailslide.go

Basic Usage

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Instantiating and Initializing FlagManager

The FlagManager struct is the entry point of this SDK. It is responsible for retrieving all the flag rulesets for a given app with its AppId and creating new Toggler structs to handle toggling of feature flags within that app. To create a FlagManager struct, a user must provide a configuration object:

import (
	tailslide "github.com/tailslide-io/tailslide.go"
)

func main(){
  config := tailslide.FlagManagerConfig{
    NatsServer:  "nats://localhost:4222",
    NatsStream:  "flags_ruleset",
    AppId:       "1",
    UserContext: "375d39e6-9c3f-4f58-80bd-e5960b710295",
    SdkKey:      "myToken",
    RedisHost:   "http://localhost",
    RedisPort:   "6379",
  }

  manager := tailslide.NewFlagManager(config)
  manager.InitializeFlags()
}

• NatsServer is the NATS JetStream server address:port
• NatsStream is the NATS JetStream’s stream name that stores all the apps and their flag rulesets
• AppId is the ID number of the app the user wants to retrieve its flag ruleset from
• UserContext is the UUID string that identifies the current user
• SdkKey is the SDK key for the Tailslide, it is used as a password for NATS JetStream token authentication
• RedisHost is the address to the Redis database
• RedisPort is the port number that the Redis database runs on

After instantiating a FlagManager, invoke the initialize method. This method connects the FlagManager instance to both NATS JetStream and Redis Timeseries, and asynchronously retrieves the latest and any new flag ruleset data.

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Using Feature Flag with Toggler

Once the FlagManager is created, it can create a Toggler, with the NewToggler method, for each feature flag that the developer wants to wrap the new and old features in. A Toggler’s IsFlagActive method checks whether the flag with its FlagName is active or not based on the flag ruleset. A Toggler’s IsFlagActive method returns a boolean value, which can be used to evaluate whether a new feature should be used or not.

flagConfig := tailslide.TogglerConfig{
  FlagName: "App 1 Flag 1",
}

flagToggler, err := manager.NewToggler(flagConfig)
if flagToggler.IsFlagActive() {
  // call new feature here
} else {
  // call old feature here
}

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Emitting Success or Failture

To use a Toggler instance to record successful or failed operations, call its EmitSuccess or EmitFailure methods:

if successCondition {
  flagToggler.EmitSuccess()
} else {
  flagToggler.EmitFailure()
}

Documentation

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FlagManager

The FlagManager struct is the entry point of the SDK. A new FlagManager object will need to be created for each app.

FlagManager Constructor

tailslide.NewFlagManager(options tailslide.FlagManagerConfig)

Parameters:

• options: An object with the following keys
  • NatsServer is the NATS JetStream server address:port
  • NatsStream is the NATS JetStream’s stream name that stores all the apps and their flag rulesets
  • AppId a number representing the application the microservice belongs to
  • SdkKey a string generated via the Tower front-end for NATS JetStream authentication
  • UserContext a string representing the user’s UUID
  • RedisHost a string that represents the url of the Redis server
  • RedisPort a number that represents the port number of the Redis server

Return Value:

• A pointer to a FlagManager struct

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Instance Methods

flagmanager.initialize()

Asynchronously initialize flagmanager connections to NATS JetStream and Redis database

Parameters:

• nil

Return Value:

• nil

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flagManager.SetUserContext(newUserContext string)

Set the current user's context for the flagmanager

Parameters:

• newUserContext: A UUID string that represents the current active user

Return Value:

• nil

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flagManager.GetUserContext()

Returns the current user context

Parameters:

• nil

Return Value:

• The UUID string that represents the current active user

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flagManager.NewToggler(options tailslide.TogglerConfig)

Creates a new toggler to check for a feature flag's status from the current app's flag ruleset by the flag's name.

Parameters:

• options: An object with key of FlagName and a string value representing the name of the feature flag for the new toggler to check whether the new feature is enabled

Return Value:

• A pointer to a Toggler object

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flagManager.Disconnect()

Asynchronously disconnects the FlagManager instance from NATS JetStream and Redis database

Parameters:

• nil

Return Value:

• nil

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Toggler

The Toggler structs provide methods that determine whether or not new feature code is run and handles success/failure emissions. Each toggler handles one feature flag, and is created by FlagManager.NewToggler().

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Instance Methods

toggler.IsFlagActive()

Checks for flag status, whitelisted users, and rollout percentage in that order to determine whether the new feature is enabled.

• If the flag's active status is false, the function returns false
• If current user's UUID is in the whitelist of users, the function returns true
• If current user's UUID hashes to a value within user rollout percentage, the function returns true
• If current user's UUID hashes to a value outside user rollout percentage, the function returns false

Parameters:

• nil

Return Value

• true or false depending on whether the feature flag is active

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toggler.EmitSuccess()

Records a successful operation to the Redis Timeseries database, with key flagId:success and value of current timestamp

Parameters:

• nil

Return Value

• nil

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toggler.emitFailure()

Records a failure operation to the Redis Timeseries database, with key flagId:success and value of current timestamp

Parameters:

• nil

Return Value

• nil