Flagger-on NPM

🦩 flagger-on

Enable / disable feature flags globally and / or rollout to a percentage of customers.

Install

npm install flagger-on

Prerequisites

Requires DynamoDB (additional DB support coming...)

Usage

const f = new Flaggeron({
  namespace: "my_namepace",
  dynamodb: {
    apiVersion: "2012-08-10",
    region: "<your-region>",
  },
});

or with DAX

const f = new Flaggeron({
  namespace: 'my_namepace',
  dynamodb: {
    apiVersion: "2012-08-10",
    service = new AmazonDaxClient({
        endpoint: dax.endpoint,
        region: '<your-region>',
      });
  },
});

Setup DynamoDB

aws dynamodb create-table --table-name FeatureFlag \
  --key-schema AttributeName=pk,KeyType=HASH AttributeName=sk,KeyType=RANGE \
  --attribute-definitions AttributeName=pk,AttributeType=S AttributeName=sk,AttributeType=S \
  --billing-mod PAY_PER_REQUEST

See DynamoDB Setup for additional setup options .

API

getFlags(featureIdPrefix?: string)

Retrieves the set of flags in this namespace that match the feature prefix. If no prefix is specified all flags in this namespace are returned.

// Retrievs flags that match the feature prefix
// if the following features exist, my.feature.1, my.feature.2, all will be returned
f.getFlags('my.feature);

getFlagsForSubject(subjectId: string, featureIdPrefix?: string)

Retrieves the set of flags in this namespace for the given subject e.g. customer that match the feature prefix. If no prefix is specified all flags in this namespace are returned.

Flags are enabled per subject as defined by the rollout configuration. See createFlag and replaceFlag

// Retrievs flags for subject user-12345 that match the feature prefix
f.getFlagsForSubject("user-12345", "my.feature");

enable

Enables a feature flag

f.enableFlag((id: "my.feature.1"));

disable

Disables a feature flag

f.disableFlag("my.feature.1");

create

Creates a feature flag

config.rollout.percentage applies only to per subject rolouts e.g. customer (see getFlagForSubject)

f.createFlag({
  id: "my.feature.1",
  config: {
    rollout: {
      percentage: 100, // rollout to 100 percent of the subject population
    },
  },
  data: {
    // custom properties
    myProp: "my value",
  },
  enabled: true,
});

replace

Reaplce a feature flag

config.rollout.percentage applies only to per subject rolouts e.g. customer

f.replaceFlag({
  id: "my.feature.1",
  config: {
    rollout: {
      percentage: 80, // rollout to 80 percent of the subject population
    },
  },
  enabled: true,
});

delete

Deletes a feature flag

f.deleteFlag("my.feature.1");

DynamoDB setup

Create a DynamoDB Table with name FeatureFlag, partition key pk, and sort key sk

Setup via CLI

NOTE: consider provisioned capacity, rather than PAY_PER_REQUEST to keep costs low

aws dynamodb create-table --table-name FeatureFlag \
  --key-schema AttributeName=pk,KeyType=HASH AttributeName=sk,KeyType=RANGE \
  --attribute-definitions AttributeName=pk,AttributeType=S AttributeName=sk,AttributeType=S \
  --billing-mod PAY_PER_REQUEST

Setup via CDK

const table = new dynamodb.Table(this, "Table", {
      partitionKey: { name: 'pk', type: dynamodb.AttributeType.STRING },
      sortKey: { name: 'sk', type: dynamodb.AttributeType.STRING },
      tableName: 'FeatureFlag',
      billingMode: dynamodb.BillingMode.PAY_PER_REQUEST,
});

Dax Setup

Setup via CDK

const daxSecurityGroup = new ec2.SecurityGroup(this, "DaxSecurityGroup", {
  vpc: props.vpc,
  allowAllOutbound: true,
  securityGroupName: "dax-security-group",
});

daxSecurityGroup.connections.allowFromAnyIpv4(
  new ec2.Port({
    protocol: ec2.Protocol.TCP,
    fromPort: 8111,
    toPort: 8111,
    stringRepresentation: "DaxPort",
  })
);

const subnetGroup = new dax.CfnSubnetGroup(this, "DaxSubnetGroup", {
  subnetIds: props.vpc.privateSubnets.map((s) => s.subnetId),
  subnetGroupName: "my-dax-subnet-group",
});

const daxRole = new iam.Role(this, "DaxRole", {
  assumedBy: new iam.ServicePrincipal("dax.amazonaws.com"),
});
daxRole.addToPrincipalPolicy(
  new iam.PolicyStatement({
    effect: iam.Effect.ALLOW,
    actions: [
      "dynamodb:DescribeTable",
      "dynamodb:PutItem",
      "dynamodb:GetItem",
      "dynamodb:UpdateItem",
      "dynamodb:DeleteItem",
      "dynamodb:Query",
      "dynamodb:Scan",
      "dynamodb:BatchGetItem",
      "dynamodb:BatchWriteItem",
      "dynamodb:ConditionCheckItem",
    ],
    resources: [this.table.tableArn],
  })
);

new dax.CfnCluster(this, "DaxCluster", {
  iamRoleArn: daxRole.roleArn,
  clusterName: "my-dax-cluster",
  availabilityZones: props.vpc.availabilityZones,
  nodeType: "dax.t3.small",
  replicationFactor: props.vpc.availabilityZones.length,
  securityGroupIds: [daxSecurityGroup.securityGroupId],
  subnetGroupName: subnetGroup.subnetGroupName,
  sseSpecification: {
    sseEnabled: true,
  },
});