launchdarkly-guarded-rollout

SKILL.md

LaunchDarkly Guarded Rollouts

You're using a skill that will guide you through configuring guarded rollouts in LaunchDarkly. Your job is to design rollout stages, select monitoring metrics, configure regression thresholds, and start the rollout.

Prerequisites

This skill requires the remotely hosted LaunchDarkly MCP server to be configured in your environment.

Required MCP tools:

start-guarded-rollout -- start a progressive rollout with monitoring

get-flag -- inspect the flag and its variations

list-metrics -- find metrics to monitor during the rollout

Optional MCP tools:

stop-guarded-rollout -- halt an active rollout immediately

toggle-flag -- ensure the flag is turned on before starting

create-metric -- create metrics if they don't exist

Core Concepts
What Are Guarded Rollouts?

A guarded rollout progressively increases traffic to a new feature flag variation through a series of stages. At each stage, LaunchDarkly monitors selected metrics for regressions. If a regression is detected, the rollout can automatically pause and notify the team — or even roll back.

Key Components

Component
Description

Test variation
The new variation being rolled out

Control variation
The existing/baseline variation

Stages
Steps with increasing traffic percentage and monitoring windows

Metrics
What to monitor for regressions (error rate, latency, etc.)

Regression threshold
How much a metric can degrade before triggering action

On regression
Whether to notify, rollback, or both when a threshold is breached

Rollout Weight Units

Rollout weights use thousandths (basis points):

1000 = 1%

10000 = 10%

50000 = 50%

100000 = 100%

Monitoring Window

The monitoring window is specified in milliseconds:

3600000 = 1 hour

86400000 = 24 hours

604800000 = 7 days

Core Principles

Start Small: Begin with a low percentage (1-5%) to catch issues early

Monitor What Matters: Choose metrics that reflect user experience

Set Realistic Thresholds: Too tight = false alarms; too loose = missed regressions

Allow Time: Each stage needs enough monitoring time for signal to emerge

Have a Rollback Plan: Always configure at least notification on regression

Workflow

Step 1: Prepare

Before starting a guarded rollout:

Use get-flag to inspect the flag — note the variation IDs for test and control

Use list-metrics to find metrics suitable for monitoring

Ensure the flag is on in the target environment (use toggle-flag if needed)

Confirm there's no active guarded rollout on this flag already

Step 2: Design Stages

Plan the rollout progression. A typical pattern:

Stage
Traffic
Monitoring Window
Purpose

1
1%
1 hour
Smoke test — catch obvious crashes

2
10%
24 hours
Early signal on metrics

3
50%
24 hours
Confidence building

4
100%
24 hours
Full rollout with monitoring

Step 3: Configure Metrics

Select metrics that indicate problems:

Metric Type
Example
Threshold
Action

Error rate
api-error-rate
0.05 (5% increase)
Rollback

Latency
p99-response-time
0.2 (20% increase)
Notify

Conversion
checkout-completed
0.1 (10% decrease)
Notify + Rollback

Step 4: Start the Rollout

Use start-guarded-rollout:

{
  "projectKey": "my-project",
  "flagKey": "new-checkout-flow",
  "environmentKey": "production",
  "testVariationId": "variation-id-for-new-flow",
  "controlVariationId": "variation-id-for-current-flow",
  "randomizationUnit": "user",
  "stages": [
    {"rolloutWeight": 1000, "monitoringWindowMilliseconds": 3600000},
    {"rolloutWeight": 10000, "monitoringWindowMilliseconds": 86400000},
    {"rolloutWeight": 50000, "monitoringWindowMilliseconds": 86400000},
    {"rolloutWeight": 100000, "monitoringWindowMilliseconds": 86400000}
  ],
  "metrics": [
    {
      "metricKey": "api-error-rate",
      "onRegression": {"notify": true, "rollback": true},
      "regressionThreshold": 0.05
    },
    {
      "metricKey": "checkout-completed",
      "onRegression": {"notify": true, "rollback": false},
      "regressionThreshold": 0.1
    }
  ]
}

Step 5: Verify

Use get-flag to confirm the guarded rollout is active

Check that the flag shows the rollout configuration in the environment

Monitor for any immediate regression notifications

Report results:

Guarded rollout started with N stages

M metrics being monitored

First stage at X% traffic for Y hours

Stopping a Rollout

If issues arise or you need to halt the rollout:

{
  "projectKey": "my-project",
  "flagKey": "new-checkout-flow",
  "environmentKey": "production"
}

This immediately stops the progressive rollout and locks the flag at its current state.

Edge Cases

Situation
Action

Flag is off
Turn it on first with toggle-flag — rollouts require the flag to be on

Active rollout exists
Stop it first with stop-guarded-rollout before starting a new one

No suitable metrics
Create metrics first with create-metric

Approval required
If the environment requires approvals, the tool will return an approval URL

What NOT to Do

Don't start a guarded rollout on a flag that's turned off

Don't skip the monitoring window design — rushing through stages defeats the purpose

Don't set regression thresholds to 0 — small fluctuations are normal

Don't forget to configure at least one metric — a rollout without monitoring is just a regular rollout