Feature Flags Guide

Overview

The Vegas Casino application uses OpenFeature with flagd for feature flag management. Feature flags allow you to enable/disable features dynamically without redeploying services.

How Feature Flags Work

graph TB
    subgraph "Kubernetes Cluster"
        CRD[FeatureFlag CRD<br/>Flag Definitions]
        FFS[FeatureFlagSource CRD<br/>Configuration]
        POD[Application Pod]
        FLAGD[flagd Sidecar<br/>Port 8014]
        APP[Application Service]
    end

    CRD -->|Reads| FLAGD
    FFS -->|Configures| FLAGD
    POD -->|Contains| FLAGD
    POD -->|Contains| APP
    APP -->|localhost:8014| FLAGD

    style CRD fill:#10b981
    style FLAGD fill:#f59e0b
    style APP fill:#9333ea

1. FeatureFlag CRD: Defines available flags and their values
2. FeatureFlagSource CRD: Configures flagd sidecar
3. flagd Sidecar: Injected into pods automatically by OpenFeature Operator
4. Application: Connects to flagd via localhost:8014 to evaluate flags

Available Feature Flags

Slots Game Flags

Flag Name	Default	Description
slots.progressive-jackpot	true	Enable/disable progressive jackpot
slots.bonus-rounds	true	Enable/disable bonus rounds
slots.cheat-detection	true	Enable/disable cheat detection
slots.min-bet	10	Minimum bet amount (variants: 5, 10, 20)
slots.max-bet	1000	Maximum bet amount (variants: 500, 1000, 2000)

Roulette Game Flags

Flag Name	Default	Description
roulette.multiple-bets	true	Allow multiple simultaneous bets
roulette.live-wheel	true	Enable live wheel animation
roulette.cheat-detection	true	Enable cheat codes

Blackjack Game Flags

Flag Name	Default	Description
blackjack.double-down	true	Enable double down option
blackjack.insurance	true	Enable insurance bets
blackjack.surrender	false	Enable surrender option

Dice Game Flags

Flag Name	Default	Description
dice.pass-line	true	Enable pass-line bets
dice.come-bets	false	Enable come bets

Casino-Wide Flags

Flag Name	Default	Description
casino.house-advantage	false	House Advantage Mode: When enabled, reduces win probability across all games to protect casino profits. This flag is NOT displayed in the UI and should only be enabled via FeatureFlag CRD or Helm values. Use with caution as it affects all games.

Viewing Current Flags

Via kubectl

# List all feature flags
kubectl get featureflag -n vegas-casino

# View flag details
kubectl get featureflag vegas-casino-flags -n vegas-casino -o yaml

# Describe flag
kubectl describe featureflag vegas-casino-flags -n vegas-casino

Via Helm Values

Flags are defined in helm/vegas-casino/values.yaml:

flagd:
  slots:
    progressive-jackpot:
      state: ENABLED
      defaultVariant: "true"
  roulette:
    multiple-bets:
      state: ENABLED
      defaultVariant: "true"
  # Casino-wide feature flags (not displayed in UI)
  casino:
    house-advantage:
      state: ENABLED
      defaultVariant: "false"  # Set to "true" to enable house advantage mode

Enabling/Disabling Flags

Method 1: Edit FeatureFlag CRD Directly

# Edit the FeatureFlag resource
kubectl edit featureflag vegas-casino-flags -n vegas-casino

Update the flag value:

spec:
  flagSpec:
    flags:
      "slots.progressive-jackpot":
        state: ENABLED
        defaultVariant: "false"  # Changed from "true" to "false"

Save and exit. The flagd sidecar will automatically reload the configuration.

Method 2: Update Helm Values

1. Edit helm/vegas-casino/values.yaml:

flagd:
  slots:
    progressive-jackpot:
      state: ENABLED
      defaultVariant: "false"  # Disable progressive jackpot

1. Upgrade Helm release:

helm upgrade vegas-casino ./helm/vegas-casino \
  --namespace vegas-casino \
  --reuse-values

Method 3: Use kubectl patch

# Disable progressive jackpot
kubectl patch featureflag vegas-casino-flags -n vegas-casino \
  --type merge \
  -p '{"spec":{"flagSpec":{"flags":{"slots.progressive-jackpot":{"defaultVariant":"false"}}}}}'

Using Variants

Some flags support multiple variants (e.g., min-bet, max-bet):

Example: Change Min Bet

spec:
  flagSpec:
    flags:
      "slots.min-bet":
        state: ENABLED
        defaultVariant: "20"  # Change from "10" to "20"
        variants:
          "5": 5
          "10": 10
          "20": 20

Verifying Flag Changes

Check flagd Logs

# View flagd sidecar logs
kubectl logs <pod-name> -c flagd -n vegas-casino

# Look for reload messages
kubectl logs <pod-name> -c flagd -n vegas-casino | grep "reload"

Test Flag Evaluation

# Exec into pod
kubectl exec -it <pod-name> -n vegas-casino -c <service-container> -- /bin/sh

# Test flag evaluation (if service supports it)
curl http://localhost:8014/schema/v1/flags

Check Application Behavior

After changing flags, test the application:

# Port forward to frontend
kubectl port-forward -n vegas-casino svc/vegas-casino-frontend 3000:3000

# Open browser and test feature
# E.g., play slots and verify progressive jackpot is disabled

Flag States

Flags can be in three states:

• ENABLED: Flag is active and can be evaluated
• DISABLED: Flag is inactive (returns default variant)
• ARCHIVED: Flag is removed (not recommended for hackathon)

Targeting Rules

Flags support targeting rules for A/B testing (advanced):

spec:
  flagSpec:
    flags:
      "slots.progressive-jackpot":
        state: ENABLED
        defaultVariant: "false"
        variants:
          "true": true
          "false": false
        targeting:
          # Enable for specific users
          if:
            - user == "vip-player":
              variant: "true"

Troubleshooting

Flag Not Updating

# Check FeatureFlag resource
kubectl get featureflag vegas-casino-flags -n vegas-casino -o yaml

# Check flagd sidecar
kubectl get pods -n vegas-casino -o jsonpath='{range .items[*]}{.metadata.name}{"\t"}{.spec.containers[*].name}{"\n"}{end}' | grep flagd

# Restart pod to force reload
kubectl delete pod <pod-name> -n vegas-casino

Sidecar Not Injected

# Check pod annotations
kubectl describe pod <pod-name> -n vegas-casino | grep openfeature

# Should see:
# openfeature.dev/enabled: "true"
# openfeature.dev/featureflagsource: "vegas-casino/vegas-casino-flag-source"

# Check FeatureFlagSource
kubectl get featureflagsource -n vegas-casino

Application Can't Connect to flagd

# Check flagd is running
kubectl get pods -n vegas-casino -o jsonpath='{range .items[*]}{.metadata.name}{"\t"}{.spec.containers[*].name}{"\n"}{end}'

# Check flagd logs
kubectl logs <pod-name> -c flagd -n vegas-casino

# Verify port 8014 is open
kubectl exec -it <pod-name> -n vegas-casino -c <service-container> -- \
  nc -zv localhost 8014

Best Practices

1. Use Descriptive Names: Flag names should clearly indicate their purpose
2. Document Flags: Add comments in Helm values explaining flag purpose
3. Test Changes: Always test flag changes before enabling in production
4. Monitor Impact: Watch application metrics after changing flags
5. Clean Up: Remove unused flags to reduce complexity

Example: Disable Progressive Jackpot

# 1. Edit FeatureFlag
kubectl edit featureflag vegas-casino-flags -n vegas-casino

# 2. Change defaultVariant to "false"
#    Save and exit

# 3. Verify change
kubectl get featureflag vegas-casino-flags -n vegas-casino -o yaml | grep -A 5 progressive-jackpot

# 4. Test in application
kubectl port-forward -n vegas-casino svc/vegas-casino-frontend 3000:3000
# Play slots and verify progressive jackpot is disabled

Example: Enable House Advantage Mode

House Advantage Mode

Use with caution! This flag reduces win probability across all games to protect casino profits. It's designed for casino managers to enable during high-traffic periods or when profits need protection.

Via Helm Values

1. Edit helm/vegas-casino/values.yaml:

flagd:
  casino:
    house-advantage:
      state: "ENABLED"
      defaultVariant: "true"  # Enable house advantage

1. Upgrade Helm release:

helm upgrade vegas-casino ./helm/vegas-casino \
  --namespace vegas-casino \
  --reuse-values

Via FeatureFlag CRD

# Edit the FeatureFlag resource
kubectl edit featureflag vegas-casino-flags -n vegas-casino

Update the flag:

spec:
  flagSpec:
    flags:
      "casino.house-advantage":
        state: ENABLED
        defaultVariant: "true"  # Enable house advantage

Verify House Advantage is Active

# Check flag value
kubectl get featureflag vegas-casino-flags -n vegas-casino -o yaml | grep -A 5 house-advantage

# Test in application - play games and observe reduced win rates
kubectl port-forward -n vegas-casino svc/vegas-casino-frontend 3000:3000

Important

• This flag affects all games (Slots, Roulette, Dice, Blackjack)
• The flag is not visible in the UI - it's a backend-only control
• Changes take effect immediately after flagd reloads (usually within seconds)
• Monitor game statistics after enabling to verify the impact

Next Steps

• Source Code Locations: Find where flags are used in code
• Updating with Helm: Learn how to update deployments
• DevContainer Environment: Understand the environment