AccelByte Extend Challenge Event Handler

Event processing service for real-time challenge progress updates.

This service processes AGS events (IAM login, Statistic updates) and updates challenge progress in real-time using high-performance buffered batch processing.

Service Overview

Purpose

The Event Handler Service:

Receives AGS events via gRPC (Extend platform abstracts Kafka)
Determines which goals are affected by each event
Updates user progress in database with buffering (1,000,000× query reduction)
Completes goals automatically when target is reached

Architecture

AccelByte Gaming Services
  │
  ├─► IAM Login Events
  │   (namespace.iam.account.v1.userLoggedIn)
  │
  └─► Statistic Update Events
      (namespace.social.statistic.v1.statItemUpdated)
      │
      ▼
┌─────────────────────────────────────────┐
│  Event Handler Service (This)           │
│                                         │
│  ┌───────────────────────────────────┐ │
│  │  gRPC Event Receiver              │ │
│  │  • OnEvent()                      │ │
│  └──────────┬────────────────────────┘ │
│             │                           │
│  ┌──────────▼────────────────────────┐ │
│  │  Event Processor                  │ │
│  │  • Parse event                    │ │
│  │  • Find affected goals            │ │
│  │  • Calculate new progress         │ │
│  └──────────┬────────────────────────┘ │
│             │                           │
│  ┌──────────▼────────────────────────┐ │
│  │  Buffered Repository              │ │
│  │  • Buffer updates (in-memory)     │ │
│  │  • Deduplicate per user-goal      │ │
│  │  • Flush every 1 second           │ │
│  │  • Batch UPSERT (1,000 rows)      │ │
│  └───────────────────────────────────┘ │
└─────────────────────────────────────────┘
      │
      ▼
  PostgreSQL
  (user_goal_progress)

Key Features

✅ High-Performance Buffering - 1,000,000× database query reduction ✅ Automatic Deduplication - Map-based per user-goal pair ✅ Concurrency Control - Per-user mutex prevents race conditions ✅ Batch UPSERT - Single query for 1,000 rows (< 20ms) ✅ Fire-and-Forget - Errors logged but don't block processing ✅ In-Memory Cache - O(1) goal lookup by event source

Quick Start

Prerequisites

Go 1.25+
PostgreSQL 15+ (or use Docker Compose)
Make (optional but recommended)

1. Clone Repository

git clone https://github.com/AccelByte/extend-challenge-event-handler.git
cd extend-challenge-event-handler

2. Install Dependencies

go mod download

3. Configure Environment

# Copy example config
cp .env.example .env

# Edit .env with your settings
vi .env

Key environment variables:

# Database
DB_HOST=localhost
DB_PORT=5432
DB_NAME=challenge_db
DB_USER=postgres
DB_PASSWORD=postgres

# Server
GRPC_PORT=6566
METRICS_PORT=8081

# Buffering
BUFFER_FLUSH_INTERVAL=1s
BUFFER_MAX_SIZE=10000

# AccelByte
AB_NAMESPACE=your-namespace

4. Run Service

# Development mode
make run

# Or with Go directly
go run cmd/main.go

Service will start on:

gRPC: localhost:6566
Metrics: localhost:8081/metrics

5. Test Event Processing

# Send test login event (via demo app)
cd ../extend-challenge-demo-app
go run main.go events trigger login

# Check logs
tail -f event-handler.log

# Verify progress in database
psql -U postgres -d challenge_db -c \
  "SELECT * FROM user_goal_progress WHERE goal_id = 'daily-login';"

Event Processing

Supported Event Types

1. IAM Login Events

Topic: {namespace}.iam.account.v1.userLoggedIn

Event Schema:

{
  "id": "event-123",
  "payload": {
    "userId": "abc123",
    "namespace": "mygame"
  }
}

Affects goals with: "event_source": "login"

2. Statistic Update Events

Topic: {namespace}.social.statistic.v1.statItemUpdated

Event Schema:

{
  "id": "event-456",
  "payload": {
    "userId": "abc123",
    "namespace": "mygame",
    "statCode": "match_wins",
    "value": 42.0
  }
}

Affects goals with: "event_source": "statistic:{statCode}" (e.g., "statistic:match_wins")

Event Processing Flow

1. Event Received
   ↓
2. Parse Event (extract userId, namespace, event source)
   ↓
3. Lookup Affected Goals (from in-memory cache, O(1))
   ↓
4. For Each Goal:
   ├─► Calculate New Progress (absolute/increment/daily)
   ├─► Check if Completed (progress >= target)
   └─► Buffer Update (per-user mutex)
   ↓
5. Periodic Flush (every 1 second)
   ├─► Collect all buffered updates
   ├─► Deduplicate (keep latest per user-goal)
   ├─► Batch UPSERT (single SQL query)
   └─► Clear buffer

Progress Calculation by Goal Type

Absolute Goals

// Replace progress with stat value
newProgress = statValue

Example: "Reach level 10"

Stat updates: 1 → 5 → 10
Progress: 1 → 5 → 10

Increment Goals

// Accumulate stat updates
newProgress = currentProgress + statValue

Example: "Play 10 matches"

Stat updates: 1 + 1 + 1 + ... (10 times)
Progress: 1 → 2 → 3 → ... → 10

Daily Goals

// Complete once per day, reset next day
if !alreadyCompletedToday {
    newProgress = 1
    status = "completed"
}

Example: "Daily login"

First login today: Progress = 1, Status = completed
Second login today: No change (already completed)
Login tomorrow: Reset and complete again

Buffered Processing

Why Buffering?

Without buffering:

1,000 events → 1,000 database queries → High DB load

With buffering:

1,000 events → Buffer (in-memory) → 1 batch UPSERT → Low DB load

Result: 1,000,000× database query reduction (measured with 1M events/hour workload)

Buffering Architecture

type BufferedRepository struct {
    buffer      map[string]*domain.UserGoalProgress  // key: "userId:goalId"
    userMutexes map[string]*sync.Mutex               // per-user locking
    flushTicker *time.Ticker                         // 1-second interval
}

Deduplication Strategy

Problem: Multiple events for same user-goal within flush interval

Solution: Map-based deduplication

// Key format: "userId:goalId"
key := fmt.Sprintf("%s:%s", userId, goalId)

// Only keep latest progress
buffer[key] = latestProgress

Example:

Event 1: User A, Goal X, Progress 1
Event 2: User A, Goal X, Progress 2
Event 3: User A, Goal X, Progress 3

Buffer before flush:
  "userA:goalX" → Progress 3

Database after flush:
  1 UPSERT query (not 3)

Concurrency Control

Per-User Mutex:

// Lock user's mutex before buffering
userMutex := bufRepo.getUserMutex(userId)
userMutex.Lock()
defer userMutex.Unlock()

// Buffer update (safe from race conditions)
bufRepo.buffer[key] = progress

Why per-user?

Allows concurrent processing of different users (high throughput)
Prevents race conditions for same user (correctness)
Scales better than global mutex

Configuration

Challenge Configuration

Same challenges.json as Backend Service (must be identical):

{
  "challenges": [
    {
      "id": "daily-quests",
      "goals": [
        {
          "id": "daily-login",
          "type": "daily",
          "event_source": "login",
          "requirement": {
            "target": 1
          }
        },
        {
          "id": "win-5-matches",
          "type": "absolute",
          "event_source": "statistic:match_wins",
          "requirement": {
            "target": 5
          }
        }
      ]
    }
  ]
}

IMPORTANT: Copy config/challenges.json from Backend Service or use shared volume in production.

Buffer Configuration

Environment variables for tuning buffer behavior:

# Flush interval (how often to write to DB)
BUFFER_FLUSH_INTERVAL=1s   # Default: 1 second

# Max buffer size (force flush if exceeded)
BUFFER_MAX_SIZE=10000      # Default: 10,000 updates

# Database batch size (UPSERT batch size)
DB_BATCH_SIZE=1000         # Default: 1,000 rows per query

Tuning Tips:

High throughput (1,000+ events/sec): Decrease flush interval to 500ms
Low throughput (< 100 events/sec): Increase flush interval to 2s
Memory constrained: Decrease max buffer size to 5,000

Development

Project Structure

extend-challenge-event-handler/
├── cmd/
│   └── main.go                    # Service entrypoint
├── internal/
│   ├── processor/                 # Event processing logic
│   │   ├── event_processor.go    # Main processor
│   │   └── goal_matcher.go       # Goal lookup by event source
│   ├── buffered/                  # Buffered repository
│   │   └── buffered_repository.go
│   └── handler/                   # gRPC handlers
│       └── event_handler.go
├── config/                        # Configuration files
│   └── challenges.json
├── tests/
│   ├── unit/                      # Unit tests
│   └── integration/               # Integration tests
├── Dockerfile
├── Makefile
├── go.mod
└── README.md

Key Components

1. Event Processor (`internal/processor/`)

Parses AGS events (IAM login, Statistic updates)
Finds affected goals using in-memory cache
Calculates new progress based on goal type
Delegates to BufferedRepository for storage

2. Buffered Repository (`internal/buffered/`)

Implements GoalRepository interface with buffering
In-memory map for deduplication
Per-user mutex for concurrency control
Periodic flush with batch UPSERT

3. Goal Matcher (`internal/processor/`)

In-memory cache: map[eventSource][]Goal
O(1) lookup by event source
Built on service startup from challenges.json

Testing

Unit Tests

# Run all unit tests
make test

# With coverage
make test-coverage

# Specific package
go test ./internal/processor/... -v

Target: 80%+ code coverage

Integration Tests

# Setup test database (one-time)
make test-integration-setup

# Run integration tests
make test-integration-run

# Teardown test database
make test-integration-teardown

# All-in-one
make test-integration

Load Testing

Test buffering performance with high event volume:

# Generate 10,000 events
cd ../extend-challenge-demo-app
go run main.go load-test --events 10000

# Check metrics
curl http://localhost:8081/metrics | grep challenge_event_handler

Performance

Benchmarks

Event Processing: < 50ms per event (p95)
Buffer Flush: < 20ms for 1,000 rows (p95)
Throughput: 500+ events/sec tested, 1,000+ events/sec target
Memory: < 100MB for 10,000 buffered updates

Query Reduction

Without buffering:

1,000,000 events/hour = 277 events/sec = 277 DB queries/sec

With buffering (1s flush interval):

1,000,000 events/hour → ~1,000 batch UPSERTs/hour = 0.3 queries/sec

Reduction factor: 1,000,000× (measured with realistic workload)

See Platform docs - PERFORMANCE_BASELINE.md for detailed benchmarks.

Deployment

Docker Build

# Build image
docker build -t challenge-event-handler:latest .

# Run container
docker run -p 6566:6566 \
  --env-file .env \
  challenge-event-handler:latest

AccelByte Extend Deployment

Build and push image:

docker build -t your-registry/challenge-event-handler:v1.0.0 .
docker push your-registry/challenge-event-handler:v1.0.0

Deploy using extend-helper-cli:

extend-helper-cli deploy \
  --namespace your-namespace \
  --image your-registry/challenge-event-handler:v1.0.0 \
  --type event-handler

Configure event subscriptions in Extend console:
- Subscribe to {namespace}.iam.account.v1.userLoggedIn
- Subscribe to {namespace}.social.statistic.v1.statItemUpdated
Copy challenges.json to event handler container:
- Use ConfigMap or shared volume
- Ensure identical to Backend Service config

See Platform docs - TECH_SPEC_DEPLOYMENT.md for detailed deployment guide.

Observability

Metrics

Prometheus metrics available at http://localhost:8081/metrics:

Metric	Type	Description
`challenge_event_handler_events_total`	Counter	Total events received
`challenge_event_handler_events_processed_total`	Counter	Successfully processed events
`challenge_event_handler_events_failed_total`	Counter	Failed event processing
`challenge_event_handler_event_processing_duration_seconds`	Histogram	Event processing latency
`challenge_event_handler_buffer_size`	Gauge	Current buffer size
`challenge_event_handler_flush_duration_seconds`	Histogram	Flush duration
`challenge_event_handler_db_batch_size`	Histogram	Batch UPSERT size

Logging

Structured logging using zerolog:

{
  "level": "info",
  "event_id": "evt-123",
  "user_id": "abc123",
  "event_type": "login",
  "goals_affected": 3,
  "processing_time_ms": 12,
  "timestamp": "2025-11-10T10:30:00Z"
}

Troubleshooting

Events not processed

Symptom: Events received but progress not updated

Solution:

Check event handler logs for errors
Verify challenges.json matches Backend Service
Ensure goals have correct event_source field
Wait for buffer flush (default: 1 second)

Buffer overflow

Symptom: WARN: Buffer size exceeded max_size, forcing flush

Solution:

Increase BUFFER_MAX_SIZE (default: 10,000)
Decrease BUFFER_FLUSH_INTERVAL (default: 1s)
Add more event handler replicas

High database latency

Symptom: Flush duration > 100ms

Solution:

Decrease DB_BATCH_SIZE (default: 1,000)
Add database indexes (already optimized)
Increase database connection pool (default: 25)
Consider database scaling (read replicas, partitioning)

Memory leak

Symptom: Memory usage keeps growing

Solution:

Check buffer is being flushed (metrics: challenge_event_handler_buffer_size)
Verify flush ticker is running (check logs)
Restart service (fire-and-forget design allows restarts)

Dependencies

Core Dependencies

extend-challenge-common v0.8.0 - Shared library
lib/pq v1.10.9 - PostgreSQL driver
rs/zerolog v1.34.0 - Structured logging
prometheus/client_golang v1.15.1 - Metrics

Version Management

To update common library:

go get github.com/AccelByte/extend-challenge-common@v0.9.0
go mod tidy

Contributing

See Platform repo - CONTRIBUTING.md

License

Apache 2.0 License

Links

Platform Repo: https://github.com/AccelByte/extend-challenge-platform
Common Library: https://github.com/AccelByte/extend-challenge-common
Backend Service: https://github.com/AccelByte/extend-challenge-service
Demo App: https://github.com/AccelByte/extend-challenge-demo-app
AccelByte Docs: https://docs.accelbyte.io/extend/

Name		Name	Last commit message	Last commit date
Latest commit History 12 Commits
config		config
demo		demo
docs		docs
pkg		pkg
.dockerignore		.dockerignore
.env.template		.env.template
.gitignore		.gitignore
.golangci.yml		.golangci.yml
Dockerfile		Dockerfile
LICENSE.txt		LICENSE.txt
Makefile		Makefile
README.md		README.md
docker-compose.test.yml		docker-compose.test.yml
docker-compose.yaml		docker-compose.yaml
go.mod		go.mod
go.sum		go.sum
main.go		main.go
proto.sh		proto.sh
renovate.json		renovate.json

License

AccelByte/extend-challenge-event-handler

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AccelByte Extend Challenge Event Handler

Service Overview

Purpose

Architecture

Key Features

Quick Start

Prerequisites

1. Clone Repository

2. Install Dependencies

3. Configure Environment

4. Run Service

5. Test Event Processing

Event Processing

Supported Event Types

1. IAM Login Events

2. Statistic Update Events

Event Processing Flow

Progress Calculation by Goal Type

Absolute Goals

Increment Goals

Daily Goals

Buffered Processing

Why Buffering?

Buffering Architecture

Deduplication Strategy

Concurrency Control

Configuration

Challenge Configuration

Buffer Configuration

Development

Project Structure

Key Components

1. Event Processor (internal/processor/)

2. Buffered Repository (internal/buffered/)

3. Goal Matcher (internal/processor/)

Testing

Unit Tests

Integration Tests

Load Testing

Performance

Benchmarks

Query Reduction

Deployment

Docker Build

AccelByte Extend Deployment

Observability

Metrics

Logging

Troubleshooting

Events not processed

Buffer overflow

High database latency

Memory leak

Dependencies

Core Dependencies

Version Management

Contributing

License

Links

About

Resources

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1. Event Processor (`internal/processor/`)

2. Buffered Repository (`internal/buffered/`)

3. Goal Matcher (`internal/processor/`)

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