loadtest

Load Test Example

A performance benchmark for the Event Sourcing pillar, measuring throughput and latency of aggregate operations.

What it demonstrates

1. Event Sourcing performance

   • Load/save cycles with optimistic concurrency
   • Snapshot optimization impact
   • Event replay performance

2. Backend comparison

   • NATS JetStream (production)
   • In-memory (baseline)

3. Caching strategies

   • LRU cache effectiveness
   • Memory vs throughput tradeoffs

Running

cd examples/loadtest
go run .

The benchmark will:

1. Start a NATS container (via testcontainers)
2. Run N aggregate operations across U unique users
3. Report progress every B operations
4. Print final throughput and memory stats

Configuration

All settings are configurable via environment variables:

Examples

# Quick test with in-memory backend
BACKEND=mem N=10000 go run .

# Test without snapshots (replay all events)
SNAPSHOT=false N=10000 go run .

# Test with caching enabled
CACHE=true N=50000 go run .

# Full verification mode (load after each save)
LOAD_AFTER_SAVE=true N=10000 go run .

Sample output

=== Load Test Configuration ===
  Backend:         nats
  Total ops:       50000
  Unique users:    100
  Batch size:      1000
  Snapshots:       true
  Cache:           false
  Load after save: false

level=INFO msg="starting NATS container..."
level=INFO msg="NATS ready" url=nats://172.17.0.2:4222
level=INFO msg="=== Starting Load Test ==="
.......... |  1000 ops |    892 ms |   1121 ops/s | 24/36 MiB (heap/sys)
.......... |  1000 ops |    756 ms |   1323 ops/s | 26/36 MiB (heap/sys)
.......... |  1000 ops |    743 ms |   1346 ops/s | 28/36 MiB (heap/sys)
...

=== Results ===
  Total time:    38.234 seconds
  Total ops:     50000
  Avg rate:      1308 ops/s
  Final memory:  18 MiB heap, 36 MiB sys

Interpreting results

• ops/s - Higher is better; affected by backend, network, and snapshot frequency
• heap/sys - Memory usage; heap grows with aggregate cache, sys is total from OS
• Batch variance - Large swings may indicate GC pauses or snapshot writes

Typical performance

Code structure

// 1. Define aggregate with events
type User struct {
    es.BaseAggregate
    Email string
}

func (u *User) ChangeEmail(email string) error {
    return es.RaiseAndApply(u, &EmailChanged{NewEmail: email})
}

// 2. Load, modify, save cycle
user, _ := repo.GetOrCreate(ctx, userID, es.WithSnapshot(true))
user.ChangeEmail("new@example.com")
repo.Save(ctx, user, es.WithSnapshot(true))

Task integration

This benchmark is also available via the task runner:

task loadtest                    # Default settings
N=100000 CACHE=true task loadtest  # Custom settings