golib/monitor/info

Info Package

Dynamic metadata management for monitors with lazy evaluation, caching, and thread-safe access.

AI Disclaimer: AI tools are used solely to assist with testing, documentation, and bug fixes under human supervision, in compliance with EU AI Act Article 50.4.

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Overview

The info package provides dynamic metadata management for monitor components. It enables lazy-loaded, cached metadata generation with support for both static and runtime-generated information.

Key Features

• Dynamic Name Generation: Generate component names at runtime
• Lazy Evaluation: Info data is generated only when first accessed
• Automatic Caching: Generated data is cached for subsequent reads (zero-copy)
• Thread-Safe: Lock-free reads after initial generation
• Multiple Encoding: JSON, Text, and custom format support
• Flexible Registration: Register generators for name and data separately

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Installation

go get github.com/nabbar/golib/monitor/info

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Quick Start

Static Info

import "github.com/nabbar/golib/monitor/info"

// Create with static name
inf, err := info.New("database-monitor")
if err != nil {
    panic(err)
}

// Access name
fmt.Println(inf.Name())  // Output: database-monitor

Dynamic Info

// Create info with dynamic data
inf, _ := info.New("api-service")

// Register dynamic info generator
inf.RegisterInfo(func() (map[string]interface{}, error) {
    return map[string]interface{}{
        "version":     "1.2.3",
        "build":       getBuildTime(),
        "connections": getActiveConnections(),
        "memory":      getMemoryUsage(),
    }, nil
})

// Info is generated on first access and cached
data := inf.InfoMap()
fmt.Printf("Version: %s\n", data["version"])

// Subsequent calls use cached data (zero-copy)
data2 := inf.InfoMap()  // No function call, instant return

Dynamic Name

inf, _ := info.New("")

// Register name generator
inf.RegisterName(func() (string, error) {
    hostname, _ := os.Hostname()
    return fmt.Sprintf("service-%s", hostname), nil
})

// Name is generated on first access
name := inf.Name()  // Calls generator
name2 := inf.Name()  // Returns cached value

---

Architecture

Component Structure

info/
├── interface.go     # Info interface definition
├── model.go         # Info state management
├── info.go          # Core implementation
└── encode.go        # Encoding support (JSON, Text)

Data Flow

┌─────────────────────────────────────┐
│    Info Instance                     │
│                                      │
│  ┌─────────────┐  ┌──────────────┐ │
│  │ Name Cache  │  │  Data Cache  │ │
│  │ (atomic)    │  │  (atomic)    │ │
│  └──────┬──────┘  └──────┬───────┘ │
│         │                 │         │
│  ┌──────▼──────┐  ┌──────▼───────┐ │
│  │Name         │  │Info          │ │
│  │Generator    │  │Generator     │ │
│  │(FuncName)   │  │(FuncInfo)    │ │
│  └─────────────┘  └──────────────┘ │
└─────────────────────────────────────┘
        │                   │
        │ First access      │ First access
        ▼                   ▼
   "service-name"    {"version": "1.0"}

Thread Safety

• Reads: Lock-free after initial generation (atomic.Value)
• Writes: Protected during registration
• Generation: One-time execution, then cached
• Concurrent Safe: Multiple goroutines can safely access

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API Reference

Info Interface

type Info interface {
    // Name returns the component name
    Name() string
    
    // RegisterName registers a function to generate the name dynamically
    RegisterName(func() (string, error))
    
    // Info returns the info data as a map
    Info() map[string]interface{}
    
    // RegisterInfo registers a function to generate info data dynamically
    RegisterInfo(FuncInfo)
    
    // Encoding
    MarshalText() ([]byte, error)
    MarshalJSON() ([]byte, error)
}

Types

// Function type for dynamic info generation
type FuncInfo func() (map[string]interface{}, error)

// InfoData interface for static info providers
type InfoData interface {
    Info() map[string]interface{}
}

// InfoName interface for static name providers
type InfoName interface {
    Name() string
}

---

Usage Examples

Example 1: Service Metadata

inf, _ := info.New("user-service")

inf.RegisterInfo(func() (map[string]interface{}, error) {
    return map[string]interface{}{
        "version":    version.Get(),
        "build_time": buildTime,
        "git_commit": gitCommit,
        "go_version": runtime.Version(),
    }, nil
})

// First access generates data
data := inf.InfoMap()
log.Printf("Service: %s v%s\n", inf.Name(), data["version"])

// Subsequent accesses use cache (instant)
for i := 0; i < 1000000; i++ {
    _ = inf.InfoMap()  // Zero overhead
}

Example 2: Dynamic Name from Environment

inf, _ := info.New("")

inf.RegisterName(func() (string, error) {
    env := os.Getenv("ENVIRONMENT")
    hostname, _ := os.Hostname()
    return fmt.Sprintf("%s-%s-monitor", env, hostname), nil
})

// Name is generated from environment
name := inf.Name()  // e.g., "production-server01-monitor"

Example 3: Runtime Statistics

inf, _ := info.New("database-pool")

inf.RegisterInfo(func() (map[string]interface{}, error) {
    var mem runtime.MemStats
    runtime.ReadMemStats(&mem)
    
    return map[string]interface{}{
        "goroutines":    runtime.NumGoroutine(),
        "heap_alloc":    mem.HeapAlloc,
        "total_alloc":   mem.TotalAlloc,
        "num_gc":        mem.NumGC,
        "db_conns":      db.Stats().OpenConnections,
        "db_idle":       db.Stats().Idle,
    }, nil
})

// Snapshot current state
data := inf.InfoMap()
fmt.Printf("Goroutines: %d\n", data["goroutines"])

Example 4: Static Info Provider

type ServiceInfo struct {
    Version   string
    BuildTime time.Time
}

func (s ServiceInfo) Info() map[string]interface{} {
    return map[string]interface{}{
        "version":    s.Version,
        "build_time": s.BuildTime.Format(time.RFC3339),
    }
}

// Use static provider
svc := ServiceInfo{
    Version:   "1.0.0",
    BuildTime: time.Now(),
}

inf, _ := info.New("service")
inf.RegisterInfo(func() (map[string]interface{}, error) {
    return svc.Info(), nil
})

Example 5: Error Handling

inf, _ := info.New("external-service")

inf.RegisterInfo(func() (map[string]interface{}, error) {
    // Attempt to fetch info from external source
    resp, err := http.Get("https://api.example.com/info")
    if err != nil {
        // Return error - info won't be cached
        return nil, fmt.Errorf("fetch info: %w", err)
    }
    defer resp.Body.Close()
    
    var data map[string]interface{}
    if err := json.NewDecoder(resp.Body).Decode(&data); err != nil {
        return nil, fmt.Errorf("decode info: %w", err)
    }
    
    return data, nil
})

// If error occurs, function is called again next time
data := inf.InfoMap()  // May be empty if error occurred

---

Encoding

Text Encoding

// Format: key1: value1, key2: value2, ...
text, err := inf.MarshalText()
fmt.Println(string(text))
// Output: version: 1.0.0, build: 2024-01-15, uptime: 3600

JSON Encoding

json, err := inf.MarshalJSON()
fmt.Println(string(json))
// Output: {"version":"1.0.0","build":"2024-01-15","uptime":3600}

---

Performance

Benchmarks

Measured on: AMD Ryzen 9 5950X, 64GB RAM, Go 1.21

Operation	Time	Memory	Notes
Info Creation	850 ns	1.2 KB	One-time
First Name()	450 ns	64 B	Generates + caches
Subsequent Name()	12 ns	0 B	Lock-free read
First InfoMap()	2.1 µs	512 B	Generates + caches
Subsequent InfoMap()	45 ns	0 B	Lock-free read
RegisterInfo	95 ns	48 B	One-time
MarshalText	1.8 µs	320 B	Per call
MarshalJSON	2.3 µs	450 B	Per call

Memory Profile

• Per Info Instance: ~1.2KB base overhead
• Cached Name: ~64B (string)
• Cached Data: Variable (depends on map size)
• After Caching: Zero additional allocations

Caching Efficiency

// First access (cache miss)
data1 := inf.InfoMap()  // Calls generator function

// Subsequent accesses (cache hit)
for i := 0; i < 1000000; i++ {
    data := inf.InfoMap()  // Lock-free, zero allocations
}

// ~45ns per access, 0 allocations per operation

---

Best Practices

1. Generator Functions

// DO: Keep generators lightweight
inf.RegisterInfo(func() (map[string]interface{}, error) {
    return map[string]interface{}{
        "version": "1.0.0",
        "pid":     os.Getpid(),
    }, nil
})

// DON'T: Perform heavy operations
inf.RegisterInfo(func() (map[string]interface{}, error) {
    // Bad: This runs once but blocks first access
    result := heavyComputation()  // Takes seconds
    return map[string]interface{}{
        "result": result,
    }, nil
})

// BETTER: Use background precomputation
inf.RegisterInfo(func() (map[string]interface{}, error) {
    // Access pre-computed value
    return map[string]interface{}{
        "result": cachedResult.Load(),
    }, nil
})

2. Error Handling

// DO: Return errors for failures
inf.RegisterInfo(func() (map[string]interface{}, error) {
    data, err := fetchData()
    if err != nil {
        return nil, err  // Will retry on next access
    }
    return data, nil
})

// DO: Handle errors when accessing
data := inf.InfoMap()
if len(data) == 0 {
    log.Warn("Info data unavailable")
}

3. Data Mutability

// DON'T: Mutate returned map
data := inf.InfoMap()
data["new_key"] = "value"  // Bad: Mutates cached data

// DO: Copy if you need to modify
data := inf.InfoMap()
copied := make(map[string]interface{})
for k, v := range data {
    copied[k] = v
}
copied["new_key"] = "value"  // Safe: Modifies copy

4. Name Generation

// DO: Use static names when possible
inf, _ := info.New("service-name")

// DO: Use dynamic names only when necessary
inf, _ := info.New("")
inf.RegisterName(func() (string, error) {
    return fmt.Sprintf("service-%s", getEnvironment()), nil
})

// DON'T: Use complex generation for simple cases
inf, _ := info.New("")
inf.RegisterName(func() (string, error) {
    // Overkill for static name
    return "service-name", nil
})

---

Testing

Test Coverage

Current coverage: 85.3%

# Run tests
go test ./...

# With coverage
go test -coverprofile=coverage.out ./...

# With race detection
CGO_ENABLED=1 go test -race ./...

Test Files

• info_test.go: Core functionality
• encode_test.go: Encoding formats
• integration_test.go: Real-world scenarios
• edge_cases_test.go: Corner cases
• internal_test.go: Internal implementation
• security_test.go: Security validation

Example Tests

Describe("Info", func() {
    It("should cache generated data", func() {
        callCount := 0
        inf.RegisterInfo(func() (map[string]interface{}, error) {
            callCount++
            return map[string]interface{}{"test": "value"}, nil
        })
        
        // First call triggers generation
        inf.InfoMap()
        Expect(callCount).To(Equal(1))
        
        // Subsequent calls use cache
        inf.InfoMap()
        inf.InfoMap()
        Expect(callCount).To(Equal(1))
    })
})

See ../TESTING.md for detailed testing documentation.

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Contributing

See ../README.md#contributing for contribution guidelines.

AI Usage Reminder: Do not use AI to generate package code. AI may assist with tests, documentation, and bug fixes only.

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Use Cases

1. Microservice Metadata

Expose service version, build info, and runtime statistics:

inf, _ := info.New("user-service")
inf.RegisterInfo(func() (map[string]interface{}, error) {
    return map[string]interface{}{
        "version":     version.Version,
        "commit":      version.GitCommit,
        "build_time":  version.BuildTime,
        "go_version":  runtime.Version(),
        "uptime":      time.Since(startTime).Seconds(),
    }, nil
})

2. Database Connection Info

Track database connection metrics:

inf, _ := info.New("postgres-pool")
inf.RegisterInfo(func() (map[string]interface{}, error) {
    stats := db.Stats()
    return map[string]interface{}{
        "open_connections": stats.OpenConnections,
        "in_use":          stats.InUse,
        "idle":            stats.Idle,
        "wait_count":      stats.WaitCount,
        "max_lifetime":    stats.MaxLifetime.String(),
    }, nil
})

3. Environment-Specific Naming

Generate names based on deployment environment:

inf, _ := info.New("")
inf.RegisterName(func() (string, error) {
    env := os.Getenv("ENV")  // prod, staging, dev
    region := os.Getenv("REGION")  // us-east, eu-west
    return fmt.Sprintf("%s-%s-monitor", env, region), nil
})

4. Cache Monitoring

Expose cache statistics:

inf, _ := info.New("redis-cache")
inf.RegisterInfo(func() (map[string]interface{}, error) {
    info, err := redisClient.Info("stats").Result()
    if err != nil {
        return nil, err
    }
    
    return parseRedisInfo(info), nil
})

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License

MIT License - Copyright (c) 2022 Nicolas JUHEL

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Resources

• Parent Package: github.com/nabbar/golib/monitor
• GoDoc: pkg.go.dev/github.com/nabbar/golib/monitor/info
• Examples: See example_test.go for more usage examples