golib/httpserver/pool

HTTP Server Pool Manager

Thread-safe pool manager for multiple HTTP servers with unified lifecycle control, advanced filtering, and monitoring integration.

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Table of Contents

• Overview
  • Design Philosophy
  • Key Features
• Architecture
  • Component Diagram
  • Data Flow
• Performance
  • Characteristics
  • Complexity
  • Memory Usage
• Use Cases
• Quick Start
  • Installation
  • Basic Usage
  • Multiple Servers
  • Filtering
  • Lifecycle Management
• Best Practices
• API Reference
  • Pool Interface
  • Configuration
  • Filtering
  • Error Codes
• Contributing
• Improvements & Security
• Resources
• AI Transparency
• License

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Overview

The pool package provides unified management for multiple HTTP server instances through a thread-safe pool abstraction. It enables simultaneous operation of servers with different configurations while providing centralized lifecycle control, advanced filtering capabilities, and integrated monitoring.

Design Philosophy

1. Unified Management: Control multiple heterogeneous servers as a single logical unit.
2. Thread Safety First: All operations protected by sync.RWMutex for concurrent safety.
3. Flexibility: Support for dynamic server addition, removal, and configuration updates.
4. Observability: Built-in monitoring and health check integration for all pooled servers.
5. Error Aggregation: Collect and report errors from all servers systematically.

Key Features

• ✅ Unified Lifecycle: Start, stop, and restart all servers with single operations.
• ✅ Thread-Safe Operations: Concurrent-safe server management using sync.RWMutex.
• ✅ Advanced Filtering: Query servers by name, bind address, or expose address with regex support.
• ✅ Dynamic Management: Add, remove, and update servers during operation without downtime.
• ✅ Monitoring Integration: Collect health and metrics data from all servers.
• ✅ Configuration Helpers: Bulk operations on server configurations with validation.
• ✅ Extensive Testing: 80.4% coverage with race detection and comprehensive test scenarios.

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Architecture

Component Diagram

┌────────────────────────────────────────────────────┐
│                        Pool                        │
├────────────────────────────────────────────────────┤
│                                                    │
│  ┌──────────────┐        ┌──────────────────────┐  │
│  │   Context    │        │   Handler Function   │  │
│  │   Provider   │        │   (shared optional)  │  │
│  └──────┬───────┘        └──────────┬───────────┘  │
│         │                           │              │
│         ▼                           ▼              │
│  ┌──────────────────────────────────────────────┐  │
│  │     Server Map (libctx.Config[string])       │  │
│  │     Key: Bind Address (e.g., "0.0.0.0:8080") │  │
│  │     Value: libhtp.Server instance            │  │
│  └──────────────────────────────────────────────┘  │
│         │                                          │
│         ▼                                          │
│  ┌─────────────────────────────────────────────┐   │
│  │  Individual Server Instances                │   │
│  │                                             │   │
│  │  Server 1 ──┐  Server 2 ──┐  Server N ──┐   │   │
│  │  :8080      │  :8443      │  :9000      │   │   │
│  │  HTTP       │  HTTPS      │  Custom     │   │   │
│  └─────────────────────────────────────────────┘   │
│                                                    │
│  ┌─────────────────────────────────────────────┐   │
│  │          Pool Operations                    │   │
│  │  - Walk: Iterate all servers                │   │
│  │  - WalkLimit: Iterate specific servers      │   │
│  │  - Filter: Query by criteria                │   │
│  │  - Start/Stop/Restart: Lifecycle            │   │
│  │  - Monitor: Health and metrics              │   │
│  └─────────────────────────────────────────────┘   │
│                                                    │
└────────────────────────────────────────────────────┘

Data Flow

Server Lifecycle:

1. Configuration Phase: Servers defined via libhtp.Config
2. Pool Creation: New() creates empty pool or with initial servers
3. Server Addition: StoreNew() validates config and adds server to map
4. Lifecycle Control: Start() initiates all servers concurrently
5. Runtime Operations: Filter, Walk, Monitor during operation
6. Graceful Shutdown: Stop() drains and closes all servers

Error Handling:

1. Validation errors collected during config validation
2. Startup errors aggregated during Start()
3. Shutdown errors collected during Stop()
4. All errors use liberr.Error with proper code hierarchy

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Performance

Characteristics

Operation Complexity:

• Store/Load/Delete: O(1) average, O(n) worst case (map operations)
• Walk/WalkLimit: O(n) where n is number of servers
• Filter: O(n) with regex matching overhead
• List: O(n) + O(m) where m is filtered result size
• Start/Stop/Restart: O(n) parallel server operations

Memory Usage:

• Base pool overhead: ~200 bytes
• Per-server overhead: ~100 bytes (map entry)
• Total: Base + (n × Server size) + (n × Overhead)
• Typical pool with 10 servers: ~50KB

Concurrency:

• Read operations scale with goroutines (RLock)
• Write operations serialize (Lock)
• Server lifecycle operations run concurrently
• No goroutine leaks during normal operation
• Zero race conditions verified with -race detector

Complexity

Operation	Time	Space	Notes
New	O(1)	O(1)	Constant initialization
StoreNew	O(1)	O(1)	Map insertion
Load	O(1)	O(1)	Map lookup
Delete	O(1)	O(1)	Map deletion
Walk	O(n)	O(1)	Iterate all servers
Filter	O(n)	O(m)	m = result size
Start	O(n)	O(n)	Parallel goroutines
Stop	O(n)	O(n)	Parallel goroutines

Memory Usage

• Sequential Write: Zero allocations per operation
• Parallel Write: ~1 allocation per writer (goroutine stack)
• Struct Overhead: ~1KB base size (atomic values, maps)

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Use Cases

Multi-Port HTTP Server

Run HTTP and HTTPS servers simultaneously:

httpCfg := libhtp.Config{
    Name:   "http",
    Listen: ":80",
    Expose: "http://example.com",
}

httpsCfg := libhtp.Config{
    Name:   "https",
    Listen: ":443",
    Expose: "https://example.com",
}

p := pool.New(nil, sharedHandler)
p.StoreNew(httpCfg, nil)
p.StoreNew(httpsCfg, nil)
p.Start(context.Background())

Microservices Gateway

Route different services on different ports:

configs := pool.Config{
    makeConfig("users-api", ":8081"),
    makeConfig("orders-api", ":8082"),
    makeConfig("payments-api", ":8083"),
}

p, _ := configs.Pool(nil, nil, logger)
p.Start(context.Background())

Development vs Production

Different configurations per environment:

var configs pool.Config
if isProd {
    configs = makeTLSConfigs()
} else {
    configs = makeHTTPConfigs()
}

p, _ := configs.Pool(ctx, handler, logger)

Admin and Public Separation

Isolate administrative interfaces:

publicCfg := libhtp.Config{
    Name:   "public",
    Listen: "0.0.0.0:8080",
    Expose: "https://api.example.com",
}

adminCfg := libhtp.Config{
    Name:   "admin",
    Listen: "127.0.0.1:9000", // localhost only
    Expose: "http://localhost:9000",
}

---

Quick Start

Installation

go get github.com/nabbar/golib/httpserver/pool

Basic Usage

package main

import (
    "context"
    "net/http"
    
    libhtp "github.com/nabbar/golib/httpserver"
    "github.com/nabbar/golib/httpserver/pool"
)

func main() {
    // Create pool
    p := pool.New(nil, nil)
    
    // Configure server
    cfg := libhtp.Config{
        Name:   "api-server",
        Listen: "0.0.0.0:8080",
        Expose: "http://localhost:8080",
    }
    cfg.RegisterHandlerFunc(func() map[string]http.Handler {
        return map[string]http.Handler{
            "/": http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
                w.Write([]byte("Hello from pool!"))
            }),
        }
    })
    
    // Add to pool
    p.StoreNew(cfg, nil)
    
    // Start server
    p.Start(context.Background())
    
    // Graceful shutdown
    defer p.Stop(context.Background())
}

Multiple Servers

configs := pool.Config{
    {Name: "api", Listen: ":8080", Expose: "http://localhost:8080"},
    {Name: "admin", Listen: ":9000", Expose: "http://localhost:9000"},
}

configs.SetHandlerFunc(sharedHandler)

p, err := configs.Pool(nil, nil, nil)
if err != nil {
    log.Fatal(err)
}

p.Start(context.Background())

Filtering

// Filter by name pattern
apiServers := p.Filter(srvtps.FieldName, "", "^api-.*")

// Filter by bind address
localServers := p.Filter(srvtps.FieldBind, "", "^127\\.0\\.0\\.1:.*")

// List server names
names := p.List(srvtps.FieldName, srvtps.FieldName, "", ".*")

Lifecycle Management

// Check if servers are running
if p.IsRunning() {
    log.Println("Servers are active")
}

// Get uptime
uptime := p.Uptime()

// Restart all servers
p.Restart(context.Background())

// Get monitoring data
version := libver.Version{}
monitors, _ := p.Monitor(version)

---

Best Practices

DO:

• ✅ Validate all configurations before pool creation
• ✅ Use unique bind addresses for each server
• ✅ Set appropriate context timeouts for Start/Stop operations
• ✅ Check error codes for specific failure types
• ✅ Use Filter operations to manage subsets of servers
• ✅ Clean up pools with defer Stop(ctx)
• ✅ Use monitoring integration for production observability

DON'T:

• ❌ Don't assume all operations succeed (check errors)
• ❌ Don't use the same bind address for multiple servers
• ❌ Don't ignore validation errors
• ❌ Don't block indefinitely on Start/Stop (use context timeouts)
• ❌ Don't modify server configurations directly (use pool methods)
• ❌ Don't forget to handle partial failures during batch operations

---

API Reference

Pool Interface

Lifecycle Management:

• Start(ctx context.Context) error - Start all servers
• Stop(ctx context.Context) error - Stop all servers gracefully
• Restart(ctx context.Context) error - Restart all servers
• IsRunning() bool - Check if at least one server is running
• Uptime() time.Duration - Get maximum uptime of all servers

Server Management:

• Store(srv libhtp.Server) - Add pre-configured server
• StoreNew(cfg libhtp.Config, def liblog.FuncLog) error - Create and add server
• Load(bindAddress string) libhtp.Server - Retrieve server by bind address
• Delete(bindAddress string) - Remove server from pool
• LoadAndDelete(bindAddress string) (libhtp.Server, bool) - Atomic load and delete
• Clean() - Remove all servers

Iteration:

• Walk(fct FuncWalk) - Iterate all servers
• WalkLimit(fct FuncWalk, bindAddress ...string) - Iterate specific servers

Filtering:

• Has(bindAddress string) bool - Check if server exists
• Len() int - Get server count
• Filter(field srvtps.Field, pattern, regex string) Pool - Create filtered pool
• List(source, target srvtps.Field, pattern, regex string) []string - Extract field values

Pool Operations:

• Clone(ctx context.Context) Pool - Create independent copy
• Merge(p Pool, def liblog.FuncLog) error - Merge another pool
• Handler(fct srvtps.FuncHandler) - Register shared handler

Monitoring:

• MonitorNames() []string - Get monitor identifiers
• Monitor(vrs libver.Version) ([]montps.Monitor, liberr.Error) - Collect monitoring data

Configuration

Config Type:

type Config []libhtp.Config

Methods:

• SetHandlerFunc(fct srvtps.FuncHandler) - Set handler for all configs
• SetDefaultTLS(cfg *tls.Config) - Set TLS configuration
• SetContext(ctx context.Context) - Set context provider
• Pool(ctx context.Context, hdl srvtps.FuncHandler, log liblog.FuncLog) (Pool, liberr.Error) - Create pool
• Walk(fct FuncWalkConfig) - Iterate configurations
• Validate() liberr.Error - Validate all configurations

Filtering

Field Types:

• FieldName - Server name
• FieldBind - Bind address (e.g., "127.0.0.1:8080")
• FieldExpose - Expose address (e.g., "http://localhost:8080")

Pattern Matching:

• Exact match: Use pattern parameter
• Regex match: Use regex parameter
• Case-insensitive for exact matches
• Go regex syntax for regex matches

Error Codes

• ErrorParamEmpty - Invalid or empty parameters
• ErrorPoolAdd - Failed to add server to pool
• ErrorPoolValidate - Configuration validation failure
• ErrorPoolStart - One or more servers failed to start
• ErrorPoolStop - One or more servers failed to stop
• ErrorPoolRestart - One or more servers failed to restart
• ErrorPoolMonitor - Monitoring operation failure

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Contributing

Contributions are welcome! Please ensure:

• ✅ All tests pass with race detector enabled
• ✅ Code coverage remains ≥80%
• ✅ GoDoc comments for all exported functions
• ✅ Follow existing code style and patterns
• ✅ Add tests for new features

See TESTING.md for detailed test documentation.

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Improvements & Security

Current Status

The pool package is production-ready with:

• ✅ Thread-safe concurrent operations
• ✅ 80.4% test coverage with comprehensive scenarios
• ✅ Zero race conditions verified with -race detector
• ✅ Error handling with liberr.Error hierarchy

Future Enhancements (Non-urgent)

The following enhancements could be considered for future versions:

1. Automatic Port Allocation: Dynamic port assignment for servers
2. Health Checks: Automatic server health monitoring and restart
3. Load Balancing: Built-in traffic distribution between servers
4. Configuration Reload: Hot-reload of server configurations
5. Metrics Export: Optional integration with Prometheus

These are optional improvements and not required for production use. The current implementation is stable and performant.

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Resources

Package Documentation

• GoDoc - Complete API reference with function signatures, method descriptions, and runnable examples. Essential for understanding the public interface and usage patterns.

• doc.go - In-depth package documentation including design philosophy, architecture diagrams, thread-safety guarantees, and implementation details. Provides detailed explanations of internal mechanisms and best practices for production use.

• TESTING.md - Comprehensive test suite documentation covering test architecture, BDD methodology with Ginkgo v2, 80.4% coverage analysis, and guidelines for writing new tests. Includes troubleshooting and test inventory.

Related golib Packages

• github.com/nabbar/golib/httpserver - Individual HTTP server implementation with TLS support, graceful shutdown, and monitoring integration.

• github.com/nabbar/golib/httpserver/types - Server type definitions and interfaces used throughout the pool package.

• github.com/nabbar/golib/context - Context management utilities for server operations.

External References

• net/http - Go standard library HTTP package. The pool manages multiple http.Server instances with unified control.

• Effective Go - Official Go programming guide covering best practices for interfaces, error handling, and concurrency patterns.

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AI Transparency

In compliance with EU AI Act Article 50.4: AI assistance was used for testing, documentation, and bug resolution under human supervision. All core functionality is human-designed and validated.

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License

MIT License - See LICENSE file for details.

Copyright (c) 2025 Nicolas JUHEL

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Maintained by: Nicolas JUHEL Package: github.com/nabbar/golib/httpserver/pool Version: See releases for versioning