Generic Pub/Sub Library

A comprehensive, production-ready Go library that provides a unified interface for publish-subscribe messaging across multiple cloud providers and messaging services. This library abstracts the complexity of different pub/sub implementations while providing advanced features like batch publishing, health monitoring, and graceful shutdown.

🚀 Features

Core Functionality

• Universal Interface: Single API that works with multiple pub/sub providers
• Single & Batch Publishing: Publish individual messages or batches for improved performance
• Asynchronous Consumption: Non-blocking message consumption with multiple listeners
• Message Acknowledgment: Reliable message processing with acknowledgment support
• Health Monitoring: Built-in health checks and connectivity monitoring
• Graceful Shutdown: Proper resource cleanup and coordinated shutdown

Supported Providers

• ✅ PubNub: Real-time messaging with global distribution
• ✅ Google Cloud Pub/Sub: Scalable, fully-managed messaging service
• 🔄 More providers coming soon (AWS SNS/SQS, Azure Service Bus, Apache Kafka)

Advanced Features

• Connection Management: Automatic reconnection with configurable backoff policies
• Error Handling: Comprehensive error categorization and monitoring
• Structured Logging: Integration with structured logging libraries
• Metrics Collection: Detailed publishing and consumption metrics
• Concurrent Processing: Optimized for high-throughput scenarios
• Production Ready: Battle-tested patterns for enterprise environments

📦 Installation

go get github.com/piyushkumar96/generic-pubsub

🏁 Quick Start

PubNub Example

package main

import (
    "context"
    "log"
    
    ae "github.com/piyushkumar96/app-error"
    l "github.com/piyushkumar96/generic-logger"
    pubsub "github.com/piyushkumar96/generic-pubsub"
)

func main() {
    // Create error channel
    errorChan := make(chan *ae.AppError, 5)
    
    // Create PubNub client
    client := pubsub.NewPubNubClient(&pubsub.PubNubOptions{
        UUID:             "your-unique-client-id",
        PublishKey:       "your-publish-key",
        SubscribeKey:     "your-subscribe-key",
        PublishChannel:   "my-channel",
        SubscriptionList: []string{"my-channel"},
        IsSSLSecure:      true,
        MaxRetry:         3,
    }, l.Logger, errorChan)
    
    ctx := context.Background()
    
    // Publish a message
    message := []byte(`{"hello": "world"}`)
    txnData, err := client.Publish(ctx, message)
    if err != nil {
        log.Fatalf("Failed to publish: %v", err)
    }
    
    log.Printf("Published message ID: %s", txnData.EventID)
}

GCP Pub/Sub Example

package main

import (
    "context"
    "log"
    
    ae "github.com/piyushkumar96/app-error"
    l "github.com/piyushkumar96/generic-logger"
    pubsub "github.com/piyushkumar96/generic-pubsub"
)

func main() {
    // Create error channel
    errorChan := make(chan *ae.AppError, 5)
    
    // Create GCP client
    client, err := pubsub.NewGCPPubSubClient(context.Background(), &pubsub.GCPPubSubOptions{
        ProjectID:      "your-gcp-project",
        TopicID:        "your-topic",
        SubscriptionID: "your-subscription",
        CredsFilePath:  "/path/to/service-account.json",
    }, l.Logger, errorChan)
    if err != nil {
        log.Fatalf("Failed to create client: %v", err)
    }
    defer client.Teardown(context.Background())
    
    // Publish a message
    message := []byte(`{"hello": "world"}`)
    txnData, err := client.Publish(context.Background(), message)
    if err != nil {
        log.Fatalf("Failed to publish: %v", err)
    }
    
    log.Printf("Published message ID: %s", txnData.EventID)
}

📚 Comprehensive Examples

We provide detailed examples for different use cases and complexity levels:

🔰 Getting Started

• PubNub Example: Complete PubNub implementation with advanced features
• GCP Pub/Sub Example: Enterprise-grade GCP Pub/Sub implementation

📖 Example Features

Feature	PubNub Example	GCP Pub/Sub Example
Single Message Publishing	✅	✅
Batch Message Publishing	✅ (5 messages)	✅ (8 messages)
Multiple Listeners	✅ (2 listeners)	✅ (2 listeners)
Message Acknowledgment	✅ Message Actions	✅ Native Ack
Health Monitoring	✅ Heartbeat	✅ Topic Existence
Graceful Shutdown	✅ Signal Handling	✅ Coordinated Cleanup
Error Monitoring	✅ Categorized	✅ Production Patterns
Metrics Collection	✅ Detailed Stats	✅ Batch Analytics

🔧 API Reference

Core Interface

type IPubSub interface {
    // Publish sends a single message
    Publish(ctx context.Context, msg []byte) (EventTxnData, *ae.AppError)
    
    // PublishBatch sends multiple messages
    PublishBatch(ctx context.Context, msgs [][]byte) ([]EventTxnData, *ae.AppError)
    
    // Listen starts consuming messages
    Listen(ctx context.Context) *ae.AppError
    
    // ListenWithWait integrates with WaitGroup
    ListenWithWait(ctx context.Context, wg *sync.WaitGroup) *ae.AppError
    
    // AcknowledgeMessage confirms message processing
    AcknowledgeMessage(ctx context.Context, msgID string) *ae.AppError
    
    // CheckHealth verifies client connectivity
    CheckHealth(ctx context.Context) (bool, *ae.AppError)
    
    // Teardown cleans up resources
    Teardown(ctx context.Context)
}

Data Structures

EventTxnData

Contains comprehensive metadata about published messages:

type EventTxnData struct {
    EventID            string        // Unique message identifier
    SequenceNo         int           // Position in batch (for batch operations)
    IsPublished        bool          // Success status
    MessageSizeInBytes int           // Message payload size
    TimeTakenToPublish time.Duration // Publishing latency
    Timestamp          int64         // Unix timestamp
    Error              error         // Error if publishing failed
}

ConsumedMessage

Represents received messages with metadata:

type ConsumedMessage struct {
    Data []byte                    // Raw message payload
    Meta map[string]interface{}    // Provider-specific metadata
}

⚙️ Configuration

PubNub Options

type PubNubOptions struct {
    UUID                    string                    // Client identifier
    PublishKey              string                    // PubNub publish key
    SubscribeKey            string                    // PubNub subscribe key
    SecretKey               string                    // Optional secret key
    IsSSLSecure             bool                      // Enable SSL/TLS
    PublishChannel          string                    // Default publish channel
    SubscriptionList        []string                  // Channels to subscribe to
    BackoffPolicy           PubnubReconnectBackoff   // Reconnection strategy
    ConnectTimeoutInSec     int                      // Connection timeout
    MaxRetry                int32                    // Max retry attempts
    CloseListenersOnExit    bool                     // Auto-close on exit
    EnableDebugMode         bool                     // Debug logging
}

GCP Pub/Sub Options

type GCPPubSubOptions struct {
    ProjectID       string // GCP project identifier
    TopicID         string // Pub/Sub topic name
    SubscriptionID  string // Subscription name
    CredsFilePath   string // Service account key path
    EnableDebugMode bool   // Debug logging
}

🔒 Authentication & Security

PubNub

• API Keys: Use publish/subscribe keys from PubNub console
• SSL/TLS: Enable IsSSLSecure for encrypted connections
• Secret Keys: Optional additional security layer

GCP Pub/Sub

• Service Account: Use JSON key file for authentication
• IAM Permissions: Ensure account has pubsub.editor or appropriate roles
• Network Security: Configure VPC and firewall rules as needed

🚦 Error Handling

The library provides comprehensive error categorization:

General Errors (ERR_PS_1xxx)

• PublishEvent: Single message publishing failure
• PublishEventBatch: Batch publishing failure
• ContextCancelled: Operation cancelled
• HealthCheck: Health monitoring failure

PubNub Errors (ERR_PS_2xxx)

• EmptySubscriptionList: No channels configured
• AlreadyListening: Client already in listening state
• PNCliBadRequest: Invalid request parameters
• PNCliAccessDenied: Authentication failure

GCP Pub/Sub Errors (ERR_PS_3xxx)

• GCPPSClientInit: Client initialization failure
• GCPPSReceiveEvent: Message receiving failure
• GCPPSClientTeardown: Cleanup failure

📊 Monitoring & Observability

Built-in Metrics

• Publishing Metrics: Message size, latency, success rates
• Consumption Metrics: Processing time, acknowledgment rates
• Connection Metrics: Health status, reconnection events
• Error Metrics: Categorized error counts and rates

Logging Integration

The library integrates with structured logging libraries:

import l "github.com/piyushkumar96/generic-logger"

// All operations include structured logging
client := pubsub.NewPubNubClient(options, l.Logger, errorChan)

🏗️ Production Best Practices

Resource Management

// Always use context with timeout
ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
defer cancel()

// Proper cleanup
defer client.Teardown(ctx)

Error Monitoring

// Monitor errors in separate goroutine
go func() {
    for err := range errorChan {
        log.Printf("Pub/Sub Error: %s (Code: %s)", err.GetMsg(), err.GetErrCode())
        // Send to monitoring system, implement retry logic, etc.
    }
}()

Graceful Shutdown

// Handle shutdown signals
sigChan := make(chan os.Signal, 1)
signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)

select {
case <-sigChan:
    log.Println("Shutdown signal received")
    client.Teardown(ctx)
}

🧪 Testing

The library includes comprehensive mocks for testing:

import "github.com/piyushkumar96/generic-pubsub/mocks"

func TestMyService(t *testing.T) {
    mockPubSub := mocks.NewMockIPubSub(t)
    mockPubSub.EXPECT().Publish(mock.Anything, mock.Anything).Return(
        pubsub.EventTxnData{EventID: "test-id", IsPublished: true}, nil)
    
    // Test your service with the mock
}

🤝 Contributing

We welcome contributions! Here's how you can help:

1. Fork the Repository
2. Create a Feature Branch: git checkout -b feature/amazing-feature
3. Commit Changes: git commit -m 'Add amazing feature'
4. Push to Branch: git push origin feature/amazing-feature
5. Open a Pull Request

Development Guidelines

• Write Tests: Ensure good test coverage for new features
• Document Code: Add comprehensive comments and documentation
• Follow Conventions: Use existing code style and patterns
• Update Examples: Add examples for new features

📋 Requirements

• Go: Version 1.21 or higher
• Dependencies: See go.mod for complete list

Key Dependencies

• cloud.google.com/go/pubsub - GCP Pub/Sub client
• github.com/pubnub/go/v7 - PubNub Go SDK
• github.com/piyushkumar96/app-error - Structured error handling
• github.com/piyushkumar96/generic-logger - Logging interface

📊 Performance Characteristics

Throughput Benchmarks

• PubNub: Up to 1000 messages/second per client
• GCP Pub/Sub: Up to 10,000 messages/second per client (batch mode)

Latency

• PubNub: ~50-100ms global latency
• GCP Pub/Sub: ~10-50ms within region

Resource Usage

• Memory: ~10MB base + ~1KB per queued message
• CPU: Low overhead with goroutine-based concurrency
• Network: Efficient batching reduces connection overhead

🗺️ Roadmap

Upcoming Features

• AWS SNS/SQS Support: Amazon messaging services
• Azure Service Bus: Microsoft cloud messaging
• Apache Kafka: Distributed streaming platform
• Redis Streams: Redis-based messaging
• NATS: Cloud-native messaging system

Enhancements

• Circuit Breaker: Fault tolerance patterns
• Rate Limiting: Built-in rate limiting capabilities
• Message Encryption: End-to-end encryption support
• Schema Registry: Message schema validation
• Dead Letter Queues: Failed message handling

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

🙏 Acknowledgments

• PubNub Team: For providing excellent real-time messaging infrastructure
• Google Cloud: For the robust and scalable Pub/Sub service
• Go Community: For the amazing ecosystem and tools
• Contributors: Everyone who has contributed to making this library better

📞 Support

• Documentation: Check our comprehensive examples and API reference
• Issues: Report bugs or request features via GitHub Issues
• Discussions: Join community discussions for help and best practices

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