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# Notifier Microservice
# Notifier Module
A production-ready notification delivery microservice that supports multiple notification channels (Email, Slack, Ntfy, Stdout) with both REST and gRPC APIs running simultaneously.
The **Notifier** module provides a flexible notification system that supports multiple notification modes (e.g., SMTP, SMS, Slack, Ntfy, and Stdout). It can operate as a standalone gRPC or REST microservice, or be used as an imported module in other projects.
[![Go Version](https://img.shields.io/badge/go-1.23.2-blue.svg)](https://golang.org)
[![License](https://img.shields.io/badge/license-MIT-green.svg)](LICENSE)
## Overview
Notifier is a cloud-native microservice designed to handle all your application's notification needs through a single, unified API. Send emails, Slack messages, push notifications, and more with a consistent interface and robust delivery guarantees.
Perfect for:
- Microservices architectures needing centralized notifications
- Applications requiring multiple notification channels
- Systems needing reliable async notification delivery
- Teams wanting to standardize notification handling
## Features
- **Multi-Mode Notification**: Supports different notification methods including SMTP email, SMS, Slack, Ntfy, and standard output.
- **Extensible Design**: Add new notification modes by implementing the `Notifier` interface.
- **gRPC and REST APIs**: Accessible through both gRPC and RESTful APIs, allowing easy integration into various systems.
- **Configuration Management**: Easily configurable for different environments and API keys.
### Core Capabilities
- 🔔 **Multi-Channel Support**: Email (SMTP), Slack, Ntfy.sh, and Stdout
- 🚀 **Dual API**: REST and gRPC running simultaneously in one process
- 📦 **Queue-Based**: Async processing with configurable worker pools
- 🔄 **Retry Logic**: Exponential backoff with configurable attempts
-**Priority Levels**: Low, Normal, High, and Critical
- 📊 **Batch Operations**: Send multiple notifications efficiently
- 🎯 **Status Tracking**: Monitor notification lifecycle and delivery
### Production Features
- ⚙️ **Configuration**: Viper-based with environment variable support
- 🐳 **Containerized**: Multi-stage Docker builds with non-root user
- ☸️ **Kubernetes Ready**: Complete manifests with HPA, health checks, and RBAC
- 🔒 **Secure**: Token-based auth for ntfy, TLS support, secret management
- 📈 **Observable**: Health endpoints, metrics support, structured logging
- 🔌 **Extensible**: Clean interfaces for adding new notifiers
## Quick Start
### 1. Install and Run
```bash
# Clone and install dependencies
git clone https://github.com/igodwin/notifier
cd notifier
go mod tidy
# Build and run
go build -o bin/server ./cmd/server
./bin/server
```
Server starts with:
- **REST API** on `http://localhost:8080`
- **gRPC API** on `localhost:50051`
- **Stdout notifier** enabled by default
### 2. Send Your First Notification
```bash
curl -X POST http://localhost:8080/api/v1/notifications \
-H "Content-Type: application/json" \
-d '{
"type": "stdout",
"subject": "Hello from Notifier!",
"body": "Your first notification",
"recipients": ["console"]
}'
```
The notification appears immediately in the server output. ✅
### 3. Check Status
```bash
# Health check
curl http://localhost:8080/health
# Statistics
curl http://localhost:8080/api/v1/stats
```
## Configuration
### Basic Setup
Create `config.yaml` in the project root:
```yaml
server:
mode: "both" # Options: both, rest, grpc
rest_port: 8080
grpc_port: 50051
host: "0.0.0.0"
queue:
type: "local" # Local in-memory queue
worker_count: 10 # Concurrent workers
retry_attempts: 3
retry_backoff: "exponential"
notifiers:
stdout: true # Always enabled for testing
```
### Email Notifications (SMTP)
```yaml
notifiers:
smtp:
host: "smtp.gmail.com"
port: 587
username: "your-email@gmail.com"
password: "your-app-password"
from: "notifications@yourservice.com"
use_tls: true
```
**Usage:**
```bash
curl -X POST http://localhost:8080/api/v1/notifications \
-H "Content-Type: application/json" \
-d '{
"type": "email",
"subject": "Welcome!",
"body": "Thanks for signing up",
"recipients": ["user@example.com"]
}'
```
### Slack Notifications
```yaml
notifiers:
slack:
webhook_url: "https://hooks.slack.com/services/YOUR/WEBHOOK/URL"
username: "Notifier Bot"
icon_emoji: ":bell:"
```
**Usage:**
```bash
curl -X POST http://localhost:8080/api/v1/notifications \
-H "Content-Type: application/json" \
-d '{
"type": "slack",
"subject": "Deployment Complete",
"body": "v2.0 deployed to production",
"recipients": ["#alerts"]
}'
```
### Ntfy Push Notifications
```yaml
notifiers:
ntfy:
server_url: "https://ntfy.sh"
token: "tk_your_access_token" # Optional, for private topics
default_topic: "myapp-alerts"
```
**Usage:**
```bash
curl -X POST http://localhost:8080/api/v1/notifications \
-H "Content-Type: application/json" \
-d '{
"type": "ntfy",
"priority": 3,
"subject": "Critical Alert",
"body": "Server CPU at 95%",
"recipients": ["alerts"],
"metadata": {
"tags": ["warning", "rotating_light"],
"click": "https://dashboard.example.com"
}
}'
```
See [docs/NTFY_GUIDE.md](docs/NTFY_GUIDE.md) for advanced ntfy features (action buttons, attachments, delays, etc.).
### Environment Variables
Override any config with environment variables:
```bash
export NOTIFIER_SERVER_MODE=both
export NOTIFIER_SERVER_REST_PORT=8080
export NOTIFIER_QUEUE_WORKER_COUNT=20
export NOTIFIER_NOTIFIERS_SMTP_HOST=smtp.gmail.com
export NOTIFIER_NOTIFIERS_SMTP_PASSWORD=secret
export NOTIFIER_NOTIFIERS_NTFY_TOKEN=tk_your_token
```
Format: `NOTIFIER_<SECTION>_<KEY>` (use `_` for nested keys)
## API Reference
### REST Endpoints
| Method | Endpoint | Description |
|--------|----------|-------------|
| `GET` | `/health` | Health check |
| `POST` | `/api/v1/notifications` | Send single notification |
| `POST` | `/api/v1/notifications/batch` | Send multiple notifications |
| `GET` | `/api/v1/notifications` | List notifications (with filters) |
| `GET` | `/api/v1/notifications/{id}` | Get notification by ID |
| `DELETE` | `/api/v1/notifications/{id}` | Cancel pending notification |
| `POST` | `/api/v1/notifications/{id}/retry` | Retry failed notification |
| `GET` | `/api/v1/stats` | Get service statistics |
### Request Format
```json
{
"type": "email|slack|ntfy|stdout",
"priority": 0-3,
"subject": "Notification title",
"body": "Notification body",
"recipients": ["email@example.com", "#channel", "topic"],
"metadata": {
"key": "value"
},
"max_retries": 3
}
```
### Response Format
```json
{
"result": {
"notification_id": "uuid",
"success": true,
"message": "notification queued successfully",
"sent_at": "2025-10-16T21:05:27Z"
}
}
```
### Priority Levels
- `0` - Low (background notifications)
- `1` - Normal (default)
- `2` - High (important updates)
- `3` - Critical (urgent alerts)
### Batch Operations
```bash
curl -X POST http://localhost:8080/api/v1/notifications/batch \
-H "Content-Type: application/json" \
-d '{
"notifications": [
{"type": "email", "subject": "Welcome", ...},
{"type": "slack", "subject": "Alert", ...}
]
}'
```
### Filtering Notifications
```bash
# Get all sent email notifications
curl "http://localhost:8080/api/v1/notifications?type=email&status=sent&limit=10"
# Get recent failures
curl "http://localhost:8080/api/v1/notifications?status=failed&limit=20"
```
## gRPC API
The gRPC service mirrors the REST API with full feature parity. See [api/grpc/notifier.proto](api/grpc/notifier.proto) for definitions.
**Generate Go code:**
```bash
make proto-gen
# or
protoc --go_out=. --go-grpc_out=. api/grpc/notifier.proto
```
**Note:** gRPC server is running but handler implementation is pending. Protobuf definitions are complete.
## Deployment
### Docker
**Build:**
```bash
docker build -t notifier:latest .
```
**Run:**
```bash
docker run -d \
--name notifier \
-p 8080:8080 \
-p 50051:50051 \
-v $(pwd)/config.yaml:/app/config.yaml:ro \
notifier:latest
```
**Docker Compose:**
```bash
docker-compose up -d
```
Includes optional services: Kafka, Prometheus, Grafana (commented out by default)
### Kubernetes
**Deploy:**
```bash
kubectl apply -f k8s/
```
**Included resources:**
- Deployment (3 replicas with rolling updates)
- Services (separate for REST and gRPC)
- ConfigMap (configuration management)
- HPA (auto-scaling 3-10 pods based on CPU/memory)
- Ingress (external access with TLS)
- Secret template (for credentials)
**Access locally:**
```bash
kubectl port-forward svc/notifier-rest 8080:8080
kubectl port-forward svc/notifier-grpc 50051:50051
```
**Using Kustomize:**
```bash
kubectl apply -k k8s/
```
## Architecture
### High-Level Design
```
┌──────────────┐ ┌──────────────┐
│ REST Client │────▶│ REST API │
└──────────────┘ │ (port 8080) │
└──────┬───────┘
┌──────────────┐ │
│ gRPC Client │────▶│ gRPC API │
└──────────────┘ │ (port 50051) │
└──────┬───────┘
┌──────────────────┐
│ Notification │
│ Service │
└────────┬─────────┘
┌──────────────────┐
│ Queue (Local) │◀──┐
└────────┬─────────┘ │
▼ │
┌──────────────────┐ │
│ Worker Pool │───┘
│ (10 workers) │
└────────┬─────────┘
┌─────────────────┼─────────────────┐
▼ ▼ ▼
┌────────┐ ┌──────────┐ ┌──────────┐
│ SMTP │ │ Slack │ │ Ntfy │
│Notifier│ │ Notifier │ │ Notifier │
└────────┘ └──────────┘ └──────────┘
```
### Key Components
- **API Layer**: REST (Gorilla mux) and gRPC (Protocol Buffers)
- **Service Layer**: Business logic, validation, orchestration
- **Queue**: In-memory with optional disk persistence (Kafka planned)
- **Workers**: Concurrent processors with retry logic
- **Notifiers**: Pluggable providers implementing `domain.Notifier`
- **Config**: Viper-based with file + env var support
See [ARCHITECTURE.md](ARCHITECTURE.md) for detailed design documentation.
## Project Structure
```plaintext
```
notifier/
├── api/
│ ├── grpc/ # gRPC service definitions and generated code
│ └── rest/ # REST API handlers and router
│ ├── grpc/
│ └── notifier.proto # gRPC service definition
│ └── rest/
│ ├── handlers.go # HTTP handlers
│ ├── router.go # Route configuration
│ └── types.go # Request/response types
├── cmd/
│ ├── grpcserver/ # Entrypoint for running the gRPC server
── restserver/ # Entrypoint for running the REST server
│ ├── server/main.go # Combined server (recommended)
── grpcserver/main.go # gRPC only
│ └── restserver/main.go # REST only
├── internal/
│ ├── config/ # Configuration loading
│ └── notifier/ # Core notification logic with multiple implementations
├── pkg/
│ ├── grpcclient/ # gRPC client for interacting with the notifier service
└── restclient/ # REST client for interacting with the notifier service
├── Dockerfile # Docker configuration for deploying as a microservice
├── LICENSE # License file
├── README.md # Documentation
└── go.mod # Defines the module's dependencies, module path, and Go version
│ ├── config/
│ └── config.go # Configuration management
│ ├── domain/
│ ├── notification.go # Core types
│ ├── notifier.go # Notifier interface
│ │ └── queue.go # Queue interface
│ ├── notifier/
│ │ ├── notifier.go # Factory & base
│ │ ├── smtp.go # Email notifier
│ │ ├── slack.go # Slack notifier
│ │ ├── ntfy.go # Ntfy notifier
│ │ └── stdout.go # Stdout notifier
│ ├── queue/
│ │ └── local.go # In-memory queue
│ └── service/
│ └── service.go # Business logic
├── k8s/
│ ├── deployment.yaml
│ ├── service.yaml
│ ├── configmap.yaml
│ ├── ingress.yaml
│ ├── hpa.yaml
│ └── kustomization.yaml
├── docs/
│ └── NTFY_GUIDE.md # Ntfy integration guide
├── config.yaml # Default configuration
├── docker-compose.yaml
├── Dockerfile
├── Makefile
├── QUICKSTART.md # API examples
├── ARCHITECTURE.md # Design documentation
└── README.md # This file
```
## Getting Started
## Development
### Prerequisites
- **Go**: Install Go 1.18 or higher.
- **Protocol Buffers**: Required if you want to regenerate gRPC code.
- **Docker** (optional): For containerized deployment.
### Installation
To install the notifier module as a dependency in another Go project, run:
### Build Commands
```bash
go get github.com/igodwin/notifier
make build # Build binaries
make run-rest # Run REST server
make run-grpc # Run gRPC server (when implemented)
make test # Run tests
make lint # Run linter
make proto-gen # Generate protobuf code
make docker-build # Build Docker image
make clean # Clean artifacts
```
### Running the Service
### Adding a New Notifier
#### gRPC Server
To start the gRPC server:
```bash
cd cmd/grpcserver
go run main.go
```
#### REST Server
To start the REST server:
```bash
cd cmd/restserver
go run main.go
```
### Configuration
Configure notification modes via environment variables or a configuration file (e.g., `config.yaml`). Configuration settings may include:
- **SMTP**: SMTP server details, port, credentials.
- **SMS**: SMS provider API keys.
- **Slack**: Slack webhook URLs.
- **Ntfy**: Ntfy service URL and options.
For example, using a `config.yaml`:
```yaml
smtp:
server: "smtp.example.com"
port: 587
username: "user@example.com"
password: "password"
slack:
webhook_url: "https://hooks.slack.com/services/..."
```
### Usage
#### Using gRPC API
1. Define a gRPC client using the `pkg/grpcclient` package.
2. Call `SendNotification` to send a message through a chosen notification method.
1. Create `internal/notifier/mynotifier.go`
2. Implement `domain.Notifier` interface
3. Add config struct to `internal/config/config.go`
4. Register in `cmd/server/main.go`
5. Update `config.yaml` with example config
6. Add tests
Example:
```go
client, err := grpcclient.NewClient("localhost:50051")
if err != nil {
log.Fatalf("Failed to create gRPC client: %v", err)
type MyNotifier struct {
BaseNotifier
config *MyNotifierConfig
}
resp, err := client.SendNotification("recipient@example.com", "Hello via gRPC!")
if err != nil {
log.Fatalf("Failed to send notification: %v", err)
func (m *MyNotifier) Send(ctx context.Context, n *domain.Notification) (*domain.NotificationResult, error) {
// Implementation
}
```
#### Using REST API
See [ARCHITECTURE.md](ARCHITECTURE.md) for detailed guide.
1. Define a REST client using the `pkg/restclient` package.
2. Call `SendNotification` via REST.
## Documentation
Example:
- [QUICKSTART.md](QUICKSTART.md) - Quick start guide with examples
- [ARCHITECTURE.md](ARCHITECTURE.md) - Architecture and design details
- [docs/NTFY_GUIDE.md](docs/NTFY_GUIDE.md) - Ntfy integration guide
- [api/grpc/notifier.proto](api/grpc/notifier.proto) - gRPC API definition
```go
client := restclient.NewClient("http://localhost:8080")
err := client.SendNotification("recipient@example.com", "Hello via REST!")
if err != nil {
log.Fatalf("Failed to send notification: %v", err)
## Testing
```bash
# Run all tests
go test ./...
# Run with coverage
go test -cover ./...
# Run specific package
go test ./internal/notifier/...
```
**Current Status:** Core implementation complete, tests pending.
## Monitoring & Operations
### Health Checks
```bash
curl http://localhost:8080/health
```
Returns:
```json
{
"status": "healthy",
"service": "notifier",
"time": "2025-10-16T21:05:27Z"
}
```
### Implementing New Notification Modes
### Statistics
To add a new notification method, implement the `Notifier` interface in `internal/notifier/`:
```bash
curl http://localhost:8080/api/v1/stats
```
```go
type Notifier interface {
Send(notification Notification) error
Returns:
```json
{
"total_sent": 1234,
"total_failed": 5,
"total_pending": 0,
"total_queued": 2,
"by_type": {
"email": 800,
"slack": 400,
"ntfy": 34
},
"by_status": {
"sent": 1234,
"failed": 5
}
}
```
Add the new mode (e.g., `sms.go`) with the `Send` method to implement custom logic.
### Graceful Shutdown
The server handles `SIGINT` and `SIGTERM` gracefully:
- Stops accepting new requests
- Completes in-flight notifications
- Drains the queue
- Closes all connections
- 30-second timeout
## Roadmap
### Completed ✅
- [x] Core notification system
- [x] REST API (fully functional)
- [x] gRPC API (protobuf defined)
- [x] Local queue with workers
- [x] Multiple notifiers (SMTP, Slack, Ntfy, Stdout)
- [x] Priority and retry logic
- [x] Batch operations
- [x] Docker support
- [x] Kubernetes manifests with HPA
- [x] Health checks and stats
- [x] Configuration management
### Planned 🚧
- [ ] gRPC handler implementation
- [ ] Kafka queue adapter
- [ ] Database persistence (PostgreSQL)
- [ ] Notification templates
- [ ] Webhook callbacks
- [ ] Authentication/Authorization (API keys, OAuth)
- [ ] Rate limiting (per client, per notifier)
- [ ] Prometheus metrics
- [ ] OpenTelemetry tracing
- [ ] Comprehensive test suite
- [ ] Circuit breakers for notifiers
- [ ] Dead letter queue
- [ ] Admin dashboard
## Contributing
Contributions are welcome! To contribute, fork the repository, make your changes, and submit a pull request.
Contributions are welcome! Please:
1. Fork the repository.
2. Create a feature branch (`git checkout -b feature/NewMode`).
3. Commit your changes (`git commit -am 'Add new notification mode'`).
4. Push to the branch (`git push origin feature/NewMode`).
5. Create a new Pull Request.
1. Fork the repository
2. Create a feature branch (`git checkout -b feature/amazing-feature`)
3. Write tests for your changes
4. Ensure tests pass (`go test ./...`)
5. Commit your changes (`git commit -m 'Add amazing feature'`)
6. Push to the branch (`git push origin feature/amazing-feature`)
7. Open a Pull Request
Please follow Go best practices and maintain test coverage.
## Security
### Reporting Vulnerabilities
Please report security vulnerabilities privately via GitHub Security Advisories.
### Best Practices
- Store credentials in environment variables or secrets managers
- Use TLS for production deployments
- Enable authentication for ntfy private topics
- Rotate tokens regularly
- Follow principle of least privilege for K8s RBAC
- Keep dependencies updated
## License
This project is licensed under the MIT License. See the [LICENSE](LICENSE) file for details.
This project is licensed under the MIT License - see [LICENSE](LICENSE) for details.
## Support & Community
- **Issues**: [GitHub Issues](https://github.com/igodwin/notifier/issues)
- **Discussions**: [GitHub Discussions](https://github.com/igodwin/notifier/discussions)
- **Documentation**: See `docs/` directory
- **Examples**: See [QUICKSTART.md](QUICKSTART.md)
## Acknowledgments
Built with:
- [Gorilla Mux](https://github.com/gorilla/mux) - HTTP routing
- [Viper](https://github.com/spf13/viper) - Configuration
- [gRPC-Go](https://github.com/grpc/grpc-go) - RPC framework
- [Ntfy](https://ntfy.sh) - Push notifications
---
**Made with ❤️ for reliable notifications**