191 lines
4.8 KiB
Markdown
191 lines
4.8 KiB
Markdown
# Dokku Docker Compose Plugin Architecture
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## Overview
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This document describes the architecture of the Dokku Docker Compose plugin, which enables importing Docker Compose files into Dokku while maintaining compatibility with existing Dokku plugins and features.
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## High-Level Architecture
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```mermaid
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graph TD
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A[Docker Compose File] --> B[Parser]
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B --> C[Service Graph]
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C --> D[Transformer]
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D --> E[Dokku Resources]
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E --> F[Dokku Core]
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G[Plugins] --> F
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H[CLI] --> B
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H --> D
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H --> F
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```
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## Core Components
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### 1. Parser
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- **Responsibility**: Parse and validate Docker Compose files
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- **Input**: `docker-compose.yml` (v2/v3)
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- **Output**: Normalized service definitions
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- **Features**:
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- YAML parsing with schema validation
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- Environment variable interpolation
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- Extension point for custom validators
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### 2. Service Graph
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- **Responsibility**: Model service dependencies and relationships
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- **Components**:
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- Dependency resolver
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- Cycle detection
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- Topological sorter
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- **Features**:
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- Builds directed acyclic graph (DAG) of services
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- Determines execution order
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- Identifies independent services for parallel processing
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### 3. Transformer
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- **Responsibility**: Convert Docker Compose concepts to Dokku resources
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- **Components**:
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- Resource mappers (networks, volumes, etc.)
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- Plugin detector
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- Environment variable processor
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- **Features**:
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- Handles Docker-specific configurations
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- Integrates with Dokku plugins
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- Manages resource naming and references
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### 4. Executor
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- **Responsibility**: Coordinate the creation/update of Dokku resources
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- **Components**:
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- Operation planner
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- Dependency manager
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- Rollback handler
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- **Features**:
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- Transactional updates
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- Parallel execution where possible
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- Automatic rollback on failure
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## Data Flow
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1. **Initialization**:
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- Load and parse `docker-compose.yml`
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- Resolve environment variables
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- Validate against schema
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2. **Analysis**:
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- Build service dependency graph
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- Detect plugin integrations
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- Plan operations
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3. **Execution**:
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- Create/update resources in dependency order
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- Handle plugin integrations
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- Configure networking and storage
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4. **Verification**:
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- Run health checks
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- Verify service availability
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- Perform post-deployment tasks
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## Key Design Decisions
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### 1. Plugin Integration
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- **Approach**: Use Dokku's plugin system for service management
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- **Rationale**: Leverage existing, well-tested implementations
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- **Implementation**:
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- Detect compatible plugins based on image names
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- Map Docker Compose configurations to plugin commands
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- Fall back to container-based deployment when no plugin is available
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### 2. State Management
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- **Approach**: Store minimal state in Dokku's configuration
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- **Rationale**: Ensure consistency and enable recovery
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- **Implementation**:
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- Store original compose file checksum
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- Track resource mappings
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- Maintain version history
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### 3. Error Handling
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- **Approach**: Fail fast with clear error messages
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- **Rationale**: Prevent partial or inconsistent states
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- **Implementation**:
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- Input validation
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- Pre-flight checks
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- Transactional updates with rollback
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## Integration Points
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### Dokku Core
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- App management
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- Network configuration
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- Volume management
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- Process management
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### External Systems
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- Docker Registry (for image pulls)
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- Docker Daemon (for container operations)
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- System Package Manager (for plugin installation)
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## Security Considerations
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1. **Input Validation**:
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- Sanitize all inputs
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- Validate against schema
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- Restrict file system access
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2. **Secret Management**:
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- Handle environment variables securely
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- Support Dokku's secret management
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- Avoid logging sensitive data
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3. **Access Control**:
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- Respect file permissions
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- Run with least privilege
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- Validate user permissions
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## Performance Considerations
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1. **Parallel Processing**:
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- Process independent services concurrently
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- Limit concurrency to prevent resource exhaustion
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2. **Caching**:
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- Cache parsed compose files
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- Store intermediate build artifacts
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3. **Optimizations**:
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- Lazy loading of resources
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- Incremental updates
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- Batch operations where possible
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## Monitoring and Observability
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1. **Logging**:
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- Structured logging
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- Different log levels
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- Operation context
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2. **Metrics**:
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- Operation duration
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- Resource usage
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- Success/failure rates
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3. **Tracing**:
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- Request tracing
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- Dependency tracking
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- Performance analysis
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## Future Extensions
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1. **Plugin System**:
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- Custom transformers
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- Additional validators
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- Post-processing hooks
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2. **Export Functionality**:
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- Generate compose files from existing Dokku apps
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- Support for different output formats
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3. **Advanced Features**:
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- Blue/green deployments
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- Canary releases
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- A/B testing support
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