Microservices Orchestration Implementation¶

Overview¶

This document summarizes the implementation of the microservices orchestration system for Drun, as specified in spec/microservices-orchestration.md.

Implemented Components¶

1. AST Nodes (`internal/ast/ast_orchestration.go`)¶

ServiceStatement: Represents a microservice definition with all configuration options
OrchestrateStatement: Represents an orchestration group
Supporting Types:
RepositoryConfig: Git repository configuration
HealthCheckConfig: Health check settings (HTTP, TCP, Docker, DNS, Custom)
BuildConfig: Build configuration with Makefile support
ComposeConfig: Docker Compose configuration
ComposeOptions: Detailed Docker Compose options
EnvFileConfig: Environment file management

2. Lexer Tokens (`internal/lexer/token.go`)¶

Added 70+ new tokens for orchestration features:

ORCHESTRATE, SERVICES, STRATEGY, SEQUENTIAL, CIRCUIT, BREAKER
HEALTH, DNS, TCP, DOMAIN, INTERVAL, RETRIES
MAKEFILE, TARGET, ARGS, REPOSITORY
ENV_FILE, REQUIRED, MISSING, etc.

3. Parser (`internal/parser/parser_orchestration.go`)¶

Comprehensive parser implementation for:

Service declarations with all options
Orchestration group declarations
Repository configuration
Health check configuration (all types)
Build configuration with Makefile support
Docker Compose configuration
Environment file configuration
Helper functions for parsing arrays, maps, and nested structures

4. Domain Types (`internal/domain/orchestration/`)¶

`service.go`¶

Service domain model with runtime state
ServiceStatus enum (unknown, starting, running, healthy, unhealthy, stopping, stopped, failed)
Health check methods (MarkHealthy, MarkUnhealthy, etc.)

`orchestration.go`¶

Orchestration domain model with strategies
OrchestrationStrategy enum (sequential, parallel, dependency-based)
UpdateStrategy enum (rolling, recreate, blue-green)
Circuit breaker state management
Recovery configuration

`registry.go`¶

ServiceRegistry: Thread-safe service registration and lookup
OrchestrationRegistry: Thread-safe orchestration registration and lookup

5. Health Check System (`internal/healthcheck/healthcheck.go`)¶

Implemented all health check types:

HTTP: Status code validation, custom headers
TCP: Port connectivity checks
Docker: Container health status inspection
DNS: Domain resolution with record type validation (A, AAAA, CNAME, MX)
Custom: Shell command execution

Features:

Configurable timeouts and intervals
Retry logic with configurable attempts
Start period support
Continuous monitoring with callbacks

6. Repository Management (`internal/repository/repository.go`)¶

Git repository operations:

Clone with branch/tag selection
SSH key support
Update/pull operations
Status checking
Branch and tag detection
Repository validation

7. Makefile Integration (`internal/makeexec/makeexec.go`)¶

Makefile execution features:

Target execution with arguments
Parallel job support (-j flag)
Pre/post command execution
Timeout handling
Retry with exponential backoff
Fallback command support
Dry run capability
Target listing and validation

8. Environment File Management (`internal/envfile/envfile.go`)¶

Environment file operations:

Automatic .env file creation from templates
Key-value parsing and writing
Variable replacement
Validation of required variables
Backup and restore
File merging
Permission management (secure mode 600)
Variable interpolation

9. Service Lifecycle Executor (`internal/engine/executor_orchestration.go`)¶

Service lifecycle management:

Service registration from AST
Start/stop operations
Pre-task and post-task execution
Repository cloning
Environment file setup
Build execution (Makefile or command)
Docker Compose integration
Health check monitoring

10. Orchestration Coordinator (`internal/engine/orchestration_coordinator.go`)¶

Advanced orchestration features:

Sequential Strategy: Start services one after another
Parallel Strategy: Start all services simultaneously
Dependency-Based Strategy: Topological sort with dependency resolution

Key features:

Dependency graph building
Cycle detection
Circuit breaker implementation
Health monitoring with automatic recovery
Graceful shutdown with reverse order
Global pre/post task execution
Failure threshold tracking
Service status reporting

11. Built-in Functions (`internal/builtins/builtins_orchestration.go`)¶

20+ new built-in functions:

service_status, service_health, service_healthy, service_running
orchestrate_status, orchestrate_health_status, orchestrate_healthy
dns_resolve, dns_check, dns_validate
git_status, git_branch, git_tag
docker_ps, docker_logs, docker_stats
compose_config
make_list, make_dry_run

12. Example Drunfiles¶

Created 6 comprehensive examples:

64-microservices-basic.drun: Basic microservices setup
65-microservices-repository-cloning.drun: Repository cloning and management
66-microservices-env-file-management.drun: Environment file handling
67-microservices-global-tasks.drun: Global pre/post tasks
68-microservices-dns-health-check.drun: DNS health checks and domain validation
69-microservices-complete.drun: Complete e-commerce platform example

Features Implemented¶

Core Features¶

Service definitions with dependencies
Orchestration groups with multiple strategies
Health monitoring (HTTP, TCP, Docker, DNS, Custom)
Circuit breaker pattern
Dependency resolution with topological sort
Repository cloning and management
Makefile integration
Environment file management
Global pre/post tasks
Service-specific pre/post tasks

Docker Compose Integration¶

Custom compose file support
Project name configuration
Force recreate option
Build before start
Pull policy (always, missing, never)
Wait for services
Scaling configuration
Timeout settings

Health Checks¶

HTTP with status code validation
TCP port connectivity
Docker container health
DNS resolution with record types
Custom command execution
Configurable retries and intervals
Start period support

Repository Management¶

Clone if missing
Update on start
Branch selection
Tag selection
SSH key support
Status checking

Build System¶

Makefile execution
Make targets and arguments
Shell command execution (supports multiline strings)
Line continuation with backslash
Variable interpolation in build commands
Parallel jobs
Pre/post commands
Retry on failure
Fallback commands
Dry run support

Environment Files¶

Required validation
Template copying
Variable replacement
Secure permissions
Task-based setup
Validation

Orchestration Strategies¶

Sequential: Services start one after another
Parallel: All services start simultaneously
Dependency-based: Topological sort based on dependencies

Circuit Breaker¶

Failure threshold tracking
Automatic service stopping on failure
Recovery timeout
Circuit state management
Health monitoring

Usage Example¶

version: 2.0

# Define a service
service "api" in "./services/api" means "REST API":
    depends on ["database", "redis"]
    repository:
        url "https://github.com/company/api.git"
        branch "main"
        clone true  # default, can be omitted
    health check:
        type "http"
        endpoint "http://localhost:8080/health"
        timeout "10s"
        interval "15s"
        retries 3
        condition "200"
    build:
        required true
        command "npm install && npm test && npm run build"
        # Alternatively, use Makefile:
        # makefile "Makefile"
        # make_target "build"
    compose:
        file "docker-compose.yml"
    environment:
        NODE_ENV "production"

# Define orchestration
orchestrate "production" means "Production services":
    services ["database", "redis", "api"]
    strategy "dependency-based"
    circuit_breaker true
    stop_on_failure true
    health_check_interval "30s"

# Start services
task "start" means "Start production":
    orchestrate "production" start
    success "Services started!"

Architecture¶

The orchestration system follows a layered architecture:

AST Layer: Parses drunfiles into structured AST nodes
Domain Layer: Business logic and state management
Infrastructure Layer: Health checks, repository management, makefile execution
Engine Layer: Orchestration coordination and service lifecycle
Built-in Functions: User-facing API for status and operations

Key Design Decisions¶

Thread-Safe Registries: All service and orchestration registries use sync.RWMutex for concurrent access
Context-Based Execution: All operations support context cancellation for proper cleanup
Modular Health Checks: Each health check type is independently implemented
Topological Sort: Dependency resolution uses Kahn's algorithm for cycle detection
Circuit Breaker: Implements the circuit breaker pattern with configurable thresholds
Graceful Degradation: Services can continue running even if health checks fail (configurable)

Future Enhancements¶

While the core specification is implemented, the following enhancements could be added:

Testing: Comprehensive unit and integration tests
Kubernetes Integration: Native k8s support beyond Docker Compose
Service Mesh: Istio/Linkerd integration
Advanced Monitoring: Prometheus/Grafana integration
Blue-Green Deployments: Advanced deployment strategies
Canary Releases: Gradual rollout support
Auto-scaling: Dynamic scaling based on metrics

Integration with Existing Drun¶

The orchestration system is designed to integrate seamlessly with existing Drun features:

Task system for pre/post operations
Variable interpolation for dynamic configuration
Error handling with try/catch
Control flow (if/when/for)
Secret management for credentials
File operations for setup tasks

Status¶

Implementation Complete

All core features from the specification have been implemented:

AST nodes and parser
Domain models
Health check system
Repository management
Makefile integration
Environment file management
Service lifecycle executor
Orchestration coordinator
Circuit breaker
Built-in functions
Comprehensive examples

The system is ready for integration testing and real-world usage.