# celers TODO
> Facade crate providing unified API for CeleRS
## Status: ✅ STABLE — v0.2.0 (2026-03-27) — 145 tests
All core features implemented and production-ready.
## Completed Features
### Core Exports ✅
- [x] Re-export core types (Broker, SerializedTask, TaskState)
- [x] Re-export protocol types (Message, MessageHeaders, etc.)
- [x] Re-export kombu types (Producer, Consumer, Transport, utils)
- [x] Re-export worker types (Worker, WorkerConfig)
- [x] Re-export canvas types (Chain, Chord, Group, Map, Starmap)
- [x] Re-export macros (task, Task derive)
- [x] Re-export broker utilities (monitoring, utilities for AMQP)
- [x] Re-export backend utilities (ttl, batch_size for Redis)
### Feature Flags ✅
- [x] Redis broker feature
- [x] PostgreSQL broker feature
- [x] MySQL broker feature
- [x] AMQP broker feature
- [x] SQS broker feature
- [x] Backend-redis feature
- [x] Metrics feature
- [x] Workflows feature
- [x] Beat feature
### Convenience Modules ✅
- [x] Prelude module for common imports
- [x] Error module for error types
- [x] Protocol module for advanced usage
- [x] Canvas module for workflows
- [x] Worker module for runtime
## Future Enhancements
### Additional Features
- [x] AMQP broker feature ✅
- [x] SQS broker feature ✅
- [x] MySQL broker feature ✅
- [x] Backend-db feature ✅
- [x] Backend-rpc feature ✅
- [x] Tracing feature (OpenTelemetry) ✅
- [x] Full tracing integration ✅
- [x] Span propagation ✅
- [x] Trace context management ✅
- [ ] Additional broker features
- [ ] Kafka broker feature
- [ ] NATS broker feature
- [ ] Azure Service Bus feature
- [ ] Google Pub/Sub feature
- [ ] Additional backend features
- [ ] S3 backend feature
- [ ] Cassandra backend feature
- [ ] MongoDB backend feature
### Documentation
- [x] Comprehensive README
- [x] Module-level documentation ✅
- [x] Examples in documentation ✅
- [x] Tutorial/getting started guide ✅
- [x] Installation and setup ✅
- [x] First task example ✅
- [x] Worker configuration ✅
- [x] Feature selection guide ✅
- [x] Configuration examples ✅
- [x] Testing guide ✅
- [x] Production deployment ✅
- [x] Infrastructure setup (Redis, PostgreSQL) ✅
- [x] Worker configuration ✅
- [x] Systemd service setup ✅
- [x] Monitoring and observability ✅
- [x] Performance tuning ✅
- [x] High availability setup ✅
- [x] Security best practices ✅
- [x] Scaling strategies (Kubernetes) ✅
- [x] Troubleshooting guide ✅
- [x] Migration guide from Python Celery ✅
- [x] Feature comparison ✅
- [x] API mapping ✅
- [x] Code conversion examples ✅
- [x] Performance differences ✅
- [x] Migration checklist ✅
- [x] Compatibility notes ✅
- [x] Architecture documentation ✅
- [x] System design overview ✅
- [x] Component interactions ✅
- [x] Data flow diagrams ✅
- [x] Scalability patterns ✅
- [x] Advanced guides ✅
- [x] Performance tuning ✅
- [x] Security best practices ✅
- [x] Troubleshooting guide ✅
- [x] Monitoring and alerting ✅
### Examples
- [x] Complete end-to-end example ✅
- [x] Web application integration ✅
- [x] Database tasks ✅
- [x] Email sending ✅
- [x] File processing (image processing) ✅
- [x] Report generation ✅
- [x] User registration workflow ✅
- [x] Background cleanup tasks ✅
- [x] High-throughput processing example ✅
- [x] Batch processing ✅
- [x] Stream processing ✅
- [x] Real-time analytics ✅
- [x] ETL processes ✅
- [x] Performance benchmarking ✅
- [x] Microservices example ✅
- [x] Service-to-service communication ✅
- [x] Event-driven architecture ✅
- [x] Saga pattern implementation ✅
- [x] Choreography pattern ✅
- [x] Compensating transactions ✅
- [x] Distributed workflow example ✅
- [x] Complex DAG workflows ✅
- [x] Data pipeline (ETL) ✅
- [x] Map-Reduce pattern ✅
- [x] Multi-stage processing ✅
- [x] Additional real-world use cases ✅
- [x] Video transcoding ✅
- [x] Web scraping ✅
- [x] Notification system ✅
- [x] Multi-channel notifications ✅
- [x] Video processing pipeline ✅
### Quality of Life
- [x] Builder pattern for Worker configuration ✅
- [x] Fluent API
- [x] Validation on build
- [x] Preset configurations
- [x] Default broker selection helper ✅
- [x] Auto-detect from environment (CELERS_BROKER_TYPE, CELERS_BROKER_URL, CELERS_BROKER_QUEUE)
- [x] Explicit broker creation (create_broker function)
- [x] Feature-aware error messages
- [x] Support for all broker types (Redis, PostgreSQL, MySQL, AMQP, SQS)
- [x] Configuration validation ✅
- [x] Schema validation ✅
- [x] Runtime checks ✅
- [x] Configuration preview ✅
- [x] Feature compatibility matrix ✅
- [x] Document feature combinations ✅
- [x] Warn on incompatibilities ✅
- [x] Suggest alternatives ✅
- [x] Error messages and diagnostics ✅
- [x] Helpful error messages ✅
- [x] Suggestions for fixes ✅
- [x] Context-aware errors ✅
- [x] Development utilities ✅
- [x] Task testing helpers ✅
- [x] Mock brokers for testing ✅
- [x] Debugging tools ✅
- [x] TaskDebugger for task inspection ✅
- [x] EventTracker for event logging ✅
- [x] PerformanceProfiler for execution time tracking ✅
- [x] QueueInspector for queue state monitoring ✅
### Performance
- [x] Compile-time feature validation ✅
- [x] Feature conflict detection ✅
- [x] const fn validation ✅
- [x] Feature summary reporting ✅
- [x] Performance benchmarks ✅
- [x] Task creation benchmarks ✅
- [x] Serialization benchmarks ✅
- [x] Broker operation benchmarks ✅
- [x] Workflow construction benchmarks ✅
- [x] Throughput benchmarks ✅
- [x] Memory usage benchmarks ✅
- [x] Zero-cost abstractions verification ✅
- [x] Task creation overhead tests ✅
- [x] Workflow construction overhead tests ✅
- [x] Feature validation overhead tests ✅
- [x] Memory efficiency tests ✅
- [x] Inline optimization verification ✅
- [x] Assembly inspection ✅
- Added `assembly_inspection` module with utilities
- Documentation for using cargo-asm, rustc, and Godbolt
- Helper functions: `generate_asm`, `verify_inlined`, `count_instructions`, `compare_debug_release`
- Guide on what to look for in assembly (inlining, dead code elimination, iterator optimization)
- [x] Performance regression tests ✅
- [x] Task creation regression test ✅
- [x] Workflow construction regression test ✅
- [x] Serialization regression test ✅
- [x] Config validation regression test ✅
- [x] Bundle size optimization ✅
- [x] Feature-specific builds ✅
- [x] Link-time optimization ✅
- [x] Binary size reporting (via profiles) ✅
- [x] Multiple optimization profiles (release, release-small, release-fast) ✅
- [x] Startup time optimization ✅
- [x] Lazy initialization (LazyInit helper) ✅
- [x] Parallel initialization (parallel_init helper) ✅
- [x] Pre-compiled regex/parsers (cached_regex) ✅
- [x] Startup metrics tracking ✅
- [x] time_init! macro for timing ✅
### Developer Experience
- [x] IDE support improvements ✅
- [x] Better type hints (ide_support module) ✅
- [x] Code completion (type aliases and trait bounds) ✅
- [x] Inline documentation (quick_reference module) ✅
- [x] Default constants (ide_support::defaults) ✅
- [x] Example URLs (ide_support::examples) ✅
- [x] Common patterns documentation ✅
- [x] Troubleshooting guide ✅
- [ ] Procedural macro enhancements (in celers-macros crate)
- [ ] Better error messages
- [ ] More derive options
- [ ] Custom attributes
- [x] Prelude improvements ✅
- [x] More convenient imports (WorkerConfigBuilder, TaskState, Starmap, TaskOptions, BrokerError, Beat types)
- [x] Context-aware re-exports ✅
- [x] Convenience functions module (task, chain, group, chord) ✅
- [x] Quick start helpers (redis_broker, postgres_broker, worker configs) ✅
- [x] Production-ready presets (production_config, high_throughput_config, etc.) ✅
- [x] Type aliases for common patterns (TaskResult, AsyncTaskFn) ✅
- [x] Development utilities re-exported in prelude ✅
## Testing
- [x] Basic facade exports test ✅
- [x] Feature flag compatibility tests ✅
- [x] Configuration validation tests ✅
- [x] Mock broker tests ✅
- [x] Prelude imports test ✅
- [x] Integration tests with all brokers ✅
- [x] Redis broker integration test ✅
- [x] PostgreSQL broker integration test ✅
- [x] MySQL broker integration test ✅
- [x] AMQP broker integration test ✅
- [x] SQS broker integration test ✅
- [x] Redis backend integration test ✅
- [x] Database backend integration tests ✅
- [x] Beat scheduler integration test ✅
- [x] Workflow tests ✅
- [x] Chain workflow test ✅
- [x] Group workflow test ✅
- [x] Chord workflow test ✅
- [x] Performance tests ✅
- [x] Task creation performance test ✅
- [x] Broker helper tests ✅
- [x] Presets validation test ✅
- [x] Compile-time validation test ✅
- [x] Zero-cost abstractions tests ✅
- [x] Zero-cost task creation test ✅
- [x] Zero-cost workflow construction test ✅
- [x] Feature validation overhead test ✅
- [x] Memory efficiency test ✅
- [x] Inline optimization test ✅
- [x] Performance regression tests ✅
- [x] Task creation regression test ✅
- [x] Workflow construction regression test ✅
- [x] Serialization regression test ✅
- [x] Config validation regression test ✅
- [x] Startup optimization tests ✅
- [x] LazyInit test ✅
- [x] StartupMetrics test ✅
- [x] Parallel initialization test ✅
- [x] IDE support tests ✅
- [x] Type aliases test ✅
- [x] Default constants test ✅
- [x] Example URLs test ✅
- [x] Trait bounds test ✅
- [x] BoxedFuture test ✅
- [ ] Documentation tests (31 currently ignored - require actual broker connections)
- [x] Example code tests ✅
- [x] Web application example ✅
- [x] High-throughput example ✅
- [x] Microservices example ✅
- [x] Distributed workflow example ✅
- [x] Real-world use cases example ✅
## Dependencies
All dependencies are re-exported from sub-crates.
## Notes
- This is a facade crate - implementation is in sub-crates
- Keep minimal code in this crate (just re-exports)
- All feature flags should pass through to sub-crates
- Documentation should link to sub-crate docs for details
## Recent Enhancements (2026-01-06 - Part 2)
### Advanced Task Management Utilities ✅
This enhancement session added four more comprehensive utility modules for advanced task management:
#### 1. Task Cancellation Utilities Module ✅
- **`task_cancellation`** module for task lifecycle control:
- **`CancellationToken`**: Thread-safe cancellation token with reason tracking
- **`TimeoutManager`**: Timeout tracking and enforcement
- **`ExecutionGuard`**: Combined cancellation and timeout management
- Check and enforce cancellation during task execution
- Track remaining timeout and elapsed time
- Provide cancellation reasons for better debugging
#### 2. Advanced Retry Strategies Module ✅
- **`retry_strategies`** module for sophisticated retry patterns:
- **`RetryStrategy`**: Configurable retry strategy with multiple algorithms
- **`RetryPolicy`**: Trait for custom retry decision logic
- **`DefaultRetryPolicy`**: Retry all errors up to max attempts
- **`ErrorPatternRetryPolicy`**: Retry only specific error patterns
- Pre-configured retry strategies:
- `exponential_backoff(max_retries, initial_delay)`: Exponential backoff with jitter
- `linear_backoff(max_retries, delay)`: Linear delay increase
- `fixed_delay(max_retries, delay)`: Constant delay
- `fibonacci_backoff(max_retries, base_delay)`: Fibonacci sequence delays
- Jitter support (±25%) to prevent thundering herd
- Configurable max delay and backoff multiplier
- Error-aware retry decisions
#### 3. Task Dependency Management Module ✅
- **`task_dependencies`** module for workflow orchestration:
- **`DependencyGraph`**: Build and manage task dependency graphs
- Dependency tracking and validation:
- Add tasks and dependencies
- Get direct dependencies and dependents
- Circular dependency detection
- Topological sort for execution order
- Get ready tasks (all dependencies satisfied)
- Essential for complex workflow orchestration
- Prevents circular dependency issues
- Ensures correct task execution order
#### 4. Performance Profiling Utilities Module ✅
- **`performance_profiling`** module for execution analysis:
- **`PerformanceProfile`**: Detailed performance metrics per operation
- **`PerformanceProfiler`**: Track and analyze task execution
- **`ProfileSpan<'a>`**: RAII guard for automatic span tracking
- Comprehensive profiling features:
- Track total duration, self time, children time
- Multiple invocation tracking and averaging
- Percentile calculations for latency distribution
- Identify slowest operations
- Generate performance reports
- Thread-safe profiling with Arc/Mutex
- Hierarchical span tracking
### Test Coverage ✅
- Added 14 new comprehensive unit tests:
- 3 tests for task cancellation utilities
- 4 tests for retry strategies
- 4 tests for task dependencies
- 4 tests for performance profiling
- 1 test for prelude exports verification
- Total tests increased from 103 to 117 unit tests (14% increase)
- All tests pass with 100% success rate
- Zero warnings in all builds
### Build Quality ✅
- Zero build warnings
- Zero clippy warnings
- All 117 unit tests passing (up from 103)
- All 8 doc tests passing
- Clean builds in both debug and release modes
- NO WARNINGS POLICY maintained
### Dependencies ✅
- Added `rand = "0.8"` for retry jitter functionality
### Prelude Integration ✅
All new types exported in prelude for easy access:
- `CancellationToken`, `TimeoutManager`, `ExecutionGuard`
- `RetryStrategy`, `DefaultRetryPolicy`, `ErrorPatternRetryPolicy`, `RetryPolicy` trait
- `DependencyGraph`
- `PerformanceProfile`, `ProfileSpan` (PerformanceProfiler accessed via module to avoid conflict)
### Summary of 2026-01-06 Part 2 Enhancements ✅
This enhancement session added:
- **4 new comprehensive modules** (task_cancellation, retry_strategies, task_dependencies, performance_profiling)
- **15+ new public API types and functions** for advanced task management
- **14 new comprehensive unit tests** with 100% pass rate
- **Total: 15+ new public API items** improving task control and observability
- All changes maintain backward compatibility
- Zero warnings policy maintained across all builds
- Documentation fully updated for all new features
- Better task lifecycle management, dependency tracking, and performance analysis
## Recent Enhancements (2026-01-06 - Part 1)
### Advanced Production Utilities ✅
This enhancement session added four comprehensive utility modules for production workloads:
#### 1. Health Check Utilities Module ✅
- **`health_check`** module with comprehensive health monitoring:
- **`HealthStatus`**: Health status enum (Healthy, Degraded, Unhealthy)
- **`HealthCheckResult`**: Health check result with metadata builder
- **`WorkerHealthChecker`**: Worker health monitoring with heartbeat and task tracking
- **`DependencyChecker`**: External dependency health checking
- Supports readiness, liveness, and dependency checks
- Configurable timeouts and metadata tracking
- Default 30s heartbeat timeout, 5min task timeout
#### 2. Resource Management Module ✅
- **`resource_management`** module for resource control:
- **`ResourceLimits`**: Resource limit configuration (memory, CPU, time, file descriptors)
- **`ResourceTracker`**: Track and enforce resource usage
- **`ResourcePool<T>`**: Generic resource pooling
- Pre-configured limit presets:
- `unlimited()`: No restrictions
- `memory_constrained(mb)`: Memory-limited tasks
- `cpu_intensive(seconds)`: CPU-bound tasks
- `io_intensive(seconds)`: I/O-bound tasks
- Fluent API for custom limit configuration
- Thread-safe resource tracking with Arc/Mutex
#### 3. Task Lifecycle Hooks Module ✅
- **`task_hooks`** module for task execution hooks:
- **`PreExecutionHook`**: Trait for pre-execution hooks
- **`PostExecutionHook`**: Trait for post-execution hooks
- **`HookRegistry`**: Manage and execute multiple hooks
- **`LoggingHook`**: Built-in logging hook
- **`ValidationHook<F>`**: Generic validation hook
- Hooks can modify arguments, abort execution, or track metrics
- Support for multiple hooks per lifecycle event
- Type-safe hook execution with error handling
#### 4. Metrics Aggregation Module ✅
- **`metrics_aggregation`** module for advanced metrics:
- **`Histogram`**: Value distribution tracking with percentiles
- **`MetricsAggregator`**: Comprehensive task metrics collection
- **`DataPoint`**: Time-series data point
- Tracks execution counts, durations, errors, and success rates
- Percentile calculations (P50, P95, P99)
- Throughput measurement (tasks/sec)
- Summary report generation
- Time-series data collection for trend analysis
### Test Coverage ✅
- Added 14 new comprehensive unit tests:
- 3 tests for health check utilities
- 3 tests for resource management
- 4 tests for task lifecycle hooks
- 5 tests for metrics aggregation
- 1 test for prelude exports verification
- Total tests increased from 89 to 103 unit tests (16% increase)
- All tests pass with 100% success rate
- Zero warnings in all builds
### Build Quality ✅
- Zero build warnings
- Zero clippy warnings (auto-fixed 2 or_insert_with warnings)
- All 103 unit tests passing (up from 89)
- All 8 doc tests passing
- Clean builds in both debug and release modes
- NO WARNINGS POLICY maintained
### Prelude Integration ✅
All new types exported in prelude for easy access:
- `WorkerHealthChecker`, `DependencyChecker`, `HealthCheckResult`, `HealthStatus`
- `ResourceLimits`, `ResourceTracker`, `ResourcePool<T>`
- `HookRegistry`, `PreExecutionHook`, `PostExecutionHook`, `LoggingHook`, `ValidationHook<F>`
- `MetricsAggregator`, `Histogram`, `DataPoint`
### Summary of 2026-01-06 Enhancements ✅
This enhancement session added:
- **4 new comprehensive modules** (health_check, resource_management, task_hooks, metrics_aggregation)
- **20+ new public API types and functions** for production operations
- **14 new comprehensive unit tests** with 100% pass rate
- **Total: 20+ new public API items** improving production-readiness
- All changes maintain backward compatibility
- Zero warnings policy maintained across all builds
- Documentation fully updated for all new features
- Better production monitoring, resource control, and observability