claude mds instrumentation

CLAUDE.md

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+# Snowplow Python Tracker - CLAUDE.md
+
+## Project Overview
+
+The Snowplow Python Tracker is a public Python library for sending analytics events to Snowplow collectors. It enables developers to integrate Snowplow analytics into Python applications, games, and web servers. The library provides a robust event tracking system with support for various event types, custom contexts, and reliable event delivery through configurable emitters.
+
+**Key Technologies:**
+- Python 3.8+ (supported versions: 3.8-3.13)
+- requests library for HTTP communication
+- typing_extensions for enhanced type hints
+- Event-driven architecture with schema validation
+- Asynchronous and synchronous event emission
+
+## Development Commands
+
+```bash
+# Install dependencies
+pip install -r requirements-test.txt
+
+# Run tests
+./run-tests.sh
+
+# Run specific test module
+python -m pytest snowplow_tracker/test/unit/test_tracker.py
+
+# Run integration tests
+python -m pytest snowplow_tracker/test/integration/
+
+# Install package in development mode
+pip install -e .
+
+# Build Docker image for testing
+docker build -t snowplow-python-tracker .
+docker run snowplow-python-tracker
+```
+
+## Architecture
+
+The tracker follows a layered architecture with clear separation of concerns:
+
+```
+snowplow_tracker/
+├── Core Components
+│   ├── tracker.py          # Main Tracker class orchestrating events
+│   ├── snowplow.py         # High-level API for tracker management
+│   └── subject.py          # User/device context management
+├── Event Layer (events/)
+│   ├── event.py            # Base Event class
+│   ├── page_view.py        # PageView event
+│   ├── structured_event.py # Structured events
+│   └── self_describing.py  # Custom schema events
+├── Emission Layer
+│   ├── emitters.py         # Sync/Async event transmission
+│   ├── event_store.py      # Event buffering and persistence
+│   └── payload.py          # Event payload construction
+├── Configuration
+│   ├── tracker_configuration.py
+│   └── emitter_configuration.py
+└── Validation
+    ├── contracts.py        # Runtime validation
+    └── typing.py           # Type definitions
+```
+
+## Core Architectural Principles
+
+1. **Schema-First Design**: All events conform to Iglu schemas for consistency
+2. **Separation of Concerns**: Event creation, validation, and emission are separate
+3. **Configuration Objects**: Use dedicated configuration classes, not raw dictionaries
+4. **Type Safety**: Extensive use of type hints and Protocol classes
+5. **Fail-Safe Delivery**: Events are buffered and retried on failure
+6. **Immutability**: Event objects are largely immutable after creation
+
+## Layer Organization & Responsibilities
+
+### Application Layer (snowplow.py)
+- Singleton pattern for global tracker management
+- Factory methods for tracker creation
+- Namespace-based tracker registry
+
+### Domain Layer (tracker.py, events/)
+- Event creation and validation
+- Subject (user/device) context management
+- Event enrichment with standard fields
+
+### Infrastructure Layer (emitters.py, event_store.py)
+- HTTP communication with collectors
+- Event buffering and retry logic
+- Async/sync emission strategies
+
+### Cross-Cutting (contracts.py, typing.py)
+- Runtime validation with togglable contracts
+- Shared type definitions and protocols
+
+## Critical Import Patterns
+
+```python
+# ✅ Import from package root for public API
+from snowplow_tracker import Snowplow, Tracker, Subject
+from snowplow_tracker import EmitterConfiguration, TrackerConfiguration
+
+# ✅ Import specific event classes
+from snowplow_tracker.events import PageView, StructuredEvent
+
+# ❌ Don't import from internal modules
+from snowplow_tracker.emitters import Requester  # Internal class
+
+# ✅ Use typing module for type hints
+from snowplow_tracker.typing import PayloadDict, Method
+```
+
+## Essential Library Patterns
+
+### Tracker Initialization Pattern
+```python
+# ✅ Use Snowplow factory with configuration objects
+tracker = Snowplow.create_tracker(
+    namespace="my_app",
+    endpoint="https://collector.example.com",
+    tracker_config=TrackerConfiguration(encode_base64=True),
+    emitter_config=EmitterConfiguration(batch_size=10)
+)
+
+# ❌ Don't instantiate Tracker directly without Snowplow
+tracker = Tracker("namespace", emitter)  # Missing registration
+```
+
+### Event Creation Pattern
+```python
+# ✅ Use event classes with named parameters
+page_view = PageView(
+    page_url="https://example.com",
+    page_title="Homepage"
+)
+
+# ✅ Add contexts to events
+event.context = [SelfDescribingJson(schema, data)]
+
+# ❌ Don't modify event payload directly
+event.payload.add("custom", "value")  # Breaks schema validation
+```
+
+### Subject Management Pattern
+```python
+# ✅ Set subject at tracker or event level
+subject = Subject()
+subject.set_user_id("user123")
+tracker = Snowplow.create_tracker(..., subject=subject)
+
+# ✅ Override subject per event
+event = PageView(..., event_subject=Subject())
+
+# ❌ Don't modify subject after tracker creation
+tracker.subject.set_user_id("new_id")  # Not thread-safe
+```
+
+### Emitter Configuration Pattern
+```python
+# ✅ Configure retry and buffering behavior
+config = EmitterConfiguration(
+    batch_size=50,
+    buffer_capacity=10000,
+    custom_retry_codes={429: True, 500: True}
+)
+
+# ❌ Don't use magic numbers
+emitter = Emitter(endpoint, 443, "post", 100)  # Use config object
+```
+
+## Model Organization Pattern
+
+### Event Hierarchy
+```python
+Event (base class)
+├── PageView         # Web page views
+├── PagePing         # Page engagement tracking
+├── ScreenView       # Mobile screen views
+├── StructuredEvent  # Category/action/label/property/value events
+└── SelfDescribing   # Custom schema events
+```
+
+### Data Structures
+```python
+# SelfDescribingJson for custom contexts
+context = SelfDescribingJson(
+    "iglu:com.example/context/jsonschema/1-0-0",
+    {"key": "value"}
+)
+
+# Payload for event data assembly
+payload = Payload()
+payload.add("e", "pv")  # Event type
+payload.add_dict({"aid": "app_id"})
+```
+
+## Common Pitfalls & Solutions
+
+### Contract Validation
+```python
+# ❌ Passing invalid parameters silently fails in production
+tracker.track_page_view("")  # Empty URL
+
+# ✅ Enable contracts during development
+from snowplow_tracker import enable_contracts
+enable_contracts()
+```
+
+### Event Buffering
+```python
+# ❌ Not flushing events before shutdown
+tracker.track(event)
+sys.exit()  # Events lost!
+
+# ✅ Always flush before exit
+tracker.track(event)
+tracker.flush()
+```
+
+### Thread Safety
+```python
+# ❌ Sharing emitter across threads
+emitter = Emitter(endpoint)
+# Multiple threads using same emitter
+
+# ✅ Use AsyncEmitter for concurrent scenarios
+emitter = AsyncEmitter(endpoint, thread_count=2)
+```
+
+### Schema Validation
+```python
+# ❌ Hardcoding schema strings
+schema = "iglu:com.snowplow/event/1-0-0"
+
+# ✅ Use constants for schemas
+from snowplow_tracker.constants import CONTEXT_SCHEMA
+```
+
+## File Structure Template
+
+```
+project/
+├── tracker_app.py           # Application entry point
+├── config/
+│   └── tracker_config.py    # Tracker configuration
+├── events/
+│   ├── __init__.py
+│   └── custom_events.py     # Custom event definitions
+├── contexts/
+│   └── custom_contexts.py   # Custom context schemas
+└── tests/
+    ├── unit/
+    │   └── test_events.py
+    └── integration/
+        └── test_emission.py
+```
+
+## Testing Patterns
+
+### Unit Testing
+```python
+# ✅ Mock emitters for unit tests
+@mock.patch('snowplow_tracker.emitters.Emitter')
+def test_track_event(mock_emitter):
+    tracker = Tracker("test", mock_emitter)
+    tracker.track(PageView(...))
+    mock_emitter.input.assert_called_once()
+```
+
+### Contract Testing
+```python
+# ✅ Use ContractsDisabled context manager
+with ContractsDisabled():
+    # Test invalid inputs without raising
+    tracker.track_page_view(None)
+```
+
+### Integration Testing
+```python
+# ✅ Test against mock collector
+def test_event_delivery():
+    with requests_mock.Mocker() as m:
+        m.post("https://collector.test/com.snowplow/tp2")
+        # Track and verify delivery
+```
+
+## Configuration Best Practices
+
+### Environment-Based Configuration
+```python
+# ✅ Use environment variables
+import os
+endpoint = os.getenv("SNOWPLOW_COLLECTOR_URL")
+namespace = os.getenv("SNOWPLOW_NAMESPACE", "default")
+```
+
+### Retry Configuration
+```python
+# ✅ Configure intelligent retry behavior
+EmitterConfiguration(
+    max_retry_delay_seconds=120,
+    custom_retry_codes={
+        429: True,  # Retry rate limits
+        500: True,  # Retry server errors
+        400: False  # Don't retry bad requests
+    }
+)
+```
+
+## Quick Reference
+
+### Import Checklist
+- [ ] Import from `snowplow_tracker` package root
+- [ ] Use `EmitterConfiguration` and `TrackerConfiguration`
+- [ ] Import specific event classes from `snowplow_tracker.events`
+- [ ] Use type hints from `snowplow_tracker.typing`
+
+### Event Tracking Checklist
+- [ ] Create tracker with `Snowplow.create_tracker()`
+- [ ] Configure emitter with appropriate batch size
+- [ ] Set subject context if tracking users
+- [ ] Use appropriate event class for the use case
+- [ ] Add custom contexts as `SelfDescribingJson`
+- [ ] Call `flush()` before application shutdown
+- [ ] Handle failures with callbacks
+
+### Common Event Types
+- `PageView`: Web page views
+- `ScreenView`: Mobile app screens
+- `StructuredEvent`: Generic events with 5 parameters
+- `SelfDescribing`: Custom schema events
+- `PagePing`: Engagement tracking
+
+## Contributing to CLAUDE.md
+
+When adding or updating content in this document, please follow these guidelines:
+
+### File Size Limit
+- **CLAUDE.md must not exceed 40KB** (currently ~19KB)
+- Check file size after updates: `wc -c CLAUDE.md`
+- Remove outdated content if approaching the limit
+
+### Code Examples
+- Keep all code examples **4 lines or fewer**
+- Focus on the essential pattern, not complete implementations
+- Use `// ❌` and `// ✅` to clearly show wrong vs right approaches
+
+### Content Organization
+- Add new patterns to existing sections when possible
+- Create new sections sparingly to maintain structure
+- Update the architectural principles section for major changes
+- Ensure examples follow current codebase conventions
+
+### Quality Standards
+- Test any new patterns in actual code before documenting
+- Verify imports and syntax are correct for the codebase
+- Keep language concise and actionable
+- Focus on "what" and "how", minimize "why" explanations
+
+### Multiple CLAUDE.md Files
+- **Directory-specific CLAUDE.md files** can be created for specialized modules
+- Follow the same structure and guidelines as this root CLAUDE.md
+- Keep them focused on directory-specific patterns and conventions
+- Maximum 20KB per directory-specific CLAUDE.md file
+
+### Instructions for LLMs
+When editing files in this repository, **always check for CLAUDE.md guidance**:
+
+1. **Look for CLAUDE.md in the same directory** as the file being edited
+2. **If not found, check parent directories** recursively up to project root
+3. **Follow the patterns and conventions** described in the applicable CLAUDE.md
+4. **Prioritize directory-specific guidance** over root-level guidance when conflicts exist