Design Document Conventions
1. Background / Problem Statement
1.1 Background and Pain Points
- Describe current system/module limitations and deficiencies
- List specific scenarios, metrics, or incident cases that triggered this design
1.2 Impact Scope
- Affected modules, microservices, APIs, data stores, third-party dependencies
- Potential impact on performance, reliability, cost, maintainability
- Forward/backward compatibility analysis
1.3 Constraints
- Compliance/security/performance/resource restrictions
- External system or infrastructure dependencies
2. Design Goals
2.1 Functional Goals
- List Must/Should/Could core capabilities by priority
2.2 Non-Functional Goals
- Performance (throughput, latency, concurrency, resource usage)
- Scalability, maintainability, testability, observability
- Reliability (fault tolerance, HA, degradation, rollback strategies)
2.3 Constraint Goals
- Backward compatibility, API stability
- Security and compliance requirements
3. Technical Design
3.1 Architecture Diagram
- Use Mermaid for high-level component diagrams with data/control flow
3.2 Detailed Flowcharts
- Key business flows, exception flows, retry/compensation with timing and triggers
3.3 Thread/Concurrency Model
- Thread lifecycle, inter-thread communication (locks, condition variables, queues, Actor patterns)
- Sequence diagrams for concurrency interactions
3.4 Core Classes and Data Structures
- Class diagrams showing main classes, interfaces, inheritance/composition relationships
- Key data structure fields, lifecycle, thread-safety strategy
3.5 Key Algorithms or Protocols
- Pseudocode or flow for pub/sub, load balancing, retry backoff, etc.
- State machine / protocol state transition diagrams
3.6 Error Handling and Recovery
- Error classification, exception stack, retry strategies, degradation plans
- Monitoring metrics, alert trigger conditions and levels
3.7 Deployment and Operations
- Configuration items, hot-update mechanisms, canary and rollback strategies
- CI/CD, container, Service Mesh, Kubernetes resource considerations
4. Unit Testing
4.1 Test Scope and Goals
- Cover core logic, boundary conditions, concurrency scenarios, exception paths
4.2 Test Environment and Tools
- Google Test/Mock version, necessary third-party stubs/fakes
4.3 Test Scenarios and Cases
| Case ID |
Scenario |
Input |
Expected Output/Behavior |
Mock Dependencies |
| TC-01 |
Normal single log push |
Single valid LogRecord |
Returns SUCCESS, buffer size +1 |
None |
| TC-02 |
Buffer full |
capacity=N filled |
Throws BufferOverflowException |
None |
| TC-03 |
Concurrent push |
Multi-thread simultaneous push |
No data loss, order/final consistency matches design |
MutexMock |
| TC-04 |
flush clears |
M items exist, then flush |
Returns M items, buffer size=0 |
TimeProviderMock |
4.4 Boundary and Exception Testing
- Empty input, invalid input, extreme capacity, network/disk fault injection
4.5 Performance Benchmarking (optional)
- Throughput, latency, CPU/Memory profile; comparison with baseline
Notes
- Do not include project management info (estimates, schedules, milestones, Gantt charts)
- Code examples must follow team C++ coding standards (see
skills/project-knowledge/)
- Test case naming:
<Module>_<Function>_<Number> for CI coverage tracking
