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@pflooky pflooky commented Nov 14, 2025

Note

Add pattern-based load execution with rate limiting, strategy-driven foreign keys, performance metrics/validations, and Pekko-based real‑time sink routing with broad docs/examples updates.

  • Core Execution:
    • Add duration-based and pattern-based load execution (constant, ramp, spike, wave, stepped, breaking point) with rate limiting and stage/warmup/cooldown/weighted task support.
  • Foreign Keys:
    • Overhaul with strategy-based processor (cardinality, generation modes, nullability), insert/delete ordering, metadata/nested-field utilities; remove legacy FK V2 util.
  • Sinks:
    • Replace real-time writer with PekkoStreamingSinkWriter and add SinkRouter; async HTTP/JMS handling; batch vs streaming routing.
  • Metrics & Validation:
    • Introduce performance metrics (throughput/latency, TDigest), HTML exporter, and metric-based validations.
  • Parsing & Config:
    • LoadPattern parser, enhanced PlanParser; unified YAML examples and inline connections.
  • Docs/Examples/Version:
    • Update quick start/deployment, add extensive examples/tests; bump version to 0.18.0.

Written by Cursor Bugbot for commit a6f8e4c. This will update automatically on new commits. Configure here.

…tion-based and ramp load patterns, enhance validation capabilities, and improve performance metrics collection. Introduce new test plans and examples for various execution strategies, along with updates to documentation and Docker configurations.
- Add CardinalityConfigBuilder and NullabilityConfigBuilder for configuring cardinality and nullability in relationships
- Introduce new processors for foreign key uniqueness and connection resolution
- Add comprehensive tests for new features and update existing test cases
- Enhance documentation with new YAML examples and integration tests for execution strategies, including performance test examples

This implementation enables flexible foreign key management in data generation, supporting various relationship patterns and improving data integrity validation.
@pflooky pflooky added the enhancement New feature or request label Nov 14, 2025
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claude bot commented Nov 14, 2025

Pull Request Review: Feature/real time sink patterns

This is a substantial PR adding ~22k lines with significant enhancements to foreign key handling, execution strategies, and real-time sink patterns. Overall, the code quality is high with good architecture, but there are several areas that need attention.


🎯 High-Level Assessment

Strengths:

  • Well-structured architecture with clear separation of concerns (strategy pattern, processors, utilities)
  • Comprehensive integration test coverage for new features
  • Good documentation in code comments and JavaDoc
  • Immutable builder patterns consistently applied
  • Performance optimizations well thought out (broadcast joins, caching thresholds)

Concerns:

  • Very large PR (22k+ lines) makes thorough review challenging
  • Missing test files referenced in build.gradle.kts
  • Some potential performance bottlenecks in hot paths
  • Security consideration with environment variable interpolation

🐛 Critical Issues

1. Missing Test File Reference

File: api/src/test/scala/io/github/datacatering/datacaterer/api/ForeignKeyConfigBuildersTest.scala

The file path in the PR shows api/src/test/scala/.../ForeignKeyConfigBuildersTest.scala but when I tried to read it, the file doesn't exist. However, the content appears in the diff. This could be a git issue or the file wasn't properly committed.

Action: Verify all new test files are properly committed to the repository.


⚠️ Major Concerns

2. Potential Performance Issue: Collect in Streaming Path

File: app/src/main/scala/io/github/datacatering/datacaterer/core/sink/PekkoStreamingSinkWriter.scala:60

val dataToPush = df.collect().toList

Issue: Collecting the entire DataFrame to the driver memory before streaming defeats the purpose of distributed processing and could cause OOM errors with large datasets.

Recommendation: Consider using df.toLocalIterator() or processing in micro-batches instead of collecting all data at once. For true streaming, you should stream from Spark without materializing the entire dataset.

3. Cardinality Logic Complexity

File: app/src/main/scala/io/github/datacatering/datacaterer/core/foreignkey/strategy/CardinalityStrategy.scala

The dual-mode logic (group-based vs index-based) is complex and could be error-prone. The determination of which mode to use depends on targetPerFieldCount configuration.

Recommendation:

  • Add more logging at decision points to help with debugging
  • Consider extracting mode selection into a separate method for clarity
  • Add property-based tests to verify correctness across edge cases

4. Duplicate Code Between Files

Files:

  • app/src/main/scala/io/github/datacatering/datacaterer/core/foreignkey/strategy/CardinalityStrategy.scala
  • app/src/main/scala/io/github/datacatering/datacaterer/core/foreignkey/ForeignKeyApplicationUtil.scala

Both files contain similar implementations of applyCardinalityWithGrouping and applyCardinalityWithIndex. This violates DRY principle.

Recommendation: Consolidate this logic into a single location. Since CardinalityStrategy appears to be the newer implementation, consider deprecating the methods in ForeignKeyApplicationUtil and have it delegate to the strategy.

5. Count Operations Without Caching

File: app/src/main/scala/io/github/datacatering/datacaterer/core/foreignkey/strategy/CardinalityStrategy.scala:101-102

val distinctSource = sourceDf.select(sourceFields.map(col): _*).distinct()
val sourceCount = distinctSource.count()

Multiple .count() calls on DataFrames without caching could trigger recomputation.

Recommendation: Cache the DataFrame before calling count if it will be reused (which it is in lines 148, 158).


🔒 Security Considerations

6. Environment Variable Interpolation

File: app/src/main/scala/io/github/datacatering/datacaterer/core/util/EnvVarInterpolator.scala

While the implementation is clean, environment variable interpolation in configuration can be a security risk if user-provided data is interpolated.

Recommendation:

  • Document clearly that this should only be used for trusted configuration files
  • Consider adding a validation/sanitization layer if env vars will be used in SQL or shell contexts
  • Add a warning in logs when interpolation is used for sensitive operations

📊 Code Quality Issues

7. Boolean Parameter Anti-Pattern

File: app/src/main/scala/io/github/datacatering/datacaterer/core/foreignkey/ForeignKeyProcessor.scala:29

class ForeignKeyProcessor(useV2: Boolean = true)

Issue: The useV2 parameter is confusing since V1 just delegates to V2 anyway (line 296). This parameter serves no real purpose.

Recommendation: Remove the useV2 parameter entirely since V1 is deprecated and just calls V2.

8. Magic Numbers

File: app/src/main/scala/io/github/datacatering/datacaterer/core/foreignkey/ForeignKeyApplicationUtil.scala:39-41

private val BROADCAST_THRESHOLD_ROWS = 100000
private val CACHE_SIZE_THRESHOLD_MB = 200
private val SAMPLE_RATIO_FOR_SIZE_ESTIMATE = 0.01

These are defined but should be configurable or documented why these specific values were chosen.

Recommendation: Either make these configurable via ForeignKeyConfig or add comments explaining the rationale for these thresholds.

9. Unused Parameter Warning

File: app/src/main/scala/io/github/datacatering/datacaterer/core/generator/execution/ExecutionStrategy.scala:49

The batchNumber parameter is unused in the default implementation but required in the signature.

Recommendation: This is fine for a default implementation but document that subclasses should override if they need batch-specific logic.


🧪 Testing Concerns

10. Integration Test Coverage

Positive: The PR includes comprehensive integration tests:

  • ForeignKeyEndToEndIntegrationTest (611 lines)
  • EnhancedForeignKeyIntegrationTest (756 lines)
  • InstaInfraHttpIntegrationTest (533 lines)
  • UnifiedYamlIntegrationTest (613 lines)

Recommendation: Ensure all integration tests pass in CI before merging. Consider adding performance benchmarks for the new foreign key strategies.

11. Unit Test for Builders

File: api/src/test/scala/io/github/datacatering/datacaterer/api/ForeignKeyConfigBuildersTest.scala

The builder tests are excellent and follow best practices:

  • Tests immutability
  • Tests validation (e.g., percentage bounds)
  • Tests factory methods

Recommendation: None - well done!


🏗️ Architecture & Design

12. Strategy Pattern Implementation

Files: app/src/main/scala/io/github/datacatering/datacaterer/core/foreignkey/strategy/*

The strategy pattern for foreign key handling is well-implemented with clear separation:

  • ForeignKeyStrategy (base trait)
  • CardinalityStrategy
  • NullabilityStrategy
  • GenerationModeStrategy
  • DistributedSamplingStrategy

Recommendation: Consider adding a strategy registry/factory to avoid hard-coded strategy instantiation in ForeignKeyProcessor.

13. Execution Strategy Factory

File: app/src/main/scala/io/github/datacatering/datacaterer/core/generator/execution/ExecutionStrategyFactory.scala

Clean factory pattern with good separation of concerns. The pattern matching for strategy selection (line 27-50) is clear and maintainable.

Minor issue: The exception message on line 39 could be more helpful by suggesting valid configurations.


📝 Documentation & Naming

14. Excellent Documentation

The code has excellent inline documentation with:

  • Clear JavaDoc-style comments
  • Usage examples in comments (e.g., ForeignKeyConfigBuilders.scala:11-20)
  • Architecture notes in class headers

Recommendation: Consider adding a high-level design document (DESIGN.md) for the foreign key system given its complexity.

15. Naming Inconsistency

  • PekkoStreamingSinkWriter vs RealTimeSinkWriter (deleted)
  • applyForeignKeysV2 should just be applyForeignKeys if V1 is deprecated

Recommendation: Clean up naming after V1 deprecation is complete.


🔧 Performance Considerations

16. T-Digest for Percentile Calculation

File: app/src/main/scala/io/github/datacatering/datacaterer/core/generator/metrics/TDigest.scala

Good choice using T-Digest for memory-efficient percentile calculations. The threshold of 100k samples (line 89) is reasonable.

Recommendation: Benchmark the accuracy/memory tradeoff and document the compression parameter choice.

17. Broadcast Optimization

File: app/src/main/scala/io/github/datacatering/datacaterer/core/foreignkey/ForeignKeyApplicationUtil.scala:223-231

Good use of broadcast joins for small dimension tables. The 100K row threshold is reasonable for most Spark deployments.

Recommendation: Consider making this threshold configurable for different cluster sizes.


What Works Well

  1. Immutability: Consistent use of case classes and immutable builders
  2. Error Handling: Good error messages and validation
  3. Logging: Comprehensive logging at appropriate levels
  4. Separation of Concerns: Clear module boundaries
  5. Test Coverage: Extensive integration tests
  6. Builder Pattern: Clean API with method chaining
  7. Type Safety: Good use of Scala's type system

📋 Recommendations Summary

Must Fix Before Merge:

  1. ✅ Fix missing test file issue
  2. ✅ Address df.collect() in streaming path (potential OOM)
  3. ✅ Remove dead useV2 parameter
  4. ✅ Consolidate duplicate cardinality code

Should Fix Before Merge:

  1. ⚠️ Add caching before count operations
  2. ⚠️ Document/make configurable the magic numbers
  3. ⚠️ Add security warnings for EnvVarInterpolator
  4. ⚠️ Improve exception messages in ExecutionStrategyFactory

Nice to Have:

  1. 💡 Add high-level design documentation
  2. 💡 Add performance benchmarks
  3. 💡 Consider strategy registry pattern
  4. 💡 Add property-based tests for cardinality logic

🎓 Learning from CLAUDE.md

The code generally follows the project conventions documented in CLAUDE.md:

  • ✅ Uses com.softwaremill.quicklens.ModifyPimp for immutable updates
  • ✅ Provides parameterless constructors
  • ✅ Uses @JsonIgnoreProperties(ignoreUnknown = true)
  • ✅ Uses Option[T] instead of null
  • ✅ Follows package structure under io.github.datacatering.datacaterer
  • ✅ Uses exact class names for test running (good integration test examples)

📊 Overall Assessment

This is a high-quality PR that adds significant value to the project. The architecture is sound, the code is well-tested, and the implementation follows best practices. However, the size of the PR (22K+ lines) makes it challenging to review thoroughly.

Recommendation:

  • Address the critical issues (especially the collect() in streaming)
  • Consider breaking future large features into smaller, more reviewable PRs
  • Add the suggested documentation
  • Merge after critical issues are resolved

Score: 7.5/10 (would be 9/10 with the critical issues fixed)

Great work overall! The foreign key enhancements and execution strategies are well-designed and will significantly improve the tool's capabilities. 🚀

source: ForeignKeyRelation = ForeignKeyRelation(),
generate: List[ForeignKeyRelation] = List(),
delete: List[ForeignKeyRelation] = List(),
delete: List[ForeignKeyRelation] = List()
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Bug: Auxiliary constructor missing new optional parameters

The auxiliary constructor for ForeignKeyRelation doesn't pass the new optional parameters (cardinality, nullability, generationMode) to the primary constructor. It calls this(dataSource, step, List(field)) which only provides 3 arguments, but the primary constructor now expects 6 parameters. This will fail to compile because Scala requires all parameters to be provided when calling the primary constructor from an auxiliary constructor, even if they have default values. The auxiliary constructor should be: def this(dataSource: String, step: String, field: String) = this(dataSource, step, List(field), None, None, None).

Fix in Cursor Fix in Web

- Updated the build workflow to support both amd64 and arm64 architectures for packaging the application as a Debian package.
- Introduced a new workflow for testing Linux ARM64 builds, including setup for QEMU and Docker Buildx for cross-platform compatibility.
- Adjusted artifact naming conventions to clearly indicate architecture in the output files.
- Modified the build and test workflows to include the installation of fakeroot prior to executing the jpackage command, ensuring successful packaging of the application for multi-architecture builds.
}

LOGGER.info(s"Using INDEX-BASED approach: assigning FKs by row position (${recordsPerParent} records per parent)")
applyCardinalityWithIndex(sourceDf, targetDf, sourceFields, targetFields, sourceCount, recordsPerParent.toLong)
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Bug: Division by zero when cardinality config produces zero value

When using the index-based FK assignment approach, recordsPerParent is computed from CardinalityConfig values and converted to Long before being used as a divisor. If the config has min=0, max=0 (average=0), min=0, max=1 (average=0.5→0 after toLong), or ratio=0.0 (or any value less than 1.0), the division floor(col("_row_num") / recordsPerParent) at line 234 will fail with a division by zero error. Unlike NullabilityConfig which validates its bounds with a require statement, CardinalityConfig has no validation preventing these edge case values.

Additional Locations (1)

Fix in Cursor Fix in Web

val insertOrderDfs = insertOrder
.map(s => {
foreignKeyAppliedDfs.find(f => f._1.equalsIgnoreCase(s))
.getOrElse(s -> taskDfs.find(t => t._1.equalsIgnoreCase(s)).get._2)
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Bug: Unsafe .get on potentially empty Option causes runtime exception

The insertOrder is calculated from foreignKeyRelations (all FK relations) at line 130, while enabledForeignKeys (line 60) filters out invalid FKs. When building insertOrderDfs, the code tries to find each data source name in taskDfs with .get._2 at line 136. If a FK relation references a disabled or non-existent data source (which gets filtered out from enabledForeignKeys but still contributes to insertOrder), taskDfs.find(...) returns None, and calling .get throws a NoSuchElementException. The insert order should use enabledForeignKeys instead of foreignKeyRelations, or the fallback lookup should handle missing entries gracefully.

Fix in Cursor Fix in Web

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claude bot commented Dec 10, 2025

Code Review - PR #120: Feature/real time sink patterns

This is a substantial PR with 167 files changed (16k additions, 3k deletions). I have reviewed the key architectural changes and have the following feedback:


Strengths

1. Excellent Architectural Refactoring - Foreign Key Processing

  • New modular architecture: The extraction of ForeignKeyUtil (600+ lines) into a clean strategy-based architecture (ForeignKeyProcessor + strategies) is excellent
  • Strategy pattern: CardinalityStrategy, NullabilityStrategy, GenerationModeStrategy provide clear separation of concerns
  • Backward compatibility: ForeignKeyUtil now acts as a compatibility wrapper, allowing existing code to work while delegating to the new architecture
  • Pre-processing optimization: CardinalityCountAdjustmentProcessor is a smart solution - adjusting counts upfront eliminates expensive post-generation row duplication

2. Well-Designed Execution Strategy Framework

  • Strategy factory pattern: ExecutionStrategy with CountBasedExecutionStrategy, DurationBasedExecutionStrategy, PatternBasedExecutionStrategy, and BreakingPointExecutionStrategy is clean and extensible
  • Load patterns: The pattern implementations (RampLoadPattern, SpikeLoadPattern, WaveLoadPattern, SteppedLoadPattern) are well-structured
  • Rate limiting: RateLimiter and DurationTracker provide proper throttling capabilities

3. Metrics & Observability

  • Performance metrics: PerformanceMetrics with batch tracking, percentile calculations (P50-P999), and throughput analysis
  • T-Digest optimization: Smart use of T-Digest for large datasets (>100k) vs exact sorting for smaller datasets
  • Metric validation: MetricValidator enables metric-based assertions (throughput, latency, error rate)
  • Modern reporting: ModernHtmlWriter and PerformanceMetricsExporter improve observability

4. Pekko Migration

  • Clean replacement: PekkoStreamingSinkWriter replaces RealTimeSinkWriter (243 lines removed) with better streaming semantics
  • Proper throttling: Uses Pekko built-in throttle (vs manual rate limiting)
  • Dynamic timeout: Calculates timeouts based on record count and rate (with safety buffer)

5. Test Coverage

  • Comprehensive integration tests: 4 new integration test files with 583, 753, 533, and 244 lines respectively
  • Proper test structure: Tests in integrationTest directory follow project conventions

⚠️ Issues & Concerns

1. Resource Leaks in PekkoStreamingSinkWriter ⚠️

Location: app/src/main/scala/io/github/datacatering/datacaterer/core/sink/PekkoStreamingSinkWriter.scala:51-164

Issue: ActorSystem is only terminated in the finally block, but if an exception occurs, proper shutdown may not happen gracefully.

Recommendation: Ensure ActorSystem shutdown is awaited properly in exception cases.

2. Potential Division by Zero in CardinalityStrategy

Location: app/src/main/scala/io/github/datacatering/datacaterer/core/foreignkey/strategy/CardinalityStrategy.scala:100

Issue: distinctSource.count() could be 0 if source DataFrame is empty, leading to division by zero in ratio calculations.

Recommendation: Add validation for empty source DataFrames before processing.

3. Magic Numbers in Multiple Locations

Locations:

  • PekkoStreamingSinkWriter.scala:71,83: parallelism = Math.min(permitsPerSecond, 100) - why 100?
  • PekkoStreamingSinkWriter.scala:109: Math.min(estimatedDurationSeconds.toInt, 300) - why 300 seconds?
  • PatternBasedExecutionStrategy.scala:90: math.abs(targetRate - currentRate).toDouble / currentRate > 0.1 - why 10%?

Recommendation: Extract these as named constants with documentation explaining the rationale.

4. Error Handling - Silent Failures

Location: MetricValidator.scala:46-48

Issue: Returning 0.0 for unknown metrics could hide configuration errors. If a user typos "throughput" as "througput", validations would silently pass with value 0.0.

Recommendation: Throw an exception for unknown metrics to fail fast on configuration errors.

5. Thread Safety Concerns

Location: PatternBasedExecutionStrategy.scala:29-32

Issue: Mutable fields (currentRateLimiter, currentRate, etc.) are accessed across batch callbacks without synchronization. If batches run concurrently, race conditions could occur.

Recommendation: Use @volatile or document the single-threaded assumption clearly.

6. Performance - Collect in Streaming Sink

Location: PekkoStreamingSinkWriter.scala:60

Issue: Calling .collect() brings the entire DataFrame to the driver. For large datasets, this could cause OOM errors.

Recommendation:

  • Add documentation warning about dataset size limits
  • Consider using streaming APIs for large datasets
  • Add a configurable size threshold with validation

7. Incomplete Deletion Verification

Location: app/src/main/scala/io/github/datacatering/datacaterer/core/util/ForeignKeyUtilV2.scala

Issue: This file shows 657 lines deleted. Ensure all references are removed and the file is actually deleted from the repository.

Verification needed: Confirm no lingering references exist.


🔍 Code Quality & Best Practices

Positives:

  1. ✅ Proper use of Scala case classes and immutability
  2. ✅ Comprehensive logging with contextual information
  3. ✅ Clean separation of concerns (strategies, coordinators, processors)
  4. ✅ Consistent error handling patterns
  5. ✅ Good use of Option types instead of null
  6. ✅ Follows CLAUDE.md conventions (builder patterns, Jackson annotations)

Minor Suggestions:

  1. Documentation: Add ScalaDoc for complex strategies (especially CardinalityStrategy)
  2. Naming: apply method in strategies is generic - consider applyStrategy or processRelation
  3. Testing: Verify integration tests cover edge cases (empty DataFrames, zero cardinality, extreme patterns)

🔒 Security

No obvious security concerns. The code:

  • ✅ Uses parameterized queries (no SQL injection risk)
  • ✅ Does not expose sensitive data in logs
  • ✅ Properly handles user input validation

📊 Performance

Optimizations:

  • ✅ Smart use of DataFrame caching (ForeignKeyProcessor.scala:112)
  • ✅ T-Digest for efficient percentile calculation at scale
  • ✅ Broadcast optimization flags in FK config

Concerns:

  • ⚠️ .collect() in streaming sink (mentioned above)
  • ⚠️ Frequent rate limiter recreation in PatternBasedExecutionStrategy (mitigated by 10% threshold check)

🧪 Testing

Strengths:

  • ✅ 4 new integration test files with comprehensive coverage
  • ✅ Tests for foreign key end-to-end, cardinality, nullability
  • ✅ HTTP integration tests

Gaps:

  • ❓ Unit tests for individual strategies - verify coverage exists
  • ❓ Edge case tests (empty DataFrames, zero source records, concurrent execution)
  • ❓ Performance regression tests for the new FK architecture

Recommendation: Verify unit test coverage for the new strategy classes.


📝 Summary

This is a high-quality PR with significant architectural improvements. The foreign key refactoring and execution strategy framework are well-designed and follow solid software engineering principles.

Required Fixes (before merge):

  1. ⚠️ Fix resource leak in PekkoStreamingSinkWriter
  2. ⚠️ Add empty source validation in CardinalityStrategy
  3. ⚠️ Change unknown metric handling to throw exception (not return 0.0)
  4. ⚠️ Verify ForeignKeyUtilV2 is fully removed

Recommended Improvements:

  1. Extract magic numbers to named constants
  2. Add thread safety documentation or synchronization
  3. Document size limits for streaming sink .collect()
  4. Add ScalaDoc for complex strategies

Overall Assessment:

Approve with minor changes - The architectural improvements are excellent, but the resource management and edge case handling issues should be addressed before merge.

Estimated effort to fix: 2-3 hours for required fixes + documentation.


Great work on this refactoring! The new architecture is significantly cleaner and more maintainable. 🚀

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case config if config.ratio.isDefined =>
// Ratio: set perField with fixed count
// Use requiredCount for total records, perField count for records per parent
val recordsPerParent = config.ratio.get.toInt
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Bug: Truncation of ratio causes fewer records than expected

Using .toInt and .toLong truncates the ratio value when converting from Double to integer types. For a ratio of 2.5, this becomes 2 instead of rounding to 3. This inconsistency with calculateRequiredCount (which uses math.ceil) causes the perField count to generate fewer records than the total required count calculation expects. For example, with 3 parents and ratio 2.5: total required = 8 (via ceil), but perField generates only 6 (3 * 2).

Additional Locations (1)

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claude bot commented Dec 11, 2025

Pull Request Review: Feature/real time sink patterns

This is a major architectural enhancement with 16,079 additions across 93 files.

Overall Assessment

Verdict: This PR demonstrates excellent engineering with well-structured architecture, comprehensive testing, and thoughtful design patterns. There are concerns to address before merging.

Highlights:

  • Clean separation of concerns with strategy patterns
  • Comprehensive test coverage (unit, integration, and performance tests)
  • Backward compatibility maintained via wrapper classes
  • Extensive documentation in code comments

Key Concerns

1. TDigest Implementation (HIGH PRIORITY)

TDigest.scala stores all values in memory (up to 100k) - this is NOT a true T-Digest streaming sketch algorithm. Recommendation: Rename to SimplePercentileCalculator or implement actual T-Digest.

2. Memory Risks (HIGH PRIORITY)

  • CardinalityStrategy uses distinct() operations triggering full Spark shuffles
  • PekkoStreamingSinkWriter:60 uses collect() loading all data into driver memory
  • Automatic caching without size checks (ForeignKeyProcessor:112)
    Recommendation: Add memory estimation and warnings for large datasets.

3. Race Condition (HIGH PRIORITY)

ForeignKeyProcessor:122-124 mutates taskDfs while iterating. If same target appears multiple times, later iterations use stale data.
Fix: Collect all updates first, then apply atomically.

4. Actor System Performance

PekkoStreamingSinkWriter creates/terminates actor systems per call (expensive thread pool initialization).
Recommendation: Use shared actor system across calls.

5. Timeout Configuration

300-second timeout cap may be too aggressive for large datasets with low rates.
Recommendation: Make timeout configurable.

Potential Bugs

  1. Null handling in SinkRouter:38 - NPE risk if stepOptions is null
  2. Integer overflow risk in CardinalityStrategy:131 - Double to Long conversion
  3. No bounds checking for breaking point pattern maxRate (DoS risk)

Architecture Review

Foreign Key Processing: Excellent separation of concerns with ForeignKeyProcessor and strategy pattern. InsertOrderCalculator provides topological sort with circular dependency detection.

Execution Strategies: Well-designed trait-based system with LoadPatternParser providing clean YAML mapping.

Real-Time Sink Writer: Clean refactoring with SinkRouter centralizing routing logic.

Test Coverage

Excellent coverage with 583+ lines in ForeignKeyEndToEndIntegrationTest, 753+ lines in EnhancedForeignKeyIntegrationTest. Gaps: TDigest edge cases, actor lifecycle, circular dependency errors.

Recommendations

HIGH PRIORITY (Address Before Merge):

  1. Rename TDigest or implement properly
  2. Fix foreign key race condition
  3. Add memory guards for collect() and distinct()

MEDIUM PRIORITY:

  1. Shared actor system for performance
  2. Configurable timeouts
  3. Decompose ModernHtmlWriter (1,226 lines)

Summary

High-quality work with excellent architecture and comprehensive testing. Architectural improvements significantly outweigh concerns, which are addressable.

Recommendation: Request changes for high-priority items, then approve for merge.

val nullCount = (totalCount * percentage).toLong
targetDf
.withColumn("_row_idx", row_number().over(Window.orderBy(lit(1))) - 1)
.withColumn("_should_null_fk", col("_row_idx") < nullCount)
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Bug: Nullability "head" and "tail" strategies use non-deterministic ordering

The "head" and "tail" nullability strategies are documented to apply nulls to the "first N%" and "last N%" of records respectively. However, the implementation uses Window.orderBy(lit(1)) which provides no meaningful ordering since all rows have the same constant sort key. This makes the row assignment arbitrary and non-deterministic, causing both strategies to behave essentially like "random". The documented behavior of selecting specific positional records cannot be achieved without an actual column-based ordering.

Additional Locations (1)

Fix in Cursor Fix in Web

…-based approaches

- Updated ForeignKeyEndToEndIntegrationTest to assert expected null rows for foreign keys based on deterministic hash values.
- Modified CardinalityStrategy, DistributedSamplingStrategy, GenerationModeStrategy, and NullabilityStrategy to utilize hash-based methods for consistent results across different Spark environments.
- Introduced SimplePercentileCalculator for efficient percentile calculations in performance metrics, replacing the deprecated T-Digest.
- Added tests for new deterministic behaviors in foreign key strategies and updated existing tests for consistency.
- Improved DataGenerator to support deterministic SQL generation with seed-based hash functions.
val executableTasks = context.executableTasks

val enabledSources = plan.tasks.filter(_.enabled).map(_.dataSourceName)
val sinkOptions = plan.sinkOptions.get
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Bug: Unchecked Option.get may throw NoSuchElementException

The process method calls plan.sinkOptions.get without first verifying that sinkOptions is defined. If ForeignKeyProcessor.process() is called directly (e.g., via ForeignKeyUtil.getDataFramesWithForeignKeys) with a plan where sinkOptions is None, this will throw a NoSuchElementException at runtime. The method lacks a guard clause to handle this edge case safely.

Fix in Cursor Fix in Web

// Use absolute hash value modulo sourceCount for uniform distribution
targetDf.withColumn("_fk_idx", abs(hashExpr) % sourceCount)
case None =>
targetDf.withColumn("_fk_idx", floor(rand() * sourceCount).cast(LongType))
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Bug: Division by zero when source DataFrame is empty

The apply method performs modulo and multiplication operations with sourceCount (lines 78 and 80) without checking if it's zero first. If the source DataFrame has no records, sourceCount will be 0, causing a division by zero error during the modulo operation abs(hashExpr) % sourceCount or undefined behavior with rand() * sourceCount. Unlike CardinalityStrategy which properly guards against this case, DistributedSamplingStrategy lacks this protection.

Fix in Cursor Fix in Web

- Removed obsolete integration test steps from GitHub Actions workflow.
- Improved logging in StepDataCoordinator for better debugging during record generation.
- Updated CardinalityCountAdjustmentProcessor to ensure only foreign key target steps are modified, preventing unintended changes.
- Added new YAML plan and task files for account balances and transactions, including validation of foreign key relationships.
- Introduced integration tests for YAML plan execution to verify record counts and foreign key integrity.
@pflooky pflooky merged commit 0f25083 into main Dec 18, 2025
4 checks passed
@pflooky pflooky deleted the feature/real-time-sink-patterns branch December 18, 2025 10:26
@claude
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claude bot commented Dec 18, 2025

PR Review: Feature/real time sink patterns

This is an impressive and comprehensive enhancement that adds significant new capabilities to Data Caterer. I've reviewed the key architectural changes across load execution, foreign keys, sinks, and metrics. Overall, the code quality is excellent with strong adherence to Scala best practices. Below are my findings organized by category.


🎯 Summary

Verdict:Approved with minor recommendations

This PR successfully delivers:

  • Pattern-based load execution with 6 load patterns (constant, ramp, spike, wave, stepped, breaking point)
  • Complete foreign key strategy overhaul with cardinality, nullability, and generation mode controls
  • Pekko-based streaming sink architecture with rate limiting
  • Performance metrics collection with percentile calculations
  • Extensive test coverage (20+ new test files)

💪 Strengths

1. Excellent Architecture

  • Strategy Pattern: The foreign key refactor (ForeignKeyProcessor, CardinalityStrategy, GenerationModeStrategy, NullabilityStrategy) is exemplary. Clean separation of concerns with composable strategies.
  • Execution Strategies: ExecutionStrategy trait with CountBasedExecutionStrategy, DurationBasedExecutionStrategy, and PatternBasedExecutionStrategy provides excellent extensibility.
  • Sink Router: SinkRouter centralizes routing logic that was previously scattered - great cleanup.

2. Code Quality

  • Immutability: Builders use quicklens correctly (CardinalityConfigBuilder, NullabilityConfigBuilder)
  • Null Safety: Proper use of Option[T] throughout
  • Logging: Comprehensive debug/info logging with structured context
  • Documentation: Excellent inline comments explaining complex logic (e.g., CardinalityStrategy:68-86)

3. Test Coverage

  • 20+ new test files covering unit, integration, and performance tests
  • Tests for edge cases: ForeignKeyConfigBuildersTest validates immutability and bounds checking
  • Integration tests: ForeignKeyEndToEndIntegrationTest, EnhancedForeignKeyIntegrationTest, InstaInfraHttpIntegrationTest

4. Backward Compatibility

  • Smart deprecation: ForeignKeyUtil wraps new architecture maintaining API compatibility (ForeignKeyUtil.scala:11-18)
  • @deprecated annotations with migration guidance

🔍 Issues & Recommendations

Critical Issues (None found)

High Priority

1. Thread.sleep in RateLimiter (RateLimiter.scala:52)

Location: app/src/main/scala/io/github/datacatering/datacaterer/core/generator/execution/rate/RateLimiter.scala:52

Thread.sleep(sleepTime)

Issue: Thread.sleep blocks the thread, which can cause issues in concurrent environments or when interrupted.

Recommendation:

  • Consider using Thread.sleep with interrupt handling:
try {
  Thread.sleep(sleepTime)
} catch {
  case _: InterruptedException =>
    Thread.currentThread().interrupt() // Restore interrupt status
    LOGGER.warn("Rate limiting interrupted")
}
  • For Scala 2.13+, consider scala.concurrent.blocking wrapper for thread pool awareness

2. ActorSystem Lifecycle in PekkoStreamingSinkWriter

Location: PekkoStreamingSinkWriter.scala:74-78, 192-196

Current Behavior: Creates/destroys ActorSystem per call when not shared (line 77-78, 192-196)

Issue: ActorSystem creation is expensive (~100-500ms startup time). In loop scenarios (batch processing), this overhead multiplies.

Recommendation:

  • Document that callers should provide sharedActorSystem for repeated calls
  • Consider adding metrics/warnings when creating many short-lived actor systems
  • Example for docs:
// Efficient for multiple calls
implicit val system = ActorSystem("shared")
val writer = new PekkoStreamingSinkWriter(config, Some(system))
// ... multiple saveWithRateControl calls ...
writer.shutdown()

Medium Priority

3. SimplePercentileCalculator Memory Bounds (SimplePercentileCalculator.scala:9-14)

Location: app/src/main/scala/io/github/datacatering/datacaterer/core/generator/metrics/SimplePercentileCalculator.scala:19

Current: Silently drops values beyond 100k limit (line 32-34)

while (i < weight && values.size < maxStoredValues) {
  values += value
  i += 1
}

Issue: Silent data loss can lead to inaccurate percentiles for large datasets. Docs warn about this (line 9-13), but no runtime indication.

Recommendation:

  • Add a flag/counter tracking dropped values
  • Log warning when first drop occurs
  • Include dropped count in summary() method
private var droppedCount: Long = 0

def add(value: Double, weight: Long = 1): Unit = {
  // ... existing code ...
  if (i < weight && droppedCount == 0) {
    LOGGER.warn(s"SimplePercentileCalculator reached max capacity (). Further values will be sampled.")
  }
  droppedCount += (weight - i)
}

4. PatternBasedExecutionStrategy Rate Change Threshold (PatternBasedExecutionStrategy.scala:25)

Location: app/src/main/scala/io/github/datacatering/datacaterer/core/generator/execution/PatternBasedExecutionStrategy.scala:25

private val RATE_CHANGE_THRESHOLD = 0.1  // 10%

Issue: Hardcoded 10% threshold may not be optimal for all patterns (spike patterns may need more granular rate changes)

Recommendation:

  • Make threshold configurable via pattern config or execution strategy options
  • Document why 10% was chosen (probably performance vs accuracy tradeoff)

5. Division by Zero Protection

Location: PatternBasedExecutionStrategy.scala:96

math.abs(targetRate - currentRate).toDouble / currentRate > RATE_CHANGE_THRESHOLD

Issue: If currentRate == 0, this will throw ArithmeticException

Recommendation:

val shouldUpdate = currentRateLimiter.isEmpty ||
  (currentRate > 0 && math.abs(targetRate - currentRate).toDouble / currentRate > RATE_CHANGE_THRESHOLD) ||
  (currentRate == 0 && targetRate > 0)

6. PekkoStreamingSinkWriter Timeout Calculation (PekkoStreamingSinkWriter.scala:133-138)

val estimatedDurationSeconds = if (permitsPerSecond > 0) {
  Math.max((dataToPush.size.toDouble / permitsPerSecond) * 1.5, 10.0)
} else {
  10.0
}

Issue: 50% buffer (1.5x multiplier) may be insufficient for:

  • HTTP endpoints with high latency
  • Network issues causing retries
  • Max parallelism throttling (MAX_ASYNC_PARALLELISM = 100)

Recommendation:

  • Make buffer percentage configurable
  • Consider adaptive timeout based on actual vs expected rate after first N records
  • Add timeout extension for slow but progressing operations

Low Priority

7. Magic Numbers

Several hardcoded constants lack configuration options:

  • PekkoStreamingSinkWriter.MAX_ASYNC_PARALLELISM = 100 (line 43)
  • PekkoStreamingSinkWriter.MAX_STREAMING_TIMEOUT_SECONDS = 300 (line 49)
  • CardinalityStrategy.MIN_SOURCE_COUNT_FOR_MODULO = 1L (line 28)

Recommendation: Consider moving to configuration or documenting why these specific values were chosen.

8. ForeignKeyProcessor Configuration Cross-Contamination Comment (ForeignKeyProcessor.scala:51-52)

Great catch documenting the issue! The comment at lines 51-52 is excellent:

// DO NOT use gatherForeignKeyRelations as it aggregates ALL FKs with the same source,
// which causes configuration cross-contamination

Recommendation: If gatherForeignKeyRelations is now an anti-pattern, consider deprecating or removing it to prevent future misuse.


🔒 Security Considerations

No security issues found

  • Proper resource cleanup (ActorSystem termination, DataFrame unpersist)
  • No SQL injection vectors (uses Spark DataFrame API)
  • Exception handling prevents information leakage
  • Rate limiting prevents resource exhaustion

🚀 Performance Considerations

Optimizations Applied

  1. Broadcast optimization: ForeignKeyConfig.enableBroadcastOptimization = true (line 84)
  2. Caching threshold: ForeignKeyConfig.cacheThresholdMB = 200 (line 85)
  3. Lazy DataFrame caching: Only cache if not already cached (ForeignKeyProcessor.scala:112)
  4. Percentile calculation optimization: Switches to approximate for datasets > 100k (PerformanceMetrics.scala:89)

Potential Bottlenecks

  1. PekkoStreamingSinkWriter.collect() (PekkoStreamingSinkWriter.scala:89)

    val dataToPush = df.collect().toList
    • Pulls entire DataFrame into memory
    • For large datasets, this could cause OOM
    • Mitigation: SinkRouter only routes to streaming when rate control is configured, implying smaller datasets
  2. SimplePercentileCalculator.quantile() sorts on every call (SimplePercentileCalculator.scala:55)

    • For frequent percentile queries, consider caching sorted array
    • Trade-off: memory vs compute

Best Practices Adherence

Follows CLAUDE.md Guidelines

  • ✅ Uses quicklens for immutable updates (CardinalityConfigBuilder)
  • ✅ Parameterless constructors provided
  • @JsonIgnoreProperties(ignoreUnknown = true) on models
  • Option[T] instead of null
  • ✅ Package structure under io.github.datacatering.datacaterer
  • ✅ Case class data models
  • ✅ Builder pattern for configuration

Testing Best Practices

  • ✅ Exact test class names (no wildcards)
  • ✅ Unit, integration, and performance test separation
  • ✅ Mock usage for external dependencies
  • ✅ Edge case coverage (nullability bounds, immutability verification)

📊 Test Coverage Assessment

New Test Files: 20+ (unit + integration + performance)

Coverage Highlights:

  • ✅ Foreign key strategies: DistributedSamplingStrategyTest, NullabilityStrategyTest, ForeignKeyValidatorTest
  • ✅ Execution patterns: LoadPatternTest, RateLimiterTest, DurationTrackerTest
  • ✅ Metrics: PerformanceMetricsTest, SimplePercentileCalculatorTest
  • ✅ End-to-end: ForeignKeyEndToEndIntegrationTest, InstaInfraHttpIntegrationTest
  • ✅ Edge cases: ForeignKeyConfigBuildersTest tests immutability, bounds validation

Recommendation: Consider adding performance regression tests for:

  • Rate limiter accuracy under high load
  • Foreign key performance with large cardinality ratios
  • Percentile calculation performance at 100k threshold boundary

🎓 Documentation Quality

Excellent

  • Inline comments explain complex logic (e.g., CardinalityStrategy group-based vs index-based modes)
  • KDoc/ScalaDoc on public APIs
  • Architecture diagrams in comments (ForeignKeyProcessor:18-26)

Suggestions

  1. Add examples to LoadPattern implementations showing typical use cases
  2. Document performance characteristics of each foreign key strategy
  3. Add migration guide from old ForeignKeyUtil to new ForeignKeyProcessor

🔧 Code Cleanup Observations

Excellent Cleanup

  • Removed legacy code: ForeignKeyUtilV2.scala (deleted)
  • Replaced: RealTimeSinkWriter.scalaPekkoStreamingSinkWriter.scala
  • Reduced file size: ForeignKeyUtil.scala from 637 lines to 50 lines (compatibility wrapper)

Minor

  • Deleted workflow files: .github/workflows/build.yml and check.yml (218 lines removed)
    • Question: Were these intentionally removed or should they be in a separate PR?

📈 Metrics & Monitoring

New Capabilities:

  • ✅ Batch-level metrics (throughput, latency)
  • ✅ Percentile calculations (P50, P75, P90, P95, P99, P999)
  • ✅ Phase tracking (warmup, execution, cooldown)
  • ✅ HTML report generation (PerformanceHtmlWriter, ModernHtmlWriter)

Recommendation: Consider adding:

  • Prometheus/Grafana export format
  • Real-time metrics streaming for long-running jobs
  • Alert thresholds for performance degradation

🎯 Final Recommendations

Before Merge

  1. ✅ Fix division-by-zero in PatternBasedExecutionStrategy.scala:96
  2. ✅ Add interrupt handling to RateLimiter.scala:52
  3. ✅ Document PekkoStreamingSinkWriter shared ActorSystem best practices

Post-Merge (Future PRs)

  1. Make rate change threshold configurable
  2. Add dropped value tracking to SimplePercentileCalculator
  3. Consider adaptive timeout for PekkoStreamingSinkWriter
  4. Add performance regression tests
  5. Create migration guide for foreign key API

📝 Summary

This PR represents a major architectural improvement with excellent code quality, comprehensive testing, and strong adherence to best practices. The strategy pattern implementation for foreign keys is particularly well-designed and sets a great example for future enhancements.

Impact:

  • 17,432 additions / 3,724 deletions
  • Major features: Load patterns, FK strategies, streaming sinks, performance metrics
  • Breaking changes: Minimal (backward compatibility maintained)
  • Test coverage: Excellent (20+ new test files)

Recommendation:Merge after addressing high-priority issues

Great work! 🚀

val optTargetStep = executableTasks.flatMap(tasks =>
tasks
.find(_._1.dataSourceName == target.dataSource)
.flatMap(_._2.steps.find(_.name == target.step))
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Bug: Inconsistent case sensitivity in data source name comparison

The lookup for targetPerFieldCount at line 94 uses case-sensitive comparison (==) when comparing dataSourceName with target.dataSource, while all other DataFrame lookups in the same file (lines 123, 135, 136, 139, 148) use equalsIgnoreCase. This inconsistency causes targetPerFieldCount to be None when data source names differ only by case, even though the DataFrames are successfully found elsewhere. This affects the selection between group-based and index-based cardinality strategies, potentially causing incorrect FK assignments.

Fix in Cursor Fix in Web

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