June 2026 performance summary for scylladb/scylla-cluster-tests: Delivered reliability improvements for node replacement, hardened TWCS configuration handling, enhanced log collection, and stressed-test stability. Implemented robust error handling to preserve cluster node count, improved observability, and reduced risk of out-of-space during large-scale stress tests. Demonstrated chaos engineering patterns, data streaming during init, and improved test infrastructure.

May 2026 (2026-05) monthly summary for scylladb/scylla-cluster-tests. This period delivered a major new Scylla Multi-Data Center (MDC) lifecycle and testing capability along with CI/test infrastructure reliability improvements, driving stronger resilience, observability, and business value. The MDC feature introduces a dedicated data-center management module, enhances AddRemoveDcNemesis, supports adding multiple nodes to a new DC with updated replication factor, and updates system keyspaces replication, expanding multi-datacenter testing coverage and resilience. In parallel, CI/CD reliability and logging improvements were implemented to stabilize performance tests and simplify test configuration, improving overall pipeline reliability and observability. Key investments and outcomes include: - MDC lifecycle and testing feature delivery, with modularized components and RF-aware DC provisioning to validate complex multi-DC topologies. - CI/CD reliability and observability improvements, including environment variable handling for perf tests, refined logging controls, and configuration cleanup to reduce flakiness.

April 2026 — Reliability and monitoring improvements for scylla-cluster-tests with a focus on safer scaling, robust monitoring, and safer resource management. Implemented cluster-wide tablet migration synchronization during node additions, stabilized Docker monitoring by switching to a label-file workflow to correctly handle spaces in label values, and added disk-utilization safeguards to prevent materialized view creation under high risk. Improved streaming timeouts during concurrent operations with additional debug visibility, and corrected a multi-DC operation naming issue to ensure accurate telemetry. These changes reduce outage risk during scaling, improve observability, and enable safer, more predictable deployments across environments.

March 2026 monthly summary for scylladb/scylla-cluster-tests: Focused on reliability hardening of Nemesis chaos testing, expanded test coverage, and configuration safeguards. Implemented adaptive timeouts and metrics for tablet operations to enable data-driven planning. Ensured GCE root disk type adherence across node types to improve multi-DC compatibility. In parallel, CI/test infrastructure improvements accelerated feedback and reduced resource leaks in failure scenarios. Overall, these efforts deliver more stable chaos testing, safer cluster disruptions, and clearer observability and deployment correctness.

February 2026 monthly summary for scylla-cluster-tests focusing on reliability, stability, and developer tooling. Key efforts included stabilizing long-running test workflows, enhancing cluster stability and network reliability, and improving observability and developer experience.

Month: 2026-01 – scylladb/scylla-cluster-tests Key features delivered - ScyllaDB Task Management Enhancements: Added parse_scylla_task_list and wait_for_tasks utilities to parse nodetool tasks list and wait for specific tasks; commits: 222e3b3d1ba2c476421f2350202a89c202559ef7 - Code quality improvement: Removed trailing spaces in unit tests to align with coding standards; commit: b5cdf499bceac82ff02fbb001ad6103da56bd028 Major bugs fixed - Bug: Prevent target node from being used as verification node during nemesis operations to avoid failures if the target is killed; commit: a98b4620892257ffa5138757ad1dc3fdf0af11a1 Overall impact and accomplishments - Improved test reliability during fault injection, reduced flake risk, and enhanced task automation, enabling faster feedback and safer chaos testing. - Cleaner, more maintainable codebase with standardized formatting. Technologies/skills demonstrated - Python tooling and utilities for task parsing and orchestration - Nodetool task output parsing - Chaos engineering practices (nemesis testing) - CI/code hygiene and quality practices

December 2025 monthly summary: Delivered targeted features and reliability improvements across Scylla Cloud projects, focusing on cluster resilience, installation simplicity, and test stability. Key work spans two repositories: scylla-cluster-tests and scylladb, with notable contributions in feature delivery, dependency upgrades, and test instrumentation. Results include enhanced failure tolerance during decommission operations, streamlined Python dependency installation, robust node exporter setup, and improved noise filtering in crash testing to boost reliability and confidence in releases.

November 2025 monthly summary for scylla-cluster-tests focusing on Nemesis robustness and test infrastructure enhancements.

Monthly summary for 2025-10 focusing on the scylladb/scylla-cluster-tests repo. Highlights include key features delivered, critical bug fixes, overall impact on reliability and performance testing, and the technologies demonstrated during the period. The work emphasizes business value through more robust monitoring, realistic test configurations, and streamlined CI/CD pipelines.

Month 2025-09 focused on strengthening test infrastructure resilience and KMS configuration reliability for cluster tests. Delivered a robust teardown validator for SSTables during node shutdown scrub, preventing flaky teardown failures, and refactored KMS enabling conditions logic for AWS and Azure backends to improve clarity, configurability, and error handling. Result: more stable test runs, faster feedback loops, and better alignment with security/compliance requirements for cluster testing.

August 2025: Delivered disk usage monitoring enhancements for scylla-cluster-tests, boosting observability, capacity planning, and rack balance. Implemented a per-node disk usage retrieval method and a context manager to periodically collect and forward disk usage data to Argus. These changes provide real-time visibility into cluster utilization, enable proactive actions, and strengthen the reliability of the monitoring pipeline. Commits reference: cf3f876f1b02b0c2aa6a2b0ca4ed4ba16eee4fe1 and cbc599ad3b792e9bd3dc31cbb5d85c938127fb1c integrated into the repository's monitoring workflow.

July 2025 monthly summary for scylladb/scylla-cluster-tests: Delivered key reliability enhancements for cluster testing, strengthened resilience against cloud and container issues, and improved observability with detailed coredump diagnostics. These changes reduce flaky test runs, accelerate troubleshooting, and improve overall test stability for production-grade deployments.

June 2025: In scylla-cluster-tests, delivered reliability-focused improvements and feature tweaks to support stable, scalable test runs across Azure. Key changes included a fix to the Bloom Filter False Positive Guardrail to prevent memory allocation issues, an increase to the nemesis rebuild timeout to accommodate longer rebuilds, and a set of test stability enhancements to reduce flakiness and enforce invariants during capacity changes. Overall impact: more trustworthy test results, reduced failure modes during upgrades/rebuilds, and better support for multi-backend environments. Technologies/skills demonstrated: chaos engineering with nemesis, timeout tuning, robust error handling, and cross-backend test orchestration.

May 2025 focused on stabilizing CQL quoting and Materialized View workflows in scylla-cluster-tests. Delivered robust CQL identifier quoting and MV creation improvements with comprehensive unit tests; fixed CQL identifier regex to prevent misquoting; expanded unit tests for quote/unquote utilities. Business impact: reduced test flakiness and MV-creation errors in CI, enabling safer deployments and faster feedback. Technologies demonstrated: CQL tooling, regex validation, and Python-based test utilities.

April 2025 monthly summary for scylla-cluster-tests focusing on delivering robust test configurations and improved diagnostics. Highlights include a new configuration option to control tablet behavior for new keyspaces and enhanced logging for retryable remote command failures, improving test reliability and diagnosability across configurations.

For March 2025, delivered key enhancements to the ScyllaDB cluster tests suite, focusing on debugging and reliability under load. The work improves regression visibility, validates space management under high utilization, and expands elastic cloud performance testing to cover scale-out/scale-in scenarios. These efforts support faster defect diagnosis, more robust resource utilization, and data-driven assessments of elastic deployment behavior.

February 2025 monthly summary for scylla-cluster-tests focused on strengthening performance regression testing infrastructure and reliability features. Delivered enhancements enable configurable test scenarios beyond cassandra-stress and improved data persistence for accurate monitoring.

Month: 2025-01 — Focused on stabilizing AWS-based tests in scylla-cluster-tests. Delivered a critical bug fix that hardens region_name handling in Nemesis, improving safety and reliability of cross-region, multi-DC configurations and snapshot selection. The change reduces test flakiness, accelerates debugging, and strengthens test coverage for AWS deployments, contributing to higher confidence in cluster behavior across regions.

November 2024 monthly summary for scylladbbot/scylla-cluster-tests: Stabilized CI tooling by addressing a formatting-tool incompatibility, enabling reliable, repeatable test runs and faster feedback to developers. The primary action was pinning pycodestyle to 2.10.0 to resolve a clash with autopep8 introduced in newer versions, ensuring consistent behavior of code formatting checks in CI.