September 2025 monthly summary for scylladb/scylla-cluster-tests: Prioritized reliability and safe cleanup in chaos-testing workflows. No new user-facing features deployed this month; major progress centered on stability and resource lifecycle management within the test harness.

August 2025 monthly summary for scylla-cluster-tests: Delivered a reliability improvement by tuning the disrupt_load_and_stream nemesis timeout, addressing premature timeouts during load/stream sequences. The change reduces flaky outcomes in performance tests and enhances CI stability, enabling more accurate validation of cluster testing workflows.

July 2025: In scylladb/scylla-cluster-tests, delivered a major enhancement to the LWT longevity testing framework and hardened nemesis testing against empty ks_cfs. The LWT configuration now uses Latte-based loader simulations with tablet testing to stress merge/split tablet behavior and validate LWT correctness under varied conditions, replacing the prior client-server setup. The nemesis stability patch explicitly raises an UnsupportedNemesis exception when ks_cfs is empty, reducing test flakiness and improving resilience. These changes broaden test coverage, shorten feedback loops, and mitigate production risk by catching edge cases earlier.

June 2025 monthly summary for scylla-cluster-tests: Focused on reliability, test stability, and robust repair workflows. Delivered safeguards around nemesis-driven data manipulations, improved test environment hygiene, and introduced a repair workflow that tolerates downed nodes to increase CI resilience. These changes reduce flakiness, safeguard data, and accelerate CI feedback loops, enabling safer code deployments.

May 2025 — scylladb/scylla-cluster-tests: Implemented observability enhancement for the FlakyRetryPolicy. Added debug logging to capture the first five server error occurrences per request, including the query, consistency level, attempt number, and error, while preserving existing retry semantics. This provides actionable insights into flaky-server behavior with no impact on retry logic.

April 2025 monthly summary for scylladb/scylla-cluster-tests, focusing on test infrastructure improvements that enhance debuggability and reliability of cluster tests.

March 2025 monthly summary for scylla-cluster-tests: Delivered reliability improvements and safety features to strengthen cluster testing workflows and data integrity. Focused on stabilizing test behavior under edge conditions and preventing cascading failures during disruption scenarios.

February 2025 monthly summary: Focused on hardening the cluster test harness and decommission workflows for ScyllaDB, delivering reliability improvements, test stabilization, and edge-case fixes that reduce risk in datacenter operations and CQL testing.

January 2025 monthly summary for scylla-cluster-tests: - Key features delivered: Nemesis Compaction Testing Enhancements: broadened testing coverage for nemesis-driven compaction strategies by enabling a wider range of parameter settings in modify_table_twcs_window_size and modify_table_compaction. Commit: 7e6b39c267b1d569799d6e4fd9eff9ec5a28c71a. - Major bugs fixed: CDC Log Reader Thread Robustness and Nemesis Termination Bug Fix: corrected the run method to properly calculate loaders and handle nemesis termination, ensuring worker IDs stay within valid range and preventing errors during cluster stress tests. Commit: c03df5c566b04da6549c09466990bc63ad4a829e. - Overall impact and accomplishments: strengthened chaos testing for Scylla clusters, increasing test coverage and reliability under stress, reducing flaky failures, and accelerating feedback for performance and resilience improvements. - Technologies/skills demonstrated: chaos engineering practices, concurrency/threading robustness, targeted refactoring for maintainability, enhanced test instrumentation and observability.

December 2024 — scylla-cluster-tests: Raft topology error filtering improvements delivered to stabilize test-logs during node start/stop and rolling upgrades. Implemented regex-based filtering in DbEventsFilter for flexible error matching, reducing noise from ignorable Raft topology errors and improving CI reliability. These changes enable more deterministic test outcomes and faster feedback to developers during upgrade scenarios.