2026.5.1

What's Changed

• DM-54490: Minor code cleanup at Czar (maintenance)
• DM-54589: Qserv Replication system records incorrect timestamps of chunk replicas in the system's metadata database (bugs)
• DM-54599: validateDominantDbs() is called more frequently than it's necessary (performance)
• DM-54631: Fixed bugs, race conditions, and minor problems in the code of the Replication/Ingest system of Qserv (bugs)
• DM-54632: Eliminated obsolete/useless code from the Qserv query analysis/dispatch classes (refactoring)
• DM-54798: The Replication Controller should not terminate after failed self-registration at the Qserv Service Registry (bugs)
• DM-54815: Small Qserv fixups (refactoring)
• DM-54828: Upgrade Qserv to Apache Arrow and Parquet version 24 (maintenance)

Known issues

• DM-53046: Sub-optimal performance of the ANTLR4-based query parser when the query text size is large (many kilobytes). The problem is still under investigation. It may be addressed in a later release (performance)

Full Changelog: 2026.5.1-rc1...2026.3.3-rc1

2026.3.3

What's Changed

• DM-54321: The race conditions were fixed in the implementation of the XRootD/SSI software stack. The bugs were causing occasional deadlocks of queries in which the result sets are constrained byLIMIT <N> (TOP <N> in ADQL). (bugs)
• DM-54443: Prevent Qserv worker crashes after DNS resolution hiccups. (bugs)

Known issues

• DM-53046: Sub-optimal performance of the ANTLR4-based query parser when the query text size is large (many kilobytes). The problem is still under investigation. It may be addressed in a later release (performance

Full Changelog: 2026.3.3-rc1...2026.3.2-rc1

2026.3.2

What's Changed

• DM-54392: Small fixes to Qserv build base Dockerfile (deployment)
• DM-54401: The query analysis plugin in Qserv uses the incorrect director table when joining between partitioned and fully-replicated tables of different catalogs (bugs)
• DM-52781: Joining tables of catalogs that have non-exact spatial coverage (features)

Notes

• The last two improvements are essential for processing queries against the user-generated tables: https://qserv.lsst.io/user/http-frontend-ingest.html

Known issues

• DM-53046: Sub-optimal performance of the ANTLR4-based query parser when the query text size is large (many kilobytes). The problem is still under investigation. It may be addressed in a later release (performance
• DM-54321: A possible race condition in the XRootD/SSI software stack exists in the release. It may cause occasional deadlocks of queries where the result set is constrained byLIMIT <N> (TOP <N> in ADQL). The problem is typically seen in 1 out of 10,000 such queries in which the constraint is actually enforced. Normally, the locked-up queries do not prevent Qserv from processing other queries. However, at some point, the total number of the internally locked threads will reach a configuration limit for the number of the XRootD/SSI CB (call-back) threads. After that, the query processing stalls. Cancelling the locked-up queries doesn't help to address the problem, as the cancellation doesn't release the locked threads. The frontend affected by the problem needs to be restarted. (bugs)

Full Changelog: 2026.3.2-rc1...2026.3.1-rc1

2026.3.1

What's Changed

• DM-52017: Race conditions in the implementation the Qserv query processor for some queries (bugs)

Notes:

• A significant (many orders of magnitude) reduced probability of the query lock-ups.
• Lockups of the Individual queries no longer result in locking up the corresponding frontend (Czar). An exception is a case explained in the Known Issues section.
• A "leak" of the TCP sockets open by the frontends during the internal result processing has been eliminated. The previous version of Qserv demonstrated a steady growth of the open (TCP state CONNECTED) sockets when processing results of queries constrained by LIMIT <N>. Eventually, the number of open file descriptors (sockets) would hit the limit configured for the frontend's process. After that, the frontend will misbehave (fail to process queries, accept user requests, etc.).

Known issues

• DM-53046: Sub-optimal performance of the ANTLR4-based query parser when the query text size is large (many kilobytes). The problem is still under investigation. It may be addressed in a later release (performance
• DM-54321: A possible race condition in the XRootD/SSI software stack exists in the release. It may cause occasional deadlocks of queries where the result set is constrained byLIMIT <N> (TOP <N> in ADQL). The problem is typically seen in 1 out of 10,000 such queries in which the constraint is actually enforced. Normally, the locked-up queries do not prevent Qserv from processing other queries. However, at some point, the total number of the internally locked threads will reach a configuration limit for the number of the XRootD/SSI CB (call-back) threads. After that, the query processing stalls. Cancelling the locked-up queries doesn't help to address the problem, as the cancellation doesn't release the locked threads. The frontend affected by the problem needs to be restarted. (bugs)

Full Changelog: 2026.3.1-rc1...2026.2.2-rc1

2026.2.2

What's Changed

• DM-53922: Partial migration of the Qserv code from boost::filesystem to std::filesystem (refactoring)
• DM-54091: Backported the original algorithm for populating the persistent chunks map (refactoring)
• DM-53950: Migrate container management tools from DockerHub to GHCR (refactoring)
• DM-54248: A temporary workaround for the unstable remote source of the JS Highcharts library (stability)
• DM-54050: Extending Qserv REST API to allow ingesting partitioned user tables which depend on existing directors (features)

Notes:

• Qserv REST API version is now 55.

Known issues

• DM-53046: Sub-optimal performance of the ANTLR4-based query parser when the query text size is large (many kilobytes). The problem is still under investigation. It may be addressed in a later release (performance)
• DM-52017: Race conditions in the implementation the Qserv query processor for some queries (bugs)

Full Changelog: 2026.1.2-rc1...2026.2.1-rc1

2026.2.1

What's Changed

• DM-54026: The Replication system may fail to sync the database state with Qserv workers (bugs)

Notes:

• This is the bug fix release that is meant to improve the stability of the user table ingest service.

Known issues

• DM-53046: Sub-optimal performance of the ANTLR4-based query parser when the query text size is large (many kilobytes). The problem is still under investigation. It may be addressed in a later release (performance)
• DM-52017: Race conditions in the implementation the Qserv query processor for some queries (bugs)

Full Changelog: 2026.1.2-rc1...2026.2.1-rc1

2026.1.2

What's Changed

• DM-53665: Qserv Worker Replication service may crash after databases are deleted (bugs)
• DM-53898: Investigating a suspected memory leak in the Qserv Replication Controller (improvements)
• DM-52370: Extending Qserv REST API to allow ingesting partitioned user tables (features)

Notes:

• The version number of the Qserv REST API is now 54

Known issues

• DM-53046: Sub-optimal performance of the ANTLR4-based query parser when the query text size is large (many kilobytes). The problem is still under investigation. It may be addressed in a later release (performance)
• DM-52017: Race conditions in the implementation the Qserv query processor for some queries (bugs)

Full Changelog: 2026.1.1-rc1...2026.1.2-rc1

2026.1.1

What's Changed

• DM-53780: Migrate the Qserv Replication/Ingest System to use FQDN instead of IP addresses in internal communications (temporary workaround for UKDF)
• DM-53847: Migrate the Qserv Replication and Ingest system back to rely on the IP addresses and improve the service Registry (permanent solution for UKDF)
• DM-53852: Base image updates (maintainance)
• DM-53874: Upgrade Qserv to Apache Arrow and Parquet version 23 (maintainance)
• DM-53361: Table exportation services in Qserv (new features)

Notes:

• The version number of the Qserv REST API is now 53

Known issues

• DM-53046: Sub-optimal performance of the ANTLR4-based query parser when the query text size is large (many kilobytes). The problem is still under investigation. It may be addressed in a later release (performance)
• DM-52017: Race conditions in the implementation the Qserv query processor for some queries (bugs)

Full Changelog: 2025.12.1-rc1...2026.1.1-rc1

2025.12.1

What's Changed

• DM-53597: Fix spurious crashes of the Replication Controller after the previously ingested user databases are deleted (bugs)

Known issues

• DM-53046: Sub-optimal performance of the ANTLR4-based query parser when the query text size is large (many kilobytes). The problem is still under investigation. It may be addressed in a later release (performance)
• DM-52017: Race conditions in the implementation the Qserv query processor for some queries (bugs)

Full Changelog: 2025.11.1-rc1...2025.12.1-rc1

2025.11.1

What's Changed

• DM-53152: Improve error handling in the implementation of the HTTP-based frontend of Qserv (bugs,improvements)
• DM-53041: Thread-safe implementation of CssAccess (bugs)
• DM-48502: Extend Qserv Replication system to automatically create missing databases when new workers are added to Qserv (improvements)
• DM-53037: Upgraded Apache Arrow and Parquet libraries to version 22 (dependencies)

Known issues

• DM-53046: Sub-optimal performance of the ANTLR4-based query parser when the query text size is large (many kilobytes). The problem is still under investigation. It may be addressed in a later release (performance)
• DM-52017: Race conditions in the implementation the Qserv query processor for some queries (bugs)

Full Changelog: 2025.10.1-rc1...2025.11.1-rc1