Scylla Open Source Release 4.2

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New features in Scylla 4.2

Performance: Enable binary search in SSTable promoted index

  • Middle: Queried row is in the middle of a (large) partition
  • Head: Queried row is at the head, as the first element of a (large) partition


  • New Alternator’s SSL options (Alternator Client to Node Encryption on Transit)
    Till this release, Alternator SSL configuration was set in the section server_encryption_options of Scylla configuration file. The name was misleading, as the section was also used for the unrelated node-to-node encryption on transit.
  • docker: add an option to start Alternator with HTTPS. When using Scylla Docker, you can now use --alternator-https-port in addition to the existing --alternator-port. #6583
  • Implement FilterExpression
    Adding FilterExpression — a newer syntax for filtering results of Query and Scan requests #5038
  • Example usage in query API:
    aws dynamodb query \
    --table-name Thread \
    --key-condition-expression "ForumName = :fn and Subject = :sub" \
    --filter-expression "#v >= :num" \
    --expression-attribute-names '{"#v": "Views"}' \
    --expression-attribute-values file://values.json

  • Alternator: support additional filtering operators #5028
  • All operators are now supported. Previously, only the “EQ” operator was implemented.
  • Either “OR” or “AND” of conditions (previously only “AND”).
  • Correctly returning Count and ScannedCount for post-filter and pre-filter item counts, respectively.

Additional Features

  • SSTable Reshard and Reshape in upload to directory
    Reshard and Reshape are two transformation on SSTables:
  • Reshard — Splitting a SSTable, that is owned by more than one shard (core), into SSTables that are owned by a single shard, for example, when restoring data from a different server, importing sstSSTables from Apache Cassandra, or changing the number of cores in a machine (upscale)
  • Reshape — Rewrite a set of SSTable to to satisfy a compaction strategy’s criteria., for example, restoring data from an old backup, before the strategy update.
  • Setup: swapfile setup is now part of scylla_setup.
    Scylla setup already warns users when the swap is not set. Now it prompts for the swap file directory #6539
  • Setup: default root disk size is increased from 10G to 30GB. scylla-machine-image #48

Experimental features in Scylla 4.2

  • Change Data Capture (CDC). While functionally complete, we are still testing CDC to validate it is production-ready towards GA in a following Scylla 4.x release. No API updates are expected. Refer to the Scylla Open Source 4.1 Release Notes for more information.
  • There’s a new nodetool command #6498
  • CDC is explicitly disabled on counters #6553
  • Preimage is no longer created for missing rows #7119
  • Postimage is no longer created for deleted rows #7120
  • CDC tables were renamed #6577

Other bugs fix and updates in the release

  • CQL: Impossible WHERE condition returns a non-empty slice #5799
  • Stability: reactor stalled during repair abort #6190
  • Stability: a rare race condition between topology change (like adding a node) and MV insert may cause an “seastar::broken_promise (broken promise)” error message, although there is no real error #5459
  • UX: scylla-housekeeping, a service which checks for the latest Scylla version, return a “cannot serialize” error instead of propagating the actual error #6690
  • UX: scylla_setup: on RAID disk prompt, typing the same disk twice cause traceback #6711
    Stability: Counter write read-before-write is issued with no timeout, which may lead to unbounded internal concurrency if the enclosing write operation timed out. #5069
    replace_first_boot_test and replace_stopped_node_test fail in 4.1: Replace failed to stream #6728
  • Setup: scylla_swap_setup: swap size become 0 when memory size less than 1GB #6659
  • Stability: Scylla freezes when casting a decimal with a negative scale to a float #6720
  • Log: Compaction data reduction log message misses % sign #6727
  • Stability: Prevent possible deadlocks when repair from two or more nodes in parallel #6272
  • Setup: Sscylla fails to identify recognize swap #6650
  • Setup: scylla_setup: systemctl shows up warning after scylla_setup finished #6674
    CDC: cdc: report unexpected exceptions using “error” level in generation management code #6557
  • Storage: SSTable upgrade has a 2x disk space requirement #6682
    Stability: Compaction Backlog can be calculated incorrectly #6021
  • UX: cql transport report a broken pipe error to the log when a client closes its side of a connection abruptly #5661
  • Nodetool: for a multi DC cluster using a non- network topology strategy, Nodetool decommission can not find a new node in local dc despite the node exist #6564
  • Monitoring: Use higher resolution histograms gets more accurate values #5815 #4746
  • Scylla will now ignore a keyspace that is removed while being repaired, or without tables, rather than failing the repair operation. #5942 #6022
  • Monitoring new compaction_manager backlog metrics
  • REST API storage_service/ownership/ (get_effective_ownership) can cause stalls #6380
  • Performance: over-aligned SSTable reads due to file buffer tracking #6290
  • Wrong order of initialization in messaging service constructor #6628
  • Stream ended with unclosed partition and coredump #6478
  • CDC: failed to restore cdc log table from snapshot for postimage enabled only with refresh operation #6561
  • CDC: wrong value for set in cdc_log table after second insert #6084
  • CDC: reactor stalled up to 17000 ms after change cdc log table property #6098
  • Stability: Classify queries based on initiator, instead of target table #5919
  • Setup: scylla_raid_setup cause traceback on CentOS7 #6954
  • CQL: min()/max() return wrong results on some collections and User Defined Type, naively comparing just the byte representations of arguments. #6768
  • CQL: Impossible to set list element to null using scylla_timeuuid_index #6828
  • Setup: Using Systemd slices on CentOS7, with percentage-based parameters does not work and generate warnings and error messages during instance (ami) load #6783
  • Stability: Commitlog replay segfaults when mutations use old schema and memtable space is full #6953
  • Setup: scylla_setup on Ubuntu 16 / GCE fails #6636
  • Stability: a race condition when a node fails while it is both streaming data (as part as repair) and is decommissioned. #6868 #6853
  • Stability: index reader fails to handle failure properly, which may lead to unexpected exit #6924
  • Stability: a rare deadlock when creating staging sstable, for example when repairing a table which has materialized views #6892 #6603
  • Stability: Fix issues introduced by classifying queries based on initiator, instead of target table (#5919), introduced in 4.2 #6907 #6908 #6613
  • Stability: TWCS compaction: partition estimate can become 0, causing an assert in sstables::prepare_summary() #6913
  • Stability: Post-repair view updates keep too many SSTable readers open #6707
  • Stability: Staging SSTables are incorrectly removed or added to backlog after ALTER TABLE / TRUNCATE #6798
  • Stability: Fix schema integrity issues that can arise in races involving materialized views #7420 #7480
  • Install: python scripts core dump with non-default locale #7408
  • Stability: Possible read resources leak #7256
  • Stability: materialized view builder: Scylla stucks on stopping #7077
  • LWT: Aborted reads of writes which fail with “Not enough replicas available” #7258
  • Stability: “No query parameter set for a session requesting a slow_query_log record” error while tracing slow batch queries #5843
  • Stability: appending_hash<row> ignores cells after first null #4567
  • Stability: Race in schema version recalculation leading to stale schema version in gossip, and warning that schema versions differ on nodes after scylla was restarted with require resharding #7291
  • CQL: min()/max() return wrong results on some collections and User Defined Type, naively comparing just the byte representations of arguments. #6768
  • CQL: Impossible to set list element to null using scylla_timeuuid_index #6828
  • Stability: Unnecessary LCS Reshape compaction after startup due to overly sensitive SSTable overlap ratio #6938
  • AWS: update enhanced networking supported instance list #6991
  • Stability: large reactor stalls when recalculating TLS diffie-helman parameters #6191
  • Stability: a bug introduced in 4.2 may cause unexpected exit for expire timers #7117
  • Stability: too aggressive TWCS compactions after upgrading #6928
  • redis: EXISTS command with multiple keys causes SEGV #6469
  • Performance: removing a potential stall on sstable clean up #6662 #6730
  • Stability: Status of drained node after restart stayed as DN in the output of “nodetool status” on another node #7032
  • Alternator: ignore disabled SSESpecification #7031
  • Alternator: return an error for create-table, but the table is created #6809
  • Stability: RPC handlers are not unregistered on stop #6904
  • Stability: Schema change, adding a counter column into a non-counter table, is incorrectly persisted and results in a crash #7065
  • Debugging: trace decoding on doesn’t work #6982
  • Debugging: gdb scylla databases gives the same address for different shards #7016
  • CDC: better classify errors when fetching CDC generations #6804
  • Stability: Connection dropped: RPC frame LZ4 decompression failure #6925
  • Stability: repair may cause stalls under different failure cases #6940 #6975 #6976 #7115
  • Stability: Materialized view updates use incorrect schema to interpret writes after base table schema is altered #7061
  • Stability: Possible priority inversion between hints and normal write in storage_proxy #7177
  • Stability: Segfault in evaluating multi-column restrictions #7198
  • Stability: in some rare cases, a node may crash when calculating effective ownership #7209
  • Alternator: a bug in the PutItem implementation with write_islation = always_use_lwt. In case of contention but a successful write, the written data could have not matched the intent. #7218
  • Stability: in some rare cases, error recovery from an out-of-memory condition while processing an unpaged query that consumes all of available memory may cause the coordinator node to exit #7240
  • Stability: Coredump during the decommission process on decommissioning node #7257
  • Stability: out-of-range range tombstones emitted on reader recreation cause fragment stream monotonicity violations #7208
  • Stability: race in schema version recalculation leading to stale schema version in gossip #7200




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