Apache Kudu 1.13.0 Release Notes

The Sentry integration has been removed and the Ranger integration should now be used in its place for fine-grained authorization.

Support for Python 2.x and Python 3.4 and earlier is deprecated and may be removed in the next minor release.

The kudu-mapreduce integration has been deprecated and may be removed in the next minor release. Similar functionality and capabilities now exist via the Apache Spark, Apache Hive, Apache Impala, and Apache NiFi integrations.

Added table ownership support. All newly created tables are automatically owned by the user creating them. It is also possible to change the owner by altering the table. You can also assign privileges to table owners via Apache Ranger (see KUDU-3090).

An experimental feature is added to Kudu that allows it to automatically rebalance tablet replicas among tablet servers. The background task can be enabled by setting the --auto_rebalancing_enabled flag on the Kudu masters. Before starting auto-rebalancing on an existing cluster, the CLI rebalancer tool should be run first (see KUDU-2780).

Bloom filter column predicate pushdown has been added to allow optimized execution of filters which match on a set of column values with a false-positive rate. Support for Impala queries utilizing Bloom filter predicate is available yielding performance improvements of 19% to 30% in TPC-H benchmarks and around 41% improvement for distributed joins across large tables. Support for Spark is not yet available. (see KUDU-2483).

AArch64-based (ARM) architectures are now supported including published Docker images.

The Java client now supports the columnar row format returned from the server transparently. Using this format can reduce the server CPU and size of the request over the network for scans. The columnar format can be enabled via the setRowDataFormat() method on the KuduScanner.

An experimental feature that can be enabled by setting the --enable_workload_score_for_perf_improvement_ops prioritizes flushing and compacting hot tablets.

Hive metastore synchronization now supports Hive 3 and later.

The Spark KuduContext accumulator metrics now track operation counts per table instead of cumulatively for all tables.

The kudu local_replica delete CLI tool now accepts multiple tablet identifiers. Along with the newly added --ignore_nonexistent flag, this helps with scripting scenarios when removing multiple tablet replicas from a particular Tablet Server.

Both Master’s and Tablet Server’s web UI now displays the name for a service thread pool group at the /threadz page

Introduced queue_overflow_rejections_ metrics for both Masters and Tablet Servers: number of RPC requests of a particular type dropped due to RPC service queue overflow.

Introduced a CoDel-like queue control mechanism for the apply queue. This helps to avoid accumulating too many write requests and timing them out in case of seek-bound workloads (e.g., uniform random inserts). The newly introduced queue control mechanism is disabled by default. To enable it, set the --tablet_apply_pool_overload_threshold_ms Tablet Server’s flag to appropriate value, e.g. 250 (see KUDU-1587).

Java client’s error collector can be resized (see KUDU-1422).

Calls to the Kudu master server are now drastically reduced when using scan tokens. Previously deserializing a scan token would result in a GetTableSchema request and potentially a GetTableLocations request. Now the table schema and location information is serialized into the scan token itself avoiding the need for any requests to the master when processing them.

The default size of Master’s RPC queue is now 100 (it was 50 in earlier releases). This is to optimize for use cases where a Kudu cluster has many clients working concurrently.

Masters now have an option to cache table location responses. This is targeted for Kudu clusters which have many clients working concurrently. By default, the caching of table location responses is disabled. To enable table location caching, set the proper capacity of the table location cache using Master’s --table_locations_cache_capacity_mb flag (setting to 0 disables the caching). Up to 17% of improvement is observed in GetTableLocations request rate when enabling the caching.

Removed lock contention on Raft consensus lock in Tablet Servers while processing a write request. This helps to avoid RPC queue overflows when handling concurrent write requests to the same tablet from multiple clients (see KUDU-2727).

Master’s performance for handling concurrent GetTableSchema requests has been improved. End-to-end tests indicated up to 15% improvement in sustained request rate for high concurrency scenarios.

Kudu servers now use protobuf Arena objects to perform all RPC request/response-related memory allocations. This gives a boost for overall RPC performance, and with further optimization the result request rate was increased significantly for certain methods. For example, the result request rate increased up to 25% for Master’s GetTabletLocations() RPC in case of highly concurrent scenarios (see KUDU-636).

Tablet Servers now use protobuf Arena for allocating Raft-related runtime structures. This results in substantial reduction of CPU cycles used and increases write throughput (see KUDU-636).

Tablet Servers now use protobuf Arena for allocating EncodedKeys to reduce allocator contention and improve memory locality (see KUDU-636).

Bloom filter predicate evaluation for scans can be computationally expensive. A heuristic has been added that verifies rejection rate of the supplied Bloom filter predicate below which the Bloom filter predicate is automatically disabled. This helped reduce regression observed with Bloom filter predicate in TPC-H benchmark query #9 (see KUDU-3140).

Improved scan performance of dictionary and plain-encoded string columns by avoiding copying them (see KUDU-2844).

Improved maintenance manager’s heuristics to prioritize larger memstores (see KUDU-3180).

Spark client’s KuduReadOptions now supports setting a snapshot timestamp for repeatable reads with READ_AT_SNAPSHOT consistency mode (see KUDU-3177).

Kudu scans now honor location assignments when multiple tablet servers are co-located with the client.

Fixed a bug that caused IllegalArgumentException to be thrown when trying to create a predicate for a DATE column in Kudu Java client (see KUDU-3152).

Fixed a potential race when multiple RPCs work on the same scanner object.

Kudu 1.13 clients may connect to servers running Kudu 1.0 or later. If the client uses features that are not available on the target server, an error will be returned.

Rolling upgrade between Kudu 1.12 and Kudu 1.13 servers is believed to be possible though has not been sufficiently tested. Users are encouraged to shut down all nodes in the cluster, upgrade the software, and then restart the daemons on the new version.

Kudu 1.0 clients may connect to servers running Kudu 1.13 with the exception of the below-mentioned restrictions regarding secure clusters.

If a Kudu 1.13 cluster is configured with authentication or encryption set to "required", clients older than Kudu 1.3 will be unable to connect.

If a Kudu 1.13 cluster is configured with authentication and encryption set to "optional" or "disabled", older clients will still be able to connect.

Jim Apple

Kevin J McCarthy

Li Zhiming

Mahesh Reddy

Romain Rigaux

RuiChen

Shuping Zhou

ningw

wenjie

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