Apache Kudu 1.8.0 Release Notes

Upgrading directly from Kudu 1.7.0 is supported and no special upgrade steps are required. A rolling upgrade may work, however it has not been tested. When upgrading Kudu, it is recommended to first shut down all Kudu processes across the cluster, then upgrade the software on all servers, then restart the Kudu processes on all servers in the cluster.

Kudu Flume Sink released with Kudu 1.8.0 is compiled against Apache Flume 1.8 and might not function with earlier versions of Flume. Note that Flume 1.8 requires Java 1.8 or higher.

Hadoop 3.0+ requires Java 8 at runtime even though the Kudu Hadoop integration is Java 7 compatible. Hadoop 3.1 is the default dependency version as of Kudu 1.8.0, used by certain features in the Java client.

The -table_num_buckets configuration option of the kudu perf loadgen tool is now removed in favor of -table_num_hash_partitions and -table_num_range_partitions (see KUDU-1861).

Support for Java 7 has been deprecated since Kudu 1.5.0 and may be removed in the next major release.

The producer.skipMissingColumn, producer.skipBadColumnValue, and producer.warnUnmatchedRows Kudu Flume sink configuration parameters have been deprecated in favor of producer.missingColumnPolicy, producer.badColumnValuePolicy, and producer.unmatchedRowPolicy respectively (see KUDU-1882).

Examples showcasing functionality in C++, Java, and Python, previously hosted in a separate repository have been added. They can be found in the examples/ top-level subdirectory.

Added kudu diagnose parse_stacks, a tool to parse sampled stack traces out of a diagnostics log (see KUDU-2353).

Added support for IS NULL and IS NOT NULL predicates to the Kudu Python client (see KUDU-2399).

Introduced manual data rebalancer into the kudu CLI tool. The rebalancer can be used to redistribute table replicas among tablet servers. The rebalancer can be run via kudu cluster rebalance sub-command. Using the new tool, it’s possible to rebalance Kudu clusters of version 1.4.0 and newer.

Added kudu tserver get_flags and kudu master get_flags, two tools that allow superusers to retrieve all the values of command line flags from remote Kudu processes. The get_flags tools support filtering the returned flags by tag, and by default will return only flags that were explicitly set.

Added kudu tablet unsafe_replace_tablet, a tool to replace a tablet with a new one. This tool is meant to be used to recover a table when one of its tablets has permanently lost all replicas. The data in the tablet that is replaced is lost, so this tool should only be used as a last resort (see KUDU-2290).

There is a new metric for each tablet replica tracking the number of election failures since the last successful election attempt and the time since the last heartbeat from the leader (see KUDU-2287).

Kudu now supports building and running on Ubuntu 18.04 (“Bionic Beaver”) (see KUDU-2427).

Kudu now supports building and running against OpenSSL 1.1 (see KUDU-1889).

Added Kerberos support to the Kudu Flume sink (see KUDU-2012).

The Kudu Spark connector now supports Spark Streaming DataFrames (see KUDU-2539).

Added -tables filtering argument to kudu table list (see KUDU-2529).

Clients now support setting a limit on the number of returned rows in scans (see KUDU-16).

Added Pandas support to the Python client (see KUDU-1276).

Enabled configuration of mutation buffer in the Python client (see KUDU-2441).

Added a keepAlive API call to the KuduScanner and AsyncKuduScanner in the Java client. This API can be used to keep the scanners alive on the server when processing of messages will take longer than the scanner TTL (see KUDU-2095).

The Kudu Spark integration now uses the keepAlive API when reading data. By default it will call keepAlive on a scanner with a period of 15 seconds. This will ensure that Spark jobs with large batch sizes or slow processing times do not fail with scanner not found errors (see KUDU-2563).

Number of reactor threads in the C++ client is now configurable (see KUDU-2368).

Added an optimization to reduce CPU consumption when performing hot metadata lookups in the C++ client (see KUDU-1977).

Added an optimization to avoid bottlenecks on getpwuid_r() in libnss during a Raft leader election storm (see KUDU-2395).

Improved rowset tree pruning making scans with open-ended intervals on primary key (see KUDU-2566).

The kudu perf loadgen tool now supports generating range-partitioned tables. The -table_num_buckets configuration is now removed in favor of -table_num_hash_partitions and -table_num_range_partitions (see KUDU-1861).

CFile checksum failures will now cause the affected tablet replicas to be failed and re-replicated elsewhere (see KUDU-2469).

Servers are now able to start up with data directories missing on disk (see KUDU-2359).

The kudu perf loadgen tool now creates tables with a period-separated database name, for example default.loadgen_auto_abc123. This new behavior does not take effect if the --table flag is provided. The database of the table can be changed using a new --auto_database flag. This change is made in anticipation of an eventual Kudu/HMS integration (see KUDU-2191).

Introduced FAILED_UNRECOVERABLE replica health status. This is to mark replicas which are not able to catch up with the leader due to GC-collected segments of WAL and other unrecoverable cases like disk failure. With that, the replica management scheme becomes hybrid: the system evicts replicas with FAILED_UNRECOVERABLE health status before adding a replacement if it anticipates that it can commit the transaction, while in other cases it first adds a non-voter replica and removes the failed one only after promoting a newly added replica to voter role.

Two additional configuration parameters, socketReadTimeoutMs and scanRequestTimeout have been added to the Spark connector to allow better tuning to avoid scan timeouts under high load.

The kudu table tool now supports two new options to rename tables and columns, rename_table and rename_column respectively.

Kudu will now wait for the clock to become synchronized at startup, controlled by a new flag -ntp_initial_sync_wait_secs (see KUDU-2242).

Tablet deletions are now throttled, which will help Kudu clusters remain stable even when many tablets are deleted at once. The number of tablets that a tablet server will delete at once is controlled by the new flag -num_tablets_to_delete_simultaneously (see KUDU-2289).

The kudu cluster ksck tool has been significantly enhanced. It now checks master health and consensus status, displays any unsafe or hidden flags set in the cluster, and produces a summary of the Kudu versions running on the master and tablet servers. In addition, it now supports JSON output, both in pretty-printed and compact form. The output format is controlled by the -ksck_format flag.

When a tablet server was wiped and recreated with the same RPC address, ksck listed it twice, both as healthy, even though only one of them was there. This bug is now fixed by verifying the UUID of the server (see KUDU-2364).

Fixed an issue preventing Kudu from starting when using Vormetric’s encrypted filesystem (secfs2) on ext4 (see KUDU-2406).

Fixed an issue where Kudu’s block cache memory tracking (as seen on the /mem-trackers web UI page) wasn’t accounting for all of the overhead of the cache itself (see KUDU-972).

Fixed an issue where the C++ client would fail to reopen an expired scanner; instead, the client would retry in a tight loop and eventually timeout (see KUDU-2414).

When a tablet is deleted, its write-ahead log recovery directory is also deleted, if it exists (see KUDU-1038).

Fixed a tablet server crash when a tablet is scanned with two predicates on its primary key and the predicates do not overlap (see KUDU-2447).

Fixed an issue where the Kudu MapReduce connector’s KuduTableInputFormat may exhaust its scan too early (see KUDU-2525).

Fixed an issue with failed tablet copies that would cause subsequent tablet copies to crash the tablet server (see KUDU-2293).

Fixed a bug in which incorrect results would be returned in scans following a server restart (see KUDU-2463).

Fixed a bug causing a tablet server crash when a write batch request from a client failed coarse-grained authorization (see KUDU-2540).

Fixed use-after-free in case of WAL replay error (see KUDU-2509).

Fixed authentication token reacquisition in the C++ client (see KUDU-2580).

Fixed a bug where leader logged excessively when the followers fell behind (see KUDU-2322).

Fixed reporting of leader health during lifecycle transitions (see KUDU-2335).

Fixed moving single-replica tablets (see KUDU-2443).

Fixed an error that would cause the kudu CLI tool to unexpectedly exit when the connection to the master or tserver was abruptly closed.

Fixed a rare issue where system failure could leave unexpected null bytes at the end of metadata files, causing Kudu to be unable to restart (see KUDU-2260).

Fixed an issue where kudu cluster ksck running a snapshot checksum scan would use a single snapshot timestamp for all tablets. This caused the checksum process to fail if the checksum process took a long time and the number of tablets was sufficiently large. The tool should now be able to checksum tables even if the process takes many hours. (see KUDU-2179).

Kudu 1.8 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.

Kudu 1.0 clients may connect to servers running Kudu 1.8 with the exception of the below-mentioned restrictions regarding secure clusters.

If a Kudu 1.8 cluster is configured with authentication or encryption set to "required", clients older than Kudu 1.3 will be unable to connect.

If a Kudu 1.8 cluster is configured with authentication and encryption set to "optional" or "disabled", older clients will still be able to connect.

Anupama Gupta

Attila Piros

Brian McDevitt

Fengling Wang

Ferenc Szabó

Greg Solovyev

Kiyoshi Mizumaru

Shriya Gupta

Thomas Tauber-Marshall

Tigerquoll

Yao Xu

ZhangYao

helifu

jinxing64

qqchang2nd

Kudu Website

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