Repository: kudu Updated Branches: refs/heads/master 3975c1d3d -> b46c4ecf9
Release note updates for 1.1 Change-Id: Ifa6bf79830d0b7fd2595d1ba64ea3673e90e5008 Reviewed-on: http://gerrit.cloudera.org:8080/5079 Reviewed-by: Jean-Daniel Cryans <[email protected]> Reviewed-by: Adar Dembo <[email protected]> Tested-by: Kudu Jenkins Tested-by: Todd Lipcon <[email protected]> Project: http://git-wip-us.apache.org/repos/asf/kudu/repo Commit: http://git-wip-us.apache.org/repos/asf/kudu/commit/b46c4ecf Tree: http://git-wip-us.apache.org/repos/asf/kudu/tree/b46c4ecf Diff: http://git-wip-us.apache.org/repos/asf/kudu/diff/b46c4ecf Branch: refs/heads/master Commit: b46c4ecf9826de35a2a68d7a18a9dfc117cd7613 Parents: 3975c1d Author: Todd Lipcon <[email protected]> Authored: Mon Nov 14 15:25:53 2016 -0800 Committer: Todd Lipcon <[email protected]> Committed: Mon Nov 14 23:50:37 2016 +0000 ---------------------------------------------------------------------- docs/release_notes.adoc | 42 +++++++++++++++++++++++++++++------------- 1 file changed, 29 insertions(+), 13 deletions(-) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/kudu/blob/b46c4ecf/docs/release_notes.adoc ---------------------------------------------------------------------- diff --git a/docs/release_notes.adoc b/docs/release_notes.adoc index 7ca9b70..ccc5207 100644 --- a/docs/release_notes.adoc +++ b/docs/release_notes.adoc @@ -67,6 +67,27 @@ the known leader replica. The default remains the latter. Use the relevant `ReplicaSelection` enum with the scanner's builder to change this behavior. +* Tablet servers use a new policy for retaining write-ahead log (WAL) segments. + Previously, servers used the 'log_min_segments_to_retain' flag to prioritize + any flushes which were retaining log segments past the configured value (default 2). + This policy caused servers to flush in-memory data more frequently than necessary, + limiting write performance. ++ +The new policy introduces a new flag 'log_target_replay_size_mb' which + determines the threshold at which write-ahead log retention will prioritize flushes. + The new flag is considered experimental and users should not need to modify + its value. ++ +The improved policy has been seen to improve write performance in some use cases + by a factor of 2x relative to the old policy. + +* Kudu's implementation of the Raft consensus algorithm has been improved to include + a "pre-election" phase. This can improve the stability of tablet leader election + in high-load scenarios, especially if each server hosts a high number of tablets. + +* Tablet server start-up time has been substantially improved in the case that + the server contains a high number of tombstoned tablet replicas. + === Command line tools * The tool `kudu tablet leader_step_down` has been added to manually force a leader to step down. @@ -80,7 +101,14 @@ == Wire protocol compatibility -XXX +Kudu 1.1.0 is wire-compatible with previous versions of Kudu: + +* Kudu 1.1 clients may connect to servers running Kudu 1.0. If the client uses the new + 'IN LIST' predicate type, an error will be returned. +* Kudu 1.0 clients may connect to servers running Kudu 1.1 without limitations. +* Rolling upgrade between Kudu 1.0 and Kudu 1.1 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. [[rn_1.1.0_incompatible_changes]] == Incompatible changes in Kudu 1.1.0 @@ -162,24 +190,12 @@ space immediately. * Updates, inserts, and deletes via Impala are non-transactional. If a query fails part of the way through, its partial effects will not be rolled back. -* All queries will be distributed across all Impala hosts which host a replica - of the target table(s), even if a predicate on a primary key could correctly - restrict the query to a single tablet. This limits the maximum concurrency of - short queries made via Impala. - * No timestamp and decimal type support. * The maximum parallelism of a single query is limited to the number of tablets in a table. For good analytic performance, aim for 10 or more tablets per host or use large tables. -* Impala is only able to push down predicates involving `=`, `<=`, `>=`, - or `BETWEEN` comparisons between any column and a literal value, and `<` and `>` - for integer columns only. For example, for a table with an integer key `ts`, and - a string key `name`, the predicate `WHERE ts >= 12345` will convert into an - efficient range scan, whereas `where name > 'lipcon'` will currently fetch all - data from the table and evaluate the predicate within Impala. - === Security Limitations * Authentication and authorization features are not implemented.
