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Release Notes RonDB 21.04.12#

RonDB 21.04.12 is the twelveth release of RonDB 21.04.

RonDB 21.04 is based on MySQL NDB Cluster 8.0.23. It is a bug fix release based on RonDB 21.04.9. The releases 21.04.10 and 21.04.11 was only used internally in Hopsworks.

RonDB 21.04.12 is released as open source software with binary tarballs for usage in Linux. It is developed on Linux and Mac OS X and using WSL 2 on Windows (Linux on Windows) for automated testing.

RonDB 21.04.12 can be used with both x86_64 and ARM64 architectures although ARM64 is still in beta state.

The RonDB 21.04.12 is tested and verified on both x86_64 and ARM platforms using both Linux and Mac OS X. It is however only released with a binary tarball for x86_64 on Linux.

In the git log there is also a lot of commits relating to the REST API server. This is still under heavy development, thus we don’t mention in the release notes the changes related to this development until the REST API server is released.

Also build fixes are not listed in the release notes, but can be found in the git log.

Description of RonDB#

RonDB is designed to be used in a managed environment where the user only needs to specify the type of the virtual machine used by the various node types. RonDB has the features required to build a fully automated managed RonDB solution.

It is designed for appplications requiring the combination of low latency, high availability, high throughput and scalable storage.

You can use RonDB in a serverless version on In this case Hopsworks manages the RonDB cluster and you can use it for your machine learning applications. You can use this version for free with certain quotas on the number of Feature Groups (tables) and memory usage. Getting started with this is a matter of a few minutes, since the setup and configuration of the database cluster is already taken care of by Hopsworks.

You can also use the managed version of RonDB available on This sets up a RonDB cluster in your own AWS, Azure or GCP account using the Hopsworks managed software. It creates a RonDB cluster provided a few details on the HW resources to use. These details can either be added through a web-based UI or using Terraform. The RonDB cluster is integrated with Hopsworks and can be used for both RonDB applications as well as for Hopsworks applications.

You can use the cloud scripts that will enable you to set up in an easy manner a cluster on AWS, Azure or GCP. This requires no previous knowledge of RonDB, the script only needs a description of the HW resources to use and the rest of the setup is automated.

You can use the open source version and build and set it up yourself. This is the command you can use to download a binary tarball:

# Download x86_64 on Linux

RonDB 21.04 is a Long Term Support version that will be maintained until at least 2024.

Maintaining 21.04 means mainly fixing critical bugs and minor change requests. It doesn’t involve merging with any future release of MySQL NDB Cluster, this will be handled in newer RonDB releases.

Backports of critical bug fixes from MySQL NDB Cluster will happen when deemed necessary.

Summary of changes in RonDB 21.04.12#

RonDB has 7 bug fixes since RonDB 21.04.9 and 3 new features. In total RonDB 21.04 contains 27 new features on top of MySQL Cluster 8.0.23 and a total of 124 bug fixes.

Test environment#

RonDB uses four different ways of testing. MTR is a functional test framework built using SQL statements to test RonDB. The Autotest framework is specifically designed to test RonDB using the NDB API. The Autotest is mainly focused on testing high availability features and performs thousands of restarts using error injection as part of a full test suite run. Benchmark testing ensures that we maintain the throughput and latency that is unique to RonDB. Finally we also test RonDB in the Hopsworks environment where we perform both normal actions as well as many actions to manage the RonDB clusters.

RonDB has a number of unit tests that are executed as part of the build process to improve the performance of RonDB.

In addition RonDB is tested as part of testing Hopsworks.

MTR testing#

RonDB has a functional test suite using the MTR (MySQL Test Run) that executes more than 500 RonDB specific test programs. In addition there are thousands of test cases for the MySQL functionality. MTR is executed on both Mac OS X and Linux.

We also have a special mode of MTR testing where we can run with different versions of RonDB in the same cluster to verify our support of online software upgrade.


RonDB is highly focused on high availability. This is tested using a test infrastructure we call Autotest. It contains many hundreds of test variants that takes around 36 hours to execute the full set. One test run with Autotest uses a specific configuration of RonDB. We execute multiple such configurations varying the number of data nodes, the replication factor and the thread and memory setup.

An important part of this testing framework is that it uses error injection. This means that we can test exactly what will happen if we crash in very specific situations, if we run out of memory at specific points in the code and various ways of changing the timing by inserting small sleeps in critical paths of the code.

During one full test run of Autotest RonDB nodes are restarted thousands of times in all sorts of critical situations.

Autotest currently runs on Linux with a large variety of CPUs, Linux distributions and even on Windows using WSL 2 with Ubuntu.

Benchmark testing#

We test RonDB using the Sysbench test suite, DBT2 (an open source variant of TPC-C), flexAsynch (an internal key-value benchmark), DBT3 (an open source variant of TPC-H) and finally YCSB (Yahoo Cloud Serving Benchmark).

The focus is on testing RonDBs LATS capabilities (low Latency, high Availability, high Throughput and scalable Storage).

Hopsworks testing#

Finally we also execute tests in Hopsworks to ensure that it works with HopsFS, the distributed file system built on top of RonDB, and HSFS, the Feature Store designed on top of RonDB, and together with all other use cases of RonDB in the Hopsworks framework.

These tests include both functional tests of the Hopsworks framework as well as load testing of HopsFS and Hopsworks.

New features#

RONDB-199: Ensured that pid file contains PID of data node, not of angel#

The data node uses two processes - one is an angel process which is the first process started. This process is daemonized after which it is forked into another process which is the real data node process.

When interacting with environments like systemd it is easier to handle this if the pid file contains the pid file of the real data node process.

Stopping the angel process doesn’t stop the data node process. Thus keeping track of this PID isn’t of any great value.

Thus in using RonDB data nodes in combination it is recommended to not set StopOnError to 1 since this means that the angel will restart the ndbmtd no matter how it stopped. Thus it is better to set StopOnError=0 and to use the pid file ( in the same directory as the log files) to find the data node pid to stop or kill.

RONDB-224: Standardise error codes from MySQL server for temporary node failure/recovery errors#

Ensure that more error codes are handled as temporary errors using the common error codes for temporary errors in MySQL.

RONDB-230: Handle failure when IPv6 disabled at boot#

It is possible to disable IPv6 support at startup of Linux. This means that one cannot use IPv6 sockets in any fashion. This causes a number of issues in RonDB.

Since before RonDB handles that data nodes can use IPv4 sockets only by default. This is used for communicating using Dolphin SCI sockets that don’t support IPv6.

Using this code one can retry creating a socket using IPv4 instead if the IPv6 setup fails. This is expected to fix connect and bind issues when disabling IPv6.


RONDB-200: MGM Server didn’t stop when started with node deactivated#

Also updated tests for activate/deactivate.

RONDB-195: Fixed unloadSchema for re-created tables#

There was a problem in that class key was used to find the table to unload. However in cases when the table was recreated the class was no longer present, but the new table was still there. Changed to ensure that we unload all tables with the table name unloaded. This is a bug in ClusterJ.

RONDB-196: Fixes for session cache and Unload Schema API#

This bug fix and RONDB-263 ensures that Hopsworks can start using the Session cache and the Dynamic Objects cache. This has been shown to increase throught by 3-4x.

RONDB-263: DTOCache fails on HashMap.put as dynamic objects do not implement function#

With the release of 21.04.12 the interface changes to ClusterJ is set to GA quality.


Backported from MySQL Server.

Bug34568135 Long Message Buffer usage is constantly increasing#

Backported from MySQL Server.

Bug23539857 - WL8069: "LCP_SCANNED_BIT == 0 FAILED" does not hold#

Backported from MySQL Server.