Volt Active Data
14.0.0
VoltDB Operator 3.2.0 |
September 30, 2024
This document provides information about known issues and limitations to the current release of VoltDB. If you encounter any problems not listed below, please be sure to report them to support@voltactivedata.com. Thank you.
Volt Active Data V14 is a major release that includes a redesign and enhancement to how you configure the database, as well as general cleanup of old and obsolete functions. The key new features and enhancements in V14.0 include:
Redesign of Database Configuration — Traditionally, VoltDB has been configured using a single XML file. Once the database was running, you could update the configuration using the voltadmin update command and passing it an updated XML file. But that file had to be complete; any options configured on initialization had to also be set for the update or else the update would fail or options would be reset to the default. You could not simply specify the one or two options to change.
VoltDB now uses YAML properties for defining the configuration. The use of YAML has multiple advantages:
Ease-of-Use: YAML is a simple indented text format that is easier to read and edit than XML.
Modularity: You are no longer restricted to a single configuration file. You can specify multiple YAML files when you initialize the database and the contents are merged. This allows you to group and manage configuration options by category, such as security, export, directory paths, etc. For example, you could have a single file for configuring two XDCR databases identically and have separate YAML files for the XDCR settings, which require a unique ID per cluster:
$ voltdb initialize -C common.yaml,xdcr_cluster1.yaml
Getting and Setting Individual Properties: You can now get and set individual configuration properties on a running database using the voltadmin get and set commands, rather than having to relist all of the original properties. For example:
$ voltadmin set deployment.snapshot.frequency=2d
You can also set multiple properties in a single set command using a list of dot notation settings or a YAML file of just those properties you want to change. Of course, you can still use the voltadmin update command, providing a complete set of properties in either YAML or XML.
See the section on understanding YAML syntax in the Using VoltDB manual for more information on how to use YAML effectively.
Finally, although XML format for configuring databases is now deprecated in favor of YAML — and we encourage the use of YAML — XML is still supported and continues to work as in previous releases for both the voltdb init and voltadmin update commands. So your existing scripts for starting and/or updating a database do not have to change at this time.
New voltadmin get and set Commands — As mentioned above, there are two new voltadmin commands: get and set. The voltadmin get command lets you retrieve part or all of the current configuration settings in YAML. If you specify "deployment" as the argument, you get all of the settings. Or you can specify a single property or group of properties by specifying the desired settings in dot notation. For example, you can get just the current K-safety factor with the voltadmin get deployment.cluster.kfactor command or all export settings with voltadmin get deployment.export. See the appendix of YAML properties in the Using VoltDB manual for details.
Similarly, the voltadmin set command lets you modify individual properties. You can either specify an individual property using dot notion (such as voltadmin set deployment.snapshot.enabled=true) or a YAML file for setting multiple properties at once (for example, voltadmin set --file=newusers.yaml)
Updated results for @SystemInformation OVERVIEW — The return results for the @SystemInformation system procedure OVERVIEW selector have been updated and a new field added to make it clearer when a cluster is at full K-safety or not. Originally, the field CLUSTERSAFETY could be misleading because it only reported on whether a hash mismatch had forced the cluster into reduced K-safety. Its value did not change if one or more nodes had failed for other reasons. To make it less misleading, CLUSTERSAFETY now reports FULL or REDUCED depending on whether the cluster is fully functional or nodes are missing for any reason. A new field, REDUCEDSAFETY, reports on whether K-safety has been intentionally reduced due to a hash mismatch.
Updated Platform Support — Volt Active Data now supports Kubernetes up through version 1.30, Ubuntu version 24.04, and Java versions 17 and 21.
Removing Obsolete Functionality — Over the life cycle of version 13, a number of older features were deprecated and replaced by improved and enhanced implementations. WIth the release of V14, these deprecated items are being removed from the product. These include:
Embedded Volt Management Center (VMC) and HTTP JSON API
Standalone Prometheus agent
The new features in VoltDB V14.0 add capabilities without altering the behavior of existing applications. However, there are a few changes that require action for users upgrading from earlier versions. Existing customers should take note of the following changes:
Deprecated Features Removed
Several obsolete technologies that have already been deprecated have now be removed from the product. Specifically:
Embedded VMC and HTTP JSON API — The embedded Volt Management Console (VMC) and HTTP programming interface has been deprecated and replaced with a VMC service that must be started separately on bare metal. (In Kubernetes, the new VMC service is started by default.) If you have been depending on VMC or the HTTP API starting automatically on bare metal, you will need to install and start the VMC service manually. See the Volt Administrator's Guide for information on running the VMC service.
Standalone Prometheus agent — The standalone Prometheus agent is no longer included in the Volt Active Data software kit. Instead, Prometheus metrics are available directly from the VoltDB servers, with each server reporting its own performance metrics. To use the new metrics, be sure to enable metrics in the database configuration, as described in the Volt Administrator's Guide. For example:
deployment: metrics: enabled: true
Updated System Requirements
The operating system and software requirements for Volt Active Data have been updated to add support for new releases and to remove products that have reached end of life. Specifically, the new requirements are:
Operating System:
Red Hat (RHEL) and Rocky version 8.8 or later, including subsequent releases. Version 8.6 is no longer supported.
Ubuntu 20.04, 22.04, and 24.04 and subsequent releases. Support for Ubuntu 24.04 has been added.
Macintosh OS X 13.0 and later (for development only). Support for versions 11 and 12 has been dropped.
Java for VoltDB server: Java 17 or 21. Java 11 is no longer supported for running the Volt server. (Note that Java 8, 11, 17, and 21 are all supported for Java clients.)
Cloud Computing: Kubernetes versions 1.25 through 1.30 are tested and supported, along with subsequent releases.
The process for upgrading from the recent versions of VoltDB is as follows:
Shutdown the database, creating a final snapshot (using voltadmin shutdown --save).
Upgrade the VoltDB software.
Restart the database (using voltdb start).
For Kubernetes, see the section on "Upgrading the VoltDB Software and Helm Charts" in the VoltDB Kubernetes Administrator's Guide. For DR clusters, see the section on "Upgrading VoltDB Software" in the VoltDB Administrator's Guide for special considerations related to DR upgrades. If you are upgrading from versions before V6.8, see the section on "Upgrading Older Versions of VoltDB Manually" in the same manual.
Finally, for all customers upgrading from earlier versions of VoltDB, please be sure to read the Volt Upgrade Guide, paying special attention to the notes for your current and subsequent releases, including V8, V10, V11, V12, and V13.
Users of previous versions of VoltDB should take note of the following changes that might impact their existing applications. See the Volt Operator Release Notes for changes specific to the use of VoltDB on the Kubernetes platform.
1. Release V14.0.0 (September 30, 2024) | |||
In addition to the new features described in the section called “What's New in Volt Active Data V14”, the following changes and improvements have been made since the last release. | |||
1.1. | New @Statistics selector DEPLOYMENTUPDATE | ||
There is a new selector for the @Statistics system procedure and corresponding metrics records. The DEPLOYMENTUPDATE selector returns performance information concerning the execution of configuration updates to the database including the length of time required to perform the update and how long other transactions are blocked during the update. See the description of @Statistics in the Using VoltDB manual for details. | |||
1.2. | Passwords in the configuration automatically masked on input | ||
The voltdb mask command allows you to mask passwords in the configuration file before submitting them to initialize or update the database. Now, as an additional security measure, passwords entered in plain text are automatically masked on input guaranteeing that no plain text passwords are stored in the system. | |||
1.3. | Security updates | ||
The following outstanding CVEs in the Universal Base Image (UBI) will be addressed as soon as a fix becomes available from Red Hat:
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1.4. | Additional improvements | ||
The following limitations in previous versions have been resolved:
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The following are known limitations to the current release of VoltDB. Workarounds are suggested where applicable. However, it is important to note that these limitations are considered temporary and are likely to be corrected in future releases of the product.
The following notes provide details concerning how certain VoltDB features operate. The behavior is not considered incorrect. However, this information can be important when using specific components of the VoltDB product.
1. Networking | |||||
1.1. | Support for IPv6 addresses | ||||
VoltDB works in IPv4, IPv6, and mixed network environments. Although the examples in the documentation use IPv4 addresses, you can use IPv6 when configuring your database, making connections through applications, or using the VoltDB command line utilities, such as voltdb and voltadmin. When specifying IPv6 addresses on the command line or in the configuration file, be sure to enclose the address in square brackets. If you are specifying both an IPv6 address and port number, put the colon and port number after the square brackets. For example: voltadmin status --host=[2001:db8:85a3::8a2e:370:7334]:21211 | |||||
1.2. | Issues with Jumbo Frames | ||||
There have been reports that VoltDB does not operate correctly when the networking environment is configured to use jumbo frames. The symptoms are that TCP packets with MTU>9000 are dropped. However, this is not a Volt-specific issue. When configuring the network to use jumbo frames, it is crucial to thoroughly test the network to guarantee that TCP packets are not fragmented or have their segments reordered during reassembly. If not, there is a danger of lost packets in the network layer, unrelated to the specific application involved. | |||||
2. XDCR | |||||
2.1. | Upgrading existing XDCR clusters for Dynamic Schema Change | ||||
Volt Active Data V12.3 introduces a new feature, dynamic schema change for XDCR clusters. To use this feature, clusters must be configured to enable the feature and must be using the latest DR protocol. However, existing clusters that upgrade from earlier versions will not automatically use the new protocol. Instead, you must explicitly upgrade the DR protocol using the voltadmin dr protocol --update command. First, to use dynamic schema change you must enable the feature in the configuration file. This must be done
when you initialize the cluster which, for existing XDCR clusters, is easiest to when performing the version
upgrade. To upgrade XDCR clusters, you must drop the cluster from the XDCR environment, upgrade the software, then
reinitialize and restart the cluster. While reinitializing the cluster, add the <deployment>
<dr id="1" role="xcdr">
<schemachange enabled="true"/>
<connection source="paris.mycompany.com,rome.mycompany.com"/>
</dr>
</deployment> Similarly, for Kubernetes, the YAML would be: cluster:
config:
deployment:
dr:
id: 1
role: xdcr
schemachange:
enabled: true
connection:
source: paris.mycompany.com,rome.mycompany.com Once all of the clusters are upgraded to the appropriate software version, you can upgrade the DR protocol. When used by itself, the voltadmin dr protocol command displays information about what versions of the DR protocol the XDCR clusters support and which version they are using. When the XDCR relationship starts, the clusters use the highest supported protocol. However, when an existing XDCR group is upgraded, they do not automatically upgrade the originally agreed-upon protocol. In this case, you must go to each cluster and issue the voltadmin dr protocol --update command to use the highest protocol that all the clusters can support. Once you issue the voltadmin dr protocol --update command on all of the clusters, you are then ready to perform dynamic schema changes on your XDCR environment. | |||||
3. Volt Management Center | |||||
3.1. | Schema updates clear the stored procedure data table in the Management Center Monitor section | ||||
Any time the database schema or stored procedures are changed, the data table showing stored procedure statistics at the bottom of the Monitor section of the VoltDB Management Center get reset. As soon as new invocations of the stored procedures occur, the statistics table will show new values based on performance after the schema update. Until invocations occur, the procedure table is blank. | |||||
3.2. | TLS/SSL for the HTTPD port on Kubernetes | ||||
Prior to VoltDB V12.0, encryption for the httpd port which VMC uses was automatically enabled on Kubernetes
when you enabled TLS/SSL for the server using the Starting with V12.0, VMC on Kubernetes is run as a separate service by default and you can enable or disable
TLS/SSL encryption for VMC independently using the | |||||
4. SQL | |||||
4.1. | You cannot partition a table on a column defined as ASSUMEUNIQUE. | ||||
The ASSUMEUNIQUE attribute is designed for identifying columns in partitioned tables where the column values are known to be unique but the table is not partitioned on that column, so VoltDB cannot verify complete uniqueness across the database. Using interactive DDL, you can create a table with a column marked as ASSUMEUNIQUE, but if you try to partition the table on the ASSUMEUNIQUE column, you receive an error. The solution is to drop and add the column using the UNIQUE attribute instead of ASSUMEUNIQUE. | |||||
4.2. | Adding or dropping column constraints (UNIQUE or ASSUMEUNIQUE) is not supported by the ALTER TABLE ALTER COLUMN statement. | ||||
You cannot add or remove a column constraint such as UNIQUE or ASSUMEUNIQUE using the ALTER TABLE ALTER COLUMN statement. Instead to add or remove such constraints, you must first drop then add the modified column. For example: ALTER TABLE employee DROP COLUMN empID; ALTER TABLE employee ADD COLUMN empID INTEGER UNIQUE; | |||||
4.3. | Do not use UPDATE to change the value of a partitioning column | ||||
For partitioned tables, the value of the column used to partition the table determines what partition the row belongs to. If you use UPDATE to change this value and the new value belongs in a different partition, the UPDATE request will fail and the stored procedure will be rolled back. Updating the partition column value may or may not cause the record to be repartitioned (depending on the old and new values). However, since you cannot determine if the update will succeed or fail, you should not use UPDATE to change the value of partitioning columns. The workaround, if you must change the value of the partitioning column, is to use both a DELETE and an INSERT statement to explicitly remove and then re-insert the desired rows. | |||||
4.4. | Ambiguous column references no longer allowed. | ||||
Starting with VoltDB 6.0, ambiguous column references are no longer allowed. For example, if both the Customer and Placedorder tables have a column named Address, the reference to Address in the following SELECT statement is ambiguous: SELECT OrderNumber, Address FROM Customer, Placedorder . . . Previously, VoltDB would select the column from the leftmost table (Customer, in this case). Ambiguous column references are no longer allowed and you must use table prefixes to disambiguate identical column names. For example, specifying the column in the preceding statement as Customer.Address. A corollary to this change is that a column declared in a USING clause can now be referenced using a prefix. For example, the following statement uses the prefix Customer.Address to disambiguate the column selection from a possibly similarly named column belonging to the Supplier table: SELECT OrderNumber, Vendor, Customer.Address FROM Customer, Placedorder Using (Address), Supplier . . . | |||||
5. Runtime | |||||
5.1. | File Descriptor Limits | ||||
VoltDB opens a file descriptor for every client connection to the database. In normal operation, this use of file descriptors is transparent to the user. However, if there are an inordinate number of concurrent client connections, or clients open and close many connections in rapid succession, it is possible for VoltDB to exceed the process limit on file descriptors. When this happens, new connections may be rejected or other disk-based activities (such as snapshotting) may be disrupted. In environments where there are likely to be an extremely large number of connections, you should consider increasing the operating system's per-process limit on file descriptors. | |||||
5.2. | Use of Resources in JAR Files | ||||
There are two ways to access additional resources in a VoltDB database. You can place the resources in the
LOAD CLASSES is used primarily to load classes associated with stored procedures and user-defined functions. However, it will also load any additional resource files included in subfolders of the JAR file. You can remove classes that are no longer needed using the REMOVE CLASSES directive. However, there is no explicit command for removing other resources. Consequently, if you rename resources or move them to a different location and reload the JAR file, the database will end up having multiple copies. Over time, this could result in more and more unnecessary memory being used by the database. To remove obsolete resources, you must first reinitialize the database root directory, start a fresh database, reload the schema (including the new JAR files with only the needed resources) and then restore the data from a snapshot. | |||||
5.3. | Servers with Multiple Network Interfaces | ||||
If a server has multiple network interfaces (and therefore multiple IP addresses) VoltDB will, by default, open ports on all available interfaces. You can limit the ports to an single interface in two ways:
Also, when using an IP address to reference a server with multiple interfaces in command line utilities (such as voltadmin stop node), use the @SystemInformation system procedure to determine which IP address VoltDB has selected to identify the server. Otherwise, if you choose the wrong IP address, the command might fail. | |||||
5.4. | Using VoltDB where the /tmp directory is noexec | ||||
On startup, VoltDB extracts certain native libraries into the /tmp directory before loading them. This works in all standard operating environments. However, in custom installations where the /tmp storage is mounted with the "noexec" option, VoltDB cannot extract the libraries and, in the past, refused to start. For those cases where the /tmp directory is assigned on storage mounted with the ‘noexec’ option, you can assign an alternative storage for VoltDB to use for extracting and executing temporary files. This is now done automatically on Kubernetes and does not require any user intervention. On non-Kubernetes environments, you can identify an alternative location by assigning it to
export VOLTDB_OPTS="-Dvolt.tmpdir=/volttemp \ -Dorg.xerial.snappy.tempdir=/volttemp \ -Djna.tmpdir=/volttemp" When using an alternate temporary directory, files can accumulate over time since the directory is not automatically purged on startup. So you should make sure you periodically delete old files from the directory. | |||||
5.5. | Text Data and Character Sets | ||||
Volt Active Data processes and stores text data as UTF-8 encoded strings. When using the Volt Java API, the Java String datatype always stores text in Unicode. So there is no conversion necessary when passing string data to Volt stored procedures. If the application must handle data in alternate character encodings you can use existing Java functionality to convert the data to Unicode on input. For example, using the second argument to specify the character encoding when instantiating a buffered reader: BufferedReader myfile = Files.newBufferedReader(filename,charset); On the other hand, when users enter data interactively using an alternate character encoding, Volt automates the conversion of the character set of the current session to UTF-8 on input and output. In other words, if the user's session is localized to use a specific character set, when entering data at the sqlcmd prompt (for example, when executing an INSERT statement) the data is automatically converted to UTF-8 before processing. Similarly, on output (such as displaying the results of a SELECT statement) the UTF-8 data is converted to the user's localized character set. When processing text files, such as CSV files or sqlcmd scripts, the command line utilities
provide a Finally, which character sets are supported depends on which Java virtual machine (JVM) release you are using on your servers (for export) or client machines (for sqlcmd and csvloader). For established character sets, such as Shift_JIS or ISO-8859-1, all supported JVM releases provide support. For newer character sets, you may need a more recent release of the JVM. For example, the recent Simplified Chinese character set GB18030-2022 requires a JVM released in 2023 or later. For OpenJDK this includes the following releases:
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5.6. | Using Java 11 in Client Applications | ||||
When running a client application linked against the VoltDB Java API and using the Java 11 runtime, the application may issue warnings about an " illegal reflective access operation." The message does not impact the actual operation of the client or the database itself. You can suppress this warning using the --add-opens qualifier on the java command. For example: $ java --add-opens=java.base/java.lang=ALL-UNNAMED \ --add-opens=java.base/sun.nio.ch=ALL-UNNAMED \ --add-opens=java.base/java.net=ALL-UNNAMED \ --add-opens=java.base/java.nio=ALL-UNNAMED \ myclientapp | |||||
6. Kubernetes | |||||
6.1. | Do not change the UID on the Kubernetes account used to run VoltDB | ||||
In the security context section of the Helm chart for VoltDB, the user account UID is set to 1001. This value is required. Do not change or override any of the following properties when configuring your database:
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6.2. | OpenShift and Transparent Huge Pages (THP) | ||||
For production, VoltDB requires that Transparent Huge Pages (THP) are disabled because they interfere with memory-intensive applications. However, THP may be enabled on OpenShift containers and the containers themselves not have permission to disable them. To overcome this situation, you must run the Helm chart for disabling THP from a privileged container: $ helm -n kube-system install thp voltdb/transparent-hugepages \ --set thp.securityContext.privileged=true | |||||
6.3. | Kubernetes Compatibility | ||||
See the Volt Kubernetes Compatibility Chart for information on which versions of the Volt Operator and Helm charts support which version of VoltDB. See the VoltDB Operator Release Notes for additional information about individual releases of the VoltDB Operator. |