The following CVEs were resolved:

The following outstanding CVE in the Universal Base Image (UBI) will be addressed as soon as a fix becomes available from Red Hat:

The following limitations in previous versions have been resolved:

The following limitations in previous versions have been resolved:

The following high and critical CVEs were resolved:

This release removes all known high and critical security vulnerabilities found in the RedHat Universal Base Image (UBI).

The following limitations in previous versions have been resolved:

With this release, the base image for running Volt under Kubernetes has been upgraded from Alpine to the Red Hat Universal Base Image (UBI). UBI provides Volt Active Data with an established and supported base image on which to build. This change also corrects issues encountered when running Volt under recent releases of OpenShift.

The following high and critical CVEs were resolved:

Note that, with the switch to RedHat Universal Base Image (UBI), there are a few known security vulnerabilities in the UBI implementation of Bind. These will be corrected as soon as Red Hat provides an upgraded UBI release with the appropriate patches.

The following limitations in previous versions have been resolved:

All known high and critical CVEs were resolved as of the date of this release, including:

The following limitations in previous versions have been resolved:

VoltDB has introduced a new license file format with a more flexible structure to allow for new features in the future. This LTS release adds support for the new file format to ensure it can run using both existing and new licenses. In addition to supporting the new format, several minor changes related to license management have been made:

All known high and critical CVEs were resolved as of the date of this release, including:

The following limitations in previous versions have been resolved:

All known high and critical CVEs were resolved as of the date of this release, including:

The following limitations in previous versions have been resolved:

The following limitations in previous versions have been resolved:

All known high and critical CVEs were resolved as of the date of this release, including:

In addition, the following limitations in previous versions have been resolved:

The current release, Volt Active Data V12.3, is the Long-Term Support (LTS) release for version 12. We encourage all customers using V12 to upgrade to the V12.3 release to ensure ongoing support through minor version updates. See the chapter on Long-Term Support in the Volt Upgrade Guide for more information on the advantages of LTS releases and subsequent chapters on how to upgrade from previous major releases.

It is now possible to use existing LDAP users and groups to authenticate and authorize access to VoltDB databases in place of builtin VoltDB accounts. LDAP integration allows users and programs to pass LDAP credentials to the database server, which in turn passes those credentials to LDAP for authentication. VoltDB then looks up what groups the LDAP user is a member of to identify what roles they have and ultimately what permissions they are granted by the database. VoltDB LDAP integration supports both plain and secure LDAP. See the chapter on Security in the Using VoltDB manual for details.

When done carefully, it is possible to add and remove DR tables from a XDCR VoltDB schema without having to pause the databases. However, previously, there was no safe way to modify the tables themselves. VoltDB V12.3 introduces dynamic schema change which, as the name implies, allows you to apply selected modifications to DR tables without pausing the database and while continuing to process transactions for those tables.

Dynamic schema change allows you to add or remove columns from the end of a table. You can also modify the length of VARCHAR columns. During the transition, when the schema of the clusters do not match, VoltDB follows set rules for applying the binary logs to mismatched tables. In many cases — such as if applications use the default values for new columns — the clusters can process transactions normally during the transition and the clusters' contents will match once the schema change is complete.

Of course, there is always certain amount of risk to dynamic changes if you do not manage your client applications correctly, so VoltDB keeps a count of how many binary logs are applied to mismatched tables so you can determine how much risk there is. New data columns to existing selectors and new selectors (such as DRSCHEMA and XDCR) for the @Statistics system procedure help you monitor the status of schema changes in your databases.

Since dynamic schema change does introduce some additional risk of divergence to the clusters, it is not enabled by default. Before applying schema changes without pausing, you must enable dynamic schema change in the configuration file. See the documentation on updating the schema in the chapter on Database Replication of the Using VoltDB manual for details. Also, if you want to use this feature in existing XDCR databases, see the section later in this document for upgrading XDCR clusters to use dynamic schema change.

VoltDB V12.3 includes the beta release of a new reporting system aimed at providing a simpler, more consistent interface to statistics about the database status and performance. The new system is built into the server (unlike the previous external Prometheus agent), meaning it starts and stops automatically as part of the overall database system. Each server reports its own status. And the system as a whole integrates seamlessly with Prometheus and Grafana

To learn more about the new metrics system, see the beta release documentation which is available online.

Both Red Hat Enterprise Linux (RHEL) version 9 and Kubernetes 1.26 are now supported as platforms for production use.

The VoltDB base image on Kubernetes has been upgraded to use Alpine 3.18 and Java 17.

VoltDB uses temporary memory to store changes in case a transaction needs to rollback. Rather than allocate and deallocate memory for each transaction, VoltDB maintains an undo pool that is reused for this purpose. The pool is extended if a transaction requires more undo memory. The pool then stays at the larger size assuming a future transaction is likely to need the same amount of undo memory.

Previously, the current allocation of the undo pool was not visible. A new field has been added to the @Statistics MEMORY output reporting the current allocation. In addition, the voltadmin defrag command now resets the undo pool as part of its memory optimization function.

The @Statistics system procedure returns new and enhanced data on a number of different topics:

See the @Statistics reference page in the Using VoltDB manual for more information.

All known high and critical CVEs were resolved as of the date of this release, including:

In addition, the following limitations in previous versions have been resolved:

All known high and critical CVEs were resolved as of the date of this release, including:

In addition, the following limitations in previous versions have been resolved:

Packages within Volt Active Data have been updated to eliminate the following known security vulnerability: CVE-2023-0464.

The Volt Operator for Kubernetes has been updated to improve stability, extensibility, and to support Kubernetes V1.23 through V1.25. The new version of the Operator, V2.0, is required for both Volt V12.2 and Kubernetes V1.25.

The transition from V1.x to V2.0 of the Operator is the same as any other update, with one exception: when upgrading to V2.0 you must use the kubectl replace command to update the CRD instead of the kubectl apply command, as was documented in previous releases. On the other hand, use of replace instead of apply works when updating any version of the Volt software. So the documentation has been revised to recommend the use of replace for all software upgrades.

Because Volt Operator and Helm chart V2.0 are required for Kubernetes 1.25, customers upgrading to 1.25 must upgrade the components in the following order:

In previous releases, the Volt Operator established permissions for the Kubernetes pods to provide Volt with the rights needed to function properly. This was done using Kubernetes pod security policies (PSP). Starting with the Volt Operator and charts V2.0, pod security policies are no longer enabled by default. This means the Volt pods have no specific limitations set for them.

For Kubernetes V1.23 and V1.24, you can enable PSP constraints by setting the Helm property global.rbac.pspEnabled to "true". However, PSP has been deprecated by Kubernetes and is no longer available in V1.25. So the preferred method for applying security constraints on pods is+ to use the built-in Kubernetes Pod Security admission controller or to use a third-party admission controller. In either case, the Volt pods require the equivalent of the baseline admissions to operate properly. For example, the following kubectl command enables the baseline permissions for the mydatacenter namespace:

$ kubectl label --override namespace mydatacenter pod-security.kuberneted.io/enforce=baseline

Volt Active Data now supports cloud native placement groups. K-Safety guarantees the database cluster can survive a certain number of node failures. Placement groups allow you to define groups of nodes that are logically connected so that Volt can avoid losing the database if an entire group goes offline. In Kubernetes, if you enable the new cloud native placement capability, Volt maximizes its availability, using knowledge of the Kubernetes regions and zones to intelligently distribute copies of the database partitions so that even if an availability zone is lost, the database can remain operational. See the section on "Configuring High Availability" in the Volt Kubernetes Administrator's Guide for more information.

One feature of TLS/SSL is that the client can verify that the certificate is assigned to the same host name or address they connect to. In fact, it can allow for multiple names and even wildcards using Subject Alternative Names (SAN). By default, Volt does not utilize this feature. However, starting with Volt V12.2 the Volt Java client can enable alternative name support and verify that the certificate matches the requested address. See the note on using TLS alternative name support later in this document for details.

Because version 3.6 is no longer supported, the minimal version of Python required by Volt Active Data has been updated to V3.9.

To resolve certain security vulnerabilities the Kafka client library has been upgraded. However, the newer library requires Kafka producers to explicitly disable idempotency when sending messages to Volt topics, which was not required before. Important: if you are using a Kafka producer to send data to Volt topics and do not explicitly disable idempotency, you will need to update the client to add the property enable.idempotence setting the property to "false" before upgrading to Volt V12.2. See the section on "Calling Topics from Consumers and Producers" in the Using VoltDB manual for details.

When configuring security in VoltDB, you must specify usernames and passwords, which previously appeared in plain text in the YAML configuration file. You can now use the Helm voltadmin plugin to mask those passwords, so they are not readily viewable in the YAML. See the description of the Helm plugin mask command in the Volt Kubernetes Administrator's Guide for details.

The Volt JDBC API now supports the getMaxConnection method, which returns the integer value of zero (0) indicating the maximum is unspecified.

Previously, when enabling TLS/SSL encryption for XDCR clusters in Kubernetes, all of the clusters needed to use the same certificate. Although the property cluster.config.deployment.dr.connection.ssl existed, it was not applied and the credentials of the local cluster were used to contact the remote clusters in the XDCR mesh.

It is now possible to specify separate TSL/SSL credentials for each XDCR cluster. When specifying the credentials of the remote XDCR cluster, use the new properties cluster.config.deployment.dr.connection.ssl.truststore.file and cluster.config.deployment.dr.connection.ssl.truststore.password, or specify a Kubernetes secret using the property cluster.config.deployment.dr.connection.ssl.sslSecret.certSecretName where the secret defines the keys dr_conn_truststore_data and dr_conn_truststore_password.

When upgrading an existing cluster to operator 2.0 and using the new XDCR TLS/SSL properties, be sure to remove any existing definition of the cluster.config.deployment.dr.connection.ssl property by setting it to an empty mapping . For example:

$ helm upgrade mydb voltdb/voltdb --reuse-values \
   --set cluster.config.deployment.dr.connection.ssl={}

In addition to the new features and capabilities described above, the following limitations in previous versions have been resolved:

All known high and critical CVEs were resolved as of the date of this release, including:

The latest Operator release simplifies the process for updating TLS/SSL certificates and eliminates the need to stop and restart the cluster to apply the new certificate. In Kubernetes,if you store the TLS/SSL credentials using Kubernetes secrets, either created manually or through the cert-manager, the Operator now automatically updates the configuration on the running cluster once the secret changes. So, if you created the secret manually, you simply need to delete and recreate the secret with the new credentials. If you use cert-manager, cert-manager itself updates the credentials when the expiration date approaches. In either case, the Operator recognizes the change and updates the running cluster without any further operator intervention.

The @Statistics system procedure has a new selector, HOST, that returns information about the nodes of the cluster, including what partitions it hosts and whether it is safe to stop the node in a K-safe cluster. See the description of the @Statistics system procedure in the Using VoltDB manual for details.

Support for a new selector, ENV, has been added to the @SystemInformation system procedure. The ENV selector returns information about the environment variables defined for the database server process, one row for each variable on each host. See the description of the @SystemInformation system procedure in the Using VoltDB manual for details.

The TLS/SSL protocol versions 1.0 and 1.1 were deprecated and removed from most industry applications and browsers in 2020. Going forward, these obsolete protocol versions are no longer available in VoltDB either.

The following limitations in previous versions have been resolved:

Memory management for the database table data has been rewritten and optimized to reduce certain impediments in the previous implementation. Although this change is primarily internal and transparent to you as a customer, it does have two direct benefits in terms of eliminating development and operational roadblocks:

Volt Active Data has added Ubuntu 22.04 and Rocky OS as supported platforms for VoltDB.

When enabling TLS/SSL in Kubernetes, you can now store your TLS/SSL credentials (including the keystore, truststore, and passwords) in a Kubernetes secret. This avoids having to specify passwords on the Helm command line and simplifies the commands needed to start and update database instances. See the section on configuring TLS/SSL in the Volt Kubernetes Administrator's Guide for details.

You can now specify an expiration date for user accounts in the database configuration file. Once the specified date is past, the associated account can no longer access the database, until the configuration for the user account is updated. The expiration date is optional. See the section on defining users and roles in the Using VoltDB manual for details.

The LAG() function accesses previous rows from the window results using an offset. See the section on windowing functions in the SELECT reference page for more information.

By default, Volt in Kubernetes now creates a separate pod for the Volt Management Center (VMC) and HTTP API. This provides a single service name for accessing these resources, as well as a single instance for the entire cluster (rather than separate instances for each host). The new pod is available from the service name {release-name}-voltdb-vmc where {release-name} is the name of the Helm release for the database cluster.

Starting with V12, the voltdb init command must find and load a license file or the initialization of the database root directory will fail. The license file can either be specified explicitly using the -l or --license flag or it can be found in one of the three default locations (the current working directory, the user's home directory, or the voltdb folder where VoltDB is installed). It is still possible to specify a license file on the voltdb start command — in case you need to change or update the license after initialization — but a license must be specified on the voltdb init command first.

To support different versions of the Kafka API, two versions of the kafkaloader utility were provided in the past: kafkaloader and kafkaloader10. Now that support for older versions of Kafka has been dropped, the legacy loader, kafkaloader10, has been deprecated and will be removed in a future release.

Several obsolete methods in the Java client API that were previously deprecated have now been removed. Those methods were setClientAffinity, setSendReadsToReplicas, and setReconnectOnConnectionLoss.

The procedure for upgrading the VoltDB software using limited hardware is no longer supported. The associated command, plan_upgrade, has been removed from the voltadmin utility.

The results of the @Statistics system procedure DRCONSUMER selector have been altered slightly. Specifically, the last column of the third results table has been renamed to be more descriptive from LAST_FAILURE to LAST_FAILURE_CODE.

The @SystemInformation system procedure now includes additional information regarding the number of processors, both existing and available for use. This is important because in certain situations (most notably, Kubernetes) not all processors are available to the application. The new results field is called JAVAAVAILABLEPROCESSORS.

The following limitations in previous versions have been resolved:

VoltDB reserves the subfolder "segments" under the command log directory for storing the actual command log files. Do not add, remove, or modify any files in this directory. In particular, do not set the command log snapshot directory to a subfolder "segments" of the command log directory, or else the server will hang on startup.

Because DR data is buffered on the master database and then delivered asynchronously to the replica, there is always the danger that data does not reach the replica if a master node stops. This situation is mitigated in a K-safe environment by all copies of a partition buffering on the master cluster. Then if a sending node goes down, another node on the master database can take over sending logs to the replica. However, if multiple nodes go down and rejoin in rapid succession, it is possible that some buffered DR data — from transactions when one or more nodes were down — could be lost when another node with the last copy of that buffer also goes down.

If this occurs and the replica recognizes that some binary logs are missing, DR stops and must be restarted.

To avoid this situation, especially when cycling through nodes for maintenance purposes, the key is to ensure that all buffered DR data is transmitted before stopping the next node in the cycle. You can do this using the @Statistics system procedure to make sure the last ACKed timestamp (using @Statistitcs DR on the master cluster) is later than the timestamp when the previous node completed its rejoin operation.

Bulk operations, such as large deletes, inserts, or updates are possible within a single stored procedure. However, if the binary logs generated for DR are larger than 45MB, the operation will fail. To avoid this situation, it is best to break up large bulk operations into multiple, smaller transactions. A general rule of thumb is to multiply the size of the table schema by the number of affected rows. For deletes and inserts, this value should be under 45MB to avoid exceeding the DR binary log size limit. For updates, this number should be under 22.5MB (because the binary log contains both the starting and ending row values for updates).

There are a number of VoltDB features that help manage the database by constraining memory size and resource utilization. These features are extremely useful in avoiding crashes as a result of unexpected or unconstrained growth. However, these features could interfere with the normal operation of DR when passing data from one cluster to another, especially if the two clusters are different sizes. Therefore, as a general rule of thumb, DR overrides these features in favor of maintaining synchronization between the two clusters.

Specifically, DR ignores any resource monitor limits defined in the deployment file when applying binary logs on the consumer cluster. This means, for example, if the replica database in passive DR has less memory or fewer unique partitions than the master, it is possible that applying binary logs of transactions that succeeded on the master could cause the replica to run out of memory. Note that these resource monitor limits are applied on any original transactions local to the cluster (for example, transactions on the master database in passive DR).

Database Replication (DR) now supports replication across clusters of different sizes. However, if the replica cluster is smaller than the master cluster, it may require a significantly larger Java heap setting. Specifically, if the replica has fewer unique partitions than the master, each partition on the replica must manage the incoming binary logs from more partitions on the master, which places additional pressure on the Java heap.

A simple rule of thumb is that the worst case scenario could require an additional P * R * 20MB space in the Java heap , where P is the number of sites per host on the replica server and R is the ratio of unique partitions on the master to partitions on the replica. For example, if the master cluster is 5 nodes with 10 sites per host and a K factor of 1 (i.e. 25 unique partitions) and the replica cluster is 3 nodes with 8 sites per host and a K factor of 1 (12 unique partitions), the Java heap on the replica cluster may require approximately 320MB of additional space in the heap:

An alternative is to reduce the size of the DR buffers on the master cluster by setting the DR_MEM_LIMIT Java property. For example, you can reduce the DR buffer size from the default 10MB to 5MB using the VOLTDB_OPTS environment variable before starting the master cluster.

Changing the DR buffer limit on the master from 10MB to 5MB proportionally reduces the additional heap size needed. So in the previous example, the additional heap on the replica is reduced from 320MB to 160MB.

The voltadmin status --dr command provides real-time status on the state of database replication (DR). Normally, this includes the status of the current cluster as well as other clusters in the DR environment. (For example, both the master and replica in passive DR or all clusters in XDCR.) However, if the clusters are configured to use different port numbers for the client port, VoltDB cannot reach the other clusters and the command hangs until it times out waiting for a response from the other clusters.

Part of the replication process for XDCR is to verify that the record's starting and ending states match on both clusters, otherwise known as conflict resolution. To do that, XDCR must find the record first. Finding uniquely indexed records is efficient; finding non-unique records is not and can impact overall database performance.

To make you aware of possible performance impact, VoltDB issues a warning if you declare a table as a DR table and it does not have a unique index.

You cannot start XDCR if both databases already have data in the DR tables. Only one of the two participating databases can have preexisting data when DR starts for the first time.

When starting XDCR for the first time, where one database already contains data, a snapshot of that data is sent to the other database. While receiving and processing that snapshot, the receiving database is paused. That is, it is in read-only mode. Once the snapshot is completed and the two database are synchronized, the receiving database is automatically unpaused, resuming normal read/write operations.

Normally, XDCR will automatically restart where it left off after one of the clusters stops and recovers from its command logs (using the voltdb recover command). However, if the workload is predominantly multi-partition write transactions, a failed cluster may not be able to restart XDCR after it recovers. In this case, XDCR must be restarted from scratch, using the content from one of the clusters as the source for synchronizing and recreating the other cluster (using the voltdb create --force command) without any content in the DR tables.

TRUNCATE TABLE is optimized to delete all data from a table rather than deleting tuples row by row. This means that the binary log does not identify which rows are deleted. As a consequence, a TRUNCATE TABLE statement and a simultaneous write operation to the same table can produce a conflict that the XDCR clusters cannot detect or report in the conflict log.

Therefore, do not use TRUNCATE TABLE with XDCR. Instead, explicitly delete all rows with a DELETE statement and a filter. For example, DELETE * FROM table WHERE column=column ensures all deleted rows are identified in the binary log and any conflicts are accurately reported. Note that DELETE FROM table without a WHERE clause is not sufficient, since its execution plan is optimized to equate to TRUNCATE TABLE.

VoltDB provides a way to generate a deterministically unique ID within a stored procedure using the getUniqueId method. This method guarantees uniqueness within the current cluster. However, the method could generate the same ID on two distinct database clusters. Consequently, when using XDCR, you should combine the return values of VoltProcedure.getUniqueId with VoltProcedure.getClusterId, which returns the current cluster's unique DR ID, to generate IDs that are unique across all clusters in your environment.

In an XDCR environment involving three or more clusters, command logging is used to ensure the durability of the XDCR "conversations" between clusters. If not, when a cluster stops, the remaining clusters can be at different stages of their conversation with the downed cluster, resulting in divergence.

For example, assume there are three clusters (A, B, and C) and cluster B is processing binary logs faster than cluster C. If cluster A stops, cluster B will have more binary logs from A than C has. You can think of B being "ahead" of C. With command logging enabled, when cluster A restarts, it will continue its XDCR conversations and cluster C will catch up with the missing binary logs. However, without command logging, when A stops, it must restart from scratch. There is no mechanism for resolving the difference in binary logs processed by clusters B and C before the failure.

This is why command logging is required to ensure the durability of XDCR conversations in a multi-cluster (that is , three or more) XDCR environment. The alternative, if not using command logging, is to restart all but one of the remaining clusters to ensure they are starting from the same base point.

There are two ways to remove an cluster from an XDCR relationship: you can use voltadmin drop on a running cluster to remove it from the XDCR network, or you can use voltadmin dr reset from the remaining clusters to remove a cluster that is no longer available. But you should not use voltadmin dr reset to remove a cluster that is still running and connected to the network. Resetting a running cluster will break DR for that cluster, but will result in errors on the remaining clusters and leave their DR queues for the reset cluster in an ambiguous state. Ultimately, this can result in the removed cluster not being able to rejoin the XDCR network at a later time.

TTL, or time to live, is a feature that automatically deletes old records based on a timestamp or integer column. For replicated tables, the process of checking whether records need to be deleted is performed as a write transaction — even if no rows are deleted. As a consequence, any replicated DR table with TTL defined will generate frequent DR log entries, whether there are any changes or not, significantly increasing DR traffic.

Because of the possible performance impact this behavior can have on the database, use of TTL with replicated tables and DR is not recommended at this time.

A bug in the Apache Kafka client can result in file descriptors being allocated but not released if the producer.type attribute is set to "sync" (which is the default). The consequence is that the system eventually runs out of file descriptors and the VoltDB server process will crash.

Until this bug is fixed, use of synchronous Kafka export is not recommended. The workaround is to set the Kafka producer.type attribute to "async" using the VoltDB export properties.

If, while Kafka import is enabled, the Kafka broker that VoltDB is connected to stops (for example, if the server crashes or is taken down for maintenance), some messages may be lost between Kafka and VoltDB. To ensure no data is lost, we recommend you disable VoltDB import before taking down the associated Kafka broker. You can then re-enable import after the Kafka broker comes back online.

There is an issue with the Kafka importer where, if multiple nodes in the cluster fail and restart, the importer can lose track of some of the data that was being processed when the nodes failed. Normally, these pending imports are replayed properly on restart. But if multiple nodes fail, it is possible for some in-flight imports to get lost. This issue will be addressed in an upcoming release.

When entering a multi-line statement at the sqlcmd prompt, if a line ends in a comment (indicated by two hyphens) and the comment contains an unmatched single quote character, the following lines of input are not interpreted correctly. Specifically, the comment is incorrectly interpreted as continuing until the next single quote character or a closing semi-colon is read. This is most likely to happen when reading in a schema file containing comments. This issue is specific to the sqlcmd utility.

A fix for this condition is planned for an upcoming point release

VoltDB currently intercepts assertions as part of its handling of stored procedures. Attempts to use assertions in stored procedures for debugging or to find programmatic errors will not work as expected.

The UPPER() and LOWER() functions return a string converted to all uppercase or all lowercase letters, respectively. However, for the initial release, these functions only operate on characters in the ASCII character set. Other case-sensitive UTF-8 characters in the string are returned unchanged. Support for all case-sensitive UTF-8 characters will be included in a future release.

There is a problem with how the math library used to build the C++ client library handles large decimal values on 32-bit operating systems. As a result, the C++ library cannot serialize and pass Decimal datatypes reliably on these systems.

Note that the C++ client interface can send and receive Decimal values properly on 64-bit platforms.

Enabling SNMP can take up to 2 minutes to complete. This delay does not always occur and can vary in length. If SNMP is enabled when the database server starts, the delay occurs after the server logs the message "Initializing SNMP" and before it attempts to connect to the cluster. If you enable SNMP while the database is running, the delay can occur when you issue the voltadmin update command or modify the setting in the VoltDB Management Center Admin tab. This issue results from a Java constraint related to secure random numbers used by the SNMP library.

The command line utilities, such as sqlcmd, voltadmin, and the data loaders, have an --ssl flag to specify the truststore for user-created certificates. However, if you use commercial certificates, there is no truststore. In that case, you need to specify an empty string to the --ssl command qualifier to access the database. For example:

$ sqlcmd --ssl=""

Shutting down a VoltDB cluster by specifying a replica count of zero should shut down the cluster and remove the pods on which it ran. However, on very rare occasions Kubernetes does not delete the pods. As a result, the cluster cannot be restarted. This is an issue with Kubernetes. The workaround is to manually delete the pods before restarting the cluster.

The property cluster.clusterSpec.additionalVolumes lets you specify additional resources to include in the server classpath. However, if you specify an invalid or misconfigured volume, Helm will not be able to start the cluster and the process will stall.

The Helm --set-file argument lets you set the value of a property as the contents of a file. However, if the contents of the file are binary, they can become corrupted if you try to resize the cluster with the helm upgrade command, using the --reuse-values argument. For example, this can happen if you use --set-file to assign a JAR file of stored procedure classes to the cluster.config.classes property.

This is a known issue for Kubernetes and Helm. The workaround is either to explicitly include the --set-file argument again on the helm upgrade command. Or you can include the content through a different mechanism. For example, you can include class files by mounting them on a separate volume that you then include with the cluster.clusterSpec.additionalVolumes property.

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

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 <schemachange enabled="true"/> element to the configuration file. For example:

<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.

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.

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 cluster.config.deployment.ssl.enabled property. You could then selectively enable SSL for other ports using the .dr, .internal, and .external subproperties of cluster.config.deployment.ssl.

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 vmc.service.ssl... properties. However, if you choose not to run VMC as a separate service, by setting the vmc.enabled property to "false", VMC encryption is managed the same way as in earlier releases using the cluster.config.deployment.ssl... properties as described above.

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.

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;

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.

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
    . . .

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.

There are two ways to access additional resources in a VoltDB database. You can place the resources in the /lib folder where VoltDB is installed on each server in the cluster or you can include the resource in a subfolder of a JAR file you add using the sqlcmd LOAD CLASSES directive. Adding resources via the /lib directory is useful for stable resources (such as third-party software libraries) that do not require updating. Including resources (such as XML files) in the JAR file is useful for resources that may need to be updated, as a single transaction, while the database is running.

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.

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.

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 volt.tmpdir, org.xerial.snappy.tmpdir, and jna.tmpdir in the VOLTDB_OPTS environment variable before starting the server process. The specified location must exist, must be an absolute path, and cannot be on storage mounted with the "noexec" option. For example, the following command assigns an alternate temporary directory called /volttemp:

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.

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

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.