Upgrades for DataStax Enterprise 6.7.x patch releases

General recommendations

Be sure to read the DataStax Enterprise 6.7 release notes.

DataStax recommends upgrading to the latest DSE 6.7.5.

General restrictions and limitations during the upgrade process

Restrictions and limitations apply while a cluster is in a partially upgraded state. The cluster continues to work as though it were on the earlier version of DataStax Enterprise until all of the nodes in the cluster are upgraded.

Restrictions for all nodes during an upgrade

• Do not enable new features.
• Do not run nodetool repair.
• Do not bootstrap or decommission nodes.
• Failure to upgrade SSTables when required results in a significant performance impact and increased disk usage. Upgrading is not complete until the SSTables are upgraded.

Note: Nodes on different versions might show a schema disagreement during an upgrade.

DSE Search (Solr) upgrade restrictions and limitations

• Do not update schemas.
• Do not reindex DSE Search nodes during upgrade.
• Do not issue these types of queries during a rolling restart: DDL or TRUNCATE.

Security upgrade restrictions

• Do not change security credentials or permissions until after the upgrade is complete.
• If you are not already using Kerberos, do not set up Kerberos authentication before upgrading. First upgrade the cluster, then set up Kerberos.

DSE Graph

• Because DSE Graph is generally run with other workloads, follow the same upgrade limitations for those workloads.
• Do not create or update any graph or other schemas during the upgrade.
• You can safely ignore gremlin and graph related errors during the upgrade.

Preparing to upgrade

1. Back up your data. DataStax recommends backing up your data prior to any version upgrade, including logs and custom configurations. A backup provides the ability to revert and restore all the data used in the previous version if necessary.
   Tip: OpsCenter provides a Backup Service that manages enterprise-wide backup and restore operations for DataStax Enterprise clusters. OpsCenter 6.7 and later is recommended.
2. Verify your current product version:

   dse -v

3. Before upgrading, be sure that each node has ample free disk space.

   The required space depends on the compaction strategy. See Disk space.

4. Familiarize yourself with the changes and features in DataStax Enterprise and Apache Cassandra™. See:
   • DataStax Enterprise release notes for the upgrade version and complete all required actions.

     DataStax Enterprise 6.7 release notes include required planning, components, changes and enhancements, known issues, and resolved issues.

   • General upgrading advice for any version and New features for Apache Cassandra in NEWS.txt. Be sure to read the NEWS.txt all the way back to your current version.
   • Apache Cassandra changes in CHANGES.txt.
   • DataStax driver changes.
5. Back up the configuration files to a folder that is not in the directory where you normally run commands.

   The configuration files are overwritten with default values during installation of the new version.

6. Run nodetool repair to ensure that data on each replica is consistent with data on other nodes.
7. DSE Search nodes:
   • Ensure that the catalina.properties and context.xml files are present in the Tomcat conf dir. DSE will not start after upgrade if these files are missing.
     The default location of the Tomcat conf directory depends on the type of installation:

     • Package installations: /etc/dse/tomcat/conf
     • Tarball installations: installation_location/resources/tomcat/conf

Upgrade steps

The upgrade process for DataStax Enterprise provides minimal downtime (ideally zero). During this process, upgrade and restart one node at a time while other nodes continue to operate online. With a few exceptions, the cluster continues to work as though it were on the earlier version of DataStax Enterprise until all of the nodes in the cluster are upgraded.

1. If you have the OpsCenter Repair Service configured, turn off the Repair Service.
2. Upgrade order matters. Upgrade nodes in this order:
   • In multiple datacenter clusters, upgrade every node in one datacenter before upgrading another datacenter.
   • Upgrade the seed nodes within a datacenter first.
   • Upgrade nodes in this order:
     1. DSE Analytics datacenters
     2. Transactional/DSE Graph datacenters
     3. DSE Search datacenters
3. Run nodetool drain to flush the commit log of the old installation:

   nodetool -h hostname drain

   This step saves time when nodes start up after the upgrade, and prevents DSE Search nodes from reindexing data.

4. Stop the node.
5. Use the appropriate method to install the new product version.
6. To configure the new product version:
   1. Compare your backup configuration files to the new configuration files:
      • Look for any deprecated, removed, or changed settings.
      • Be sure you are familiar with the Apache Cassandra and DataStax Enterprise changes and features in the new release.
      • Check for any other configuration files that you might have changed. See Default file locations.
   2. Merge the applicable modifications into the new version.
7. When upgrading DSE to versions earlier than 5.1.16, 6.0.8, or 6.7.4 inclusive, if any tables are using DSE Tiered Storage, remove all txn_compaction log files from second-level tiers and lower. For example, given the following dse.yaml configuration, remove txn_compaction log files from /mnt2 and /mnt3 directories:

   tiered_storage_options:
       strategy1:
           tiers:
               - paths:
                   - /mnt1
               - paths:
                   - /mnt2
               - paths:
                   - /mnt3

   The following example removes the files using the find command:

   find /mnt2 -name "*_txn_compaction_*.log" -type f -delete &&
   find /mnt3 -name "*_txn_compaction_*.log" -type f -delete

   Warning: Failure to complete this step may result in data loss.
8. Start the node.
9. Verify that the upgraded datacenter names match the datacenter names in the keyspace schema definition:

   nodetool status

10. Review the logs for warnings, errors, and exceptions.

    Warnings, errors, and exceptions are frequently found in the logs when starting an upgraded node. Some of these log entries are informational to help you execute specific upgrade-related steps. If you find unexpected warnings, errors, or exceptions, contact DataStax Support.

11. Repeat the upgrade and restart on each node (rolling restart) in the cluster following the recommended upgrade order as described in 2.
12. After the new version is installed on each node, DataStax recommends upgrading the SSTables on each node.

    Upgrading SSTables is recommended for optimal performance, but is not required for patch releases.

    nodetool upgradesstables

    If the SSTables are already on the current version, the command returns immediately and no action is taken.

    Use the --jobs option to set the number of SSTables that upgrade simultaneously. The default setting is 2, which minimizes impact on the cluster. Set to 0 to use all available compaction threads. For information about nodetool upgradesstables, including how to speed it up, see the DataStax Support KB article Nodetool upgradesstables FAQ.

13. If you use the OpsCenter Repair Service, turn on the Repair Service.