IMPORTANT! Before running any Accumulo 2.1 upgrade utilities or services, you will need to upgrade to Java 11, Hadoop 3, and at least ZooKeeper 3.5 (at least 3.8 was current at the time of this writing and is recommended).

The basic upgrade sequence is:

upgrade to at least Accumulo 1.10 first (if necessary)
stop Accumulo 1.10 or 2.0
prepare your installation of Accumulo 2.1 through whatever means you obtain the binaries and configure it in your environment
start ZooKeeper and HDFS.
(optional - but recommended) create a ZooKeeper snapshot
(optional - but recommended) validate the ZooKeeper ACLs. See ZooKeeper ACLs
(required if not using the provided scripts to start 2.1) run the RenameMasterDirInZK utility
(optional) run the pre-upgrade utility to convert the configuration in ZooKeeper
start Accumulo 2.1 for the first time to complete the upgrade

IMPORTANT! before starting any upgrade process you need to make sure there are no outstanding FATE transactions. This includes transactions that have completed with SUCCESS or FAILED but have not been removed by the automatic clean-up process. This is required because the internal serialization of FATE transactions is not guaranteed to be compatible between versions, so ANY FATE transaction that is present will fail the upgrade. Procedures to manage FATE transactions, including commands to fail and delete transactions, are included in the FATE Administration documentation.

Two significant changes occurred in 2.1 that are particularly important to note for upgrades:

properties and services that referenced master are renamed manager and
the internal property storage format in ZooKeeper has changed - instead of each table, namespace, and the system configuration using separate ZooKeeper nodes for each of their properties, they each now use only a single ZooKeeper node for all of their respective properties.

Details on renaming the properties and the ZooKeeper property conversion are provided in the following sections. Additional information on configuring 2.1 is available here.

Create ZooKeeper snapshot (optional - but recommended)

Before upgrading to 2.1, it is suggested that you create a snapshot of the current ZooKeeper contents to be a backup in case issues occur and you need to rollback. There are no provisions to roll back to a previous Accumulo version once an upgrade process has been completed other than restoring from a snapshot of ZooKeeper.

$ACCUMULO_HOME/bin/accumulo dump-zoo --xml --root /accumulo | tee PATH_TO_SNAPSHOT

If you need to restore from the ZooKeeper snapshot see these instructions.

Rename master Properties, Config Files, and Script References

It is strongly recommended as a part of the upgrade to rename any properties in accumulo.properties (or properties specified on the command line) starting with master. to use the equivalent property starting with manager. instead, as the old properties will not be available in subsequent major releases. This version may log or display warnings if older properties are observed.

Any reference to master in other scripts (e.g., invoking accumulo-service master from an init script) should be renamed to manager (for example, accumulo-service manager).

If the manager is not started using the provided accumulo-cluster or accumulo-service scripts, then a one-time upgrade step will need to be performed. Run the RenameMasterDirInZK utility after installing 2.1 but before starting it.

${ACCUMULO_HOME}/bin/accumulo org.apache.accumulo.manager.upgrade.RenameMasterDirInZK

Pre-Upgrade the property storage in ZooKeeper (optional)

As mentioned above, the property storage in ZooKeeper has changed from many nodes per table, namespace, and the system configuration, to just a single node for each of those. Upgrading to use the new format does happen automatically when Accumulo 2.1 servers start up. However, you can optionally choose to convert them using a pre-upgrade step with the following command line utility.

The property conversion can be done using a command line utility or it will occur automatically when the manager is started for the first time. Using the command line utility is optional, but may provide more flexibility in handling issues if they were to occur. With ZooKeeper running, the command to convert the properties is:

$ACCUMULO_HOME/bin/accumulo config-upgrade

The utility will print messages about its progress as it converts them.

2022-11-03T14:35:44,596 [conf.SiteConfiguration] INFO : Found Accumulo configuration on classpath at /opt/fluo-uno/install/accumulo-3.0.0-SNAPSHOT/conf/accumulo.properties
2022-11-03T14:35:45,511 [util.ConfigPropertyUpgrader] INFO : Upgrade system config properties for a1518a8b-f007-41ee-af2c-5cc760abe7fd
2022-11-03T14:35:45,675 [util.ConfigTransformer] INFO : property transform for SystemPropKey{InstanceId=a1518a8b-f007-41ee-af2c-5cc760abe7fd'} took 29ms ms, delete count: 1, error count: 0
2022-11-03T14:35:45,683 [util.ConfigPropertyUpgrader] INFO : Upgrading namespace +accumulo base path: /accumulo/a1518a8b-f007-41ee-af2c-5cc760abe7fd/namespaces/+accumulo/conf
...
2022-11-03T14:35:45,737 [util.ConfigPropertyUpgrader] INFO : Upgrading table !0 base path: /accumulo/a1518a8b-f007-41ee-af2c-5cc760abe7fd/tables/!0/conf
2022-11-03T14:35:45,813 [util.ConfigTransformer] INFO : property transform for TablePropKey{TableId=!0'} took 72ms ms, delete count: 26, error count: 0
...

If the upgrade utility is not used, similar messages will print to the server logs when 2.1 starts.

When the property conversion is complete, you can verify the configuration using the zoo-info-viewer utility (new in 2.1)

$ACCUMULO_HOME/bin/accumulo zoo-info-viewer  --print-props

Create new cluster configuration file

The accumulo-cluster script now uses a single file that defines the location of the managers, tservers, etc. You can create this file using the command accumulo-cluster create-config. You will then need to transfer the contents of the current individual files to this new consolidated file.

Encrypted Instances

Warning: Upgrading a previously encrypted instance with the experimental encryption properties is not supported as the implementation and properties have changed. You may be able to disable encryption and compact your files without encryption, in order to upgrade. Encryption remains an experimental feature, and may change between versions. It should be used with care. If you need help, consider reaching out to our mailing list.

Upgrading from 1.8/9/10 to 2.0

Follow the steps below to upgrade your Accumulo instance and client to 2.0.

Upgrade Accumulo instance

IMPORTANT! Before upgrading to Accumulo 2.0, you will need to upgrade to Java 8 and Hadoop 3.x.

Upgrading to Accumulo 2.0 is done by stopping Accumulo 1.8/9 and starting Accumulo 2.0.

Before stopping Accumulo 1.8/9, install Accumulo 2.0 and configure it by following the 2.0 quick start.

There are several changes to scripts and configuration in 2.0 so be careful when using configuration or automated setup designed for 1.8/9. Below are some changes in 2.0 that you should be aware of:

accumulo.properties has replaced accumulo-site.xml. You can either convert accumulo-site.xml by hand from XML to properties or use the following Accumulo command.
```
accumulo convert-config -x old/accumulo-site.xml -p new/accumulo.properties
```
The following server properties were deprecated for 2.0:
accumulo-client.properties has replaced client.conf. The client properties in the new file are different so take care when customizing.
accumulo-cluster script has replaced the start-all.sh & stop-all.sh scripts.
- Default host files (i.e masters, monitor, gc) are no longer in conf/ directory of tarball but can be created using accumulo-cluster create-config
- Tablet server hosts must be listed in a tservers file instead of a slaves file. To minimize confusion, Accumulo will not start if the old slaves file is present.
accumulo-service script can be used to start/stop Accumulo services (i.e master, tablet server, monitor) on a single node.
- Can be used even if Accumulo was started using accumulo-cluster script.
accumulo-env.sh constructs environment variables (such as JAVA_OPTS and CLASSPATH) used when running Accumulo processes
- This file was used in Accumulo 1.x but has changed significantly for 2.0
- Environment variables (such as $cmd, $bin, $conf) are set before accumulo-env.sh is loaded and can be used to customize environment.
- The JAVA_OPTS variable is constructed in accumulo-env.sh to pass command line arguments to the java command that the starts Accumulo processes (i.e. java $JAVA_OPTS main.class.for.$cmd).
- The CLASSPATH variable sets the Java classpath used when running Accumulo processes. It can be modified to upgrade dependencies or use vendor-specific distributions of Hadoop.
Logging is configured in accumulo-env.sh for Accumulo processes. The following log4j configuration files in the conf/ directory will be used if accumulo-env.sh is not modified. These files can be modified to turn on/off logging for Accumulo processes:
- log4j-service.properties for all Accumulo services (except monitor)
- logj4-monitor.properties for Accumulo monitor
- log4j.properties for Accumulo clients and commands
MapReduce jobs that read/write from Accumulo must configure their dependencies differently.
Run the command accumulo shell to access the shell using configuration in conf/accumulo-client.properties

When your Accumulo 2.0 installation is properly configured, stop Accumulo 1.8/9 and start Accumulo 2.0:

./accumulo-1.9.3/bin/stop-all.sh
./accumulo-2.0.1/bin/accumulo-cluster start

It is recommended that users test this upgrade on development or test clusters before attempting it on production clusters.

Upgrade Accumulo clients

There several client API changes in 2.0. In most cases, new API was introduced and the old API was only deprecated. While it is recommended that users start using the new API, the old API will continue to be supported through 2.x.

Below is a list of client API changes that users are required to make for 2.0:

Update your pom.xml use Accumulo 2.0. Also, update any Hadoop & ZooKeeper dependencies in your pom.xml to match the versions running on your cluster.
```
<dependency>
  <groupId>org.apache.accumulo</groupId>
  <artifactId>accumulo-core</artifactId>
  <version>2.0.1</version>
</dependency>
```
ClientConfiguration objects can no longer be created using new ClientConfiguration().
- Use ClientConfiguration.create() instead
Some API deprecated in 1.x releases was dropped
Aggregators have been removed

Below is a list of recommended client API changes:

The API for creating Accumulo clients has changed in 2.0.
- The old API using ZooKeeperInstance, Connector, Instance, and ClientConfiguration has been deprecated.
- Connector objects can be created from an AccumuloClient object using Connector.from()
Accumulo’s MapReduce API has changed in 2.0.
- A new API has been introduced in the org.apache.accumulo.hadoop package of the accumulo-hadoop-mapreduce jar.
- The old API in the org.apache.accumulo.core.client package of the accumulo-core has been deprecated and will eventually be removed.
- For both the old and new API, you must configure dependencies differently when creating your MapReduce job.

Upgrading from 1.7 to 1.8

Upgrades from 1.7 to 1.8 are possible with little effort as no changes were made at the data layer and RPC changes were made in a backwards-compatible way. The recommended way is to stop Accumulo 1.7, perform the Accumulo upgrade to 1.8, and then start 1.8. Like previous versions, after 1.8 is started on a 1.7 instance, a one-time upgrade will happen by the Master which will prevent a downgrade back to 1.7. Upgrades are still one way. Upgrades from versions prior to 1.7 to 1.8 should follow the below path to 1.7 and then perform the upgrade to 1.8 – direct upgrades to 1.8 for versions other than 1.7 are untested.

Existing configuration files from 1.7 should be compared against the examples provided in 1.8. The 1.7 configuration files should all function with 1.8 code, but you will likely want to include changes found in the 1.8.0 release notes and these release notes for 1.8.1.

For upgrades from prior to 1.7, follow the upgrade instructions to 1.7 first.

Upgrading from 1.7.x to 1.7.y

The recommended way to upgrade from a prior 1.7.x release is to stop Accumulo, upgrade to 1.7.y and then start 1.7.y.

When upgrading, there is a known issue if the upgrade fails due to outstanding FATE operations, see ACCUMULO-4496 The workaround if this situation is encountered:

Start tservers
Start shell
Run fate print to list all
If completed, just delete with fate delete
Start masters once there are no more fate operations

If any of the FATE operations are not complete, you should rollback the upgrade and troubleshoot completing them with your prior version. When performing an upgrade between major versions, the upgrade is one-way, therefore it is important that you do not have any outstanding FATE operations before starting the upgrade.

Upgrading from 1.6 to 1.7

Upgrades from 1.6 to 1.7 are possible with little effort as no changes were made at the data layer and RPC changes were made in a backwards-compatible way. The recommended way is to stop Accumulo 1.6, perform the Accumulo upgrade to 1.7, and then start 1.7. Like previous versions, after 1.7.0 is started on a 1.6 instance, a one-time upgrade will happen by the Master which will prevent a downgrade back to 1.6. Upgrades are still one way. Upgrades from versions prior to 1.6 to 1.7 should follow the below path to 1.6 and then perform the upgrade to 1.7 – direct upgrades to 1.7 for versions other than 1.6 are untested.

After upgrading to 1.7.0, users will notice the addition of a replication table in the accumulo namespace. This table is created and put offline to avoid any additional maintenance if the data-center replication feature is not in use.

Existing configuration files from 1.6 should be compared against the examples provided in 1.7. The 1.6 configuration files should all function with 1.7 code, but you will likely want to include a new file (hadoop-metrics2-accumulo.properties) to enable the new metrics subsystem. Read the section on Hadoop Metrics2 in the Administration chapter of the Accumulo User Manual.

For each of the other new features, new configuration properties exist to support the feature. Refer to the added sections in the User Manual for the feature for information on how to properly configure and use the new functionality.

Upgrading from 1.5 to 1.6

This happens automatically the first time Accumulo 1.6 is started.

If your instance previously upgraded from 1.4 to 1.5, you must verify that your 1.5 instance has no outstanding local write ahead logs. You can do this by ensuring either:

All of your tables are online and the Monitor shows all tablets hosted
The directory for write ahead logs (logger.dir.walog) from 1.4 has no files remaining on any tablet server / logger hosts

To upgrade from 1.5 to 1.6 you must:

Verify that there are no outstanding FATE operations
- Under 1.5 you can list what’s in FATE by running $ACCUMULO_HOME/bin/accumulo org.apache.accumulo.server.fate.Admin print
- Note that operations in any state will prevent an upgrade. It is safe to delete operations with status SUCCESSFUL. For others, you should restart your 1.5 cluster and allow them to finish.
Stop the 1.5 instance.
Configure 1.6 to use the hdfs directory and zookeepers that 1.5 was using.
Copy other 1.5 configuration options as needed.
Start Accumulo 1.6.

Upgrading from 1.4 to 1.6

To upgrade from 1.4 to 1.6 you must perform a manual initial step.

Prior to upgrading you must:

Verify that there are no outstanding FATE operations
- Under 1.4 you can list what’s in FATE by running $ACCUMULO_HOME/bin/accumulo org.apache.accumulo.server.fate.Admin print
- Note that operations in any state will prevent an upgrade. It is safe to delete operations with status SUCCESSFUL. For others, you should restart your 1.4 cluster and allow them to finish.
Stop the 1.4 instance.
Configure 1.6 to use the hdfs directory, walog directories, and zookeepers that 1.4 was using.
Copy other 1.4 configuration options as needed.

Prior to starting the 1.6 instance you will need to run the LocalWALRecovery tool on each node that previously ran an instance of the Logger role.

$ACCUMULO_HOME/bin/accumulo org.apache.accumulo.tserver.log.LocalWALRecovery

The recovery tool will rewrite the 1.4 write ahead logs into a format that 1.6 can read. After this step has completed on all nodes, start the 1.6 cluster to continue the upgrade.

The upgrade process must make changes to Accumulo’s internal state in both ZooKeeper and the table metadata. This process may take some time if Tablet Servers have to go through recovery. During this time, the Monitor will claim that the Master is down and some services may send the Monitor log messages about failure to communicate with each other. While the upgrade is in progress, the Garbage Collector may complain about invalid paths. The Master may also complain about failure to create the trace table because it already exists. These messages are safe to ignore. If other error messages occur, you should seek out support before continuing to use Accumulo. If you need detail on the upgrade’s progress you should view the local logs on the Tablet Servers and active Master.

Note that the LocalWALRecovery tool does not delete the local files. Once you confirm that 1.6 is successfully running, you should delete these files on the local filesystem.

Upgrading from 1.4 to 1.5

This happens automatically the first time Accumulo 1.5 is started.

Stop the 1.4 instance.
Configure 1.5 to use the hdfs directory, walog directories, and zookeepers that 1.4 was using.
Copy other 1.4 configuration options as needed.
Start Accumulo 1.5.

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