Preparing to Upgrade Core

After you have planned your upgrade process, prepare the cluster for upgrade while your existing cluster is fully operational. Prepare to upgrade as described in this section to minimize downtime and eliminate unnecessary risk. Design and run health tests and back up critical data. Performing these tasks during upgrading reduces the number of times you have to touch each node, but increases down-time during upgrade. Upgrade a test cluster before upgrading your production cluster.

Complete the following pre-upgrade steps:

1. Verify System Requirements for All Nodes

Verify that all nodes meet the following minimum requirements for the new version of core software:

Software dependencies. Package dependencies in the HPE Ezmeral Data Fabric distribution can change from version to version. If the new HPE Ezmeral Data Fabric version has dependencies that were not present in the older version, you must address them on all nodes before upgrading your software. Installing dependency packages can be done while the cluster is operational. See Package Dependencies. If you are using a package manager, you can specify a repository that contains the dependency package(s), and allow the package manager to automatically install them when you upgrade the HPE Ezmeral Data Fabric packages. If you are installing from package files, you must pre-install dependencies on all nodes manually.
Hardware requirements. The newer version of packages might have greater hardware requirements. Hardware requirements must be met before upgrading.
OS requirements. HPE Ezmeral Data Fabric OS requirements do not change frequently. If the OS on a node doesn’t meet the requirements for the newer HPE Ezmeral Data Fabric version, plan to decommission the node and re-deploy it with an updated OS after the upgrade. See Operating System Support Matrix (Release 6.x) and Operating System Support Matrix (MapR 5.x).
Certificate requirements. Recent versions of Safari and Chrome web browsers have removed support for older certificate cipher algorithms, including those used by some HPE Ezmeral Data Fabric versions. For more information about resolving this issue, see Unable to Establish a Secure Connection.

2. Design Health Checks

Plan what kind of test jobs and scripts you will use to verify cluster health as part of the upgrade process. You will verify cluster health several times before, during, and after upgrade to ensure success at every step, and to isolate issues whenever they occur. Create both simple tests to verify that cluster services start and respond, as well as non-trivial tests that verify workload-specific aspects of your cluster.

Design Simple Tests

Here are a few examples of simple tests you can design to check node health:

Use maprcli commands to see if any alerts exist and to verify that services are running as expected. For example:

# maprcli node list -columns svc
              service                                                     hostname  ip          
              nodemanager,cldb,fileserver,hoststats                       centos55  10.10.82.55 
              nodemanager,fileserver,hoststats                            centos56  10.10.82.56 
              fileserver,nodemanager,hoststats                            centos57  10.10.82.57 
              fileserver,nodemanager,webserver,hoststats                  centos58  10.10.82.58 
              ...lines deleted...
              # maprcli alarm list
              alarm state  description                                                                                          entity    alarm name                             alarm statechange time 
              1            One or more licenses is about to expire within 25 days                                               CLUSTER   CLUSTER_ALARM_LICENSE_NEAR_EXPIRATION  1366142919009          
              1            Can not determine if service: nfs is running. Check logs at: /opt/mapr/logs/nfsserver.log            centos58  NODE_ALARM_SERVICE_NFS_DOWN            1366194786905

In this example you can see that an alarm is raised indicating that HPE Ezmeral Data Fabric software expects an NFS server to be running on node centos58, and the node list of running services confirms that the nfs service is not running on this node.

Batch create a set of test files.
Submit a MapReduce application.
Run simple checks on installed Hadoop ecosystem components. For example, run a Hive query.

Design Non-trivial Tests

Appropriate non-trivial tests will be specific to your particular cluster’s workload. You may have to work with users to define an appropriate set of tests. Run tests on the existing cluster to calibrate expectations for “healthy” task and job durations. On future iterations of the tests, inspect results for deviations. Some examples:

Run performance benchmarks relevant to the cluster’s typical workload.
Run a suite of common jobs. Inspect for correct results and deviation from expected completion times.
Test correct inter-operation of all components in the Hadoop stack and third-party tools.
Confirm the integrity of critical data stored on the cluster.

3. Verify Cluster Health

Run the test you designed in step 2 to verify the cluster health prior to upgrade.

Run the suite of simple tests to verify that basic features of the core are functioning correctly, and that any alarms are known and accounted for.
Run the suite of non-trivial tests to verify that the cluster is running as expected for a typical workload, including integration with Hadoop ecosystem components and third-party tools.

Proceed with the upgrade only if the cluster is in an expected, healthy state.

4. Back Up Critical Data

Data in the cluster persists across upgrades from version to version. However, as a precaution, you might want to back up critical data before upgrading. If you deem it practical and necessary, you can do any of the following:

Copy data out of the cluster using distcp to a separate, non-Hadoop datastore.
Mirror critical volume(s) into a separate HPE Ezmeral Data Fabric cluster, creating a read-only copy of the data which can be accessed via the other cluster.

When services for the new version are activated, filesystem will update data on disk automatically. The migration is transparent to users and administrators. Once the cluster is active with the new version, you cannot roll back.

5. Run Your Upgrade Plan on a Test Cluster

Before executing your upgrade plan on the production cluster, perform a complete dry run on a test cluster. You can perform the dry run on a smaller cluster than the production cluster, but make the dry run as similar to the real-world circumstances as possible. For example, install all Hadoop ecosystem components that are in use in production, and replicate data and jobs from the production cluster on the test cluster. The goals for the dry run are:

Eliminate surprises. Get familiar with all upgrade operations you will perform as you upgrade the production cluster.
Uncover any upgrade-related issues as early as possible so you can accommodate them in your upgrade plan. Look for issues in the upgrade process itself, as well as operational and integration issues that could arise after the upgrade.

6. Pause Cross-Cluster Operations

Complete the steps for each cross-cluster feature used by this cluster:

Volume Mirroring. If volumes from another cluster are mirrored on this cluster, use one of the following options to stop the mirroring of volumes on this cluster:

Using the Control System	See Stopping the Mirror.
Using a `maprcli` command	Run the `maprcli volume mirror stop` command on this cluster. See volume mirror stop.

Table Replication. If source tables on this cluster are replicated to tables on another cluster, pause the replication of tables on this cluster. Use one of the following options for each source table on this cluster:

Using the Control System	Log in to the Control System and go to the source table information page. On the Replications tab associated with the source table, select each replica and then click Actions > Pause Replication > .
Using a `maprcli` command	Run the `maprcli table replica pause` command. See table replica pause.

Note: Once you have completed the core upgrade and the Post-Upgrade Steps for Core, you can resume cross-cluster operations.

7. Back up Configuration Files

If you are upgrading the FUSE-based POSIX client on Ubuntu, create a backup copy of your custom settings in the fuse.conf file in /opt/mapr/conf directory. If you do not create a backup copy, you might lose your custom settings for the POSIX client because the new fuse.conf file with default settings will overwrite your current fuse.conf file with custom settings.

If you are upgrading the FUSE-based POSIX client on other supported operating systems, during upgrade the software automatically sets up the fuse.conf.backup file in addition to the new fuse.conf file in the /opt/mapr/conf directory.

Consider creating the env_override.sh file to store custom settings for environmental variables. Upgrading to a new release causes the env.sh file to be replaced and removes any custom settings. Creating the env_override.sh file can simplify the management of environmental variables. For more information, see About env_override.sh.

8. Migrate from MapReduce Version 1

MapReduce version 1 (MRv1) is deprecated for MapR 6.0 or later. If you were previously using MRv1, you must prepare your cluster to run MapReduce version 2 (MRv2) applications before upgrading to core 6.0 or later:

Ensure that the MapReduce mode on your cluster is set to yarn. MRv2 is an application that runs on top of YARN.
Uninstall all packages associated with MRv1.

For more information about how to prepare your cluster to run MRv2 applications, see Migrating from MapReduce Version 1 to MapReduce Version 2.

9. Migrate from Mahout and Storm

Mahout and Storm are not supported on core 6.0 or later. Before the upgrade, disable applications that use these components, and remove the Mahout and Storm packages. To view the ecosystem components supported on data-fabric releases, see Component Versions for Released MEPs.

10. Prepare to Upgrade the Ecosystem Pack

Complete the pre-upgrade steps in Preparing to Upgrade the Ecosystem Pack. Then return to this section.

What's Next

Go to Upgrading Core With the Installer or Upgrading Core Without the Installer.