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4.5.2.3 Creating and Configuring the Target Cluster

The next task is to create a “target” cluster. Once this is done, we modify the target cluster's configuration until it matches that of the wild cluster that we want to import. At a later point in the example, we also show how to test the configuration in a dry run before attempting to perform the actual configuration import.

To create and then configure the target cluster, follow these steps:

  1. Install MySQL Cluster Manager and start mcmd on all hosts with the same system user who started the wild cluster processes. Once you have done this, you can start the mcm client (see Section 4.3, “Starting the MySQL Cluster Manager Client”) on any one of these hosts to perform the next few steps.

    Important

    The cluster import is going to fail due to insufficient rights for the mcmd agents to perform their tasks if the mcmd agents are not started by the same system user who started the wild cluster processes.

  2. Create a MySQL Cluster Manager site encompassing all four of the wild cluster's hosts, using the create site command, as shown here: 

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    mcm> create site --hosts=198.51.100.102,198.51.100.103,198.51.100.104 newsite;
+---------------------------+
| Command result            |
+---------------------------+
| Site created successfully |
+---------------------------+
1 row in set (0.15 sec)

    We have named this site newsite. You should be able to see it listed in the output of the list sites command, similar to what is shown here: 

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    mcm> list sites;
+---------+------+-------+----------------------------------------------+
| Site    | Port | Local | Hosts                                        |
+---------+------+-------+----------------------------------------------+
| newsite | 1862 | Local | 198.51.100.102,198.51.100.103,198.51.100.104 |
+---------+------+-------+----------------------------------------------+
1 row in set (0.01 sec)

  3. Add a MySQL Cluster Manager package referencing the MySQL NDB Cluster binaries using the add package command; use the command's --basedir option to point to the correct location of the MySQL NDB Cluster executables. The command shown here creates such a package, named newpackage: 

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    mcm> add package --basedir=/home/ari/bin/cluster newpackage;
+----------------------------+
| Command result             |
+----------------------------+
| Package added successfully |
+----------------------------+
1 row in set (0.70 sec)

    You do not need to include the bin directory containing the MySQL NDB Cluster executables in the --basedir path. If the executables are in /home/ari/bin/cluster/bin, it is sufficient to specify /home/ari/bin/cluster; MySQL Cluster Manager automatically checks for the binaries in a bin directory within the directory specified by --basedir.

  4. Create the target cluster including at least some of the same processes and hosts used by the standalone cluster. Do not include any processes or hosts that are not part of this cluster. In order to prevent potentially disruptive process or cluster operations from interfering by accident with the import process, it is strongly recommended that you create the cluster for import using the --import option for the create cluster command.

    You must also take care to preserve the correct node ID (as listed in the config.ini file shown previously) for each node.

    The following command creates the cluster newcluster for import and includes the management and data nodes, but not the SQL or “free” API node (which we add in the next step): 

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    mcm> create cluster --import --package=newpackage \
      --processhosts=ndb_mgmd:50@198.51.100.102,ndbd:2@198.51.100.103,ndbd:3@198.51.100.104 \
       newcluster;
+------------------------------+
| Command result               |
+------------------------------+
| Cluster created successfully |
+------------------------------+
1 row in set (0.96 sec)

    You can verify that the cluster was created correctly by checking the output of show status with the --process (-r) option, like this: 

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    mcm> show status -r newcluster;
+--------+----------+----------------+--------+-----------+------------+
| NodeId | Process  | Host           | Status | Nodegroup | Package    |
+--------+----------+----------------+--------+-----------+------------+
| 50     | ndb_mgmd | 198.51.100.102 | import |           | newpackage |
| 2      | ndbd     | 198.51.100.103 | import | n/a       | newpackage |
| 3      | ndbd     | 198.51.100.104 | import | n/a       | newpackage |
+--------+----------+----------------+--------+-----------+------------+
3 rows in set (0.05 sec)

  5. If necessary, add any remaining processes and hosts from the wild cluster not included in the previous step using one or more add process commands. We have not yet accounted for two of the nodes from the wild cluster: the SQL node with node ID 51, on host 198.51.100.102, and the API node with node ID 52, which is not bound to any specific host. You can use the following command to add both of these processes to newcluster: 

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    mcm> add process --processhosts=mysqld:51@198.51.100.102,ndbapi:52@* newcluster;
+----------------------------+
| Command result             |
+----------------------------+
| Process added successfully |
+----------------------------+
1 row in set (0.41 sec)

    Once again checking the output from show status -r, we see that the mysqld and ndbapi processes were added as expected: 

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    mcm> show status -r newcluster;
+--------+----------+----------------+--------+-----------+------------+
| NodeId | Process  | Host           | Status | Nodegroup | Package    |
+--------+----------+----------------+--------+-----------+------------+
| 50     | ndb_mgmd | 198.51.100.102 | import |           | newpackage |
| 2      | ndbd     | 198.51.100.103 | import | n/a       | newpackage |
| 3      | ndbd     | 198.51.100.104 | import | n/a       | newpackage |
| 51     | mysqld   | 198.51.100.102 | import |           | newpackage |
| 52     | ndbapi   | *              | import |           |            |
+--------+----------+----------------+--------+-----------+------------+
5 rows in set (0.06 sec)

    You can also see that since newcluster was created using the create cluster command's --import option, the status of all processes in this cluster—including those we just added—is import. This means we cannot yet start newcluster or any of its processes. The import status and its effects on newcluster and its cluster processes persist until we have completed importing another cluster into newcluster.

    The target newcluster cluster now has the same processes, with the same node IDs, and on the same hosts as the original standalone cluster. We are ready to proceed to the next step.

  6. Duplicate the wild cluster's configuration attributes in the target cluster using the import config command. Test out first the effects of the command by running it with the --dryrun option (the step only works if you have created the mcmd user on the cluster's mysqld nodes):

    Important

    Before executing this command it is necessary to set any non-default ports for ndb_mgmd and mysqld processes using the set command in the mcm client. 

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    mcm> import config --dryrun newcluster;
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Command result                                                                                                                                                                      |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Import checks passed. Please check /home/ari/bin/mcm_data/clusters/newcluster/tmp/import_config.49d541a9_294_0.mcm on host localhost.localdomain for settings that will be applied. |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (6.87 sec)

    As indicated by the output from import config --dryrun, you can see the configuration attributes and values that would be copied to newcluster by the command without the --dryrun option in the file /path-to-mcm-data-repository/clusters/clustername/tmp/import_config.message_id.mcm. If you open this file in a text editor, you will see a series of set commands that would accomplish this task, similar to what is shown here: 

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    # The following will be applied to the current cluster config:
set NoOfReplicas:ndbd=2 newcluster;
set DataDir:ndb_mgmd:50=/home/ari/bin/cluster/wild-cluster/50/data newcluster;
set DataDir:ndbd:2=/home/ari/bin/cluster/wild-cluster/2/data newcluster;
set DataDir:ndbd:3=/home/ari/bin/cluster/wild-cluster/3/data newcluster;
set basedir:mysqld:51=/home/ari/bin/cluster/ newcluster;
set datadir:mysqld:51=/home/ari/bin/cluster/wild-cluster/51/data/ newcluster;
set sql_mode:mysqld:51="NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES" newcluster;
set ndb_connectstring:mysqld:51=198.51.100.102 newcluster;

    Options used at the command line instead of in a configuration file to start a node of the standalone cluster are not imported into the target cluster by the import config command; moreover, they will cause one of the following to happen when the import config --dryrun is run:

    1. For some options, MySQL Cluster Manager will issue a warning that “Option <param> may be removed on next restart of process <type><nodeid>,” meaning that those options will not be imported into the target cluster, and thus will not be applied when those nodes are restarted after the import. Here are the lists of such options for each node type:

    2. For some other options, while their values will also not be imported into the target cluster, no warnings will be issued for them. Here are lists of such options for each node type:

    3. For options that belong to neither of the two groups described above, having started the standalone cluster's nodes with them at the command line will cause the import config --dryrun command to fail with an error, complaining that the options are unsupported.

    When you run into the first or third case described above, you have to do one of the following:

    • If the options are required for the target cluster and they can be set using the set command (see Command-line-only attributes), set them for the target cluster using the set command, and then retry the import config --dryrun command.

    • If the options are not needed for the target cluster, or it cannot be set using the set command, restart the wild cluster's node without those options, and then retry the import config --dryrun command.

    After the successful dry run, you are now ready to import the wild cluster's configuration into newcluster, with the command shown here: 

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    mcm> import config newcluster;
+------------------------------------------------------------------------------------------------------------------+
| Command result                                                                                                   |
+------------------------------------------------------------------------------------------------------------------+
| Configuration imported successfully. Please manually verify plugin options, abstraction level and default values |
+------------------------------------------------------------------------------------------------------------------+

    As an alternative, instead of importing all the settings using the import config command, you can make changes to the /path-to-mcm-data-repository/clusters/clustername/tmp/import_config.message_id.mcm file generated by the dry run as you wish, and then import the settings by executing the file with the mcm agent: 

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    mcm> source /path-to-mcm-data-repository/clusters/clustername/tmp/import_config.message_id.mcm

    You should check the resulting configuration of newcluster carefully against the configuration of the wild cluster. If you find any inconsistencies, you must correct these in newcluster using the appropriate set commands.


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