25.6.7.3 Adding NDB Cluster Data Nodes Online: Detailed Example

In this section we provide a detailed example illustrating how to add new NDB Cluster data nodes online, starting with an NDB Cluster having 2 data nodes in a single node group and concluding with a cluster having 4 data nodes in 2 node groups.

Starting configuration.  For purposes of illustration, we assume a minimal configuration, and that the cluster uses a config.ini file containing only the following information:

[ndbd default]
DataMemory = 100M
IndexMemory = 100M
NoOfReplicas = 2
DataDir = /usr/local/mysql/var/mysql-cluster

[ndbd]
Id = 1
HostName = 198.51.100.1

[ndbd]
Id = 2
HostName = 198.51.100.2

[mgm]
HostName = 198.51.100.10
Id = 10

[api]
Id=20
HostName = 198.51.100.20

[api]
Id=21
HostName = 198.51.100.21

Note

We have left a gap in the sequence between data node IDs and other nodes. This make it easier later to assign node IDs that are not already in use to data nodes which are newly added.

We also assume that you have already started the cluster using the appropriate command line or my.cnf options, and that running SHOW in the management client produces output similar to what is shown here:

-- NDB Cluster -- Management Client --
ndb_mgm> SHOW
Connected to Management Server at: 198.51.100.10:1186 (using cleartext)
Cluster Configuration
---------------------
[ndbd(NDB)]     2 node(s)
id=1    @198.51.100.1  (9.1.0-ndb-9.1.0, Nodegroup: 0, *)
id=2    @198.51.100.2  (9.1.0-ndb-9.1.0, Nodegroup: 0)

[ndb_mgmd(MGM)] 1 node(s)
id=10   @198.51.100.10  (9.1.0-ndb-9.1.0)

[mysqld(API)]   2 node(s)
id=20   @198.51.100.20  (9.1.0-ndb-9.1.0)
id=21   @198.51.100.21  (9.1.0-ndb-9.1.0)

Finally, we assume that the cluster contains a single NDBCLUSTER table created as shown here:

USE n;

CREATE TABLE ips (
    id BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    country_code CHAR(2) NOT NULL,
    type CHAR(4) NOT NULL,
    ip_address VARCHAR(15) NOT NULL,
    addresses BIGINT UNSIGNED DEFAULT NULL,
    date BIGINT UNSIGNED DEFAULT NULL
)   ENGINE NDBCLUSTER;

The memory usage and related information shown later in this section was generated after inserting approximately 50000 rows into this table.

Note

In this example, we show the single-threaded ndbd being used for the data node processes. You can also apply this example, if you are using the multithreaded ndbmtd by substituting ndbmtd for ndbd wherever it appears in the steps that follow.

Step 1: Update configuration file.  Open the cluster global configuration file in a text editor and add [ndbd] sections corresponding to the 2 new data nodes. (We give these data nodes IDs 3 and 4, and assume that they are to be run on host machines at addresses 198.51.100.3 and 198.51.100.4, respectively.) After you have added the new sections, the contents of the config.ini file should look like what is shown here, where the additions to the file are shown in bold type:

[ndbd default]
DataMemory = 100M
IndexMemory = 100M
NoOfReplicas = 2
DataDir = /usr/local/mysql/var/mysql-cluster

[ndbd]
Id = 1
HostName = 198.51.100.1

[ndbd]
Id = 2
HostName = 198.51.100.2

[ndbd]
Id = 3
HostName = 198.51.100.3

[ndbd]
Id = 4
HostName = 198.51.100.4

[mgm]
HostName = 198.51.100.10
Id = 10

[api]
Id=20
HostName = 198.51.100.20

[api]
Id=21
HostName = 198.51.100.21

Once you have made the necessary changes, save the file.

Step 2: Restart the management server.  Restarting the cluster management server requires that you issue separate commands to stop the management server and then to start it again, as follows:

1. Stop the management server using the management client STOP command, as shown here:

   ndb_mgm> 10 STOP
   Node 10 has shut down.
   Disconnecting to allow Management Server to shutdown
   
   $>

2. Because shutting down the management server causes the management client to terminate, you must start the management server from the system shell. For simplicity, we assume that config.ini is in the same directory as the management server binary, but in practice, you must supply the correct path to the configuration file. You must also supply the --reload or --initial option so that the management server reads the new configuration from the file rather than its configuration cache. If your shell's current directory is also the same as the directory where the management server binary is located, then you can invoke the management server as shown here:

   $> ndb_mgmd -f config.ini --reload
   2008-12-08 17:29:23 [MgmSrvr] INFO     -- NDB Cluster Management Server. 9.1.0-ndb-9.1.0
   2008-12-08 17:29:23 [MgmSrvr] INFO     -- Reading cluster configuration from 'config.ini'

If you check the output of SHOW in the management client after restarting the ndb_mgm process, you should now see something like this:

-- NDB Cluster -- Management Client --
ndb_mgm> SHOW
Connected to Management Server at: 198.51.100.10:1186 (using cleartext)
Cluster Configuration
---------------------
[ndbd(NDB)]     2 node(s)
id=1    @198.51.100.1  (9.1.0-ndb-9.1.0, Nodegroup: 0, *)
id=2    @198.51.100.2  (9.1.0-ndb-9.1.0, Nodegroup: 0)
id=3 (not connected, accepting connect from 198.51.100.3)
id=4 (not connected, accepting connect from 198.51.100.4)

[ndb_mgmd(MGM)] 1 node(s)
id=10   @198.51.100.10  (9.1.0-ndb-9.1.0)

[mysqld(API)]   2 node(s)
id=20   @198.51.100.20  (9.1.0-ndb-9.1.0)
id=21   @198.51.100.21  (9.1.0-ndb-9.1.0)

Step 3: Perform a rolling restart of the existing data nodes.  This step can be accomplished entirely within the cluster management client using the RESTART command, as shown here:

ndb_mgm> 1 RESTART
Node 1: Node shutdown initiated
Node 1: Node shutdown completed, restarting, no start.
Node 1 is being restarted

ndb_mgm> Node 1: Start initiated (version 9.1.0)
Node 1: Started (version 9.1.0)

ndb_mgm> 2 RESTART
Node 2: Node shutdown initiated
Node 2: Node shutdown completed, restarting, no start.
Node 2 is being restarted

ndb_mgm> Node 2: Start initiated (version 9.1.0)

ndb_mgm> Node 2: Started (version 9.1.0)

Important

After issuing each X RESTART command, wait until the management client reports Node X: Started (version ...) before proceeding any further.

You can verify that all existing data nodes were restarted using the updated configuration by checking the ndbinfo.nodes table in the mysql client.

Step 4: Perform a rolling restart of all cluster API nodes.  Shut down and restart each MySQL server acting as an SQL node in the cluster using mysqladmin shutdown followed by mysqld_safe (or another startup script). This should be similar to what is shown here, where password is the MySQL root password for a given MySQL server instance:

$> mysqladmin -uroot -ppassword shutdown
081208 20:19:56 mysqld_safe mysqld from pid file
/usr/local/mysql/var/tonfisk.pid ended
$> mysqld_safe --ndbcluster --ndb-connectstring=198.51.100.10 &
081208 20:20:06 mysqld_safe Logging to '/usr/local/mysql/var/tonfisk.err'.
081208 20:20:06 mysqld_safe Starting mysqld daemon with databases
from /usr/local/mysql/var

Of course, the exact input and output depend on how and where MySQL is installed on the system, as well as which options you choose to start it (and whether or not some or all of these options are specified in a my.cnf file).

Step 5: Perform an initial start of the new data nodes.  From a system shell on each of the hosts for the new data nodes, start the data nodes as shown here, using the --initial option:

$> ndbd -c 198.51.100.10 --initial

Note

Unlike the case with restarting the existing data nodes, you can start the new data nodes concurrently; you do not need to wait for one to finish starting before starting the other.

Wait until both of the new data nodes have started before proceeding with the next step. Once the new data nodes have started, you can see in the output of the management client SHOW command that they do not yet belong to any node group (as indicated with bold type here):

ndb_mgm> SHOW
Connected to Management Server at: 198.51.100.10:1186 (using cleartext)
Cluster Configuration
---------------------
[ndbd(NDB)]     2 node(s)
id=1    @198.51.100.1  (9.1.0-ndb-9.1.0, Nodegroup: 0, *)
id=2    @198.51.100.2  (9.1.0-ndb-9.1.0, Nodegroup: 0)
id=3    @198.51.100.3  (9.1.0-ndb-9.1.0, no nodegroup)
id=4    @198.51.100.4  (9.1.0-ndb-9.1.0, no nodegroup)

[ndb_mgmd(MGM)] 1 node(s)
id=10   @198.51.100.10  (9.1.0-ndb-9.1.0)

[mysqld(API)]   2 node(s)
id=20   @198.51.100.20  (9.1.0-ndb-9.1.0)
id=21   @198.51.100.21  (9.1.0-ndb-9.1.0)

Step 6: Create a new node group.  You can do this by issuing a CREATE NODEGROUP command in the cluster management client. This command takes as its argument a comma-separated list of the node IDs of the data nodes to be included in the new node group, as shown here:

ndb_mgm> CREATE NODEGROUP 3,4
Nodegroup 1 created

By issuing SHOW again, you can verify that data nodes 3 and 4 have joined the new node group (again indicated in bold type):

ndb_mgm> SHOW
Connected to Management Server at: 198.51.100.10:1186 (using cleartext)
Cluster Configuration
---------------------
[ndbd(NDB)]     2 node(s)
id=1    @198.51.100.1  (9.1.0-ndb-9.1.0, Nodegroup: 0, *)
id=2    @198.51.100.2  (9.1.0-ndb-9.1.0, Nodegroup: 0)
id=3    @198.51.100.3  (9.1.0-ndb-9.1.0, Nodegroup: 1)
id=4    @198.51.100.4  (9.1.0-ndb-9.1.0, Nodegroup: 1)

[ndb_mgmd(MGM)] 1 node(s)
id=10   @198.51.100.10  (9.1.0-ndb-9.1.0)

[mysqld(API)]   2 node(s)
id=20   @198.51.100.20  (9.1.0-ndb-9.1.0)
id=21   @198.51.100.21  (9.1.0-ndb-9.1.0)

Step 7: Redistribute cluster data.  When a node group is created, existing data and indexes are not automatically distributed to the new node group's data nodes, as you can see by issuing the appropriate REPORT command in the management client:

ndb_mgm> ALL REPORT MEMORY

Node 1: Data usage is 5%(177 32K pages of total 3200)
Node 1: Index usage is 0%(108 8K pages of total 12832)
Node 2: Data usage is 5%(177 32K pages of total 3200)
Node 2: Index usage is 0%(108 8K pages of total 12832)
Node 3: Data usage is 0%(0 32K pages of total 3200)
Node 3: Index usage is 0%(0 8K pages of total 12832)
Node 4: Data usage is 0%(0 32K pages of total 3200)
Node 4: Index usage is 0%(0 8K pages of total 12832)

By using ndb_desc with the -p option, which causes the output to include partitioning information, you can see that the table still uses only 2 partitions (in the Per partition info section of the output, shown here in bold text):

$> ndb_desc -c 198.51.100.10 -d n ips -p
-- ips --
Version: 1
Fragment type: 9
K Value: 6
Min load factor: 78
Max load factor: 80
Temporary table: no
Number of attributes: 6
Number of primary keys: 1
Length of frm data: 340
Row Checksum: 1
Row GCI: 1
SingleUserMode: 0
ForceVarPart: 1
FragmentCount: 2
TableStatus: Retrieved
-- Attributes --
id Bigint PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY AUTO_INCR
country_code Char(2;latin1_swedish_ci) NOT NULL AT=FIXED ST=MEMORY
type Char(4;latin1_swedish_ci) NOT NULL AT=FIXED ST=MEMORY
ip_address Varchar(15;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
addresses Bigunsigned NULL AT=FIXED ST=MEMORY
date Bigunsigned NULL AT=FIXED ST=MEMORY

-- Indexes --
PRIMARY KEY(id) - UniqueHashIndex
PRIMARY(id) - OrderedIndex

-- Per partition info --
Partition   Row count   Commit count  Frag fixed memory   Frag varsized memory
0           26086       26086         1572864             557056
1           26329       26329         1605632             557056

You can cause the data to be redistributed among all of the data nodes by performing, for each NDB table, an ALTER TABLE ... ALGORITHM=INPLACE, REORGANIZE PARTITION statement in the mysql client.

Important

ALTER TABLE ... ALGORITHM=INPLACE, REORGANIZE PARTITION does not work on tables that were created with the MAX_ROWS option. Instead, use ALTER TABLE ... ALGORITHM=INPLACE, MAX_ROWS=... to reorganize such tables.

Keep in mind that using MAX_ROWS to set the number of partitions per table is deprecated, and you should use PARTITION_BALANCE instead; see Section 15.1.20.12, “Setting NDB Comment Options”, for more information.

After issuing the statement ALTER TABLE ips ALGORITHM=INPLACE, REORGANIZE PARTITION, you can see using ndb_desc that the data for this table is now stored using 4 partitions, as shown here (with the relevant portions of the output in bold type):

$> ndb_desc -c 198.51.100.10 -d n ips -p
-- ips --
Version: 16777217
Fragment type: 9
K Value: 6
Min load factor: 78
Max load factor: 80
Temporary table: no
Number of attributes: 6
Number of primary keys: 1
Length of frm data: 341
Row Checksum: 1
Row GCI: 1
SingleUserMode: 0
ForceVarPart: 1
FragmentCount: 4
TableStatus: Retrieved
-- Attributes --
id Bigint PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY AUTO_INCR
country_code Char(2;latin1_swedish_ci) NOT NULL AT=FIXED ST=MEMORY
type Char(4;latin1_swedish_ci) NOT NULL AT=FIXED ST=MEMORY
ip_address Varchar(15;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
addresses Bigunsigned NULL AT=FIXED ST=MEMORY
date Bigunsigned NULL AT=FIXED ST=MEMORY

-- Indexes --
PRIMARY KEY(id) - UniqueHashIndex
PRIMARY(id) - OrderedIndex

-- Per partition info --
Partition   Row count   Commit count  Frag fixed memory   Frag varsized memory
0           12981       52296         1572864             557056
1           13236       52515         1605632             557056
2           13105       13105         819200              294912
3           13093       13093         819200              294912

Note

Normally, ALTER TABLE table_name [ALGORITHM=INPLACE,] REORGANIZE PARTITION is used with a list of partition identifiers and a set of partition definitions to create a new partitioning scheme for a table that has already been explicitly partitioned. Its use here to redistribute data onto a new NDB Cluster node group is an exception in this regard; when used in this way, no other keywords or identifiers follow REORGANIZE PARTITION.

For more information, see Section 15.1.9, “ALTER TABLE Statement”.

In addition, for each table, the ALTER TABLE statement should be followed by an OPTIMIZE TABLE to reclaim wasted space. You can obtain a list of all NDBCLUSTER tables using the following query against the Information Schema TABLES table:

SELECT TABLE_SCHEMA, TABLE_NAME
    FROM INFORMATION_SCHEMA.TABLES
    WHERE ENGINE = 'NDBCLUSTER';

Note

The INFORMATION_SCHEMA.TABLES.ENGINE value for an NDB Cluster table is always NDBCLUSTER, regardless of whether the CREATE TABLE statement used to create the table (or ALTER TABLE statement used to convert an existing table from a different storage engine) used NDB or NDBCLUSTER in its ENGINE option.

You can see after performing these statements in the output of ALL REPORT MEMORY that the data and indexes are now redistributed between all cluster data nodes, as shown here:

ndb_mgm> ALL REPORT MEMORY

Node 1: Data usage is 5%(176 32K pages of total 3200)
Node 1: Index usage is 0%(76 8K pages of total 12832)
Node 2: Data usage is 5%(176 32K pages of total 3200)
Node 2: Index usage is 0%(76 8K pages of total 12832)
Node 3: Data usage is 2%(80 32K pages of total 3200)
Node 3: Index usage is 0%(51 8K pages of total 12832)
Node 4: Data usage is 2%(80 32K pages of total 3200)
Node 4: Index usage is 0%(50 8K pages of total 12832)

Note

Since only one DDL operation on NDBCLUSTER tables can be executed at a time, you must wait for each ALTER TABLE ... REORGANIZE PARTITION statement to finish before issuing the next one.

It is not necessary to issue ALTER TABLE ... REORGANIZE PARTITION statements for NDBCLUSTER tables created after the new data nodes have been added; data added to such tables is distributed among all data nodes automatically. However, in NDBCLUSTER tables that existed prior to the addition of the new nodes, neither existing nor new data is distributed using the new nodes until these tables have been reorganized using ALTER TABLE ... REORGANIZE PARTITION.

Alternative procedure, without rolling restart.  It is possible to avoid the need for a rolling restart by configuring the extra data nodes, but not starting them, when first starting the cluster. We assume, as before, that you wish to start with two data nodes—nodes 1 and 2—in one node group and later to expand the cluster to four data nodes, by adding a second node group consisting of nodes 3 and 4:

[ndbd default]
DataMemory = 100M
IndexMemory = 100M
NoOfReplicas = 2
DataDir = /usr/local/mysql/var/mysql-cluster

[ndbd]
Id = 1
HostName = 198.51.100.1

[ndbd]
Id = 2
HostName = 198.51.100.2

[ndbd]
Id = 3
HostName = 198.51.100.3
Nodegroup = 65536

[ndbd]
Id = 4
HostName = 198.51.100.4
Nodegroup = 65536

[mgm]
HostName = 198.51.100.10
Id = 10

[api]
Id=20
HostName = 198.51.100.20

[api]
Id=21
HostName = 198.51.100.21

The data nodes to be brought online at a later time (nodes 3 and 4) can be configured with NodeGroup = 65536, in which case nodes 1 and 2 can each be started as shown here:

$> ndbd -c 198.51.100.10 --initial

The data nodes configured with NodeGroup = 65536 are treated by the management server as though you had started nodes 1 and 2 using --nowait-nodes=3,4 after waiting for a period of time determined by the setting for the StartNoNodeGroupTimeout data node configuration parameter. By default, this is 15 seconds (15000 milliseconds).

Note

StartNoNodegroupTimeout must be the same for all data nodes in the cluster; for this reason, you should always set it in the [ndbd default] section of the config.ini file, rather than for individual data nodes.

When you are ready to add the second node group, you need only perform the following additional steps:

1. Start data nodes 3 and 4, invoking the data node process once for each new node:

   $> ndbd -c 198.51.100.10 --initial

2. Issue the appropriate CREATE NODEGROUP command in the management client:

   ndb_mgm> CREATE NODEGROUP 3,4

3. In the mysql client, issue ALTER TABLE ... REORGANIZE PARTITION and OPTIMIZE TABLE statements for each existing NDBCLUSTER table. (As noted elsewhere in this section, existing NDB Cluster tables cannot use the new nodes for data distribution until this has been done.)