22.5.2 Commands in the NDB Cluster Management Client

HELP

Displays information on all available commands.

CONNECT connection-string

Connects to the management server indicated by the connection string. If the client is already connected to this server, the client reconnects.

SHOW

Displays information on the cluster's status. Possible node status values include UNKNOWN, NO_CONTACT, NOT_STARTED, STARTING, STARTED, SHUTTING_DOWN, and RESTARTING. The output from this command also indicates when the cluster is in single user mode (status SINGLE USER MODE), and, in NDB 8.0.17 and later, indicates which API or SQL node has exclusive access when this mode is in effect.

node_id START

Brings online the data node identified by node_id (or all data nodes).

ALL START works on all data nodes only, and does not affect management nodes.

node_id STOP [-a] [-f]

Stops the data or management node identified by node_id.

A node affected by this command disconnects from the cluster, and its associated ndbd or ndb_mgmd process terminates.

The -a option causes the node to be stopped immediately, without waiting for the completion of any pending transactions.

Normally, STOP fails if the result would cause an incomplete cluster. The -f option forces the node to shut down without checking for this. If this option is used and the result is an incomplete cluster, the cluster immediately shuts down.

node_id RESTART [-n] [-i] [-a] [-f]

Restarts the data node identified by node_id (or all data nodes).

Using the -i option with RESTART causes the data node to perform an initial restart; that is, the node's file system is deleted and recreated. The effect is the same as that obtained from stopping the data node process and then starting it again using ndbd --initial from the system shell.

Using the -n option causes the data node process to be restarted, but the data node is not actually brought online until the appropriate START command is issued. The effect of this option is the same as that obtained from stopping the data node and then starting it again using ndbd --nostart or ndbd -n from the system shell.

Using the -a causes all current transactions relying on this node to be aborted. No GCP check is done when the node rejoins the cluster.

Normally, RESTART fails if taking the node offline would result in an incomplete cluster. The -f option forces the node to restart without checking for this. If this option is used and the result is an incomplete cluster, the entire cluster is restarted.

node_id STATUS

Displays status information for the data node identified by node_id (or for all data nodes).

The output from this command also indicates when the cluster is in single user mode.

node_id REPORT report-type

Displays a report of type report-type for the data node identified by node_id, or for all data nodes using ALL.

Currently, there are three accepted values for report-type:

report-type is case-insensitive and “fuzzy”; for MemoryUsage, you can use MEMORY (as shown in the prior example), memory, or even simply MEM (or mem). You can abbreviate BackupStatus in a similar fashion.

ENTER SINGLE USER MODE node_id

Enters single user mode, whereby only the MySQL server identified by the node ID node_id is permitted to access the database.

Beginning with NDB 8.0.17, the ndb_mgm client provides a clear acknowledgement that this command has been issued and has taken effect, as shown here:

ndb_mgm> ENTER SINGLE USER MODE 100
Single user mode entered
Access is granted for API node 100 only.

Also in NDB 8.0.17 and later, the API or SQL node having exclusive access when in single user mode is indicated in the output of the SHOW command, like this:

ndb_mgm> SHOW
Cluster Configuration
---------------------
[ndbd(NDB)]     2 node(s)
id=5    @127.0.0.1  (mysql-8.0.17 ndb-8.0.17, single user mode, Nodegroup: 0, *)
id=6    @127.0.0.1  (mysql-8.0.17 ndb-8.0.17, single user mode, Nodegroup: 0)

[ndb_mgmd(MGM)] 1 node(s)
id=50   @127.0.0.1  (mysql-8.0.17 ndb-8.0.17)

[mysqld(API)]   2 node(s)
id=100  @127.0.0.1  (mysql-8.0.17 ndb-8.0.17, allowed single user)
id=101 (not connected, accepting connect from any host)

EXIT SINGLE USER MODE

Exits single user mode, enabling all SQL nodes (that is, all running mysqld processes) to access the database.

QUIT, EXIT

Terminates the management client.

This command does not affect any nodes connected to the cluster.

SHUTDOWN

Shuts down all cluster data nodes and management nodes. To exit the management client after this has been done, use EXIT or QUIT.

This command does not shut down any SQL nodes or API nodes that are connected to the cluster.

CREATE NODEGROUP nodeid[, nodeid, ...]

Creates a new NDB Cluster node group and causes data nodes to join it.

This command is used after adding new data nodes online to an NDB Cluster, and causes them to join a new node group and thus to begin participating fully in the cluster. The command takes as its sole parameter a comma-separated list of node IDs—these are the IDs of the nodes just added and started that are to join the new node group. The number of nodes must be the same as the number of nodes in each node group that is already part of the cluster (each NDB Cluster node group must have the same number of nodes). In other words, if the NDB Cluster has 2 node groups of 2 data nodes each, then the new node group must also have 2 data nodes.

The node group ID of the new node group created by this command is determined automatically, and always the next highest unused node group ID in the cluster; it is not possible to set it manually.

For more information, see Section 22.5.15, “Adding NDB Cluster Data Nodes Online”.

DROP NODEGROUP nodegroup_id

Drops the NDB Cluster node group with the given nodegroup_id.

This command can be used to drop a node group from an NDB Cluster. DROP NODEGROUP takes as its sole argument the node group ID of the node group to be dropped.

DROP NODEGROUP acts only to remove the data nodes in the effected node group from that node group. It does not stop data nodes, assign them to a different node group, or remove them from the cluster's configuration. A data node that does not belong to a node group is indicated in the output of the management client SHOW command with no nodegroup in place of the node group ID, like this (indicated using bold text):

id=3    @10.100.2.67  (8.0.19-ndb-8.0.19, no nodegroup)

DROP NODEGROUP works only when all data nodes in the node group to be dropped are completely empty of any table data and table definitions. Since there is currently no way using ndb_mgm or the mysql client to remove all data from a specific data node or node group, this means that the command succeeds only in the two following cases:

For more information about DROP NODEGROUP, see Section 22.5.15, “Adding NDB Cluster Data Nodes Online”.

PROMPT [prompt]

Changes the prompt shown by ndb_mgm to the string literal prompt.

prompt should not be quoted (unless you want the prompt to include the quotation marks). Unlike the case with the mysql client, special character sequences and escapes are not recognized. If called without an argument, the command resets the prompt to the default value (ndb_mgm>).

Some examples are shown here:

ndb_mgm> PROMPT mgm#1:
mgm#1: SHOW
Cluster Configuration
...
mgm#1: PROMPT mymgm >
mymgm > PROMPT 'mymgm:'
'mymgm:' PROMPT  mymgm:
mymgm: PROMPT
ndb_mgm> EXIT
jon@valhaj:~/bin>

Note that leading spaces and spaces within the prompt string are not trimmed. Trailing spaces are removed.

node_id NODELOG DEBUG {ON|OFF}

Toggles debug logging in the node log, as though the effected data node or nodes had been started with the --verbose option. NODELOG DEBUG ON starts debug logging; NODELOG DEBUG OFF switches debug logging off.

START BACKUP is used to perform an online backup in the ndb_mgm client; the ABORT BACKUP command is used to cancel a backup already in progress. For more information, see Section 22.5.3, “Online Backup of NDB Cluster”.

The CLUSTERLOG command is used to perform various logging functions. See Section 22.5.6, “Event Reports Generated in NDB Cluster”, for more information and examples. NODELOG DEBUG activates or deactivates debug printouts in node logs, as described previously in this section.

For testing and diagnostics work, the client supports a DUMP command which can be used to execute internal commands on the cluster. It should never be used in a production setting unless directed to do so by MySQL Support. For more information, see MySQL NDB Cluster Internals Manual.