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17.3.4.8 TCP/IP Connections Using Direct Connections »
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17.3.4.7. Cluster TCP/IP Connections

TCP/IP is the default transport mechanism for establishing connections in MySQL Cluster. It is normally not necessary to define connections because Cluster automatically set ups a connection between each of the data nodes, between each data node and all MySQL server nodes, and between each data node and the management server. (For one exception to this rule, see Section 17.3.4.8, “TCP/IP Connections Using Direct Connections”.) [tcp] sections in the config.ini file explicitly define TCP/IP connections between nodes in the cluster.

It is necessary to define a connection only to override the default connection parameters. In that case, it is necessary to define at least NodeId1, NodeId2, and the parameters to change.

Important

Any [tcp] sections in the config.ini file should be listed last, following any other sections in the file. This is not required for a [tcp default] section. This is a known issue with the way in which the config.ini file is read by the cluster management server.

It is also possible to change the default values for these parameters by setting them in the [tcp default] section.

  • NodeId1, NodeId2

    To identify a connection between two nodes it is necessary to provide their node IDs in the [tcp] section of the configuration file. These are the same unique Id values for each of these nodes as described in Section 17.3.4.6, “Defining SQL and Other API Nodes”.

  • SendBufferMemory

    TCP transporters use a buffer to store all messages before performing the send call to the operating system. When this buffer reaches 64KB its contents are sent; these are also sent when a round of messages have been executed. To handle temporary overload situations it is also possible to define a bigger send buffer.

    The default size of the send buffer is 256 KB; 2MB is recommended in most situations in which it is necessary to set this parameter. The minimum size is 64 KB; the theoretical maximum is 4 GB.

  • SendSignalId

    To be able to retrace a distributed message datagram, it is necessary to identify each message. When this parameter is set to Y, message IDs are transported over the network. This feature is disabled by default in production builds, and enabled in -debug builds.

  • Checksum

    This parameter is a boolean parameter (enabled by setting it to Y or 1, disabled by setting it to N or 0). It is disabled by default. When it is enabled, checksums for all messages are calculated before they placed in the send buffer. This feature ensures that messages are not corrupted while waiting in the send buffer, or by the transport mechanism.

  • PortNumber (OBSOLETE)

    This formerly specified the port number to be used for listening for connections from other nodes. This parameter should no longer be used.

  • ReceiveBufferMemory

    Specifies the size of the buffer used when receiving data from the TCP/IP socket.

    The default value of this parameter from its of 64 KB; 1M is recommended in most situations where the size of the receive buffer needs to be set. The minimum possible value is 16K; the theoretical maximum is 4G.