MySQL 8.0 Reference Manual
MySQL 8.0 Release Notes
This table contains aggregated information about NDB
transporters. In NDB 8.0.37 and later, you can obtain similar
information about individual transporters from the
transporter_details table.
The transporters table contains the following
columns:
node_idThis data node's unique node ID in the cluster
remote_node_idThe remote data node's node ID
statusStatus of the connection
remote_addressName or IP address of the remote host
bytes_sentNumber of bytes sent using this connection
bytes_receivedNumber of bytes received using this connection
connect_countNumber of times connection established on this transporter
overloaded1 if this transporter is currently overloaded, otherwise 0
overload_countNumber of times this transporter has entered overload state since connecting
slowdown1 if this transporter is in slowdown state, otherwise 0
slowdown_countNumber of times this transporter has entered slowdown state since connecting
Notes
For each running data node in the cluster, the
transporters table displays a row showing the
status of each of that node's connections with all nodes in
the cluster, including itself. This
information is shown in the table's
status column, which can have any one of
the following values: CONNECTING,
CONNECTED, DISCONNECTING,
or DISCONNECTED.
Connections to API and management nodes which are configured but
not currently connected to the cluster are shown with status
DISCONNECTED. Rows where the
node_id is that of a data node which is not
currently connected are not shown in this table. (This is
similar omission of disconnected nodes in the
ndbinfo.nodes table.
The remote_address is the host name or
address for the node whose ID is shown in the
remote_node_id column. The
bytes_sent from this node and
bytes_received by this node are the numbers,
respectively, of bytes sent and received by the node using this
connection since it was established. For nodes whose status is
CONNECTING or
DISCONNECTED, these columns always display
0.
Assume you have a 5-node cluster consisting of 2 data nodes, 2
SQL nodes, and 1 management node, as shown in the output of the
SHOW command in the
ndb_mgm client:
ndb_mgm> SHOW
Connected to Management Server at: localhost:1186
Cluster Configuration
---------------------
[ndbd(NDB)] 2 node(s)
id=1 @10.100.10.1 (8.0.41-ndb-8.0.41, Nodegroup: 0, *)
id=2 @10.100.10.2 (8.0.41-ndb-8.0.41, Nodegroup: 0)
[ndb_mgmd(MGM)] 1 node(s)
id=10 @10.100.10.10 (8.0.41-ndb-8.0.41)
[mysqld(API)] 2 node(s)
id=20 @10.100.10.20 (8.0.41-ndb-8.0.41)
id=21 @10.100.10.21 (8.0.41-ndb-8.0.41)
There are 10 rows in the transporters
table—5 for the first data node, and 5 for the
second—assuming that all data nodes are running, as shown
here:
mysql> SELECT node_id, remote_node_id, status
-> FROM ndbinfo.transporters;
+---------+----------------+---------------+
| node_id | remote_node_id | status |
+---------+----------------+---------------+
| 1 | 1 | DISCONNECTED |
| 1 | 2 | CONNECTED |
| 1 | 10 | CONNECTED |
| 1 | 20 | CONNECTED |
| 1 | 21 | CONNECTED |
| 2 | 1 | CONNECTED |
| 2 | 2 | DISCONNECTED |
| 2 | 10 | CONNECTED |
| 2 | 20 | CONNECTED |
| 2 | 21 | CONNECTED |
+---------+----------------+---------------+
10 rows in set (0.04 sec)
If you shut down one of the data nodes in this cluster using the
command 2 STOP in the
ndb_mgm client, then repeat the previous
query (again using the mysql client), this
table now shows only 5 rows—1 row for each connection from
the remaining management node to another node, including both
itself and the data node that is currently offline—and
displays CONNECTING for the status of each
remaining connection to the data node that is currently offline,
as shown here:
mysql> SELECT node_id, remote_node_id, status
-> FROM ndbinfo.transporters;
+---------+----------------+---------------+
| node_id | remote_node_id | status |
+---------+----------------+---------------+
| 1 | 1 | DISCONNECTED |
| 1 | 2 | CONNECTING |
| 1 | 10 | CONNECTED |
| 1 | 20 | CONNECTED |
| 1 | 21 | CONNECTED |
+---------+----------------+---------------+
5 rows in set (0.02 sec)
The connect_count,
overloaded,
overload_count, slowdown,
and slowdown_count counters are reset on
connection, and retain their values after the remote node
disconnects. The bytes_sent and
bytes_received counters are also reset on
connection, and so retain their values following disconnection
(until the next connection resets them).
The overload state referred to by the
overloaded and
overload_count columns occurs when this
transporter's send buffer contains more than
OVerloadLimit bytes
(default is 80% of
SendBufferMemory, that
is, 0.8 * 2097152 = 1677721 bytes). When a given transporter is
in a state of overload, any new transaction that tries to use
this transporter fails with Error 1218 (Send Buffers
overloaded in NDB kernel). This affects both scans
and primary key operations.
The slowdown state referenced by the
slowdown and
slowdown_count columns of this table occurs
when the transporter's send buffer contains more than 60%
of the overload limit (equal to 0.6 * 2097152 = 1258291 bytes by
default). In this state, any new scan using this transporter has
its batch size reduced to minimize the load on the transporter.
Common causes of send buffer slowdown or overloading include the following:
Data size, in particular the quantity of data stored in
TEXTcolumns orBLOBcolumns (or both types of columns)Having a data node (ndbd or ndbmtd) on the same host as an SQL node that is engaged in binary logging
Large number of rows per transaction or transaction batch
Configuration issues such as insufficient
SendBufferMemoryHardware issues such as insufficient RAM or poor network connectivity
See also Section 4.3.14, “Configuring NDB Cluster Send Buffer Parameters”.