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26.12.3.5 The socket_instances Table
The socket_instances
table
provides a real-time snapshot of the active connections to the
MySQL server. The table contains one row per TCP/IP or Unix
socket file connection. Information available in this table
provides a real-time snapshot of the active connections to the
server. (Additional information is available in socket summary
tables, including network activity such as socket operations
and number of bytes transmitted and received; see
Section 26.12.17.9, “Socket Summary Tables”).
- *************************** 1. row ***************************
- EVENT_NAME: wait/io/socket/sql/server_unix_socket
- OBJECT_INSTANCE_BEGIN: 4316619408
- THREAD_ID: 1
- SOCKET_ID: 16
- IP:
- PORT: 0
- STATE: ACTIVE
- *************************** 2. row ***************************
- EVENT_NAME: wait/io/socket/sql/client_connection
- OBJECT_INSTANCE_BEGIN: 4316644608
- THREAD_ID: 21
- SOCKET_ID: 39
- IP: 127.0.0.1
- PORT: 55233
- STATE: ACTIVE
- *************************** 3. row ***************************
- EVENT_NAME: wait/io/socket/sql/server_tcpip_socket
- OBJECT_INSTANCE_BEGIN: 4316699040
- THREAD_ID: 1
- SOCKET_ID: 14
- IP: 0.0.0.0
- PORT: 50603
- STATE: ACTIVE
Socket instruments have names of the form
wait/io/socket/sql/
and are used like this:
socket_type
The server has a listening socket for each network protocol that it supports. The instruments associated with listening sockets for TCP/IP or Unix socket file connections have a
socket_type
value ofserver_tcpip_socket
orserver_unix_socket
, respectively.When a listening socket detects a connection, the server transfers the connection to a new socket managed by a separate thread. The instrument for the new connection thread has a
socket_type
value ofclient_connection
.When a connection terminates, the row in
socket_instances
corresponding to it is deleted.
The socket_instances
table has
these columns:
EVENT_NAME
The name of the
wait/io/socket/*
instrument that produced the event. This is aNAME
value from thesetup_instruments
table. Instrument names may have multiple parts and form a hierarchy, as discussed in Section 26.6, “Performance Schema Instrument Naming Conventions”.OBJECT_INSTANCE_BEGIN
This column uniquely identifies the socket. The value is the address of an object in memory.
THREAD_ID
The internal thread identifier assigned by the server. Each socket is managed by a single thread, so each socket can be mapped to a thread which can be mapped to a server process.
SOCKET_ID
The internal file handle assigned to the socket.
IP
The client IP address. The value may be either an IPv4 or IPv6 address, or blank to indicate a Unix socket file connection.
PORT
The TCP/IP port number, in the range from 0 to 65535.
STATE
The socket status, either
IDLE
orACTIVE
. Wait times for active sockets are tracked using the corresponding socket instrument. Wait times for idle sockets are tracked using theidle
instrument.A socket is idle if it is waiting for a request from the client. When a socket becomes idle, the event row in
socket_instances
that is tracking the socket switches from a status ofACTIVE
toIDLE
. TheEVENT_NAME
value remainswait/io/socket/*
, but timing for the instrument is suspended. Instead, an event is generated in theevents_waits_current
table with anEVENT_NAME
value ofidle
.When the next request is received, the
idle
event terminates, the socket instance switches fromIDLE
toACTIVE
, and timing of the socket instrument resumes.
The socket_instances
table has
these indexes:
Primary key on (
OBJECT_INSTANCE_BEGIN
)Index on (
THREAD_ID
)Index on (
SOCKET_ID
)Index on (
IP
,PORT
)
TRUNCATE TABLE
is not permitted
for the socket_instances
table.
The IP:PORT
column combination value
identifies the connection. This combination value is used in
the OBJECT_NAME
column of the
events_waits_
tables, to identify the connection from which socket events
come:
xxx
For the Unix domain listener socket (
server_unix_socket
), the port is 0, and the IP is''
.For client connections via the Unix domain listener (
client_connection
), the port is 0, and the IP is''
.For the TCP/IP server listener socket (
server_tcpip_socket
), the port is always the master port (for example, 3306), and the IP is always0.0.0.0
.For client connections via the TCP/IP listener (
client_connection
), the port is whatever the server assigns, but never 0. The IP is the IP of the originating host (127.0.0.1
or::1
for the local host)
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Document créé le 26/06/2006, dernière modification le 26/10/2018
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