MySQL 8.0 参考手册  / 第 4 章 MySQL 程序  /  4.10 MySQL 中的 Unix 信号处理

4.10 MySQL 中的 Unix 信号处理

在 Unix 和类 Unix 系统上，进程可以是root系统帐户或拥有该进程的系统帐户发送给它的信号的接收者。可以使用kill命令发送信号。一些命令解释器将某些键序列与信号相关联，例如 Control+C发送SIGINT 信号。本节介绍 MySQL 服务器和客户端程序如何响应信号。

服务器对信号的响应

mysqld响应信号如下：

  • SIGTERM导致服务器关闭。这就像在 SHUTDOWN不必连接到服务器的情况下执行语句（关闭服务器需要具有 SHUTDOWN特权的帐户）。

  • SIGHUP导致服务器重新加载授权表并刷新表、日志、线程缓存和主机缓存。这些动作就像FLUSH语句的各种形式。发送信号可以在无需连接到服务器的情况下执行刷新操作，这需要一个 MySQL 帐户具有足够的权限来执行这些操作。服务器还将状态报告写入具有以下格式的错误日志： 

    Status information:

Current dir: /var/mysql/data/
Running threads: 4  Stack size: 262144
Current locks:
lock: 0x7f742c02c0e0:

lock: 0x2cee2a20:
:
lock: 0x207a080:

Key caches:
default
Buffer_size:       8388608
Block_size:           1024
Division_limit:        100
Age_limit:             300
blocks used:             4
not flushed:             0
w_requests:              0
writes:                  0
r_requests:              8
reads:                   4

handler status:
read_key:           13
read_next:           4
read_rnd             0
read_first:         13
write:               1
delete               0
update:              0

Table status:
Opened tables:        121
Open tables:          114
Open files:            18
Open streams:           0

Memory status:
<malloc version="1">
<heap nr="0">
<sizes>
  <size from="17" to="32" total="32" count="1"/>
  <size from="33" to="48" total="96" count="2"/>
  <size from="33" to="33" total="33" count="1"/>
  <size from="97" to="97" total="6014" count="62"/>
  <size from="113" to="113" total="904" count="8"/>
  <size from="193" to="193" total="193" count="1"/>
  <size from="241" to="241" total="241" count="1"/>
  <size from="609" to="609" total="609" count="1"/>
  <size from="16369" to="16369" total="49107" count="3"/>
  <size from="24529" to="24529" total="98116" count="4"/>
  <size from="32689" to="32689" total="32689" count="1"/>
  <unsorted from="241" to="7505" total="7746" count="2"/>
</sizes>
<total type="fast" count="3" size="128"/>
<total type="rest" count="84" size="195652"/>
<system type="current" size="690774016"/>
<system type="max" size="690774016"/>
<aspace type="total" size="690774016"/>
<aspace type="mprotect" size="690774016"/>
</heap>
:
<total type="fast" count="85" size="5520"/>
<total type="rest" count="116" size="316820"/>
<total type="mmap" count="82" size="939954176"/>
<system type="current" size="695717888"/>
<system type="max" size="695717888"/>
<aspace type="total" size="695717888"/>
<aspace type="mprotect" size="695717888"/>
</malloc>

Events status:
LLA = Last Locked At  LUA = Last Unlocked At
WOC = Waiting On Condition  DL = Data Locked

Event scheduler status:
State      : INITIALIZED
Thread id  : 0
LLA        : n/a:0
LUA        : n/a:0
WOC        : NO
Workers    : 0
Executed   : 0
Data locked: NO

Event queue status:
Element count   : 0
Data locked     : NO
Attempting lock : NO
LLA             : init_queue:95
LUA             : init_queue:103
WOC             : NO
Next activation : never

  • SIGINT normally is ignored by the server. Starting the server with the --gdb option installs an interrupt handler for SIGINT for debugging purposes. See Section 5.8.1.4, “Debugging mysqld under gdb”.

Client Response to Signals

MySQL client programs respond to signals as follows:

  • The mysql client interprets SIGINT (typically the result of typing Control+C) as instruction to interrupt the current statement if there is one, or to cancel any partial input line otherwise. This behavior can be disabled using the --sigint-ignore option to ignore SIGINT signals.

  • 默认情况下，使用 MySQL 客户端库的客户端程序会阻止 SIGPIPE信号。这些变化是可能的：