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篮羽公爵 發表於 2025-7-2 10:13:00

用systemd管理GreatSQL服务详解

<h1 id="用systemd管理greatsql服务详解">用systemd管理GreatSQL服务详解</h1>
<h2 id="1greatsql服务文件">1.GreatSQL服务文件</h2>
<p>官网 <code>greatsql.service</code> 文件</p>
<pre><code class="language-Bash">
Description=GreatSQL Server
Documentation=man:mysqld(8)
Documentation=http://dev.mysql.com/doc/refman/en/using-systemd.html
After=network.target
After=syslog.target

WantedBy=multi-user.target


# 本文省略some limits

User=mysql
Group=mysql
Type=notify
TimeoutSec=10
PermissionsStartOnly=true
ExecStartPre=/usr/local/GreatSQL-8.0.32-27-Linux-glibc2.28-x86_64/bin/mysqld_pre_systemd
ExecStart=/usr/local/GreatSQL-8.0.32-27-Linux-glibc2.28-x86_64/bin/mysqld $MYSQLD_OPTS
EnvironmentFile=-/etc/sysconfig/mysql
Restart=on-failure
RestartPreventExitStatus=1
Environment=MYSQLD_PARENT_PID=1
PrivateTmp=false
</code></pre>
<blockquote>
<p>上述服务文件中 <code>MYSQLD_OPTS</code>、<code>MYSQLD_PARENT_PID</code> 的用途是什么？<code>Type</code> 和 <code>ExecStart</code> 有什么关系？服务停止的逻辑是什么？<code>TimeoutSec</code> 超时会怎样？</p>
</blockquote>
<h2 id="2环境变量">2.环境变量</h2>
<pre><code class="language-YAML">
ExecStart=/data/svr/greatsql/bin/mysqld --defaults-file=/data/conf/greatsql4306.cnf $MYSQLD_OPTS
EnvironmentFile=-/data/conf/greatsql
</code></pre>
<h3 id="21-mysqld_opts">2.1 MYSQLD_OPTS</h3>
<p><code>MYSQLD_OPTS</code> 是一个特殊的环境变量，用于在启动时向 MYSQLD 进程传递额外的命令行参数。适合需要动态调整参数的场景。</p>
<p>可以通过以下方式设置 <code>MYSQLD_OPTS</code></p>
<ol>
<li>systemctl，全局环境变量</li>
</ol>
<pre><code class="language-Bash"># 设置
systemctl set-environment MYSQLD_OPTS="--general_log=1"
# 取消
systemctl unset-environment MYSQLD_OPTS
</code></pre>
<ol start="2">
<li>服务文件，单个服务环境变量</li>
</ol>
<pre><code class="language-YAML">
Environment=MYSQLD_OPTS=--general_log=1
EnvironmentFile=-/data/conf/greatsql
</code></pre>
<h3 id="22-environment">2.2 Environment</h3>
<ol>
<li>服务文件中设置 Environment</li>
</ol>
<pre><code class="language-YAML">
Environment=LD_PRELOAD=/usr/local/jemalloc-5.3.0/lib/libjemalloc.so
Environment=LD_PRELOAD=/data/svr/greatsql/lib/mysql/libjemalloc.so#覆盖之前同名的变量
Environment=#清空所有环境变量
</code></pre>
<p>如果同一变量被重复设置，后续的赋值会覆盖之前的值。如果将此选项赋值为空字符串，则会重置环境变量列表，之前的所有设置均失效。</p>
<ol start="2">
<li>服务文件中设置 EnvironmentFile</li>
</ol>
<pre><code class="language-YAML">
EnvironmentFile=-/etc/sysconfig/mysql#-表示忽略文件不存在错误
EnvironmentFile=-/data/conf/greatsql
EnvironmentFile=#清空所有待读取的文件

$ cat /data/conf/greatsql
LD_PRELOAD=/data/svr/greatsql/lib/mysql/libjemalloc.so
LD_LIBRARY_PATH=/data/svr/greatsql/lib
TZ=CST
MYSQLD_OPTS=--general_log=1 --port=4307
</code></pre>
<p>EnvironmentFile 可以设置多次，所有匹配的文件均会被读取。若将此选项赋值为空字符串，则会清空待读取的文件列表，之前所有设置均失效。</p>
<p>EnvironmentFile 按顺序依次读取，后加载的变量会覆盖之前的设定，且会覆盖 Environment 中的同名变量。</p>
<p>Environment、EnvironmentFile在服务启动前解析，这些变量会被直接写入服务的环境变量列表，对所有后续命令(ExecStartPre、ExecStart、ExecStartPost)可见。</p>
<p>如果 EnvironmentFile 指定的文件在运行时动态生成，systemd 会尝试读取它，如果文件在读取时被修改，systemd 会使用最新的内容。</p>
<h2 id="3启动">3.启动</h2>
<p>systemd 通过 fork-exec + cgroups 的机制创建并严格管理服务进程，确保所有进程均为其子进程。</p>
<blockquote>
<ul>
<li>Uses fork() + execve() to spawn the new process:
<ul>
<li>fork(): Creates a child process (a copy of the systemd parent).</li>
<li>execve(): Overwrites the child process with the target binary.</li>
</ul>
</li>
<li>Assigns the process to a dedicated cgroup
<ul>
<li>Ensures all child processes remain within the same cgroup.</li>
<li>Enables resource limits and process tracking.</li>
</ul>
</li>
</ul>
</blockquote>
<h3 id="31-typesimple">3.1 Type=simple</h3>
<pre><code class="language-YAML">
Type=simple
ExecStart=/data/svr/greatsql/bin/mysqld --defaults-file=/data/conf/greatsql4306.cnf $MYSQLD_OPTS
</code></pre>
<h4 id="311-行为">3.1.1 行为</h4>
<ul>
<li>要求 ExecStart 启动的是前台命令<strong>，</strong>其将作为服务的主进程(Main Process)</li>
<li>ExecStart 进程创建即启动成功(即使进程还在初始化或监听端口未就绪)；如果进程崩溃或退出，systemd 会根据 Restart= 规则决定是否重启</li>
<li>适用于不 fork() 且不依赖其他进程的服务</li>
</ul>
<h4 id="312-错误示例">3.1.2 错误示例</h4>
<p>如果 ExecStart 启动的命令以 daemon 模式运行，daemon 进程有一个瞬间退出的中间父进程，对应就是子进程。在子进程退出时，systemd 会将其从监控队列中踢掉，同时杀掉所有附属进程(杀进程的方式由 KillMode 控制)。</p>
<pre><code class="language-Bash"># KillMode=control-group
$ systemctl start db-4306
$ systemctl status db-4306
● db-4306.service - db-4306 Server
   Loaded: loaded (/usr/lib/systemd/system/db-4306.service; enabled; vendor preset: disabled)
   Active: inactive (dead) since Fri 2025-05-30 11:03:26 CST; 9s ago
Process: 1914 ExecStart=/data/svr/greatsql/bin/mysqld --defaults-file=/data/conf/greatsql4306.cnf --daemonize $MYSQLD_OPTS (code=exited, status=0/SUCCESS)
Main PID: 1914 (code=exited, status=0/SUCCESS)

Jun 05 11:03:22 dbcluster-165 systemd: Started db-4306 Server.
$ ps aux |grep 4306 |grep -v grep
</code></pre>
<p><strong>Type=simple，执行 daemon 命令，默认启动后马上会停止。</strong></p>
<h3 id="32-typeforking">3.2 Type=forking</h3>
<pre><code class="language-YAML">
Type=forking
PIDFile=/data/dbdata/data4306/data/mysql.pid
ExecStart=/data/svr/greatsql/bin/mysqld --defaults-file=/data/conf/greatsql4306.cnf --daemonize $MYSQLD_OPTS
</code></pre>
<h4 id="321-行为">3.2.1 行为</h4>
<ul>
<li>要求 ExecStart 启动的命令以 daemon 模式运行，服务预期自行 fork() 并退出</li>
<li>ExecStart 进程 fork() 出的进程将作为服务的主进程(Main Process)，推荐设置 PIDFile 用以正确监控服务主进程，否则通过 cgroup 跟踪</li>
<li>PIDFile 只适合在 Type=forking 模式下使用，如果有设置 PIDFile，systemd 会在 ExecStart 进程退出后立即读取这个 PIDFile，读取成功后就认为该服务已经启动成功，读取失败就认为该服务启动失败</li>
<li>适用于传统 Unix 守护进程</li>
</ul>
<p>以下是 forking 模式下正常启动的服务</p>
<pre><code class="language-Bash">$ systemctl status db-4306
● db-4306.service - db-4306 Server
   Loaded: loaded (/usr/lib/systemd/system/db-4306.service; enabled; vendor preset: disabled)
   Active: active (running) since Thu 2025-05-29 22:28:03 CST; 11s ago
Process: 24262 ExecStart=/data/svr/greatsql/bin/mysqld --defaults-file=/data/conf/greatsql4306.cnf --daemonize $MYSQLD_OPTS (code=exited, status=0/SUCCESS)
Main PID: 24342 (mysqld)
    Tasks: 54
   CGroup: /system.slice/db-4306.service
         └─24342 /data/svr/greatsql/bin/mysqld --defaults-file=/data/conf/greatsql4306.cnf --daemonize

May 29 22:28:01 dbcluster-165 systemd: Starting db-4306 Server...
May 29 22:28:03 dbcluster-165 systemd: Started db-4306 Server.
</code></pre>
<p>ExecStart 启动的进程 PID=24262，且该进程的状态是已退出，退出状态码为0，这个进程是 daemon 类进程创建过程中瞬间退出的中间父进程。Main PID: 24342 (mysqld)，这是 systemd 真正监控的服务主进程。</p>
<h4 id="322-错误示例">3.2.2 错误示例</h4>
<p>如果 ExecStart 是一个前台命令，systemd 会一直等待 ExecStart 启动的进程作为中间父进程退出，在等待过程中，systemctl start 会一直卡住，直到等待超时而失败。</p>
<pre><code class="language-Bash">$ systemctl status db-4306
● db-4306.service - db-4306 Server
   Loaded: loaded (/usr/lib/systemd/system/db-4306.service; enabled; vendor preset: disabled)
   Active: activating (start) since Fri 2025-05-30 17:25:01 CST; 52s ago
Main PID: 27683 (code=exited, status=0/SUCCESS);         : 12646 (mysqld)
    Tasks: 54
   CGroup: /system.slice/db-4306.service
         └─12646 /data/svr/greatsql/bin/mysqld --defaults-file=/data/conf/greatsql4306.cnf

May 30 17:25:01 dbcluster-165 systemd: Starting db-4306 Server...
$ ps axj |grep 4306 |grep -v grep
18266 12640 12640 18266 pts/1    12640 S+       0   0:00 systemctl start db-4306
    1 12646 12646 12646 ?         -1 Ssl    986   0:02 /data/svr/greatsql/bin/mysqld --defaults-file=/data/conf/greatsql4306.cnf

$ tailf /var/log/messages |grep db-4306
May 30 17:25:01 dbcluster-165 systemd: Starting db-4306 Server...
May 30 17:26:31 dbcluster-165 systemd: db-4306.service start operation timed out. Terminating.
May 30 17:26:32 dbcluster-165 systemd: Failed to start db-4306 Server.
May 30 17:26:32 dbcluster-165 systemd: Unit db-4306.service entered failed state.
May 30 17:26:32 dbcluster-165 systemd: db-4306.service failed.
May 30 17:26:32 dbcluster-165 systemd: db-4306.service holdoff time over, scheduling restart.
May 30 17:26:32 dbcluster-165 systemd: Stopped db-4306 Server.
May 30 17:26:32 dbcluster-165 systemd: Starting db-4306 Server...
</code></pre>
<p><strong>Type=forking，执行前台命令，在Restart=on-failure场景，启动超时导致服务反复重启。</strong></p>
<h3 id="33-typenotify">3.3 Type=notify</h3>
<pre><code class="language-YAML">
Type=notify
ExecStart=/data/svr/greatsql/bin/mysqld --defaults-file=/data/conf/greatsql4306.cnf $MYSQLD_OPTS
</code></pre>
<h4 id="331-行为">3.3.1 行为</h4>
<ul>
<li>类似 simple，要求 ExecStart 启动的是前台命令<strong>，</strong>其将作为服务的主进程(Main Process)</li>
<li>进程支持 sd_notify()，必须正确配置 NotifyAccess 和超时时间</li>
<li>进程在启动完成、状态更新、停止通知后必需主动通过 sd_notify() 向 systemd 发送通知</li>
<li>适用于实现更精确的启动、运行和停止管理服务</li>
</ul>
<h3 id="34-mysqld显示更多变量">3.4 mysqld显示更多变量</h3>
<p>当使用 mysqld_safe 启动数据库时，ps 可以看到 mysqld 进程带有很多变量</p>
<pre><code class="language-Bash">$ ps aux |grep 4306
mysql   87870.00.0 1133161640 pts/1    S    08:59   0:00 /bin/sh /data/svr/greatsql/bin/mysqld_safe --defaults-file=/data/conf/greatsql4306.cnf
mysql104240.63.0 1251912 499724 pts/1Sl   08:59   0:16 /data/svr/greatsql/bin/mysqld --defaults-file=/data/conf/greatsql4306.cnf --basedir=/data/svr/greatsql --datadir=/data/dbdata/data4306/data --plugin-dir=/data/svr/greatsql/lib/plugin --log-error=/data/logs/error4306.log --open-files-limit=65535 --pid-file=/data/dbdata/data4306/data/mysql.pid --socket=/data/dbdata/data4306/data/mysql.sock --port=4306
$
</code></pre>
<p>mysqld_safe 处理逻辑如下</p>
<pre><code class="language-Bash">cmd="`mysqld_ld_preload_text`$NOHUP_NICENESS"

for i in"$ledir/$MYSQLD" "$defaults" "--basedir=$MY_BASEDIR_VERSION" \
"--datadir=$DATADIR" "--plugin-dir=$plugin_dir" "$USER_OPTION"
do
cmd="$cmd "`shell_quote_string "$i"`
done
cmd="$cmd $args"
# Avoid 'nohup: ignoring input' warning
test -n "$NOHUP_NICENESS" &amp;&amp; cmd="$cmd &lt; /dev/null"

log_notice "Starting $MYSQLD daemon with databases from $DATADIR"
</code></pre>
<p>对于 systemd service，可以添加 ExecStartPre，从 <code>--defaults-file</code> 中获取需要显示的变量</p>
<pre><code class="language-YAML">
Type=notify
ExecStartPre=-/bin/bash -c "sed 's/_/-/g; s/ //g; s/#.*//' /data/conf/greatsql4306.cnf |grep -E '^(basedir|datadir|log-error|socket|port)=' |sed 's/^/--/' |tr '\n' ' ' |sed 's/^/MYSQLD_OPTS=/' &gt; /data/conf/greatsql4306.env"
ExecStart=/data/svr/greatsql/bin/mysqld --defaults-file=/data/conf/greatsql4306.cnf $MYSQLD_OPTS
EnvironmentFile=-/data/conf/greatsql4306.env

# 启动后的效果
$ systemctl -l status db-4306
● db-4306.service - db-4306 Server
   Loaded: loaded (/usr/lib/systemd/system/db-4306.service; enabled; vendor preset: disabled)
   Active: active (running) since Fri 2025-06-06 10:27:16 CST; 7h ago
Main PID: 12020 (mysqld)
   Status: "Server is operational"
    Tasks: 53
   CGroup: /system.slice/db-4306.service
         └─12020 /data/svr/greatsql/bin/mysqld --defaults-file=/data/conf/greatsql4306.cnf --port=4306 --basedir=/data/svr/greatsql --datadir=/data/dbdata/data4306/data --pid-file=/data/dbdata/data4306/data/mysql.pid --socket=/data/dbdata/data4306/data/mysql.sock --log-error=/data/logs/error4306.log

Jun 06 10:27:14 dbcluster-165 systemd: Starting db-4306 Server...
Jun 06 10:27:16 dbcluster-165 systemd: Started db-4306 Server.
</code></pre>
<h3 id="35-mysqld先于磁盘挂载启动">3.5 mysqld先于磁盘挂载启动</h3>
<p>对于开机自动启动，如果磁盘挂载服务启动较慢，数据库服务可能会报错，可以配置数据库服务延迟启动</p>
<pre><code class="language-YAML">
Description=GreatSQL Server
After=network.target local-fs.target#部分环境After、Requires=local-fs.target无效
Requires=local-fs.target


Type=notify
Environment=LD_PRELOAD=/usr/local/jemalloc-5.3.0/lib/libjemalloc.so
ExecStartPre=-/usr/bin/sleep 5#本节采用
ExecStart=/data/svr/greatsql/bin/mysqld --defaults-file=/data/conf/greatsql4306.cnf $MYSQLD_OPTS
</code></pre>
<p>服务日志如下</p>
<pre><code class="language-Bash">$ systemctl start db-4306
$ systemctl -l status db-4306
● db-4306.service - db-4306 Server
   Loaded: loaded (/usr/lib/systemd/system/db-4306.service; enabled; vendor preset: disabled)
   Active: active (running) since Fri 2025-06-13 23:16:09 CST; 15s ago
Process: 3920 ExecStartPre=/usr/bin/sleep 5 (code=exited, status=0/SUCCESS)
Main PID: 4004 (mysqld)
   Status: "Server is operational"
    Tasks: 54
   CGroup: /system.slice/db-4306.service
         └─4004 /data/svr/greatsql/bin/mysqld --defaults-file=/data/conf/greatsql4306.cnf

Jun 13 23:16:02 dbcluster-165 systemd: Starting db-4306 Server...
Jun 13 23:16:02 dbcluster-165 sleep: ERROR: ld.so: object '/usr/local/jemalloc-5.3.0/lib/libjemalloc.so' from LD_PRELOAD cannot be preloaded: ignored.
Jun 13 23:16:09 dbcluster-165 systemd: Started db-4306 Server.
$ lsof -p 4004 |grep -i jem
mysqld4004 mysqlmem       REG                8,210479400    846986 /usr/local/jemalloc-5.3.0/lib/libjemalloc.so.2
</code></pre>
<p><code>systemctl status</code>中 ERROR 的原因：执行 ExecStartPre 会加载服务的环境变量，此时由于磁盘挂载暂未完成，导致 so 文件无法加载(这一条 ERROR 可以忽略)。只要延迟足够，在磁盘挂载完成后再执行 ExecStart，就能正常加载配置的 so 文件。</p>
<h2 id="4停止">4.停止</h2>
<h3 id="41-systemctl-stop-逻辑">4.1 systemctl stop 逻辑</h3>
<ol>
<li>执行 ExecStop (设置了才执行，否则进入第2步)
<ol>
<li>ExecStop 成功终止进程，systemd 检测到进程已退出，不再发送 SIGTERM</li>
<li>ExecStop 未终止进程，例如 ExecStop 超时(TimeoutStopSec)，ExecStop 命令与停止进程无关，进入第2步</li>
</ol>
</li>
<li>发送 SIGTERM(默认，KillSignal=SIGTERM)，优雅退出
<ol>
<li>SIGTERM 成功终止进程，服务退出</li>
<li>SIGTERM 未终止进程，例如 SIGTERM 超时(TimeoutStopSec)，进入第3步</li>
</ol>
</li>
<li>发送 SIGKILL(默认，SendSIGKILL=yes)，强制终止</li>
</ol>
<h3 id="42-systemctl-stop-执行超时">4.2 systemctl stop 执行超时</h3>
<p>对于版本升级等场景，通常会设置 innodb_fast_shutdown=0，此时关闭数据库会比较慢，如果 TimeoutStopSec 过小，可能导致 ExecStop、SIGTERM 超时，触发 SIGKILL。</p>
<ol>
<li>数据库以 systemd 服务运行</li>
</ol>
<pre><code class="language-YAML">
Type=notify
ExecStart=/data/svr/greatsql/bin/mysqld --defaults-file=/data/conf/greatsql4306.cnf
Restart=on-failure
</code></pre>
<ol start="2">
<li>ExecStop 超时，SIGTERM 超时，对应的服务日志</li>
</ol>
<pre><code class="language-Bash">$ date;systemctl stop db-4306
Tue Jun3 15:37:19 CST 2025
$ systemctl status db-4306
● db-4306.service - db-4306 Server
   Loaded: loaded (/usr/lib/systemd/system/db-4306.service; enabled; vendor preset: disabled)
   Active: failed (Result: signal) since Tue 2025-06-03 15:37:21 CST; 36s ago
Process: 26645 ExecStop=/usr/bin/sleep 60 (code=killed, signal=TERM)
Process: 26322 ExecStart=/data/svr/greatsql/bin/mysqld --defaults-file=/data/conf/greatsql4306.cnf (code=killed, signal=KILL)
Main PID: 26322 (code=killed, signal=KILL)
   Status: "Server shutdown in progress"

Jun 03 15:37:01 dbcluster-165 systemd: Starting db-4306 Server...
Jun 03 15:37:03 dbcluster-165 systemd: Started db-4306 Server.
Jun 03 15:37:19 dbcluster-165 systemd: Stopping db-4306 Server...
Jun 03 15:37:20 dbcluster-165 systemd: db-4306.service stopping timed out. Terminating.
Jun 03 15:37:21 dbcluster-165 systemd: db-4306.service stop-sigterm timed out. Killing.
Jun 03 15:37:21 dbcluster-165 systemd: db-4306.service: main process exited, code=killed, status=9/KILL
Jun 03 15:37:21 dbcluster-165 systemd: Stopped db-4306 Server.
Jun 03 15:37:21 dbcluster-165 systemd: Unit db-4306.service entered failed state.
Jun 03 15:37:21 dbcluster-165 systemd: db-4306.service failed.
</code></pre>
<p><strong>systemctl stop 超时(ExecStop、SIGTERM)，服务会被 SIGKILL。systemd 认为是一个预期的行为，不会触发重启。</strong></p>
<h3 id="43-命令行执行-shutdown-超时">4.3 命令行执行 shutdown 超时</h3>
<ol>
<li>数据库以 systemd 服务运行(同上)</li>
<li>命令行执行 shutdown</li>
</ol>
<pre><code class="language-SQL">greatsql&gt; shutdown;
</code></pre>
<p>systemd 对所有通过它管理的服务都实施完整的生命周期控制。当执行 shutdown 时，信号传递链：shutdown --&gt; 数据库服务 --&gt; systemd 服务管理器。systemd 会监控整个停止过程。</p>
<ol start="3">
<li>对应服务日志</li>
</ol>
<pre><code class="language-Bash">Jun3 17:32:23 dbcluster-165 systemd: db-4306.service stop-sigterm timed out. Killing.
Jun3 17:32:24 dbcluster-165 systemd: db-4306.service: main process exited, code=killed, status=9/KILL
Jun3 17:32:24 dbcluster-165 systemd: Unit db-4306.service entered failed state.
Jun3 17:32:24 dbcluster-165 systemd: db-4306.service failed.
Jun3 17:32:24 dbcluster-165 systemd: db-4306.service holdoff time over, scheduling restart.
Jun3 17:32:24 dbcluster-165 systemd: Stopped db-4306 Server.
Jun3 17:32:24 dbcluster-165 systemd: Starting db-4306 Server...
Jun3 17:32:25 dbcluster-165 systemd: Started db-4306 Server.
</code></pre>
<p>SIGTERM 超时，发送 SIGKILL 强制终止，进程退出原因是 Unclean signal。在 Restart=on-failure 场景，等待 RestartSec(默认100ms)后重启。</p>
<p><strong>命令行 shutdown 超时(SIGTERM)，服务会被 SIGKILL，之后会触发重启。</strong></p>
<h3 id="44-禁用-systemd-的默认信号">4.4 禁用 systemd 的默认信号</h3>
<p>如果要禁用 systemd 的默认停止行为，可以参考如下设置</p>
<pre><code class="language-YAML">
ExecStop=/path/to/your-stop-script# 必须确保此脚本终止所有进程
KillMode=none                     # 禁用systemd的默认终止行为
TimeoutStopSec=0                  # 避免超时干预
</code></pre>
<h2 id="5重启">5.重启</h2>
<blockquote>
<p>Configures whether the service shall be restarted when the service process exits, is killed, or a timeout is reached. The service process may be the main service process, but it may also be one of the processes specified with ExecStartPre=, ExecStartPost=, ExecStop=, ExecStopPost=, or ExecReload=. When the death of the process is a result of systemd operation (e.g. service stop or restart), the service will not be restarted. Timeouts include missing the watchdog "keep-alive ping" deadline and a service start, reload, and stop operation timeouts.</p>
</blockquote>
<h3 id="51-restart-的取值">5.1 Restart 的取值</h3>
<table>
<thead>
<tr>
<th><strong>Restart settings/Exit causes</strong></th>
<th><strong>no</strong></th>
<th><strong>always</strong></th>
<th><strong>on-success</strong></th>
<th><strong>on-failure</strong></th>
<th><strong>on-abnormal</strong></th>
<th><strong>on-abort</strong></th>
<th><strong>on-watchdog</strong></th>
</tr>
</thead>
<tbody>
<tr>
<td>Clean exit code or signal</td>
<td></td>
<td>X</td>
<td>X</td>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr>
<td>Unclean exit code</td>
<td></td>
<td>X</td>
<td></td>
<td>X</td>
<td></td>
<td></td>
<td></td>
</tr>
<tr>
<td>Unclean signal</td>
<td></td>
<td>X</td>
<td></td>
<td>X</td>
<td>X</td>
<td>X</td>
<td></td>
</tr>
<tr>
<td>Timeout</td>
<td></td>
<td>X</td>
<td></td>
<td>X</td>
<td>X</td>
<td></td>
<td></td>
</tr>
<tr>
<td>Watchdog</td>
<td></td>
<td>X</td>
<td></td>
<td>X</td>
<td>X</td>
<td></td>
<td>X</td>
</tr>
</tbody>
</table>
<blockquote>
<p>A clean exit means an exit code of 0, or one of the signals SIGHUP, SIGINT, SIGTERM or SIGPIPE, and additionally, exit statuses and signals specified in SuccessExitStatus=.</p>
</blockquote>
<h3 id="52-命令行执行-restart-无法重启">5.2 命令行执行 restart 无法重启</h3>
<ol>
<li>数据库以 systemd 服务运行(同上)</li>
<li>命令行执行 restart</li>
</ol>
<pre><code class="language-Bash">greatsql&gt; restart;
ERROR 3707 (HY000): Restart server failed (mysqld is not managed by supervisor process).
</code></pre>
<p>原因：没有设置相关的监控进程(https://dev.mysql.com/doc/refman/8.0/en/restart.html)</p>
<ol start="3">
<li>查看运行中数据库进程的 MYSQLD_PARENT_PID</li>
</ol>
<pre><code class="language-Bash">$ ps aux |grep 4306 |grep -v grep
mysql210550.53.1 2635940 505712 ?      SslJun03   7:31 /data/svr/greatsql/bin/mysqld --defaults-file=/data/conf/greatsql4306.cnf
$ cat /proc/21055/environ |tr '\0' '\n'
LANG=en_US.UTF-8
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin
NOTIFY_SOCKET=/run/systemd/notify
HOME=/home/mysql
LOGNAME=mysql
USER=mysql
SHELL=/bin/bash
</code></pre>
<ol start="4">
<li>设置 MYSQLD_PARENT_PID</li>
</ol>
<ul>
<li>mysqld_safe，默认将 mysqld_safe 的PID设置为监控进程</li>
</ul>
<pre><code class="language-Bash">#echo "Running mysqld: [$cmd]"
cmd="env MYSQLD_PARENT_PID=$$ $cmd"
eval "$cmd"
</code></pre>
<ul>
<li>systemd，需在服务文件添加</li>
</ul>
<pre><code class="language-Bash">
Environment=MYSQLD_PARENT_PID=1
</code></pre>
<ol start="5">
<li>重启数据库生效</li>
</ol>
<pre><code class="language-Bash">$ systemctl restart db-4306
$ ps aux |grep 4306 |grep -v grep
mysql110500.93.0 2635676 500004 ?      Ssl15:53   0:04 /data/svr/greatsql/bin/mysqld --defaults-file=/data/conf/greatsql4306.cnf
$ cat /proc/11050/environ |tr '\0' '\n' |grep MYSQLD_PARENT_PID
MYSQLD_PARENT_PID=1

greatsql&gt; restart;
Query OK, 0 rows affected (0.00 sec)
</code></pre>
<blockquote>
<p>如果要求不重启数据库就能执行 restart 命令，可通过 gdb 动态修改环境变量，gdb 会短时间阻塞数据库</p>
<pre><code class="language-Bash">$ gdb -p 21055

(gdb) call putenv("MYSQLD_PARENT_PID=1")
$2 = 0
(gdb) detach
Detaching from program: /data/svr/GreatSQL-8.0.32-26-Linux-glibc2.17-x86_64/bin/mysqld, process 21055
(gdb) quit

greatsql&gt; restart;
Query OK, 0 rows affected (0.00 sec)
</code></pre>
</blockquote>
<p><strong>clone 同样需要设置 MYSQLD_PARENT_PID，才能自动重启。</strong></p>
<h3 id="53相关参数">5.3相关参数</h3>
<p>ReStartSec：重启条件满足后等多久自动重启</p>
<p>StartLimitInterval、StartLimitBurst：限制指定时间内(StartLimitInterval)重启的次数(StartLimitBurst)</p>
<p>RestartPreventExitStatus：指定某些退出状态码或信号不重启。GreatSQL服务建议设置为1，在遇到严重错误时不重启实例，需人工介入处理</p>
<p>RestartForceExitStatus：强制将某些退出状态码或信号重启。比如 Restart=no，RestartForceExitStatus=16，则不依赖自动重启，但命令行执行 restart 可正常重启实例</p>
<h2 id="6总结">6.总结</h2>
<ul>
<li>合理设置 Type 和 ExecStart</li>
<li>建议设置一个较大的 TimeoutStopSec，避免 ExecStop 或者 SIGTERM 超时</li>
<li>Clone 和命令行 restart 需要设置 MYSQLD_PARENT_PID</li>
<li>建议设置 ReStartSec、StartLimitInterval 和 StartLimitBurst 限制重启频率</li>
<li>可以设置 ExecStartPre和EnvironmentFile，添加 ps 需要显示的变量</li>
</ul>
<hr>
<p>Enjoy GreatSQL 😃</p>
<h2 id="关于-greatsql">关于 GreatSQL</h2>
<p>GreatSQL是适用于金融级应用的国内自主开源数据库，具备高性能、高可靠、高易用性、高安全等多个核心特性，可以作为MySQL或Percona Server的可选替换，用于线上生产环境，且完全免费并兼容MySQL或Percona Server。</p>
<p>相关链接：   GreatSQL社区        Gitee        GitHub        Bilibili</p>
<h2 id="greatsql社区">GreatSQL社区：</h2>
<blockquote>
<p>社区博客有奖征稿详情：https://greatsql.cn/thread-100-1-1.html</p>
</blockquote>
<p><img src="https://img2024.cnblogs.com/other/2630741/202507/2630741-20250702101337489-175903790.png"></p>
<h2 id="技术交流群">技术交流群：</h2>
<blockquote>
<p>微信：扫码添加<code>GreatSQL社区助手</code>微信好友，发送验证信息<code>加群</code>。</p>
</blockquote>
<p><img src="https://img2024.cnblogs.com/other/2630741/202507/2630741-20250702101337781-93838305.png"></p><br><br>
来源：https://www.cnblogs.com/greatsql/p/18961041

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