clickhouse 的 GC 比较明显，每隔一段时间总是带来 CPU 峰值（目测是几秒钟一次），由于仅在需要的使用它， 不需要后台常驻，所以使用 clickhouse stop 关闭。
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$ clickhouse stop
/var/run/clickhouse-server/clickhouse-server.pid file exists and contains pid = 1653591.
The process with pid = 1653591 is running.
Sent terminate signal to process with pid 1653591.
Waiting for server to stop
/var/run/clickhouse-server/clickhouse-server.pid file exists and contains pid = 1653591.
The process with pid = 1653591 is running.
Waiting for server to stop
/var/run/clickhouse-server/clickhouse-server.pid file exists and contains pid = 1653591.
The process with pid = 1653591 is running.
Waiting for server to stop
Now there is no clickhouse-server process.
Server stopped
但我发现这个命令不能完全关闭 clickhouse，然后根据 issue #16254，但最终用以下方式禁用重启：
- 查看 systemctl 服务，得到加载文件的路径
/lib/systemd/system/clickhouse-server.service
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$ systemctl status clickhouse-server.service
Warning: The unit file, source configuration file or drop-ins of clickhouse-server.service changed on disk. Run 'systemctl daemon-reload' to reload units.
● clickhouse-server.service - ClickHouse Server (analytic DBMS for big data)
Loaded: loaded (/lib/systemd/system/clickhouse-server.service; disabled; vendor preset: enabled)
Active: active (running) since Fri 2023-02-17 12:59:27 CST; 6min ago
Main PID: 1686041 (clckhouse-watch)
Tasks: 231 (limit: 2310)
Memory: 351.9M
CGroup: /system.slice/clickhouse-server.service
├─1686041 clickhouse-watchdog --config=/etc/clickhouse-server/config.xml --pid-file=/run/clickhouse-server/clickhouse-server.pid
└─1686055 /usr/bin/clickhouse-server --config=/etc/clickhouse-server/config.xml --pid-file=/run/clickhouse-server/clickhouse-server.pid
Feb 17 12:59:27 zjp clickhouse-server[1686041]: Processing configuration file '/etc/clickhouse-server/config.xml'.
Feb 17 12:59:27 zjp clickhouse-server[1686041]: Merging configuration file '/etc/clickhouse-server/config.d/default.xml'.
Feb 17 12:59:27 zjp clickhouse-server[1686041]: Logging trace to /var/log/clickhouse-server/clickhouse-server.log
Feb 17 12:59:27 zjp clickhouse-server[1686041]: Logging errors to /var/log/clickhouse-server/clickhouse-server.err.log
Feb 17 12:59:28 zjp clickhouse-server[1686055]: Processing configuration file '/etc/clickhouse-server/config.xml'.
Feb 17 12:59:28 zjp clickhouse-server[1686055]: Merging configuration file '/etc/clickhouse-server/config.d/default.xml'.
Feb 17 12:59:28 zjp clickhouse-server[1686055]: Saved preprocessed configuration to '/var/lib/clickhouse/preprocessed_configs/config.xml'.
Feb 17 12:59:28 zjp clickhouse-server[1686055]: Processing configuration file '/etc/clickhouse-server/users.xml'.
Feb 17 12:59:28 zjp clickhouse-server[1686055]: Merging configuration file '/etc/clickhouse-server/users.d/users.xml'.
Feb 17 12:59:28 zjp clickhouse-server[1686055]: Saved preprocessed configuration to '/var/lib/clickhouse/preprocessed_configs/users.xml'.
- 修改那个文件的
Restart=always部分，可选值有no, on-success, on-failure, on-abnormal, on-watchdog, on-abort, or always，见 systemd 文档
- 关闭 clickhouse-server，会遇到需要重新加载配置文件的警告：
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$ systemctl stop clickhouse-server.service
Warning: The unit file, source configuration file or drop-ins of clickhouse-server.service changed on disk. Run 'systemctl daemon-reload' to reload units.
所以应该先运行 systemctl daemon-reload，再运行 systemctl stop clickhouse-server.service
- 如果启动 clickhouse-server，可使用
systemctl start clickhouse-server.service