【MySQL】查看log

查看运行log

// Depends on your mysql version
$ systemctl status mysqld.service
$ systemctl status mysqld.service
● mariadb.service - MariaDB database server
   Loaded: loaded (/usr/lib/systemd/system/mariadb.service; enabled; vendor preset: disabled)
   Active: inactive (dead) since Mon 2020-01-20 23:18:07 UTC; 2 months 7 days ago
 Main PID: 10307 (code=exited, status=0/SUCCESS)

Warning: Journal has been rotated since unit was started. Log output is incomplete or unavailable.

// 查看log路径
$ cat /etc/my.cnf
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
# Settings user and group are ignored when systemd is used.
# If you need to run mysqld under a different user or group,
# customize your systemd unit file for mariadb according to the
# instructions in http://fedoraproject.org/wiki/Systemd

[mysqld_safe]
log-error=/var/log/mariadb/mariadb.log
pid-file=/var/run/mariadb/mariadb.pid

#
# include all files from the config directory
#
!includedir /etc/my.cnf.d

可以从下面Log看到，MySQL是由于 Out of memory。

更准确的说，当MySQL被初始化时，我们尝试为MySQL的 buffer pool分配128M的内存，但是失败了（cannot allocate memory for the buffer pool）。

$ cat /var/log/mariadb/mariadb.log
200120 23:18:06 mysqld_safe Number of processes running now: 0
200120 23:18:06 mysqld_safe mysqld restarted
200120 23:18:07 [Note] /usr/libexec/mysqld (mysqld 5.5.60-MariaDB) starting as process 20856 ...
200120 23:18:07 [ERROR] mysqld: Out of memory (Needed 128917504 bytes)
200120 23:18:07 [ERROR] mysqld: Out of memory (Needed 96681984 bytes)
200120 23:18:07 InnoDB: The InnoDB memory heap is disabled
200120 23:18:07 InnoDB: Mutexes and rw_locks use GCC atomic builtins
200120 23:18:07 InnoDB: Compressed tables use zlib 1.2.7
200120 23:18:07 InnoDB: Using Linux native AIO
200120 23:18:07 InnoDB: Initializing buffer pool, size = 128.0M
InnoDB: mmap(137756672 bytes) failed; errno 12
200120 23:18:07 InnoDB: Completed initialization of buffer pool
200120 23:18:07 InnoDB: Fatal error: cannot allocate memory for the buffer pool
200120 23:18:07 [ERROR] Plugin 'InnoDB' init function returned error.
200120 23:18:07 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
200120 23:18:07 [Note] Plugin 'FEEDBACK' is disabled.
200120 23:18:07 [ERROR] Unknown/unsupported storage engine: InnoDB
200120 23:18:07 [ERROR] Aborting

200120 23:18:07 [Note] /usr/libexec/mysqld: Shutdown complete

200120 23:18:07 mysqld_safe mysqld from pid file /var/run/mariadb/mariadb.pid ended

$ sudo systemctl restart mariadb.service

重启后log：

$ cat /var/log/mariadb/mariadb.log
200329 04:09:47 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
200329  4:09:47 [Note] /usr/libexec/mysqld (mysqld 5.5.60-MariaDB) starting as process 13375 ...
200329  4:09:47 InnoDB: The InnoDB memory heap is disabled
200329  4:09:47 InnoDB: Mutexes and rw_locks use GCC atomic builtins
200329  4:09:47 InnoDB: Compressed tables use zlib 1.2.7
200329  4:09:47 InnoDB: Using Linux native AIO
200329  4:09:47 InnoDB: Initializing buffer pool, size = 128.0M
200329  4:09:47 InnoDB: Completed initialization of buffer pool
200329  4:09:47 InnoDB: highest supported file format is Barracuda.
InnoDB: The log sequence number in ibdata files does not match
InnoDB: the log sequence number in the ib_logfiles!
InnoDB: Restoring possible half-written data pages from the doublewrite buffer...
200329  4:09:47  InnoDB: Waiting for the background threads to start
200329  4:09:48 Percona XtraDB (http://www.percona.com) 5.5.59-MariaDB-38.11 started; log sequence number 4289175227
200329  4:09:48 [Note] Plugin 'FEEDBACK' is disabled.
200329  4:09:48 [Note] Server socket created on IP: '0.0.0.0'.
200329  4:09:48 [Note] Event Scheduler: Loaded 0 events
200329  4:09:48 [Note] /usr/libexec/mysqld: ready for connections.
Version: '5.5.60-MariaDB'  socket: '/var/lib/mysql/mysql.sock'  port: 3306  MariaDB Server