记一次MySQL5初始化被kill的问题排查

写在前面

由于测试环境JED申请比较繁琐，所以Eone提供了单机版Mysql供用户使用，近期Eone搭建Mysql5的时候发现莫名被kill了，容器规格是4C8G，磁盘30G

这不科学，之前都是可以的，镜像没变，配置没变，咋就不行了呢，一定不是我的问题，是机器的问题

问题排查

重现

通过多次搭建mysql5进行采样，发现并不是稳定复现，有一些容器是可以正常启动提供服务的，找到被mysql服务被kill的容器日志，发现是MySQL初始化被kill了，

/usr/local/mysql/bin/mysqld --defaults-file=/etc/my.cnf --basedir=/usr/local/mysql --datadir=/export/data/mysql/data --user=admin --initialize-insecure

mysql配置文件：

[client]
socket=/tmp/mysql.sock

[mysqld]
basedir=/usr/local/mysql
datadir=/export/data/mysql/data
port=3306
server_id=1
socket=/tmp/mysql.sock
log-error=/tmp/mysqld.err
pid-file=/tmp/mysqld.pid

skip-host-cache
skip-name-resolve
skip-grant-tables

问题排查

初始化为什么被kill？

手动执行了下初始化的命令，发现直接被kill了

通过dmesg命令发现，貌似oom了

纳尼？怎么用了这么多内存？容器都没这么大内存诶

通过排查，发现MySQL有一个8G的匿名内存，这是哪来的？？？

将容器规格调整为32G内存，再次尝试，发现成功启动了，但是内存占用貌似不太正常

这不科学，正常的容器内存使用情况是这样的👇

MySQL配置不合理？

难道是因为mysql设置的大小不合理？默认不设置innodb_buffer_pool_size按理说应该是128M才对，抱着侥幸心理设置下试下

然而问题依旧，改了配置也没有效果，看来不是配置的问题

真是机器的问题？

对比了一下正常启动的机器，拿着ip找到运维，发现异常的机器是近期添加的云舰系统的机器，之前centos系统宿主机是正常的，新加的云舰系统宿主机都是异常的，看来真是机器的问题，这两台机器有啥差别呢，接下来运维同学开启了排查之路：

1. 首先，看看两台宿主机是不是物理CPU总数不一样

2. 再确认下CentOS是否开启了富容器功能

对比了下两台宿主机的资源配置，发现好像是资源配置的问题

正常的机器配置是这样的

或许真的有可能，修改下open files限制再试下

ulimit -n 1048576

竟然可以了！！！MySQL正常提供服务了，真的是机器的问题

问题分析

strace log分析

28139 execve("/usr/local/mysql/bin/mysqld-debug", ["/usr/local/mysql/bin/mysqld-debu"..., "--initialize-insecure", "--basedir=/usr/local/mysql", "--datadir=/export/data/mysql/dat"..., "--user=admin"], 0x7ffe74bdcbe8 /* 294 vars */) = 0
28139 brk(NULL)                         = 0x4b50000
28139 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f93d3bf6000
28139 access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
28139 open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
28139 fstat(3, {st_mode=S_IFREG|0644, st_size=16580, ...}) = 0
28139 mmap(NULL, 16580, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f93d3bf1000
28139 close(3)                          = 0
28139 open("/lib64/libpthread.so.0", O_RDONLY|O_CLOEXEC) = 3
28139 read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\240l\0\0\0\0\0\0"..., 832) = 832
28139 fstat(3, {st_mode=S_IFREG|0755, st_size=142304, ...}) = 0
28139 mmap(NULL, 2208864, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f93d37ba000
28139 mprotect(0x7f93d37d0000, 2097152, PROT_NONE) = 0
28139 mmap(0x7f93d39d0000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x16000) = 0x7f93d39d0000
28139 mmap(0x7f93d39d2000, 13408, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f93d39d2000
28139 close(3)                          = 0
28139 open("/lib64/libdl.so.2", O_RDONLY|O_CLOEXEC) = 3
28139 read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\320\16\0\0\0\0\0\0"..., 832) = 832
28139 fstat(3, {st_mode=S_IFREG|0755, st_size=19520, ...}) = 0
28139 mmap(NULL, 2109744, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f93d35b6000
28139 mprotect(0x7f93d35b9000, 2093056, PROT_NONE) = 0
28139 mmap(0x7f93d37b8000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x2000) = 0x7f93d37b8000
28139 close(3)                          = 0
28139 open("/lib64/libaio.so.1", O_RDONLY|O_CLOEXEC) = 3
28139 read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\240\5\0\0\0\0\0\0"..., 832) = 832
28139 fstat(3, {st_mode=S_IFREG|0755, st_size=6264, ...}) = 0
28139 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f93d3bf0000
28139 mmap(NULL, 2101328, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f93d33b4000
28139 mprotect(0x7f93d33b5000, 2093056, PROT_NONE) = 0
28139 mmap(0x7f93d35b4000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0) = 0x7f93d35b4000
28139 close(3)                          = 0
28139 open("/lib64/libnuma.so.1", O_RDONLY|O_CLOEXEC) = 3
28139 read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\0004\0\0\0\0\0\0"..., 832) = 832
28139 fstat(3, {st_mode=S_IFREG|0755, st_size=50704, ...}) = 0
28139 mmap(NULL, 2144448, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f93d31a8000
28139 mprotect(0x7f93d31b2000, 2097152, PROT_NONE) = 0
28139 mmap(0x7f93d33b2000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0xa000) = 0x7f93d33b2000
28139 close(3)                          = 0
28139 open("/lib64/libcrypt.so.1", O_RDONLY|O_CLOEXEC) = 3
28139 read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\300\16\0\0\0\0\0\0"..., 832) = 832
28139 fstat(3, {st_mode=S_IFREG|0755, st_size=40816, ...}) = 0
28139 mmap(NULL, 2318912, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f93d2f71000
28139 mprotect(0x7f93d2f79000, 2093056, PROT_NONE) = 0
28139 mmap(0x7f93d3178000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x7000) = 0x7f93d3178000
28139 mmap(0x7f93d317a000, 184896, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f93d317a000
28139 close(3)                          = 0
28139 open("/lib64/librt.so.1", O_RDONLY|O_CLOEXEC) = 3
28139 read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\300\"\0\0\0\0\0\0"..., 832) = 832
28139 fstat(3, {st_mode=S_IFREG|0755, st_size=44096, ...}) = 0
28139 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f93d3bef000
28139 mmap(NULL, 2128952, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f93d2d69000
28139 mprotect(0x7f93d2d70000, 2093056, PROT_NONE) = 0
28139 mmap(0x7f93d2f6f000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x6000) = 0x7f93d2f6f000
28139 close(3)                          = 0
28139 open("/lib64/libstdc++.so.6", O_RDONLY|O_CLOEXEC) = 3
28139 read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\340\264\5\0\0\0\0\0"..., 832) = 832
28139 fstat(3, {st_mode=S_IFREG|0755, st_size=995840, ...}) = 0
28139 mmap(NULL, 3175456, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f93d2a61000
28139 mprotect(0x7f93d2b4a000, 2097152, PROT_NONE) = 0
28139 mmap(0x7f93d2d4a000, 40960, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0xe9000) = 0x7f93d2d4a000
28139 mmap(0x7f93d2d54000, 82976, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f93d2d54000
28139 close(3)                          = 0
28139 open("/lib64/libm.so.6", O_RDONLY|O_CLOEXEC) = 3
28139 read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\260T\0\0\0\0\0\0"..., 832) = 832
28139 fstat(3, {st_mode=S_IFREG|0755, st_size=1141560, ...}) = 0
28139 mmap(NULL, 3150168, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f93d275f000
28139 mprotect(0x7f93d2860000, 2093056, PROT_NONE) = 0
28139 mmap(0x7f93d2a5f000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x100000) = 0x7f93d2a5f000
28139 close(3)                          = 0
28139 open("/lib64/libgcc_s.so.1", O_RDONLY|O_CLOEXEC) = 3
28139 read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\320*\0\0\0\0\0\0"..., 832) = 832
28139 fstat(3, {st_mode=S_IFREG|0755, st_size=88720, ...}) = 0
28139 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f93d3bee000
28139 mmap(NULL, 2184192, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f93d2549000
28139 mprotect(0x7f93d255e000, 2093056, PROT_NONE) = 0
28139 mmap(0x7f93d275d000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x14000) = 0x7f93d275d000
28139 close(3)                          = 0
28139 open("/lib64/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
28139 read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0 \34\2\0\0\0\0\0"..., 832) = 832
28139 fstat(3, {st_mode=S_IFREG|0755, st_size=2112384, ...}) = 0
28139 mmap(NULL, 3936832, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f93d2187000
28139 mprotect(0x7f93d233e000, 2097152, PROT_NONE) = 0
28139 mmap(0x7f93d253e000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1b7000) = 0x7f93d253e000
28139 mmap(0x7f93d2544000, 16960, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f93d2544000
28139 close(3)                          = 0
28139 open("/lib64/libfreebl3.so", O_RDONLY|O_CLOEXEC) = 3
28139 read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\240\v\0\0\0\0\0\0"..., 832) = 832
28139 fstat(3, {st_mode=S_IFREG|0755, st_size=11376, ...}) = 0
28139 mmap(NULL, 2105536, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f93d1f84000
28139 mprotect(0x7f93d1f86000, 2093056, PROT_NONE) = 0
28139 mmap(0x7f93d2185000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1000) = 0x7f93d2185000
28139 close(3)                          = 0
28139 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f93d3bed000
28139 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f93d3bec000
28139 mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f93d3bea000
28139 arch_prctl(ARCH_SET_FS, 0x7f93d3bea740) = 0
28139 mprotect(0x7f93d253e000, 16384, PROT_READ) = 0
28139 mprotect(0x7f93d37b8000, 4096, PROT_READ) = 0
28139 mprotect(0x7f93d2185000, 4096, PROT_READ) = 0
28139 mprotect(0x7f93d275d000, 4096, PROT_READ) = 0
28139 mprotect(0x7f93d2a5f000, 4096, PROT_READ) = 0
28139 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f93d3be9000
28139 mprotect(0x7f93d2d4a000, 32768, PROT_READ) = 0
28139 mprotect(0x7f93d39d0000, 4096, PROT_READ) = 0
28139 mprotect(0x7f93d2f6f000, 4096, PROT_READ) = 0
28139 mprotect(0x7f93d3178000, 4096, PROT_READ) = 0
28139 mprotect(0x7f93d33b2000, 4096, PROT_READ) = 0
28139 mprotect(0x7f93d35b4000, 4096, PROT_READ) = 0
28139 mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f93d3be7000
28139 mprotect(0x7f93d3bf7000, 4096, PROT_READ) = 0
28139 munmap(0x7f93d3bf1000, 16580)     = 0
28139 set_tid_address(0x7f93d3beaa10)   = 28139
28139 set_robust_list(0x7f93d3beaa20, 24) = 0
28139 rt_sigaction(SIGRTMIN, {sa_handler=0x7f93d37c0780, sa_mask=[], sa_flags=SA_RESTORER|SA_SIGINFO, sa_restorer=0x7f93d37c9100}, NULL, 8) = 0
28139 rt_sigaction(SIGRT_1, {sa_handler=0x7f93d37c0810, sa_mask=[], sa_flags=SA_RESTORER|SA_RESTART|SA_SIGINFO, sa_restorer=0x7f93d37c9100}, NULL, 8) = 0
28139 rt_sigprocmask(SIG_UNBLOCK, [RTMIN RT_1], NULL, 8) = 0
28139 getrlimit(RLIMIT_STACK, {rlim_cur=8192*1024, rlim_max=RLIM64_INFINITY}) = 0
28139 brk(NULL)                         = 0x4b50000
28139 brk(0x4b71000)                    = 0x4b71000
28139 open("/proc/self/status", O_RDONLY) = 3
28139 fstat(3, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0
28139 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f93d3bf5000
28139 read(3, "Name:\tmysqld-debug\nUmask:\t0022\nS"..., 1024) = 1024
28139 read(3, "0,00000000,00000000,00000000,000"..., 1024) = 334
28139 close(3)                          = 0
28139 munmap(0x7f93d3bf5000, 4096)      = 0
28139 openat(AT_FDCWD, "/sys/devices/system/node", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 3
28139 getdents(3, /* 11 entries */, 32768) = 360
28139 open("/sys/devices/system/node/node0/meminfo", O_RDONLY) = 4
28139 fstat(4, {st_mode=S_IFREG|0444, st_size=4096, ...}) = 0
28139 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f93d3bf5000
28139 read(4, "Node 0 MemTotal:       226242196"..., 4096) = 1175
28139 stat("/etc/sysconfig/64bit_strstr_via_64bit_strstr_sse2_unaligned", 0x7ffda2f609d0) = -1 ENOENT (No such file or directory)
28139 stat("/etc/sysconfig/64bit_strstr_via_64bit_strstr_sse2_unaligned", 0x7ffda2f609d0) = -1 ENOENT (No such file or directory)
28139 read(4, "", 4096)                 = 0
28139 close(4)                          = 0
28139 munmap(0x7f93d3bf5000, 4096)      = 0
28139 getdents(3, /* 0 entries */, 32768) = 0
28139 close(3)                          = 0
28139 sched_getaffinity(0, 512, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59]) = 8
28139 openat(AT_FDCWD, "/sys/devices/system/cpu", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 3
28139 getdents(3, /* 77 entries */, 32768) = 2368
28139 getdents(3, /* 0 entries */, 32768) = 0
28139 close(3)                          = 0
28139 open("/proc/self/status", O_RDONLY) = 3
28139 fstat(3, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0
28139 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f93d3bf5000
28139 read(3, "Name:\tmysqld-debug\nUmask:\t0022\nS"..., 1024) = 1024
28139 read(3, "0,00000000,00000000,00000000,000"..., 1024) = 334
28139 read(3, "", 1024)                 = 0
28139 close(3)                          = 0
28139 munmap(0x7f93d3bf5000, 4096)      = 0
28139 futex(0x7f93d2d6696c, FUTEX_WAKE_PRIVATE, 2147483647) = 0
28139 futex(0x7f93d2d66978, FUTEX_WAKE_PRIVATE, 2147483647) = 0
28139 stat("/etc/my.cnf", {st_mode=S_IFREG|0644, st_size=370, ...}) = 0
28139 open("/etc/my.cnf", O_RDONLY)     = 3
28139 fstat(3, {st_mode=S_IFREG|0644, st_size=370, ...}) = 0
28139 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f93d3bf5000
28139 read(3, "[client]\nsocket=/tmp/mysql.sock\n"..., 4096) = 370
28139 read(3, "", 4096)                 = 0
28139 close(3)                          = 0
28139 munmap(0x7f93d3bf5000, 4096)      = 0
28139 stat("/etc/mysql/my.cnf", 0x7ffda2f5c8d0) = -1 ENOENT (No such file or directory)
28139 stat("/usr/local/mysql/etc/my.cnf", 0x7ffda2f5c8d0) = -1 ENOENT (No such file or directory)
28139 stat("/root/.my.cnf", 0x7ffda2f5c8d0) = -1 ENOENT (No such file or directory)
28139 getrlimit(RLIMIT_NOFILE, {rlim_cur=1073741816, rlim_max=1073741816}) = 0
28139 mmap(NULL, 17179869184, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f8fd1f84000
28139 +++ killed by SIGKILL +++

可以看到最后用 mmap 一次分配了 16G 内存，然后就被杀了。

mmap 前调用了 getrlimit ，猜测是 mysql 会根据系统资源限制来分配内存

MySQL源码分析

MySQL 源码中直接调用 getrlimit 的地方不多，排除了 ndb、innodb_memcached、libevent 之后，只有一处直接调用：

static uint set_max_open_files(uint max_file_limit)
{
  struct rlimit rlimit;
  uint old_cur;
  DBUG_ENTER("set_max_open_files");
  DBUG_PRINT("enter",("files: %u", max_file_limit));

  if (!getrlimit(RLIMIT_NOFILE,&rlimit))
  {
    old_cur= (uint) rlimit.rlim_cur;
    DBUG_PRINT("info", ("rlim_cur: %u  rlim_max: %u",
                        (uint) rlimit.rlim_cur,
                        (uint) rlimit.rlim_max));
    if (rlimit.rlim_cur == (rlim_t) RLIM_INFINITY)
      rlimit.rlim_cur = max_file_limit;
    if (rlimit.rlim_cur >= max_file_limit)
      DBUG_RETURN(rlimit.rlim_cur);                /* purecov: inspected */
    rlimit.rlim_cur= rlimit.rlim_max= max_file_limit;
    if (setrlimit(RLIMIT_NOFILE, &rlimit))
      max_file_limit= old_cur;                        /* Use original value */
    else
    {
      rlimit.rlim_cur= 0;                        /* Safety if next call fails */
      (void) getrlimit(RLIMIT_NOFILE,&rlimit);
      DBUG_PRINT("info", ("rlim_cur: %u", (uint) rlimit.rlim_cur));
      if (rlimit.rlim_cur)                        /* If call didn't fail */
        max_file_limit= (uint) rlimit.rlim_cur;
    }
  }
  DBUG_PRINT("exit",("max_file_limit: %u", max_file_limit));
  DBUG_RETURN(max_file_limit);

其中逻辑是：如果系统的文件打开限制是 RLIM_INFINITY 或者比要设置的 max_file_limit 大，都返回系统的限制。

这个函数也只被直接调用一次：

uint my_set_max_open_files(uint files)
{
  struct st_my_file_info *tmp;
  DBUG_ENTER("my_set_max_open_files");
  DBUG_PRINT("enter",("files: %u  my_file_limit: %u", files, my_file_limit));

  files+= MY_FILE_MIN;
  files= set_max_open_files(MY_MIN(files, OS_FILE_LIMIT)); // 获取最大打开文件数
  if (files <= MY_NFILE)
    DBUG_RETURN(files);

  // 分配内存
  if (!(tmp= (struct st_my_file_info*) my_malloc(key_memory_my_file_info,
                                                 sizeof(*tmp) * files,
                                                 MYF(MY_WME))))
    DBUG_RETURN(MY_NFILE);

  // 初始化
  /* Copy any initialized files */
  memcpy((char*) tmp, (char*) my_file_info,
         sizeof(*tmp) * MY_MIN(my_file_limit, files));
  memset((tmp + my_file_limit), 0,
        MY_MAX((int) (files - my_file_limit), 0) * sizeof(*tmp));
  my_free_open_file_info();                        /* Free if already allocated */
  my_file_info= tmp;
  my_file_limit= files;
  DBUG_PRINT("exit",("files: %u", files));
  DBUG_RETURN(files);
}

原来 MySQL5 会根据最大可打开文件数，提前为每个文件分配和初始化内存，在这个时候就可能分配过多内存，导致 OOM。MySQL8修复了这个问题。

解决

启动前设置ulimit

ENTRYPOINT ["ulimit -n 1048576 && /home/admin/start.sh"]

写在后面

在linux中，open files设置过大会出现很多问题，应该合理控制open files数量

参考文献

https://learnku.com/articles/34598

作者：京东零售杨云龙

来源：京东云开发者社区转载请注明来源