有问题的服务器用于将数据处理成报告，它有三个 cron 作业，每分钟执行一次以检查进程队列，如果发现任何内容，它们将继续运行，直到队列为空。在特别繁忙的日子（过去 3 个月的每个星期二和其他奇数天），服务器会崩溃。
通过运行，ps aux | grep 'httpd' | awk '{print $6/1024 " MB";}'我可以看到三个 httpd 工作进程以线性方式持续增加内存。由于有大量报告，进程不会结束，并且它们继续消耗更多内存。
这是一个 PHP 运行时，检查其中的内存使用情况，我们发现它根本不会成为问题。PHP 内存的硬限制为 256MB，至少在 PHP 层中，内存会在报告处理完成后释放。当前正在重复服务器上使用 PHP 内存分析器来查看 PHP 层中是否存在导致此问题的问题。但是，上面提到的 ps aux 命令显示，对于 httpd 工作程序，内存从大约 270MB 开始，并且不断增加，直到整个服务器（8GB RAM）耗尽。所以在我看来，httpd 很可能占用了 PHP 层正在使用的所有内存，而不是将其回收到 PHP 进程或系统中。以下是发生这种情况时的错误日志中的片段。
[Tue Dec 04 09:20:34.805175 2018] [mpm_prefork:error] [pid 2751] (12)Cannot allocate memory: AH00159: fork: Unable to fork new process
[Tue Dec 04 09:20:45.142735 2018] [mpm_prefork:error] [pid 2751] (12)Cannot allocate memory: AH00159: fork: Unable to fork new process
mmap() failed: [
mmap() failed: [
mmap() failed: [1122]] CCannot allocate memoryannot allocate memory12] Cannot allocate memory
mmap() failed: [
mmap() failed: [1122]] CCannot allocate memoryannot allocate memory
mmap() failed: [12] Cannot allocate memory[Tue Dec 04 09:20:45.764357 2018] [php7:error] [pid 12198] [client 127.0.0.1:37694] PHP Fatal error:
Out of memory (allocated 2097152) (tried to allocate 65536 bytes) in /var/www/html/vendor/composer/ClassLoader.php on line 440
[Tue Dec 04 09:20:45.764411 2018] [php7:error] [pid 12197] [client 127.0.0.1:37692] PHP Fatal error: Out of memory (allocated 2097152) (tried
to allocate 65536 bytes) in /var/www/html/vendor/composer/ClassLoader.php on line 440
[Tue Dec 04 09:20:45.764358 2018] [php7:error] [pid 12191] [client 127.0.0.1:37690] PHP Fatal error: Out of memory (allocated 2097152) (tried
to allocate 65536 bytes) in /var/www/html/vendor/composer/ClassLoader.php on line 440
mmap() failed: [
mmap() failed: [1122]] CCannot allocate memoryannot allocate memory
mmap() failed: [12] Cannot allocate memory
mmap() failed: [
mmap() failed: [1122]] CCannot allocate memoryannot allocate memory
mmap() failed: [12] Cannot allocate memory[Tue Dec 04 09:20:46.257438 2018] [php7:error] [pid 12191] [client 127.0.0.1:37690] PHP Fatal error:
Out of memory (allocated 2097152) (tried to allocate 73728 bytes) in /var/www/html/vendor/composer/ClassLoader.php on line 440
[Tue Dec 04 09:20:46.257439 2018] [php7:error] [pid 12197] [client 127.0.0.1:37692] PHP Fatal error: Out of memory (allocated 2097152) (tried
to allocate 73728 bytes) in /var/www/html/vendor/composer/ClassLoader.php on line 440
[Tue Dec 04 09:20:46.257481 2018] [php7:error] [pid 12198] [client 127.0.0.1:37694] PHP Fatal error: Out of memory (allocated 2097152) (tried
to allocate 73728 bytes) in /var/www/html/vendor/composer/ClassLoader.php on line 440
[Tue Dec 04 09:20:57.249945 2018] [mpm_prefork:error] [pid 2751] (12)Cannot allocate memory: AH00159: fork: Unable to fork new process
[Tue Dec 04 09:23:08.171314 2018] [mpm_prefork:error] [pid 2751] (12)Cannot allocate memory: AH00159: fork: Unable to fork new process
[Tue Dec 04 09:24:33.415351 2018] [mpm_prefork:error] [pid 2751] (12)Cannot allocate memory: AH00159: fork: Unable to fork new process
[Tue Dec 04 09:26:22.308600 2018] [mpm_prefork:error] [pid 2751] (12)Cannot allocate memory: AH00159: fork: Unable to fork new process
[Tue Dec 04 09:27:55.057324 2018] [mpm_prefork:error] [pid 2751] (12)Cannot allocate memory: AH00159: fork: Unable to fork new process
[Tue Dec 04 09:29:17.174173 2018] [mpm_prefork:error] [pid 2751] (12)Cannot allocate memory: AH00159: fork: Unable to fork new process
[Tue Dec 04 09:30:39.193341 2018] [mpm_prefork:error] [pid 2751] (12)Cannot allocate memory: AH00159: fork: Unable to fork new process
[Tue Dec 04 09:33:16.023329 2018] [mpm_prefork:error] [pid 2751] (12)Cannot allocate memory: AH00159: fork: Unable to fork new process
[Tue Dec 04 09:34:53.208958 2018] [mpm_prefork:error] [pid 2751] (12)Cannot allocate memory: AH00159: fork: Unable to fork new process
[Tue Dec 04 09:35:30.902310 2018] [mpm_prefork:error] [pid 2751] (12)Cannot allocate memory: AH00159: fork: Unable to fork new process
[Tue Dec 04 09:36:05.215192 2018] [mpm_prefork:error] [pid 2751] (12)Cannot allocate memory: AH00159: fork: Unable to fork new process
[Tue Dec 04 09:37:36.511811 2018] [mpm_prefork:error] [pid 2751] (12)Cannot allocate memory: AH00159: fork: Unable to fork new process
[Tue Dec 04 09:42:18.453045 2018] [suexec:notice] [pid 2699] AH01232: suEXEC mechanism enabled (wrapper: /usr/sbin/suexec)
正在使用的 httpd 模式：
$ sudo httpd -M
Loaded Modules:
core_module (static)
so_module (static)
http_module (static)
access_compat_module (shared)
actions_module (shared)
alias_module (shared)
allowmethods_module (shared)
auth_basic_module (shared)
auth_digest_module (shared)
authn_anon_module (shared)
authn_core_module (shared)
authn_dbd_module (shared)
authn_dbm_module (shared)
authn_file_module (shared)
authn_socache_module (shared)
authz_core_module (shared)
authz_dbd_module (shared)
authz_dbm_module (shared)
authz_groupfile_module (shared)
authz_host_module (shared)
authz_owner_module (shared)
authz_user_module (shared)
autoindex_module (shared)
cache_module (shared)
cache_disk_module (shared)
cache_socache_module (shared)
data_module (shared)
dbd_module (shared)
deflate_module (shared)
dir_module (shared)
dumpio_module (shared)
echo_module (shared)
env_module (shared)
expires_module (shared)
ext_filter_module (shared)
filter_module (shared)
headers_module (shared)
http2_module (shared)
include_module (shared)
info_module (shared)
log_config_module (shared)
logio_module (shared)
macro_module (shared)
mime_magic_module (shared)
mime_module (shared)
negotiation_module (shared)
remoteip_module (shared)
reqtimeout_module (shared)
request_module (shared)
rewrite_module (shared)
setenvif_module (shared)
slotmem_plain_module (shared)
slotmem_shm_module (shared)
socache_dbm_module (shared)
socache_memcache_module (shared)
socache_shmcb_module (shared)
status_module (shared)
substitute_module (shared)
suexec_module (shared)
unixd_module (shared)
userdir_module (shared)
version_module (shared)
vhost_alias_module (shared)
watchdog_module (shared)
dav_module (shared)
dav_fs_module (shared)
dav_lock_module (shared)
lua_module (shared)
mpm_prefork_module (shared)
proxy_module (shared)
lbmethod_bybusyness_module (shared)
lbmethod_byrequests_module (shared)
lbmethod_bytraffic_module (shared)
lbmethod_heartbeat_module (shared)
proxy_ajp_module (shared)
proxy_balancer_module (shared)
proxy_connect_module (shared)
proxy_express_module (shared)
proxy_fcgi_module (shared)
proxy_fdpass_module (shared)
proxy_ftp_module (shared)
proxy_http_module (shared)
proxy_hcheck_module (shared)
proxy_scgi_module (shared)
proxy_uwsgi_module (shared)
proxy_wstunnel_module (shared)
ssl_module (shared)
php7_module (shared)
$ httpd -l
Compiled in modules:
core.c
mod_so.c
http_core.c
httpd/http.d/http.conf
<IfModule mpm_prefork_module>
StartServers 2
MinSpareServers 2
MaxSpareServers 4
MaxRequestWorkers 10
MaxConnectionsPerChild 1
</IfModule>