为什么使用 multi_curl 同时调用多个 php 脚本时脚本执行会有延迟？

Question

我有一个脚本可以同时调用大约 40 个单独的 php 脚本（位于同一台服务器上）。我注意到每个单独的 php 脚本的启动有长达 5 秒的延迟。服务器负载 CPU 和内存看起来不错，没有交换，请参阅 top 命令向下：

top - 22:32:36 up  1:06,  1 user,  load average: 0.18, 0.05, 0.01
Tasks: 181 total,   1 running, 179 sleeping,   0 stopped,   1 zombie
Cpu(s):  0.0%us,  0.5%sy,  0.0%ni, 99.5%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:   1048576k total,  1024144k used,    24432k free,    20160k buffers
Swap:  2097144k total,        0k used,  2097144k free,   352520k cached

循环中绑定所有对 multi_curl 的请求的最后一个脚本通常具有最大的延迟。我在每个脚本一开始就测量了延迟。

我能做些什么来防止这种延迟？

下面是我的 httpd.conf

#
# This is the main Apache HTTP server configuration file.  It contains the
# configuration directives that give the server its instructions.
# See <URL:http://httpd.apache.org/docs/2.2> for detailed information.
# In particular, see 
# <URL:http://httpd.apache.org/docs/2.2/mod/directives.html>
# for a discussion of each configuration directive.
#
# Do NOT simply read the instructions in here without understanding
# what they do.  They're here only as hints or reminders.  If you are unsure
# consult the online docs. You have been warned.  

ServerRoot "/etc/httpd"
Listen 80

#LoadModule dummy_module /usr/lib/apache/mod_dummy.so
#LoadModule php5_module        /usr/lib/apache/libphp5.so
Include /etc/httpd/conf/extra/httpd-phpmodules.conf

User apache
Group apache

KeepAlive On
KeepAliveTimeout 30

ServerAdmin admin@localhost
DocumentRoot "/var/www/html"

MaxClients 800
MaxRequestsPerChild 800

<Directory /home/*>
    AllowOverride All
    Options -MultiViews -Indexes FollowSymlinks IncludesNoExec +Includes
<Limit GET POST OPTIONS PROPFIND>
    Order allow,deny
    Allow from all
</Limit>
<LimitExcept GET POST OPTIONS PROPFIND>
    Order deny,allow
    Deny from all
</LimitExcept>
</Directory>

<Directory />
    Options All
    AllowOverride All
</Directory>

<Directory "/var/www/html">
    Options Indexes FollowSymLinks
    AllowOverride All
    Order allow,deny
    Allow from all
   <IfModule mod_suphp.c>
        suPHP_Engine On
        suPHP_UserGroup webapps webapps
    SetEnv PHP_INI_SCAN_DIR
   </IfModule>
</Directory>

<IfModule mod_dir.c>
    DirectoryIndex index.html index.htm index.shtml index.php index.php5 index.php4 index.php3 index.phtml index.cgi
</IfModule>

<FilesMatch "^\.ht">
    Order allow,deny
    Deny from all
    Satisfy All
</FilesMatch>

ErrorLog /var/log/httpd/error_log
LogLevel warn

#replace %b with %O for more accurate logging
<IfModule mod_logio.c>
    LogFormat "%h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" combined
    LogFormat "%h %l %u %t \"%r\" %>s %O" common
    LogFormat "%O %I" bytes
    LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\" %I %O" combinedio
</IfModule>

    CustomLog /var/log/httpd/access_log common

<IfModule mod_alias.c>
    # Include some DirectAdmin alias
    Include conf/extra/httpd-alias.conf
</IfModule>

<Directory "/var/www/cgi-bin">
    AllowOverride None
    Options None
    Order allow,deny
    Allow from all
</Directory>

DefaultType text/plain

<IfModule mod_mime.c>
    TypesConfig conf/mime.types
    AddType application/x-gzip .tgz
    AddEncoding x-compress .Z
    AddEncoding x-gzip .gz .tgz
    AddType application/x-compress .Z
    AddType application/x-gzip .gz .tgz
    AddHandler cgi-script .cgi
    AddHandler type-map var
    AddType text/html .shtml
    AddOutputFilter INCLUDES .shtml
    AddType video/x-ms-asf .avi
    AddType video/mpeg .mpg
    AddType video/mpeg .mpeg
    AddType video/quicktime .mov
    AddType video/x-ms-wmv .wmv
</IfModule>

#EnableMMAP off
#EnableSendfile off

#######################################################################################
# Do not change anything in included files, because they are rewritten by DirectAdmin #
#######################################################################################

# This is needed for PHP
Include conf/extra/httpd-php-handlers.conf

# Server-pool management (MPM specific)
Include conf/extra/httpd-mpm.conf

# Multi-language error messages
Include conf/extra/httpd-multilang-errordoc.conf

# Fancy directory listings
Include conf/extra/httpd-autoindex.conf

# Language settings
Include conf/extra/httpd-languages.conf

# User home directories
#Include conf/extra/httpd-userdir.conf

# Real-time info on requests and configuration
Include conf/extra/httpd-info.conf

# Virtual hosts
Include conf/extra/httpd-vhosts.conf

# Local access to the Apache HTTP Server Manual
#Include conf/extra/httpd-manual.conf

# Distributed authoring and versioning (WebDAV)
Include conf/extra/httpd-dav.conf

# Various default settings
Include conf/extra/httpd-default.conf

# Secure (SSL/TLS) connections
Include conf/extra/httpd-ssl.conf

# Deflate module settings
Include conf/extra/httpd-deflate.conf

# All the DirectAdmin vhosts
Include conf/extra/directadmin-vhosts.conf

# All suPHP directives
Include conf/extra/httpd-suphp.conf

# For user configurations not maintained by DirectAdmin. Empty by default.
Include conf/extra/httpd-includes.conf

#######################################################################################
# End of included files that are rewritten by DirectAdmin                             #
#######################################################################################

<IfModule mod_ssl.c>
SSLRandomSeed startup builtin
SSLRandomSeed connect builtin
</IfModule>

Answer 1

最常见的原因是调用脚本时出现阻塞。

这可能是 php 在 session-handler 中的构建，它阻止了对同一 session-id（关键字：race-conditions）的并发请求。如果这是您的问题并且您需要解决方案，您可以实现自己的会话处理程序，它以适合您的方式处理会话数据。

另一个原因可能是文件堆积或系统 IO 压力过大（例如慢速磁盘）。