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When tried to open multiple pages from Codeigniter based custom CMS on different tabs, the first tab loads, while the subsequent tabs wait for the first tab to complete, then sequence follows randomly, which is in synchronous. How do I bring in asynchronous loading, i.e., load all the tabs without a wait. I am a developer, trying to figure out this from a long time.

Suspect, due to a webserver misconfiguration, It is not serving multiple request at a time, the same applies to static/database-free content too.

Hardware

Intel(R) Xeon(R) CPU X5650  @ 2.67GHz
20GB RAM

MPM for Httpd

source /etc/apache2/envvars; httpd -V

Server version: Apache/2.2.15 (Unix)
Server built:   Aug 13 2013 17:29:28
Server's Module Magic Number: 20051115:25
Server loaded:  APR 1.3.9, APR-Util 1.3.9
Compiled using: APR 1.3.9, APR-Util 1.3.9
Architecture:   64-bit
Server MPM:     Prefork
  threaded:     no
    forked:     yes (variable process count)
Server compiled with....
 -D APACHE_MPM_DIR="server/mpm/prefork"
 -D APR_HAS_SENDFILE
 -D APR_HAS_MMAP
 -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
 -D APR_USE_SYSVSEM_SERIALIZE
 -D APR_USE_PTHREAD_SERIALIZE
 -D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
 -D APR_HAS_OTHER_CHILD
 -D AP_HAVE_RELIABLE_PIPED_LOGS
 -D DYNAMIC_MODULE_LIMIT=128
 -D HTTPD_ROOT="/etc/httpd"
 -D SUEXEC_BIN="/usr/sbin/suexec"
 -D DEFAULT_PIDLOG="run/httpd.pid"
 -D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
 -D DEFAULT_LOCKFILE="logs/accept.lock"
 -D DEFAULT_ERRORLOG="logs/error_log"
 -D AP_TYPES_CONFIG_FILE="conf/mime.types"
 -D SERVER_CONFIG_FILE="conf/httpd.conf"

/etc/httpd/conf/httpd.conf

ServerTokens OS
ServerRoot "/etc/httpd"
PidFile run/httpd.pid
Timeout 60
KeepAlive Off
MaxKeepAliveRequests 100
KeepAliveTimeout 15

<IfModule prefork.c>
StartServers       50
MinSpareServers    5
MaxSpareServers   20
ServerLimit      3072
MaxClients       3072
MaxRequestsPerChild  4000
</IfModule>

<IfModule worker.c>
StartServers         4
MaxClients         300
MinSpareThreads     25
MaxSpareThreads     75 
ThreadsPerChild     25
MaxRequestsPerChild  0
</IfModule>

Listen 80
LoadModule auth_basic_module modules/mod_auth_basic.so
LoadModule auth_digest_module modules/mod_auth_digest.so
LoadModule authn_file_module modules/mod_authn_file.so
LoadModule authn_alias_module modules/mod_authn_alias.so
LoadModule authn_anon_module modules/mod_authn_anon.so
LoadModule authn_dbm_module modules/mod_authn_dbm.so
LoadModule authn_default_module modules/mod_authn_default.so
LoadModule authz_host_module modules/mod_authz_host.so
LoadModule authz_user_module modules/mod_authz_user.so
LoadModule authz_owner_module modules/mod_authz_owner.so
LoadModule authz_groupfile_module modules/mod_authz_groupfile.so
LoadModule authz_dbm_module modules/mod_authz_dbm.so
LoadModule authz_default_module modules/mod_authz_default.so
LoadModule ldap_module modules/mod_ldap.so
LoadModule authnz_ldap_module modules/mod_authnz_ldap.so
LoadModule include_module modules/mod_include.so
LoadModule log_config_module modules/mod_log_config.so
LoadModule logio_module modules/mod_logio.so
LoadModule env_module modules/mod_env.so
LoadModule ext_filter_module modules/mod_ext_filter.so
LoadModule mime_magic_module modules/mod_mime_magic.so
LoadModule expires_module modules/mod_expires.so
LoadModule deflate_module modules/mod_deflate.so
LoadModule headers_module modules/mod_headers.so
LoadModule usertrack_module modules/mod_usertrack.so
LoadModule setenvif_module modules/mod_setenvif.so
LoadModule mime_module modules/mod_mime.so
LoadModule dav_module modules/mod_dav.so
LoadModule status_module modules/mod_status.so
LoadModule autoindex_module modules/mod_autoindex.so
LoadModule info_module modules/mod_info.so
LoadModule dav_fs_module modules/mod_dav_fs.so
LoadModule vhost_alias_module modules/mod_vhost_alias.so
LoadModule negotiation_module modules/mod_negotiation.so
LoadModule dir_module modules/mod_dir.so
LoadModule actions_module modules/mod_actions.so
LoadModule speling_module modules/mod_speling.so
LoadModule userdir_module modules/mod_userdir.so
LoadModule alias_module modules/mod_alias.so
LoadModule substitute_module modules/mod_substitute.so
LoadModule rewrite_module modules/mod_rewrite.so
LoadModule cache_module modules/mod_cache.so
LoadModule suexec_module modules/mod_suexec.so
LoadModule disk_cache_module modules/mod_disk_cache.so
LoadModule cgi_module modules/mod_cgi.so
LoadModule version_module modules/mod_version.so

Include conf.d/*.conf
ExtendedStatus On
User apache
Group apache
ServerAdmin root@localhost
ServerName new.ibtimes.co.in:80
UseCanonicalName Off
DocumentRoot "/var/www/html"

<Directory />
Options FollowSymLinks
AllowOverride None
</Directory>
<Directory "/var/www/html">
Options Indexes FollowSymLinks
AllowOverride None
Order allow,deny
Allow from all
</Directory>

<IfModule mod_userdir.c>
UserDir disabled
</IfModule>

DirectoryIndex index.html index.html.var
AccessFileName .waccess
<Files ~ "^\.ht">
Order allow,deny
Deny from all
Satisfy All
</Files>

TypesConfig /etc/mime.types
DefaultType text/plain
<IfModule mod_mime_magic.c>
MIMEMagicFile conf/magic
</IfModule>

HostnameLookups Off
ErrorLog /data/log/httpd/error_log
LogLevel warn
LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
LogFormat "%h %l %u %t \"%r\" %>s %b" common
LogFormat "%{Referer}i -> %U" referer
LogFormat "%{User-agent}i" agent
CustomLog logs/access_log combined
ServerSignature On
Alias /icons/ "/var/www/icons/"

<Directory "/var/www/icons">
Options Indexes MultiViews FollowSymLinks
AllowOverride None
Order allow,deny
Allow from all
</Directory>

<IfModule mod_dav_fs.c>
DAVLockDB /var/lib/dav/lockdb
</IfModule>
ScriptAlias /cgi-bin/ "/var/www/cgi-bin/"
<Directory "/var/www/cgi-bin">
AllowOverride None
Options None
Order allow,deny
Allow from all
</Directory>

IndexOptions FancyIndexing VersionSort NameWidth=* HTMLTable Charset=UTF-8
AddIconByEncoding (CMP,/icons/compressed.gif) x-compress x-gzip
AddIconByType (TXT,/icons/text.gif) text/*
AddIconByType (IMG,/icons/image2.gif) image/*
AddIconByType (SND,/icons/sound2.gif) audio/*
AddIconByType (VID,/icons/movie.gif) video/*
AddIcon /icons/binary.gif .bin .exe
AddIcon /icons/binhex.gif .hqx
AddIcon /icons/tar.gif .tar
AddIcon /icons/world2.gif .wrl .wrl.gz .vrml .vrm .iv
AddIcon /icons/compressed.gif .Z .z .tgz .gz .zip
AddIcon /icons/a.gif .ps .ai .eps
AddIcon /icons/layout.gif .html .shtml .htm .pdf
AddIcon /icons/text.gif .txt
AddIcon /icons/c.gif .c
AddIcon /icons/p.gif .pl .py
AddIcon /icons/f.gif .for
AddIcon /icons/dvi.gif .dvi
AddIcon /icons/uuencoded.gif .uu
AddIcon /icons/script.gif .conf .sh .shar .csh .ksh .tcl
AddIcon /icons/tex.gif .tex
AddIcon /icons/bomb.gif core
AddIcon /icons/back.gif ..
AddIcon /icons/hand.right.gif README
AddIcon /icons/folder.gif ^^DIRECTORY^^
AddIcon /icons/blank.gif ^^BLANKICON^^
DefaultIcon /icons/unknown.gif
ReadmeName README.html
HeaderName HEADER.html
AddLanguage ca .ca
AddLanguage cs .cz .cs
AddLanguage da .dk
AddLanguage de .de
AddLanguage el .el
AddLanguage en .en
AddLanguage eo .eo
AddLanguage es .es
AddLanguage et .et
AddLanguage fr .fr
AddLanguage he .he
AddLanguage hr .hr
AddLanguage it .it
AddLanguage ja .ja
AddLanguage ko .ko
AddLanguage ltz .ltz
AddLanguage nl .nl
AddLanguage nn .nn
AddLanguage no .no
AddLanguage pl .po
AddLanguage pt .pt
AddLanguage pt-BR .pt-br
AddLanguage ru .ru
AddLanguage sv .sv
AddLanguage zh-CN .zh-cn
AddLanguage zh-TW .zh-tw
LanguagePriority en ca cs da de el eo es et fr he hr it ja ko ltz nl nn no pl pt pt-BR ru sv zh-CN zh-TW
ForceLanguagePriority Prefer Fallback
AddDefaultCharset UTF-8
AddType application/x-compress .Z
AddType application/x-gzip .gz .tgz
AddType application/x-x509-ca-cert .crt
AddType application/x-pkcs7-crl    .crl
AddHandler type-map var
AddType text/html .shtml
AddOutputFilter INCLUDES .shtml
Alias /error/ "/var/www/error/"

<IfModule mod_negotiation.c>
<IfModule mod_include.c>
<Directory "/var/www/error">
AllowOverride None
Options IncludesNoExec
AddOutputFilter Includes html
AddHandler type-map var
Order allow,deny
Allow from all
LanguagePriority en es de fr
ForceLanguagePriority Prefer Fallback
</Directory>
</IfModule>
</IfModule>

BrowserMatch "Mozilla/2" nokeepalive
BrowserMatch "MSIE 4\.0b2;" nokeepalive downgrade-1.0 force-response-1.0
BrowserMatch "RealPlayer 4\.0" force-response-1.0
BrowserMatch "Java/1\.0" force-response-1.0
BrowserMatch "JDK/1\.0" force-response-1.0
BrowserMatch "Microsoft Data Access Internet Publishing Provider" redirect-carefully
BrowserMatch "MS FrontPage" redirect-carefully
BrowserMatch "^WebDrive" redirect-carefully
BrowserMatch "^WebDAVFS/1.[0123]" redirect-carefully
BrowserMatch "^gnome-vfs/1.0" redirect-carefully
BrowserMatch "^XML Spy" redirect-carefully
BrowserMatch "^Dreamweaver-WebDAV-SCM1" redirect-carefully

<Location /server-status>
SetHandler server-status
Order deny,allow
Deny from all
Allow from .example.com
Allow from 10.0.100.30
Allow from xx.xx.xx.xx
</Location>

Apache Benchmarking test results: # ab -n 100 -c 4

Server Software:        Apache/2.2.15
Server Hostname:        xxx
Server Port:            80

Document Path:          /index.php
Document Length:        122787 bytes

Concurrency Level:      4
Time taken for tests:   36.686 seconds
Complete requests:      100
Failed requests:        0
Non-2xx responses:      100
Total transferred:      12329900 bytes
HTML transferred:       12278700 bytes
Requests per second:    2.73 [#/sec] (mean)
Time per request:       1467.428 [ms] (mean)
Time per request:       366.857 [ms] (mean, across all concurrent requests)
Transfer rate:          328.22 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.1      0       1
Processing:  1079 1451 322.7   1531    2927
Waiting:      434  453  34.3    449     742
Total:       1079 1452 322.7   1532    2927

Percentage of the requests served within a certain time (ms)
  50%   1532
  66%   1559
  75%   1579
  80%   1602
  90%   1778
  95%   1987
  98%   2345
  99%   2927
 100%   2927 (longest request)
  • Your configuration looks okay to me. I think you've jumped the gun thinking this is a server problem. Most web browsers have a limit on how many connections they will make to the same server at once. Opening more than one tab doesn't change that. Try two separate browsers (not separate windows, separate browsers). – yoonix Sep 5 '14 at 22:18
  • @yoonix I have tried them on two separate browsers-chrome & Firefox(My users use only these 2 browsers). Its still the same!! However, the same codebase when replicated on a Apache server with default config, does not wait. – nuthan Sep 6 '14 at 8:37
  • To rule out browser artefacts, use the Apache benchmarking tool "ab" to diagnose your problem, e.g. with "-c 4". Also, let people know which MPM your Apache is using (on my Ubuntu: source /etc/apache2/envvars; apache2 -V) – Nils Toedtmann Sep 9 '14 at 8:03
  • @NilsToedtmann Updated ab diagnostic results with "-c 4" and added MPM en-vars too. I don't get the problem yet. – nuthan Sep 9 '14 at 15:12
  • When you say you tried it in two browsers, do you mean "I opened 2 tabs in firefox. Then I tried 2 tabs in chrome", or do you mean "I opened one tab in firefox and one in chrome at the same time"? To see if its a browser issue you need to try the latter. – Grant Sep 9 '14 at 15:14
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Try editing /etc/sysctl.conf, with the following values:

net.ipv4.ip_local_port_range = 1024 65000
net.ipv4.tcp_rmem = 4096 87380 8388608
net.ipv4.tcp_keepalive_time = 30
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_syncookies = 1
net.ipv4.tcp_fin_timeout = 20
net.ipv4.tcp_max_syn_backlog = 20480
net.core.netdev_max_backlog = 4096
net.ipv4.tcp_max_tw_buckets = 400000
net.core.somaxconn = 4096

Then save and issue as root: # sysctl -p

Test again.

0

Its been a long time since this question was asked, but I was able to solve it by closing the session before the end of script execution.

I had a session_start() in my header, and it was not closed. I closed it at the end of the header using session_write_close()

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