Apache: fall-back mechanism

 

This is the recent requirement that i had faced w.r.t. virtual hosts.

1. at a given location see if the static resource exist
2. if it exist then serve form that location
3. otherwise fallback to a default location

after a day of investigation… this was the solution i finally discovered

 

NameVirtualHost *:81

#telling virtual host to listen on this port
<VirtualHost *:81> 
    ErrorLog logs/rewrite-log 
    CustomLog logs/rewrite-log combined 
    DocumentRoot E:/proj/nono2_2_10_3/config/
    LogLevel debug
    
    <IfModule rewrite_module> 
        RewriteLog logs/rewrite.log 
        RewriteLogLevel 3
    </IfModule> 

    RewriteEngine on    
    

    #if the file at the below path doesnt exist then the rule applies. Both these are part of the same rule
    RewriteCond %{DOCUMENT_ROOT}httpd/templates-mobile/js/$3 !-f

    #rule is to serve the files from default templates folder and skip the next rule (see s=1). Make this rule as the last rule(see L)

    #note the $1,$2,$3 are interpreted from he below rule. Each ‘()’ represents $n. where n increments per bracket

    # the above rewriteCond take $1,2,3 from this rule below
    RewriteRule ^(/ui)(/tpl/js)(.+)$ %{DOCUMENT_ROOT}httpd/templates/js/$3 [L,S=1]

    #serve from templates-mobile folder     
    RewriteRule ^(/ui)(/tpl/js)(.+)$ %{DOCUMENT_ROOT}httpd/templates-mobile/js/$3 [L]
        
</VirtualHost> 

Hope this helps somebody…

Configure Apache

We can use apache to serve static resource; infact apache is meant for this. Apache can cache data so that accessing resources is very quick. Proxy pass is the best way to do this.

<VirtualHost *:80>
    ServerAdmin abc@y.com
    DocumentRoot /root/cacheContent
<IfModule rewrite_module>
    RewriteLog logs/rewrite.log
    RewriteLogLevel 3
</IfModule>

ProxyRequests off
ProxyPass  /context/css/ !
ProxyPass /context/ http://10.10.11.176:8080/backendContext/
ProxyPassReverse /context/ http://10.10.11.176:8080/backendContext/

CacheEnable disk /
CacheEnable mem /

<IfModule mod_cache.c>
<IfModule mod_disk_cache.c>
        CacheRoot /root/cacheContent/
        CacheEnable disk /
</IfModule>
</IfModule>

</VirtualHost>

So this is how it works. When ever u get /context on this ip send it to 10.10.11.176/backendContext. When ever u have static resources dont get it from the bakendContext. So in this case it gets it from /root/cacheContext/.