如何使mod_cache与动态内容一起正常工作？

Question

I'm trying to use mod_cache to cache dynamically generated content. This is my Apache config:

CacheEnable mem /
MCacheSize 4096
MCacheMaxObjectCount 100
MCacheMinObjectSize 1
MCacheMaxObjectSize 2048
CacheIgnoreCacheControl On
CacheIgnoreNoLastMod On
CacheStorePrivate On
CacheStoreNoStore On

<Location /cgi-bin>
    SetHandler cgi-script
    Options +ExecCGI
</Location>

And this is one CGI script (just for testing):

#!/opt/app/phantomjs/bin/phantomjs
var date = new Date('Sun, 01 Jan 2012 00:00:00 GMT');
console.log('Last-Modified: '+ date.toUTCString());
console.log('Cache-Control: max-age=' + (365 * 24 * 60 * 60)+ ', public');
date.setDate(date.getDate() + 365);
console.log('Expires: '+ date.toUTCString() + '\n\n');

// lengthy operation here...

console.log(content);

This basically works. But what happens is if a client requests a cgi-bin with an If-Modified-Since header:

1. CGI-script streams headers
2. some seconds delay
3. CGI-script streams body
4. Apache sends 304

That makes no sense to me. Apache waits for the whole response before it sends a not-modified response.

What I expected :

1. CGI-script streams headers
2. Apache sends 304
3. CGI-script is canceled or body of CGI-script is discarded

Is there any way to get it done?

Answer 1

The CGI script should be changed as follows.

1. Don't use a static Last-modified date. The Last-Modified should be set for dynamic resources to the current execution time.

2. Cache Control directive contains a type error 'pulic' should be 'public'

3. Expires directive is not needed, because Cache-Control has a higher priority than Expires.

Your expected behavior "terminate CGI script" after sending header is not possible. If your cache works, the CGI script is not executed until the cache entry is invalidated.

Answer 2

This is the solution i'm talking in my last comment. Forward the CGI execution to an internal virtual host. With this configuration mod_cache will work as expected. I tested it on my machine with apache 2.2.21.

# virtual cgi host - used internally only for cgi execution
<VirtualHost *:8080>
    ##ServerAdmin postmaster@dummy-host.localhost
    DocumentRoot "C:/Project/web"
    ServerName cgi-bin.local
    ErrorLog "logs/cgi-bin-error.log"
    CustomLog "logs/cgi-bin-access.log" combined
    LogLevel debug

    <Location /cgi-bin>
        SetHandler cgi-script
        Options +ExecCGI
    </Location>

</VirtualHost>

# Virtual host used by client
<VirtualHost *:8080>
    ##ServerAdmin postmaster@dummy-host.localhost
    DocumentRoot "C:/Project/web"
    ServerName web.local
    ErrorLog "logs/web-error.log"
    CustomLog "logs/web-access.log" combined

    CacheEnable mem /
    MCacheSize 4096
    MCacheMaxObjectCount 100
    MCacheMinObjectSize 50
    MCacheMaxObjectSize 20480
    MCacheMaxStreamingBuffer 20480
    CacheIgnoreCacheControl On
    CacheIgnoreNoLastMod On
    CacheStorePrivate On
    CacheStoreNoStore On

    ProxyRequests Off
    ProxyPass /cgn-bin http://cgi-bin.local:8080/
    ProxyPassReverse /cgn-bin http://cgi-bin.local:8080/

</VirtualHost>