Santhosh Annira wrote:
> Craig,
>
> I feel that, running separate JVMs is an overkill, and it defeats the whole
> idea behind using servlets instead of old fashioned CGI processes. JVMs have
> considerable startup time
When running Apache JServ with separate JVMs, you do this yourself, separate from the
web server. Typically, an ISP would start the JVM for each of their hosting customers
once, and it would stay running all the time. This is totally unlike CGI, where you
have to pay the process startup cost on every single request.
> and each JVM needs a separate port number.
With 63k of them available (you don't get to use ports < 1024 unless you're root), I
hardly think this is going to cause you any grief :-).
The port numbers required are also invisible to users of the servlet-based web sites,
since they are only for communication between Apache and the JVMs. These port numbers
are not visible in the URLs that people accessing the web sites use.
> Also, there
> could be a limit on the number of JVMs that you can run. JVMs are started when
> Apache server is started, and how do we decide how many to start initially (one
> per every user ?).
The separate-JVM-per-user approach is the most secure, but I have seen ISPs that offer
two-tiered prices -- a higher price for a separate JVM, or a lower price if you're
willing to share JVMs with other customers (each in their own zone), at the modest
risk that the other customers you are sharing with might cause you a problem (like
executing System.exit()). The sysadmin sets up separate JVMs or not based on customer
request, just like they set up DNS entries, mailboxes, virtual hosts, database
connections, and everything else uniquely per customer. If they are doing it a lot,
they've got scripts to do all the grunt work.
The Apache JServ zone approach also allows you to run the JVMs on separate servers, if
you want. At the cost of hardware nowdays, it's not that tough to get real quick
paybacks on the hardware investment required for this.
Note also that heavily used CGI-based apps on shared servers have memory-usage impacts
as well ... different ones, but still real.
> Only Apache servlet engine is free. For JRUN, the amount that
> you pay, depends on the number of JVMs that you wish to run. WebSphere lets you run
> only one JVM per machine.
>
The only reason I bothered to respond to your initial comments at all was to point out
the incorrectness of your blanket assertions about zones. If you like CGI, then by
all means stay with it ... but my apps, even in shared environments, are going to be
servlet+JSP based.
>
> cheers
> Santhosh
>
Craig
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