Re: very much a newbie design issue...

[Srinivasan S (Systems Engineering Group)]

Exactly this is what i am thinking for, all the example in the books and
articles are static meaning only 20 or 30 connections are created just
imagine a html form consists of nearly 30 columns and the user fills those
columns after he press the submit button being 31st client in the pool he
will get an error, instead this client shall be made wait till a
connection is free in this pool.  My question is that i am running a
thread in my code which checks for any free connection and wait if not.
Another method provides connection to the user, if i call the connection
method from another code what will happen if no connection available.
for example:

Connectionpool.java

public void run()
{
    while(true)
    {
        try
        {
                synchronized(con)
                {
                        Connection con1 = (Connection)pool.pop();
                        if con1 == null
                                thread.wait();
                }
        }

    }
}

Public Connection getConnection
{
        Connection c1 = (Connection)pool.pop();
}

Public void releaseConnection
{
        thread.notify();

}

Another method named Client.java
================================

Connectionpool cp = new Connectionpool()
cp.getConenction();

I need to know what exactly will happen now if no connection is available
in the pool wil this cp.getConnection will return a Connection object or
not??

Folks any comments/suggestions to this one.

Thanks
Srini

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On Fri, 20 Aug 1999, peter greaves wrote:

> hi
>
> i've have my first simple JDBC servlet working and it's ok but it won't
> scale.  i read about connection pooling and looked at the global broker
> stuff, but i wondered if i could use a schema like this to make the  whole
> process more scalable.  any comments gratefully received!!!!
>
> 1. Use a Connection Manager and event model
>
> Seems to me that servlet incurs much of its overhead if it needs to make a
> connection to its query target each time it is called.  It is better to
> create a single static Connection Manager object (created in the init()
> method of the servlet when the web server's Servlet Manager starts up) which
> establishes a pool of connections and allocates them on demand to worker
> threads (see below) as "real" user requests come in.  There are a number of
> downloadable Connection managers classes which can be used for this purpose.
>   Here's a bit of a thinking-out-loud about how it would work.
>
> The Connection manager's job is to maintain a free pool, keep track of
> allocated conenctions, and maybe expand the pool if necessary using some
> %age free algorithm, report errors in the connection layer etc.  An
> event-based model seems useful for connecting the Connection Manager (as a
> server) to its worker threads (the clients).  When the servlet's destroy()
> method is called, a servletClosing event should be fired which will cause
> the Connection Manager to repeatedly try to close its free connections, and
> not respond to "connectionRequested" events.  This will mean that existing
> queries will be honoured, but no new ones can be created.
>
> 2.  Use Java Threading and separate worker threads for processing queries.
>
> The servlet class should maybe just create a new worker thread to handle
> each request and then go back to listening for requests. The worker should
> fire an "connectionRequested" event, which the ConnectionManager is
> listening for.  The Connection manager will reply with a Connection object
> The worker will run the query, and fire a "connectionFree" event (which
> causes the Connection manager to return the connection to the pool), deposit
> the result set wrapped in (probably) HTML on a stack and fire a
> readytoShipToClient event for which another thread is listening - this
> thread can serve the results back to the client.
>
> what do folk think?  am i overthreading? :)  obv. i want to get the design
> right at the outset.  btw, i'm running on Domino R5.
>
> peter
>
>
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