You could launch each webapps initialization code in a separate thread.
Here is what we do. Our load is very heavy and our servers are
responsive after restart much sooner using this technique.
UniverseLoader.java:
package com.example;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.ServletException;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.Date;
public class UniverseLoader extends HttpServlet {
protected long timeLoaded;
public void init() throws ServletException {
new Thread(new LoadUniverseTask()).start();
}
public void doGet(HttpServletRequest request, HttpServletResponse
response) throws ServletException, IOException {
response.getWriter().println("Universe loaded: " + new
Date(timeLoaded));
}
public void loadUniverse() throws Exception {
long timeStart = System.currentTimeMillis();
// Your initialization code
long elapsed = (System.currentTimeMillis() - timeStart) / 1000;
log("Universe loaded: " + elapsed + " seconds");
timeLoaded = System.currentTimeMillis();
}
private class LoadUniverseTask implements Runnable {
public void run(){
try {
loadUniverse();
} catch(Exception e){
StringWriter msg = new StringWriter();
PrintWriter pout = new PrintWriter(msg);
e.printStackTrace(pout);
}
}
}
}
In WEB-INF/web.xml
<servlet>
<servlet-name>UniverseLoader</servlet-name>
<servlet-class>com.example.UniverseLoader</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>UniverseLoader</servlet-name>
<url-pattern>/loaduniverse</url-pattern>
</servlet-mapping>
Regards,
Dave
On Dec 10, 2009, at 5:34 PM, sh...@radiantblue.com wrote:
Thank you Chuck. That is exactly what I was looking for.
-------- Original Message --------
Subject: RE: Context Chicken & Egg Problem
From: "Caldarale, Charles R" <chuck.caldar...@unisys.com>
Date: Thu, December 10, 2009 6:24 pm
To: Tomcat Users List <users@tomcat.apache.org>
From: sh...@radiantblue.com [mailto:sh...@radiantblue.com]
Subject: RE: Context Chicken & Egg Problem
just a curiosity as to what is happening under the Tomcat
covers during this scenario.
Tomcat initialization is single-thread, so if webapp A happens to get
initialized before B, and the initialization thread running inside A
makes an HTTP request that targets a yet-to-be initialized webapp in
the
same Tomcat instance, you have a deadlock. Someday maybe, we'll see
multi-threaded initialization.
- Chuck
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