Slug - The Slow Web Processes Manager

Jumpstart HowTo

To implement Slug based web process monitoring an application needs to implement the following steps:

  1. Add Slug servlet and session listener to the web application deployment descriptor web.xml:

    2. <?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
 xmlns="http://java.sun.com/xml/ns/j2ee"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
 	...
    <!-- Slug session cleaner -->
    <listener>
        <description>HttpSessionListener</description>
        <listener-class>com.webhydra.slug.SlugCleaner</listener-class>
    </listener>
    <!-- End Slug session cleaner -->
	 ...
    <!-- Slug servlet definition -->
    <servlet>
        <servlet-name>SlugServlet</servlet-name>
        <servlet-class>com.webhydra.slug.Slug</servlet-class>
        <init-param>
            <description>Configurations file with the runners and translators definitions.</description>
            <param-name>config</param-name>
            <param-value>/WEB-INF/slug.properties</param-value>
        </init-param>
        <init-param>
            <description>Configurations file parser (ISlugConfigParser) class implementation.</description>
            <param-name>parser</param-name>
            <param-value>com.webhydra.slug.PropertiesConfigParser</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
	 ...
    <servlet-mapping>
        <servlet-name>SlugServlet</servlet-name>
        <url-pattern>/slug/*</url-pattern>
    </servlet-mapping>
    <!-- End Slug servlet definition -->
	 ...
</web-app>


  2. Create conficurations file /WEB-INF/slug.properties from sterp one:

    3. # Define a runner
slug.runners=unlimited
# runner's class implementation
slug.runner[unlimited].impl=com.webhydra.slug.process.UnlimitedProcessRunner

# Define a translator
slug.translators=js
# translator's class implementation
slug.translator[js].impl=com.webhydra.slug.process.javascript.JavaScriptProcessStatusTranslator


    Multiple runners and translators can be defined as in the following example:

    # Define multiple translators
slug.translators=xml-xsd,xml-dtd,js
# translator's class implementations
slug.translator[xml-xsd].impl=com.webhydra.slug.process.xml.XmlXsdProcessStatusTranslator
slug.translator[xml-dtd].impl=com.webhydra.slug.process.xml.XmlDtdProcessStatusTranslator
slug.translator[js].impl=com.webhydra.slug.process.javascript.JavaScriptProcessStatusTranslator


  3. Define "slow" process implementation by extending com.webhydra.slug.process.SluggishProcess class:

    4. package demo;

import com.webhydra.slug.process.ProcessProgress;
import com.webhydra.slug.process.ProcessStatus;
import com.webhydra.slug.process.SluggishProcess;
import com.webhydra.slug.process.Status;

/**
 * Sluggish process for demo purposes.
 */
public class MySluggishPorcess extends SluggishProcess {

    /**
     * Simple SluggishProcess implementation.
     */
    public ProcessStatus execute() throws InterruptedException {
        // reprot process as started.
        setProcessStatus(new ProcessProgress(Status.RUNNING, "Started.", 0));
		  doSomething();
        setProcessStatus(new ProcessProgress(Status.RUNNING, "Task one done.", 30));
		  doSomethingElse();
        setProcessStatus(new ProcessProgress(Status.RUNNING, "Task two done.", 80));
		  doSomethingMore();
        return new ProcessProgress(Status.COMPLETED, "Done!", 99);
    }
}


  4. Instantiate the "slow" process and obtain its PID and save it as request attribute:

    5. 	String pid = SlugHelper.runProcess(request, new MySluggishPorcess());
	request.setAttribute("pid", pid);

  5. Monitor the process using:
    1. AJAX:

      2. <%@page contentType="text/html" pageEncoding="UTF-8" %>
<%@taglib uri="http://dev.webhydra.com/jstl/slug.tld" prefix="slug" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<HTML>
  <HEAD>
    <TITLE>Simple process with simple status and JavaScript raw translator.</TITLE>
    <slug:script />
    <slug:manage pid="<%= request.getAttribute(pid) %>" url="/slug" translator="js">
        document.getElementById("prStatus").innerHTML = ps.toString();
    </slug:manage>
  </HEAD>
  <BODY>
    <CENTER>
        Simple status:</br>
        <DIV id="prStatus">Slug Status here</DIV>
    </CENTER>
  </BODY>
</HTML>


      The above example is extremely simplified. Please see provided demo application for more real life like implementations.

    2. Native JSP:

      3. <%@page contentType="text/html" pageEncoding="UTF-8"
import="com.webhydra.slug.*,com.webhydra.slug.process.*"
%>
<%@taglib uri="http://dev.webhydra.com/jstl/slug.tld" prefix="slug" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<HTML>
  <HEAD>
<%
  String pid = request.getParameter("pid");
  ProcessStatus ps = null;
  if (pid == null)
  {
  	// get new pid as request attribute
  	pid = request.getAttribute("pid");
  }
  // get Status
  Status s = null;
  ps = SlugHelper.getStatus(request, pid);
  if (ps != null)
  {
    s = ps.getStatus();
    if (Status.isCompleted(s))
    {
      // consume completed process
      SluggishProcess sp = SlugHelper.consumeProcess(request, pid);
    }
    else
    {
%>
    <!-- set refresh time to a second -->
    <META HTTP-EQUIV="refresh" CONTENT="1;url=my.jsp?pid=<%= pid %>">
<%
    }
  }
%>
    <TITLE>Simple process with simple status.</TITLE>
  </HEAD>
  <BODY>
    <CENTER>
        Simple status:</br>
        <%= s %>
    </CENTER>
  </BODY>
</HTML>


      The above example is extremely simplified. Please see provided demo application for more real life like implementations.

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