Metacat

/**

 *  '$RCSfile$'

 *    Purpose: A Class that implements replication for metacat

 *  Copyright: 2000 Regents of the University of California and the

 *             National Center for Ecological Analysis and Synthesis

 *    Authors: Chad Berkley

 *    Release: @release@

 *

 *   '$Author: berkley $'

 *     '$Date: 2000-11-16 15:26:00 -0800 (Thu, 16 Nov 2000) $'

 * '$Revision: 549 $'

 */

package edu.ucsb.nceas.metacat;

import java.util.*;

import java.io.*;

import java.sql.*;

import java.net.*;

import java.lang.*;

import java.text.*;

import javax.servlet.*;

import javax.servlet.http.*;

import oracle.xml.parser.v2.*;

import org.xml.sax.*;

public class MetacatReplication extends HttpServlet

{  

  private String deltaT;

  Timer replicationDaemon;

  MetaCatUtil util = new MetaCatUtil();

  /**

   * Initialize the servlet by creating appropriate database connections

   */

  public void init(ServletConfig config) throws ServletException 

  {

    //initialize db connections to handle any update requests

    MetaCatUtil util = new MetaCatUtil();

    deltaT = util.getOption("deltaT");

    //break off a thread to do the delta-T check

    replicationDaemon = new Timer(true);

    //replicationDaemon.scheduleAtFixedRate(new replicationHandler(), 0, 

    //                                      new Integer(deltaT).intValue() * 1000);

    //System.out.println("timer scheduled at: " + new Integer(deltaT).intValue() 

    //                   + " seconds");

  }

  public void destroy() 

  {

    replicationDaemon.cancel();

    System.out.println("Replication daemon cancelled.");

  }

  public void doGet (HttpServletRequest request, HttpServletResponse response)

                     throws ServletException, IOException 

  {

    // Process the data and send back the response

    handleGetOrPost(request, response);

  }

  public void doPost(HttpServletRequest request, HttpServletResponse response)

                     throws ServletException, IOException 

  {

    // Process the data and send back the response

    handleGetOrPost(request, response);

  }

  private void handleGetOrPost(HttpServletRequest request, 

                               HttpServletResponse response) 

                               throws ServletException, IOException 

  {

    PrintWriter out = response.getWriter();

    Hashtable params = new Hashtable();

    Enumeration paramlist = request.getParameterNames();

    while (paramlist.hasMoreElements()) 

    {

      String name = (String)paramlist.nextElement();

      String[] value = request.getParameterValues(name);

      params.put(name, value);  

    }

    if(params.containsKey("action"))

    {

      if(((String[])params.get("action"))[0].equals("stop"))

      { //stop the replication server

        replicationDaemon.cancel();

        out.println("Replication Handler Stopped");

      }

      else if(((String[])params.get("action"))[0].equals("start"))

      { //start the replication server

        int rate;

        if(params.containsKey("rate"))

        {

          rate = new Integer(

                 new String(((String[])params.get("rate"))[0])).intValue();

          if(rate < 30)

          {

            out.println("Replication deltaT rate cannot be less than 30!");

            rate = 1000;

          }

        }

        else

        {

          rate = 1000;

        }

        out.println("New rate is: " + rate + " seconds.");

        replicationDaemon.cancel();

        replicationDaemon = new Timer(true);

        replicationDaemon.scheduleAtFixedRate(new ReplicationHandler(out), 0, 

                                              rate * 1000);

        out.println("Replication Handler Started");

      }

      else if(((String[])params.get("action"))[0].equals("update"))

      { //request an update list from the server

        handleUpdateRequest(out, params, response);

      }

      else if(((String[])params.get("action"))[0].equals("getdocument"))

      { //request a specific document from the server

        //note that this could be replaced by a call to metacatServlet

        //handleGetDocumentAction().

        handleGetDocumentRequest(out, params, response);

      }

    }

  }

  private void handleGetDocumentRequest(PrintWriter out, Hashtable params, 

                                   HttpServletResponse response)

  {

    try

    {

      String docid = ((String[])(params.get("docid")))[0];

      System.out.println("incoming get request for document: " +

                         docid);

      Connection conn = util.openDBConnection();

      DocumentImpl di = new DocumentImpl(conn, docid);

      response.setContentType("text/xml");

      out.print(di.toString());

      conn.close();

    }

    catch(Exception e)

    {

      System.out.println("error getting document: " + e.getMessage());

    }

  }

  private void handleUpdateRequest(PrintWriter out, Hashtable params, 

                                   HttpServletResponse response)

  {

    System.out.println("incoming update request for dt/time " + 

                       ((String[])params.get("date"))[0] +

                       " from external metacat");

    response.setContentType("text/xml");

    StringBuffer returnXML = new StringBuffer();

    returnXML.append("<?xml version=\"1.0\"?><replication>");

    StringBuffer sql = new StringBuffer();

    String updateStr = ((String[])params.get("date"))[0];

    updateStr = updateStr.replace('+', ' ');

    //pseudo algorithm:

    ///////////////////////////////////////////////////////////////////////

    //get the date/time from the requestor, query the db for any documents

    //that have an update date later than the requested date and send

    //those docids back to the requestor.  If there are no newer documents

    //then send back a null message.

    ///////////////////////////////////////////////////////////////////////

    //Timestamp update = Timestamp.valueOf(updateStr);

    SimpleDateFormat formatter = new SimpleDateFormat ("yy-MM-dd HH:mm:ss");

    java.util.Date update = new java.util.Date();

    ParsePosition pos = new ParsePosition(0);

    update = formatter.parse(updateStr, pos);

    //update = new java.util.Date(update.getTime() - 10000);

    String dateString = formatter.format(update);

    sql.append("select docid, date_updated, server_location from ");

    sql.append("xml_documents where date_updated > ");

    sql.append("to_date('").append(dateString).append("','YY-MM-DD HH24:MI:SS')");

    //System.out.println("sql: " + sql.toString());

    try

    {

      Connection conn = util.openDBConnection();

      PreparedStatement pstmt = conn.prepareStatement(sql.toString());

      pstmt.execute();

      ResultSet rs = pstmt.getResultSet();

      boolean tablehasrows = rs.next();

      //if a '1' should not represent localhost, add code here to query

      //xml_replication for the proper serverid number

      returnXML.append("<server>").append(util.getOption("server"));

      returnXML.append(util.getOption("replicationpath"));

      returnXML.append("</server><updates>");

      while(tablehasrows)

      {

        String docid = rs.getString(1);

        String dateUpdated = rs.getString(2);

        int serverCode = rs.getInt(3);

        if(serverCode == 1)

        { //check that this document is from this server.

          //servers only replicate their own documents!

          returnXML.append("<updatedDocument><docid>").append(docid);

          returnXML.append("</docid><date_updated>").append(dateUpdated);

          returnXML.append("</date_updated></updatedDocument>");

        }

        tablehasrows = rs.next();

      }

      returnXML.append("</updates></replication>");

      conn.close();

      //System.out.println(returnXML.toString());

      out.print(returnXML.toString());

    }

    catch(Exception e)

    {

      System.out.println("Exception in metacatReplication: " + e.getMessage());

    }

  }

}