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/**
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* '$RCSfile$'
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* Purpose: A Class that implements replication for metacat
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* Copyright: 2000 Regents of the University of California and the
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* National Center for Ecological Analysis and Synthesis
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* Authors: Chad Berkley
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* Release: @release@
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*
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* '$Author: berkley $'
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* '$Date: 2000-12-06 13:26:52 -0800 (Wed, 06 Dec 2000) $'
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* '$Revision: 584 $'
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*/
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package edu.ucsb.nceas.metacat;
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import java.util.*;
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import java.io.*;
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import java.sql.*;
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import java.net.*;
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import java.lang.*;
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import java.text.*;
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import javax.servlet.*;
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import javax.servlet.http.*;
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import org.xml.sax.*;
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public class MetacatReplication extends HttpServlet implements Runnable
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{
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private String deltaT;
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Timer replicationDaemon;
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private static MetaCatUtil util = new MetaCatUtil();
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private Vector fileLocks = new Vector();
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private Thread lockThread = null;
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/**
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* Initialize the servlet by creating appropriate database connections
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*/
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public void init(ServletConfig config) throws ServletException
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{
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//initialize db connections to handle any update requests
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MetaCatUtil util = new MetaCatUtil();
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deltaT = util.getOption("deltaT");
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//the default deltaT can be set from metacat.properties
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//create a thread to do the delta-T check but don't execute it yet
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replicationDaemon = new Timer(true);
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}
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public void destroy()
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{
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replicationDaemon.cancel();
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System.out.println("Replication daemon cancelled.");
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}
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public void doGet (HttpServletRequest request, HttpServletResponse response)
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throws ServletException, IOException
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{
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// Process the data and send back the response
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handleGetOrPost(request, response);
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}
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public void doPost(HttpServletRequest request, HttpServletResponse response)
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throws ServletException, IOException
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{
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// Process the data and send back the response
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handleGetOrPost(request, response);
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}
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private void handleGetOrPost(HttpServletRequest request,
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HttpServletResponse response)
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throws ServletException, IOException
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{
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PrintWriter out = response.getWriter();
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Hashtable params = new Hashtable();
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Enumeration paramlist = request.getParameterNames();
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while (paramlist.hasMoreElements())
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{
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String name = (String)paramlist.nextElement();
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String[] value = request.getParameterValues(name);
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params.put(name, value);
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}
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if(params.containsKey("action"))
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{
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if(((String[])params.get("action"))[0].equals("stop"))
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{ //stop the replication server
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replicationDaemon.cancel();
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out.println("Replication Handler Stopped");
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System.out.println("Replication Handler Stopped");
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MetacatReplication.replLog("deltaT handler stopped");
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}
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else if(((String[])params.get("action"))[0].equals("start"))
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{ //start the replication server
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int rate;
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if(params.containsKey("rate"))
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{
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rate = new Integer(
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new String(((String[])params.get("rate"))[0])).intValue();
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if(rate < 30)
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{
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out.println("Replication deltaT rate cannot be less than 30!");
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//deltaT<30 is a timing mess!
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rate = 1000;
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}
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}
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else
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{
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rate = 1000;
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}
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out.println("New rate is: " + rate + " seconds.");
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replicationDaemon.cancel();
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replicationDaemon = new Timer(true);
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replicationDaemon.scheduleAtFixedRate(new ReplicationHandler(out), 0,
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rate * 1000);
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MetacatReplication.replLog("deltaT handler started with rate=" +
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rate + " seconds");
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out.println("Replication Handler Started");
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System.out.println("Replication Handler Started");
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}
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else if(((String[])params.get("action"))[0].equals("forcereplicate"))
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{
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handleForceReplicateRequest(out, params, response);
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}
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else if(((String[])params.get("action"))[0].equals("update"))
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{ //request an update list from the server
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handleUpdateRequest(out, params, response);
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}
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else if(((String[])params.get("action"))[0].equals("read"))
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{ //request a specific document from the server
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//note that this could be replaced by a call to metacatServlet
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//handleGetDocumentAction().
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handleGetDocumentRequest(out, params, response);
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}
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else if(((String[])params.get("action"))[0].equals("getlock"))
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{
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handleGetLockRequest(out, params, response);
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}
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else if(((String[])params.get("action"))[0].equals("getdocumentinfo"))
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{
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handleGetDocumentInfoRequest(out, params, response);
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}
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else if(((String[])params.get("action"))[0].equals("gettime"))
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{
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handleGetTimeRequest(out, params, response);
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}
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}
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}
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/**
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* when a forcereplication request comes in, this method sends a read request
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* to the requesting server for the specified docid.
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*/
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private void handleForceReplicateRequest(PrintWriter out, Hashtable params,
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HttpServletResponse response)
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{
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//System.out.println("in handleforcereplicaterequest");
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String server = ((String[])params.get("server"))[0];
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//the server that the request came from
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String docid = ((String[])params.get("docid"))[0];
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//the docid of the document to get
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String dbaction = "UPDATE";
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//default action is update
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boolean override = false;
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int serverCode = 1;
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try
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{
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if(params.containsKey("dbaction"))
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{ //if the url contains a dbaction then the default action is overridden
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dbaction = ((String[])params.get("dbaction"))[0];
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serverCode = MetacatReplication.getServerCode(server);
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override = true; //we are now overriding the default action
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}
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//System.out.println("action in forcereplicate is: " + dbaction);
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//System.out.println("serverCode in forcereplicate is: " + serverCode);
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MetacatReplication.replLog("force replication request from " + server);
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int serverCheckCode = MetacatReplication.getServerCode(server);
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URL u = new URL("http://" + server + "?action=read&docid=" + docid);
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//System.out.println("sending message: " + u.toString());
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String xmldoc = MetacatReplication.getURLContent(u);
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//get the document to write
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URL docinfourl = new URL("http://" + server +
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"?action=getdocumentinfo&docid=" +
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docid);
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//we need to get the document's info so we can set the correct user
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//and group once we get the document and write it to our DB
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//System.out.println("sending message: " + docinfourl.toString());
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String docInfoStr = MetacatReplication.getURLContent(docinfourl);
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DocInfoHandler dih = new DocInfoHandler();
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//dih is the parser for the docinfo xml format
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XMLReader docinfoParser = ReplicationHandler.initParser(dih);
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docinfoParser.parse(new InputSource(new StringReader(docInfoStr)));
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Hashtable docinfoHash = dih.getDocInfo();
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String user = (String)docinfoHash.get("user_owner");
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String group = new String(user);
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//right now the user and group are the same.
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Connection conn = util.openDBConnection();
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DocumentImpl.write(conn, new StringReader(xmldoc), null, dbaction, docid,
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user, group, serverCode, override);
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MetacatReplication.replLog("document " + docid + " added to DB with " +
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"action " + dbaction);
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conn.close();
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}
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catch(Exception e)
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{
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System.out.println("error in metacatReplication.handleForceReplicate" +
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"Request: " + e.getMessage());
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}
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}
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/**
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* Grants or denies a lock to a requesting host.
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* The servlet parameters of interrest are:
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* docid: the docid of the file the lock is being requested for
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* currentdate: the timestamp of the document on the remote server
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*
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*/
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private void handleGetLockRequest(PrintWriter out, Hashtable params,
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HttpServletResponse response)
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{
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try
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{
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Connection conn = util.openDBConnection();
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String docid = ((String[])params.get("docid"))[0];
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String remoteRev = ((String[])params.get("updaterev"))[0];
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DocumentImpl requestDoc = new DocumentImpl(conn, docid);
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MetacatReplication.replLog("lock request for " + docid);
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int localRevInt = requestDoc.getRev();
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int remoteRevInt = Integer.parseInt(remoteRev);
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if(remoteRevInt >= localRevInt)
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{
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if(!fileLocks.contains(docid))
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{ //grant the lock if it is not already locked
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fileLocks.add(0, docid); //insert at the beginning of the queue Vector
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//send a message back to the the remote host authorizing the insert
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out.println("<lockgranted><docid>" +docid+ "</docid></lockgranted>");
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lockThread = new Thread(this);
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lockThread.setPriority(Thread.MIN_PRIORITY);
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lockThread.start();
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MetacatReplication.replLog("lock granted for " + docid);
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}
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else
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{ //deny the lock
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out.println("<filelocked><docid>" + docid + "</docid></filelocked>");
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MetacatReplication.replLog("lock denied for " + docid +
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"reason: file already locked");
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}
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}
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else
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{//deny the lock.
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out.println("<outdatedfile><docid>" + docid + "</docid></filelocked>");
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MetacatReplication.replLog("lock denied for " + docid +
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"reason: client has outdated file");
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}
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conn.close();
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}
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catch(Exception e)
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{
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System.out.println("error requesting file lock: " + e.getMessage());
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e.printStackTrace(System.out);
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}
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}
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/**
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* Sends all of the xml_documents information encoded in xml to a requestor
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* the format is:
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* <!ELEMENT documentinfo (docid, docname, doctype, doctitle, user_owner,
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* user_updated, public_access, rev)
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* all of the subelements of document info are #PCDATA
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*/
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private void handleGetDocumentInfoRequest(PrintWriter out, Hashtable params,
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HttpServletResponse response)
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{
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String docid = ((String[])(params.get("docid")))[0];
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StringBuffer sb = new StringBuffer();
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try
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{
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Connection conn = util.openDBConnection();
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DocumentImpl doc = new DocumentImpl(conn, docid);
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sb.append("<documentinfo><docid>").append(docid);
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sb.append("</docid><docname>").append(doc.getDocname());
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sb.append("</docname><doctype>").append(doc.getDoctype());
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sb.append("</doctype><doctitle>").append(doc.getDocTitle());
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sb.append("</doctitle><user_owner>").append(doc.getUserowner());
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sb.append("</user_owner><user_updated>").append(doc.getUserupdated());
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sb.append("</user_updated><public_access>").append(doc.getPublicaccess());
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sb.append("</public_access><rev>").append(doc.getRev());
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sb.append("</rev></documentinfo>");
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response.setContentType("text/xml");
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out.println(sb.toString());
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conn.close();
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}
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catch (Exception e)
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{
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System.out.println("error in metacatReplication.handlegetdocumentinforequest: " +
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e.getMessage());
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}
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}
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/**
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* Sends a document to a remote host
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*/
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private void handleGetDocumentRequest(PrintWriter out, Hashtable params,
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HttpServletResponse response)
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{
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try
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{
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String docid = ((String[])(params.get("docid")))[0];
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//System.out.println("incoming get request for document: " + docid);
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Connection conn = util.openDBConnection();
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DocumentImpl di = new DocumentImpl(conn, docid);
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response.setContentType("text/xml");
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out.print(di.toString());
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conn.close();
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MetacatReplication.replLog("document " + docid + " sent");
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}
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catch(Exception e)
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{
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System.out.println("error getting document: " + e.getMessage());
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}
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}
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/**
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* Sends a list of all of the documents on this sever along with their
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* revision numbers.
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* The format is:
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* <!ELEMENT replication (server, updates)>
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* <!ELEMENT server (#PCDATA)>
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* <!ELEMENT updates ((updatedDocument | deleteDocument)*)>
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* <!ELEMENT updatedDocument (docid, rev)>
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* <!ELEMENT deletedDocument (docid, rev)>
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* <!ELEMENT docid (#PCDATA)>
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* <!ELEMENT rev (#PCDATA)>
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* note that the rev in deletedDocument is always empty. I just left
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* it in there to make the parser implementation easier.
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*/
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private void handleUpdateRequest(PrintWriter out, Hashtable params,
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HttpServletResponse response)
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{
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try
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{
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//System.out.println("received update request");
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StringBuffer docsql = new StringBuffer();
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StringBuffer doclist = new StringBuffer();
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//get all docs that reside on this server
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doclist.append("<?xml version=\"1.0\"?><replication>");
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doclist.append("<server>").append(util.getOption("server"));
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doclist.append(util.getOption("replicationpath"));
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doclist.append("</server><updates>");
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docsql.append("select docid, rev from xml_documents where ");
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docsql.append("server_location = 1");
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//get any deleted documents
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StringBuffer delsql = new StringBuffer();
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delsql.append("select distinct docid from ");
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delsql.append("xml_revisions where docid not in (select docid from ");
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delsql.append("xml_documents) and server_location = 1");
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Connection conn = util.openDBConnection();
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PreparedStatement pstmt = conn.prepareStatement(docsql.toString());
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pstmt.execute();
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ResultSet rs = pstmt.getResultSet();
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boolean tablehasrows = rs.next();
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while(tablehasrows)
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{
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doclist.append("<updatedDocument>");
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doclist.append("<docid>").append(rs.getString(1));
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doclist.append("</docid><rev>").append(rs.getInt(2));
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doclist.append("</rev>");
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doclist.append("</updatedDocument>");
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tablehasrows = rs.next();
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}
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pstmt = conn.prepareStatement(delsql.toString());
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pstmt.execute();
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rs = pstmt.getResultSet();
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tablehasrows = rs.next();
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while(tablehasrows)
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{ //handle the deleted documents
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doclist.append("<deletedDocument><docid>").append(rs.getString(1));
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doclist.append("</docid><rev></rev></deletedDocument>");
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//note that rev is always empty for deleted docs
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tablehasrows = rs.next();
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}
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doclist.append("</updates></replication>");
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//System.out.println("doclist: " + doclist.toString());
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conn.close();
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response.setContentType("text/xml");
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out.println(doclist.toString());
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MetacatReplication.replLog("update request handled");
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}
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catch(Exception e)
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{
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System.out.println("error in handleupdaterequest2: " + e.getMessage());
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e.printStackTrace(System.out);
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}
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}
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/**
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* Sends the current system date to the remote server. Using this action
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* for replication gets rid of any problems with syncronizing clocks
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* because a time specific to a document is always kept on its home server.
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*/
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private void handleGetTimeRequest(PrintWriter out, Hashtable params,
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HttpServletResponse response)
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{
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SimpleDateFormat formatter = new SimpleDateFormat ("yy-MM-dd HH:mm:ss");
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java.util.Date localtime = new java.util.Date();
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String dateString = formatter.format(localtime);
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response.setContentType("text/xml");
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out.println("<timestamp>" + dateString + "</timestamp>");
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}
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/**
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425
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* this method handles the timeout for a file lock. when a lock is
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* granted it is granted for 30 seconds. When this thread runs out
|
427
|
* it deletes the docid from the queue, thus eliminating the lock.
|
428
|
*/
|
429
|
public void run()
|
430
|
{
|
431
|
try
|
432
|
{
|
433
|
//System.out.println("thread started for docid: " +
|
434
|
// (String)fileLocks.elementAt(0));
|
435
|
Thread.sleep(30000); //the lock will expire in 30 seconds
|
436
|
//System.out.println("thread for docid: " +
|
437
|
// (String)fileLocks.elementAt(fileLocks.size() - 1) +
|
438
|
// " exiting.");
|
439
|
fileLocks.remove(fileLocks.size() - 1);
|
440
|
//fileLocks is treated as a FIFO queue. If there are more than one lock
|
441
|
//in the vector, the first one inserted will be removed.
|
442
|
}
|
443
|
catch(Exception e)
|
444
|
{
|
445
|
System.out.println("error in file lock thread: " + e.getMessage());
|
446
|
}
|
447
|
}
|
448
|
|
449
|
/**
|
450
|
* Returns the name of a server given a serverCode
|
451
|
* @param serverCode the serverid of the server
|
452
|
* @return the servername or null if the specified serverCode does not
|
453
|
* exist.
|
454
|
*/
|
455
|
public static String getServer(int serverCode)
|
456
|
{
|
457
|
//System.out.println("serverid: " + serverCode);
|
458
|
try
|
459
|
{
|
460
|
Connection conn = util.openDBConnection();
|
461
|
String sql = new String("select server from " +
|
462
|
"xml_replication where serverid = " +
|
463
|
serverCode);
|
464
|
PreparedStatement pstmt = conn.prepareStatement(sql);
|
465
|
//System.out.println("getserver sql: " + sql);
|
466
|
pstmt.execute();
|
467
|
ResultSet rs = pstmt.getResultSet();
|
468
|
boolean tablehasrows = rs.next();
|
469
|
if(tablehasrows)
|
470
|
{
|
471
|
//System.out.println("server: " + rs.getString(1));
|
472
|
return rs.getString(1);
|
473
|
}
|
474
|
conn.close();
|
475
|
}
|
476
|
catch(Exception e)
|
477
|
{
|
478
|
System.out.println("Error in MetacatReplication.getServer: " +
|
479
|
e.getMessage());
|
480
|
}
|
481
|
return null;
|
482
|
//return null if the server does not exist
|
483
|
}
|
484
|
|
485
|
/**
|
486
|
* Returns a server code given a server name
|
487
|
* @param server the name of the server
|
488
|
* @return integer > 0 representing the code of the server, 0 if the server
|
489
|
* does not exist.
|
490
|
*/
|
491
|
public static int getServerCode(String server) throws Exception
|
492
|
{
|
493
|
try
|
494
|
{
|
495
|
Connection conn = util.openDBConnection();
|
496
|
PreparedStatement pstmt = conn.prepareStatement("select serverid from " +
|
497
|
"xml_replication where server " +
|
498
|
"like '" + server + "'");
|
499
|
pstmt.execute();
|
500
|
ResultSet rs = pstmt.getResultSet();
|
501
|
boolean tablehasrows = rs.next();
|
502
|
int serverCode = 0;
|
503
|
if(tablehasrows)
|
504
|
{
|
505
|
return rs.getInt(1);
|
506
|
}
|
507
|
else
|
508
|
{
|
509
|
return 0;
|
510
|
}
|
511
|
}
|
512
|
catch(Exception e)
|
513
|
{
|
514
|
throw e;
|
515
|
}
|
516
|
}
|
517
|
|
518
|
/**
|
519
|
* This method returns the content of a url
|
520
|
* @param u the url to return the content from
|
521
|
* @return a string representing the content of the url
|
522
|
* @throws java.io.IOException
|
523
|
*/
|
524
|
public static String getURLContent(URL u) throws java.io.IOException
|
525
|
{
|
526
|
//System.out.println("url: " + u.toString());
|
527
|
char istreamChar;
|
528
|
int istreamInt;
|
529
|
InputStreamReader istream = new InputStreamReader(u.openStream());
|
530
|
StringBuffer serverResponse = new StringBuffer();
|
531
|
while((istreamInt = istream.read()) != -1)
|
532
|
{
|
533
|
istreamChar = (char)istreamInt;
|
534
|
serverResponse.append(istreamChar);
|
535
|
}
|
536
|
|
537
|
return serverResponse.toString();
|
538
|
}
|
539
|
|
540
|
/**
|
541
|
* Method for writing replication messages to a log file specified in
|
542
|
* metacat.properties
|
543
|
*/
|
544
|
public static void replLog(String message)
|
545
|
{
|
546
|
try
|
547
|
{
|
548
|
FileOutputStream fos = new FileOutputStream(
|
549
|
util.getOption("replicationlog"), true);
|
550
|
PrintWriter pw = new PrintWriter(fos);
|
551
|
SimpleDateFormat formatter = new SimpleDateFormat ("yy-MM-dd HH:mm:ss");
|
552
|
java.util.Date localtime = new java.util.Date();
|
553
|
String dateString = formatter.format(localtime);
|
554
|
dateString += " :: " + message;
|
555
|
//time stamp each entry
|
556
|
pw.println(dateString);
|
557
|
pw.flush();
|
558
|
}
|
559
|
catch(Exception e)
|
560
|
{
|
561
|
System.out.println("error writing to replication log");
|
562
|
e.printStackTrace(System.out);
|
563
|
}
|
564
|
}
|
565
|
}
|