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package com.sun.gjc.util;
import com.sun.logging.LogDomains;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Timer;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* Maintains the Sql Tracing Cache used to store SQL statements used by the
* applications. This is used by the JDBCRA monitoring to display the most
* frequently used queries by applications.
*
* @author Shalini M
*/
public class SQLTraceCache {
//List of sql trace objects
private final List<SQLTrace> list;
//Maximum size of the cache.
private int numTopQueriesToReport = 10;
private long timeToKeepQueries = 60 * 1000;
private SQLTraceTimerTask sqlTraceTimerTask;
private String poolName;
private String appName;
private String moduleName;
private final static Logger _logger = LogDomains.getLogger(SQLTraceCache.class,
LogDomains.RSR_LOGGER);
private static final String LINE_BREAK = "%%%EOL%%%";
public SQLTraceCache(String poolName, String appName, String moduleName, int maxSize, long timeToKeepQueries) {
this.poolName = poolName;
this.appName = appName;
this.moduleName = moduleName;
this.numTopQueriesToReport = maxSize;
list = new ArrayList<SQLTrace>();
this.timeToKeepQueries = timeToKeepQueries * 60 * 1000;
}
public List<SQLTrace> getSqlTraceList() {
return list;
}
public String getPoolName() {
return poolName;
}
/**
* Schedule timer to perform purgeEntries on the cache after the
* specified timeToKeepQueries delay and period.
*/
public void scheduleTimerTask(Timer timer) {
if(sqlTraceTimerTask != null) {
sqlTraceTimerTask.cancel();
sqlTraceTimerTask = null;
}
sqlTraceTimerTask = initializeTimerTask();
if(timer != null) {
timer.scheduleAtFixedRate(sqlTraceTimerTask, timeToKeepQueries, timeToKeepQueries);
}
if(_logger.isLoggable(Level.FINEST)) {
_logger.finest("Scheduled Sql Trace Caching timer task");
}
}
/**
* Cancel the timer task used to perform a purgeEntries on the cache.
*/
public synchronized void cancelTimerTask() {
if(_logger.isLoggable(Level.FINEST)) {
_logger.finest("Cancelling Sql Trace Caching timer task");
}
if (sqlTraceTimerTask != null) {
sqlTraceTimerTask.cancel();
}
sqlTraceTimerTask = null;
}
/**
* Instantiate the timer task used to perform a purgeEntries on the cache
*
* @return SQLTraceTimerTask
*/
private SQLTraceTimerTask initializeTimerTask() {
if(_logger.isLoggable(Level.FINEST)) {
_logger.finest("Initializing Sql Trace Caching timer task");
}
return new SQLTraceTimerTask(this);
}
/**
* Request for adding a sql query in the form of SQLTrace to this cache.
* If the query is already found
* in the list, the number of times it is executed is incremented by one
* along with the timestamp.
* If the query is a new one, it is added to the list.
*
* @param cacheObj
* @return
*/
public void checkAndUpdateCache(SQLTrace cacheObj) {
synchronized (list) {
if (cacheObj != null) {
int index = list.indexOf(cacheObj);
if (index != -1) {
//If already found in the cache
//equals is invoked here and hence comparison based on query name is done
//Get the object at the index to update the numExecutions
SQLTrace cache = (SQLTrace) list.get(index);
cache.setNumExecutions(cache.getNumExecutions() + 1);
cache.setLastUsageTime(System.currentTimeMillis());
} else {
//First occurrence of the query. query to be added.
cacheObj.setNumExecutions(1);
cacheObj.setLastUsageTime(System.currentTimeMillis());
list.add(cacheObj);
}
}
}
}
/**
* Entries are removed from the list after sorting
* them in the least frequently used order. Only numTopQueriesToReport number of
* entries are maintained in the list after the purgeEntries.
*/
public void purgeEntries() {
synchronized(list) {
Collections.sort(list, Collections.reverseOrder());
Iterator i = list.iterator();
while (i.hasNext()) {
SQLTrace cacheObj = (SQLTrace) i.next();
if (list.size() > numTopQueriesToReport) {
if(_logger.isLoggable(Level.FINEST)) {
_logger.finest("removing sql=" + cacheObj.getQueryName());
}
i.remove();
} else {
break;
}
}
//sort by most frequently used queries first
Collections.sort(list);
}
}
/**
* Returns the String representation of the list of traced sql queries
* ordered by the number most frequently used, followed by the usage
* timestamp. Only the top 'n' queries represented by the numTopQueriesToReport are
* chosen for display.
*
* @return string representation of the list of sql queries sorted
*/
public String getTopQueries() {
purgeEntries();
StringBuffer sb = new StringBuffer();
for(SQLTrace cache : list) {
sb.append(LINE_BREAK);
sb.append(cache.getQueryName());
}
return sb.toString();
}
}