org.postgresql.util.SharedTimer Maven / Gradle / Ivy

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PostgreSQL JDBC Driver JDBC4

There is a newer version: 42.7.3

package org.postgresql.util;

import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.atomic.AtomicInteger;

import org.postgresql.core.Logger;

public class SharedTimer {
    // Incremented for each Timer created, this allows each to have a unique Timer name
    private static AtomicInteger timerCount = new AtomicInteger(0);

    private Logger log;
    private volatile Timer timer = null;
    private AtomicInteger refCount = new AtomicInteger(0);

    public SharedTimer(Logger log) {
        this.log = log;
    }

    public int getRefCount() {
        return refCount.get();
    }

    public synchronized Timer getTimer() {
        if( timer == null ) {
            int index = timerCount.incrementAndGet();
            timer = new Timer("PostgreSQL-JDBC-SharedTimer-" + index, true);
        }
        refCount.incrementAndGet();
        return timer;
    }

    public synchronized void releaseTimer() {
        int count = refCount.decrementAndGet();
        if( count > 0 ) {
            // There are outstanding references to the timer so do nothing
            log.debug("Outstanding references still exist so not closing shared Timer");
        } else if( count == 0 ) {
            // This is the last usage of the Timer so cancel it so it's resources can be release.
            log.debug("No outstanding references to shared Timer, will cancel and close it");
            if( timer != null ) {
                timer.cancel();
                timer = null;
            }
        } else {
            // Should not get here under normal circumstance, probably a bug in app code.
            log.debug("releaseTimer() called too many times; there is probably a bug in the calling code");
            refCount.set(0);
        }
    }
}