import java.util.WeakHashMap;
import java.util.concurrent.atomic.AtomicLong;
+import org.argeo.api.uuid.UuidFactory.TimeUuidState;
+
/**
* A simple base implementation of {@link TimeUuidState}, which maintains
- * different clock sequences for each thread.
+ * different clock sequences for each thread, based on a specified range. This
+ * range is defined as clock_seq_hi (cf. RFC4122) and only clock_seq_low is
+ * dynamically allocated. It means that there can be at most 256 parallel clock
+ * sequences. If that limit is reached, the clock sequence which has not be used
+ * for the most time is reallocated to the new thread. It is assumed that the
+ * context where time uUIDs will be generated will often be using thread pools
+ * (e.g. {@link ForkJoinPool#commonPool(), http server, database access, etc.)
+ * and that such reallocation won't have to happen too often.
*/
public class ConcurrentTimeUuidState implements UuidFactory.TimeUuidState {
private final static Logger logger = System.getLogger(ConcurrentTimeUuidState.class.getName());
/** The maximum possible value of the clocksequence. */
- private final static int MAX_CLOCKSEQUENCE = 16384;
+ private final static int MAX_CLOCKSEQUENCE = 0x3F00;
private final ClockSequenceProvider clockSequenceProvider;
private final ThreadLocal<ConcurrentTimeUuidState.Holder> currentHolder;
return currentHolder.get().lastTimestamp;
}
- public void reset(long nodeIdBase) {
+ protected void reset(long nodeIdBase, long range) {
synchronized (clockSequenceProvider) {
this.nodeIdBase = nodeIdBase;
- clockSequenceProvider.reset();
+ clockSequenceProvider.reset(range);
clockSequenceProvider.notifyAll();
}
}
/*
* INTERNAL CLASSSES
*/
-
private class Holder {
private long lastTimestamp;
private long clockSequence;
private void setClockSequence(long clockSequence) {
this.clockSequence = clockSequence;
-// if (nodeIdBase == null)
-// throw new IllegalStateException("Node id base is not initialised");
this.leastSig = nodeIdBase // already computed node base
| (((clockSequence & 0x3F00) >> 8) << 56) // clk_seq_hi_res
| ((clockSequence & 0xFF) << 48); // clk_seq_low
}
private static class ClockSequenceProvider {
- private int rangeSize = 256;
- private volatile int min;
- private volatile int max;
+ /** Set to an illegal value. */
+ private long range = MAX_CLOCKSEQUENCE;// this is actually clk_seq_hi
+// private int rangeSize = 256;
+ private volatile long min;
+ private volatile long max;
private final AtomicLong counter = new AtomicLong(-1);
private final SecureRandom secureRandom;
ClockSequenceProvider(SecureRandom secureRandom) {
this.secureRandom = secureRandom;
- reset();
+// reset(range);
}
- synchronized void reset() {
- int min = secureRandom.nextInt(ConcurrentTimeUuidState.MAX_CLOCKSEQUENCE - rangeSize);
- int max = min + rangeSize;
+ synchronized void reset(long range) {
+ // long min = secureRandom.nextInt(ConcurrentTimeUuidState.MAX_CLOCKSEQUENCE -
+ // rangeSize);
+ // long max = min + rangeSize;
+
+ long min, max;
+ if (range >= 0) {
+ if (range > MAX_CLOCKSEQUENCE)
+ throw new IllegalArgumentException("Range " + Long.toHexString(range) + " is too big");
+ long previousRange = this.range;
+ this.range = range & 0x3F00;
+ if (this.range != range) {
+ this.range = previousRange;
+ throw new IllegalArgumentException(
+ "Range is not properly formatted: " + range + " (0x" + Long.toHexString(range) + ")");
+ }
+
+ min = this.range;
+ max = min | 0xFF;
+ } else {// full range
+ this.range = range;
+ min = 0;
+ max = MAX_CLOCKSEQUENCE;
+ }
+ assert min == (int) min;
+ assert max == (int) max;
+
+ // TODO rather use assertions
if (min >= max)
throw new IllegalArgumentException("Minimum " + min + " is bigger than maximum " + max);
if (min < 0 || min > MAX_CLOCKSEQUENCE)
if (activeCount > getRangeSize())
throw new IllegalStateException(
"There are too many holders for range [" + min + "," + max + "] : " + activeCount);
- // reset the counter
- counter.set(min);
+
+ // reset the counter with a random value in range
+ long firstCount = min + secureRandom.nextInt(getRangeSize());
+ counter.set(firstCount);
+
+ // reset holders
for (Holder holder : active) {
// save old clocksequence?
newClockSequence(holder);
}
}
- private synchronized int getRangeSize() {
- return rangeSize;
- }
-
private synchronized void newClockSequence(Holder holder) {
// Too many holders, we will remove the oldes ones
- while (activeHolders.size() > rangeSize) {
+ while (activeHolders.size() > getRangeSize()) {
long oldestTimeStamp = -1;
Holder holderToRemove = null;
holders: for (Holder h : activeHolders.keySet()) {
int tryCount = 0;// an explicit exit condition
do {
tryCount++;
- if (tryCount >= rangeSize)
+ if (tryCount >= getRangeSize())
throw new IllegalStateException("No more clock sequence available");
newClockSequence = counter.incrementAndGet();
// TODO use an iterator to check the values
holder.setClockSequence(newClockSequence);
activeHolders.put(holder, newClockSequence);
- if (logger.isLoggable(DEBUG))
- logger.log(DEBUG,
- "New clocksequence " + newClockSequence + " for thread " + Thread.currentThread().getId());
+ if (logger.isLoggable(DEBUG)) {
+ String clockDesc = range >= 0 ? Long.toHexString(newClockSequence & 0x00FF)
+ : Long.toHexString(newClockSequence | 0x8000);
+ String rangeDesc = Long.toHexString(min | 0x8000) + "-" + Long.toHexString(max | 0x8000);
+ logger.log(DEBUG, "New clocksequence " + clockDesc + " for thread " + Thread.currentThread().getId()
+ + " (in range " + rangeDesc + ")");
+ }
+ }
+
+ private synchronized int getRangeSize() {
+ return (int) (max - min);
}
}
projects / lgpl / argeo-commons.git / commitdiff