yashmayya commented on code in PR #14847:
URL: https://github.com/apache/pinot/pull/14847#discussion_r1926939846
##########
pinot-common/src/main/java/org/apache/pinot/common/concurrency/AdjustableSemaphore.java:
##########
@@ -20,32 +20,44 @@
import com.google.common.base.Preconditions;
import java.util.concurrent.Semaphore;
+import java.util.concurrent.atomic.AtomicInteger;
/**
* A semaphore that allows adjusting the number of permits in a non-blocking
way.
*/
public class AdjustableSemaphore extends Semaphore {
- private int _totalPermits;
+ private final AtomicInteger _totalPermits;
public AdjustableSemaphore(int permits) {
super(permits);
- _totalPermits = permits;
+ _totalPermits = new AtomicInteger(permits);
}
public AdjustableSemaphore(int permits, boolean fair) {
super(permits, fair);
- _totalPermits = permits;
+ _totalPermits = new AtomicInteger(permits);
}
+ /**
+ * Sets the total number of permits to the given value without blocking.
+ */
public void setPermits(int permits) {
Preconditions.checkArgument(permits > 0, "Permits must be a positive
integer");
- if (permits < _totalPermits) {
- reducePermits(_totalPermits - permits);
- } else if (permits > _totalPermits) {
- release(permits - _totalPermits);
+ if (permits < _totalPermits.get()) {
+ reducePermits(_totalPermits.get() - permits);
+ } else if (permits > _totalPermits.get()) {
+ release(permits - _totalPermits.get());
Review Comment:
You're right, we can't actually have concurrent modifications. Only
potential concurrent reads during modifications. I think we can simply use a
volatile int instead (I guess even the volatile is not strictly necessary as we
can tolerate stale values without many issues tbh).
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