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make LazyFaultTolerance lock-free #1034

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make LazyFaultTolerance lock-free #1034

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15 changes: 7 additions & 8 deletions ...tation/core/src/main/java/io/smallrye/faulttolerance/core/apiimpl/LazyFaultTolerance.java
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
package io.smallrye.faulttolerance.core.apiimpl;

import java.util.concurrent.Callable;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Supplier;

import io.smallrye.faulttolerance.api.FaultTolerance;
Expand All @@ -9,7 +10,7 @@ public final class LazyFaultTolerance<T> implements FaultTolerance<T> {
private final Supplier<FaultTolerance<T>> builder;
private final Class<?> asyncType;

private volatile FaultTolerance<T> instance;
private final AtomicReference<FaultTolerance<T>> instance = new AtomicReference<>(null);

LazyFaultTolerance(Supplier<FaultTolerance<T>> builder, Class<?> asyncType) {
this.builder = builder;
Expand All @@ -36,15 +37,13 @@ public void run(Runnable action) {
}

private FaultTolerance<T> instance() {
FaultTolerance<T> instance = this.instance;
FaultTolerance<T> instance = this.instance.get();
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@franz1981 franz1981 Jul 12, 2024 •
edited
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this is making builder.get() to be called more than once, changing the expected behaviour for users.
Using ReentrantLock(s) is preferrable here - or use a 2 state lock-free behaviour instead

if (instance == null) {
synchronized (this) {
instance = this.instance;
if (instance == null) {
instance = builder.get();
this.instance = instance;
}
instance = builder.get();
if (this.instance.compareAndSet(null, instance)) {
return instance;
}
instance = this.instance.get();
}
return instance;
}
Expand Down