lhotari commented on code in PR #23903:
URL: https://github.com/apache/pulsar/pull/23903#discussion_r1932885264
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managed-ledger/src/main/java/org/apache/bookkeeper/mledger/util/RangeCache.java:
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@@ -116,7 +148,11 @@ V getValue(K key) {
localValue = this.value;
lock.unlockRead(stamp);
}
- if (localKey != key) {
+ // check that the given key matches the key associated with the
value in the entry
Review Comment:
> Don' we need to wrap void recycle() with the write lock?
That's not necessary since the solution already prevents race reads. In Java
on 64 bit JVMs, there's no data corruption problems with racy writes and reads
to fields. The problem to solve is about consistency across multiple fields and
about visibility of the changes. When recycling, it would just be unnecessary
overhead to add a write lock. The `getRetainedValueMatchingKey` will detect if
the key and value don't match by calling the `matchesKey` method, which in
`EntryImpl` is implemented in this way:
```java
public boolean matchesKey(Position key) {
return key.compareTo(ledgerId, entryId) == 0;
}
```
One of the goals of RangeCache is to avoid exclusive locks as much as
possible. The write lock on StampedLock is cheap, but we can also avoid that
cost in this case.
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