LuciferYang commented on PR #43502:
URL: https://github.com/apache/spark/pull/43502#issuecomment-1777630300
@zhaomin1423
Firstly, we may need to add two helper methods:
1. Add a method in `RocksDB` that can get its corresponding `WeakReference`
through `RocksDBIterator`, here I assume it's called `iteratorReference`
2. Add a method in `RocksDBIterator` to get `RocksIterator`, here I assume
it's called `internalIterator`
Then, the test case may like the following:
```java
@Test
public void testResourceCleaner() throws Exception {
File dbPathForCleanerTest = File.createTempFile(
"test_db_cleaner.", ".rdb");
dbPathForCleanerTest.delete();
RocksDB dbForCleanerTest = new RocksDB(dbPathForCleanerTest);
for (int i = 0; i < 8192; i++) {
dbForCleanerTest.write(createCustomType1(i));
}
RocksDBIterator<CustomType1> rocksDBIterator =
(RocksDBIterator<CustomType1>)
dbForCleanerTest.view(CustomType1.class).iterator();
Optional<Reference<RocksDBIterator<?>>> referenceOpt =
dbForCleanerTest.iteratorReference(rocksDBIterator);
assertTrue(referenceOpt.isPresent());
RocksIterator it = rocksDBIterator.internalIterator();
assertTrue(it.isOwningHandle()); // it has not been closed yet,
isOwningHandle should be true.
rocksDBIterator = null; // Manually set rocksDBIterator to null, to be
GC.
Reference<RocksDBIterator<?>> ref = referenceOpt.get();
// 100 times gc, the rocksDBIterator should be GCed.
int count = 0;
while (count < 100 && !ref.refersTo(null)) {
System.gc();
count++;
Thread.sleep(100);
}
assertTrue(ref.refersTo(null)); // check rocksDBIterator should be GCed
// Verify that the Cleaner will be executed after a period of time,
after which it.isOwningHandle() will become false.
assertTimeout(java.time.Duration.ofSeconds(5), () ->
assertFalse(it.isOwningHandle()));
dbForCleanerTest.close();
}
```
Of course, we can also add a state in `ResourceCleaner` to indicate whether
it has been executed, initially set to false, and turns true after execution.
These are just some of my thoughts, there might be better ways to test.
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