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Precompute the BitsetCacheKey hashCode, and account for the size of the key #132418

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Precompute the BitsetCacheKey hashCode, and account for the size of the key #132418

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a1b3a6f
Mark this class final, and whitespace
joegallo Aug 1, 2025
f60d917
Eagerly compute (and cache) the hashCode
joegallo Aug 1, 2025
02ac7a1
Account for the non-zero size of the key in the cache
joegallo Aug 1, 2025
5671066
Update docs/changelog/132418.yaml
joegallo Aug 4, 2025
6cefb2f
Merge branch 'main' into dls-cache-key-hashCode-and-size
joegallo Aug 5, 2025
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6 changes: 6 additions & 0 deletions docs/changelog/132418.yaml
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Original file line number Diff line number Diff line change
@@ -0,0 +1,6 @@
pr: 132418
summary: "Precompute the `BitsetCacheKey` `hashCode,` and account for the size of\
\ the key"
area: Authorization
type: bug
issues: []
22 changes: 19 additions & 3 deletions .../org/elasticsearch/xpack/core/security/authz/accesscontrol/DocumentSubsetBitsetCache.java
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Expand Up @@ -23,6 +23,7 @@
import org.apache.lucene.util.Accountable;
import org.apache.lucene.util.BitSet;
import org.apache.lucene.util.FixedBitSet;
import org.apache.lucene.util.RamUsageEstimator;
import org.elasticsearch.common.cache.Cache;
import org.elasticsearch.common.cache.CacheBuilder;
import org.elasticsearch.common.cache.RemovalNotification;
Expand Down Expand Up @@ -142,7 +143,7 @@ public DocumentSubsetBitsetCache(Settings settings, ThreadPool threadPool) {
this.bitsetCache = CacheBuilder.<BitsetCacheKey, BitSet>builder()
.setExpireAfterAccess(ttl)
.setMaximumWeight(maxWeightBytes)
.weigher((key, bitSet) -> bitSet == NULL_MARKER ? 0 : bitSet.ramBytesUsed())
.weigher((key, bitSet) -> BitsetCacheKey.SHALLOW_SIZE + (bitSet == NULL_MARKER ? 0 : bitSet.ramBytesUsed()))
.removalListener(this::onCacheEviction)
.build();

Expand Down Expand Up @@ -247,7 +248,7 @@ public BitSet getBitSet(final Query query, final LeafReaderContext context) thro
// A cache loader is not allowed to return null, return a marker object instead.
return NULL_MARKER;
}
final long bitSetBytes = result.ramBytesUsed();
final long bitSetBytes = result.ramBytesUsed(); // note: this ignores the size of the key itself, but that's okay
if (bitSetBytes > this.maxWeightBytes) {
logger.warn(
"built a DLS BitSet that uses [{}] bytes; the DLS BitSet cache has a maximum size of [{}] bytes;"
Expand Down Expand Up @@ -325,12 +326,21 @@ public Map<String, Object> usageStats() {

private static final class BitsetCacheKey {

// the shallow size accounts for the object itself, but it ignores the index and the query.
// the index is owned by the associated IndexReader and the query is shared, so they don't count against us here.
private static final long SHALLOW_SIZE = RamUsageEstimator.shallowSizeOfInstance(BitsetCacheKey.class);

final IndexReader.CacheKey index;
final Query query;
final int hashCode;

private BitsetCacheKey(IndexReader.CacheKey index, Query query) {
this.index = index;
this.query = query;
// compute the hashCode eagerly, since it's used multiple times in the cache implementation anyway -- the query here will
// be a ConstantScoreQuery around a BooleanQuery, and BooleanQuery already *lazily* caches the hashCode, so this isn't
// altogether that much faster in reality, but it makes it more explicit here that we're doing this
this.hashCode = computeHashCode();
}

@Override
Expand All @@ -345,9 +355,15 @@ public boolean equals(Object other) {
return Objects.equals(this.index, that.index) && Objects.equals(this.query, that.query);
}

private int computeHashCode() {
int result = index.hashCode();
result = 31 * result + query.hashCode();
return result;
}

@Override
public int hashCode() {
return Objects.hash(index, query);
return hashCode;
}

@Override
Expand Down
29 changes: 17 additions & 12 deletions ...elasticsearch/xpack/core/security/authz/accesscontrol/DocumentSubsetBitsetCacheTests.java
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Expand Up @@ -76,9 +76,14 @@
public class DocumentSubsetBitsetCacheTests extends ESTestCase {

private static final int FIELD_COUNT = 10;
// This comes from the SHALLOW_SIZE of the BitsetCacheKey
private static final long EXPECTED_BYTES_PER_BIT_SET_KEY = 24; /* key size */
// This value is based on the internal implementation details of lucene's FixedBitSet
// If the implementation changes, this can be safely updated to match the new ram usage for a single bitset
private static final long EXPECTED_BYTES_PER_BIT_SET = 56;
private static final long EXPECTED_BYTES_PER_BIT_SET = 56; /* non-null value size */
// a non-null entry will have the size of the key and the bit set, while a null entry would just be the size of the key
private static final long EXPECTED_BYTES_PER_ENTRY = EXPECTED_BYTES_PER_BIT_SET_KEY + EXPECTED_BYTES_PER_BIT_SET;

private ExecutorService singleThreadExecutor;

@Before
Expand Down Expand Up @@ -126,15 +131,15 @@ public void testNullEntriesAreNotCountedInMemoryUsage() throws Exception {
final Query query = QueryBuilders.termQuery("dne-" + i, "dne- " + i).toQuery(searchExecutionContext);
final BitSet bitSet = cache.getBitSet(query, leafContext);
assertThat(bitSet, nullValue());
assertThat(cache.ramBytesUsed(), equalTo(0L));
assertThat(cache.ramBytesUsed(), equalTo(EXPECTED_BYTES_PER_BIT_SET_KEY * i));
assertThat(cache.entryCount(), equalTo(i));
}
});
}

public void testCacheRespectsMemoryLimit() throws Exception {
// Enough to hold exactly 2 bit-sets in the cache
final long maxCacheBytes = EXPECTED_BYTES_PER_BIT_SET * 2;
final long maxCacheBytes = EXPECTED_BYTES_PER_ENTRY * 2;
final Settings settings = Settings.builder()
.put(DocumentSubsetBitsetCache.CACHE_SIZE_SETTING.getKey(), maxCacheBytes + "b")
.build();
Expand All @@ -155,24 +160,24 @@ public void testCacheRespectsMemoryLimit() throws Exception {
// The first time through we have 1 entry, after that we have 2
final int expectedCount = i == 1 ? 1 : 2;
assertThat(cache.entryCount(), equalTo(expectedCount));
assertThat(cache.ramBytesUsed(), equalTo(expectedCount * EXPECTED_BYTES_PER_BIT_SET));
assertThat(cache.ramBytesUsed(), equalTo(expectedCount * EXPECTED_BYTES_PER_ENTRY));

// Older queries should get evicted, but the query from last iteration should still be cached
if (previousQuery != null) {
assertThat(cache.getBitSet(previousQuery, leafContext), sameInstance(previousBitSet));
assertThat(cache.entryCount(), equalTo(expectedCount));
assertThat(cache.ramBytesUsed(), equalTo(expectedCount * EXPECTED_BYTES_PER_BIT_SET));
assertThat(cache.ramBytesUsed(), equalTo(expectedCount * EXPECTED_BYTES_PER_ENTRY));
}
previousQuery = query;
previousBitSet = bitSet;

assertThat(cache.getBitSet(queryBuilder.toQuery(searchExecutionContext), leafContext), sameInstance(bitSet));
assertThat(cache.entryCount(), equalTo(expectedCount));
assertThat(cache.ramBytesUsed(), equalTo(expectedCount * EXPECTED_BYTES_PER_BIT_SET));
assertThat(cache.ramBytesUsed(), equalTo(expectedCount * EXPECTED_BYTES_PER_ENTRY));
}

assertThat(cache.entryCount(), equalTo(2));
assertThat(cache.ramBytesUsed(), equalTo(2 * EXPECTED_BYTES_PER_BIT_SET));
assertThat(cache.ramBytesUsed(), equalTo(2 * EXPECTED_BYTES_PER_ENTRY));

cache.clear("testing");

Expand All @@ -183,7 +188,7 @@ public void testCacheRespectsMemoryLimit() throws Exception {

public void testLogWarningIfBitSetExceedsCacheSize() throws Exception {
// Enough to hold less than 1 bit-sets in the cache
final long maxCacheBytes = EXPECTED_BYTES_PER_BIT_SET - EXPECTED_BYTES_PER_BIT_SET / 3;
final long maxCacheBytes = EXPECTED_BYTES_PER_BIT_SET - 1; // n.b. we're ignoring the key size, it's okay
final Settings settings = Settings.builder()
.put(DocumentSubsetBitsetCache.CACHE_SIZE_SETTING.getKey(), maxCacheBytes + "b")
.build();
Expand Down Expand Up @@ -220,7 +225,7 @@ public void testLogWarningIfBitSetExceedsCacheSize() throws Exception {

public void testLogMessageIfCacheFull() throws Exception {
// Enough to hold slightly more than 1 bit-sets in the cache
final long maxCacheBytes = EXPECTED_BYTES_PER_BIT_SET + EXPECTED_BYTES_PER_BIT_SET / 3;
final long maxCacheBytes = EXPECTED_BYTES_PER_ENTRY + EXPECTED_BYTES_PER_ENTRY / 3;
final Settings settings = Settings.builder()
.put(DocumentSubsetBitsetCache.CACHE_SIZE_SETTING.getKey(), maxCacheBytes + "b")
.build();
Expand Down Expand Up @@ -282,7 +287,7 @@ public void testCacheRespectsAccessTimeExpiry() throws Exception {

public void testIndexLookupIsClearedWhenBitSetIsEvicted() throws Exception {
// Enough to hold slightly more than 1 bit-set in the cache
final long maxCacheBytes = EXPECTED_BYTES_PER_BIT_SET + EXPECTED_BYTES_PER_BIT_SET / 2;
final long maxCacheBytes = EXPECTED_BYTES_PER_ENTRY + EXPECTED_BYTES_PER_ENTRY / 2;
final Settings settings = Settings.builder()
.put(DocumentSubsetBitsetCache.CACHE_SIZE_SETTING.getKey(), maxCacheBytes + "b")
.build();
Expand Down Expand Up @@ -331,7 +336,7 @@ public void testCacheUnderConcurrentAccess() throws Exception {

// Force cache evictions by setting the size to be less than the number of distinct queries we search on.
final int maxCacheCount = randomIntBetween(FIELD_COUNT / 2, FIELD_COUNT * 3 / 4);
final long maxCacheBytes = EXPECTED_BYTES_PER_BIT_SET * maxCacheCount;
final long maxCacheBytes = EXPECTED_BYTES_PER_ENTRY * maxCacheCount;
final Settings settings = Settings.builder()
.put(DocumentSubsetBitsetCache.CACHE_SIZE_SETTING.getKey(), maxCacheBytes + "b")
.build();
Expand Down Expand Up @@ -410,7 +415,7 @@ public void testCacheUnderConcurrentAccess() throws Exception {

public void testCleanupWorksWhenIndexIsClosing() throws Exception {
// Enough to hold slightly more than 1 bit-set in the cache
final long maxCacheBytes = EXPECTED_BYTES_PER_BIT_SET + EXPECTED_BYTES_PER_BIT_SET / 2;
final long maxCacheBytes = EXPECTED_BYTES_PER_ENTRY + EXPECTED_BYTES_PER_ENTRY / 2;
final Settings settings = Settings.builder()
.put(DocumentSubsetBitsetCache.CACHE_SIZE_SETTING.getKey(), maxCacheBytes + "b")
.build();
Expand Down