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Resolve the role query and the number of docs lazily #48036

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merged 4 commits into from
Oct 25, 2019
Merged

Resolve the role query and the number of docs lazily #48036

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0c41c4e
Resolve the role query and the number of docs lazily
jimczi Oct 15, 2019
80bea3b
remove unwanted change
jimczi Oct 15, 2019
9e98a69
add a comment explaining why we don't need to use volatile on the rol…
jimczi Oct 18, 2019
c5ed858
Merge branch 'master' into lazy_role_query
jimczi Oct 22, 2019
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43 changes: 34 additions & 9 deletions .../java/org/elasticsearch/xpack/core/security/authz/accesscontrol/DocumentSubsetReader.java
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@
import org.apache.lucene.util.BitSetIterator;
import org.apache.lucene.util.Bits;
import org.apache.lucene.util.CombinedBitSet;
import org.elasticsearch.ElasticsearchException;
import org.elasticsearch.ExceptionsHelper;
import org.elasticsearch.common.cache.Cache;
import org.elasticsearch.common.cache.CacheBuilder;
Expand Down Expand Up @@ -51,7 +52,7 @@ public static DocumentSubsetDirectoryReader wrap(DirectoryReader in, DocumentSub
/**
* Compute the number of live documents. This method is SLOW.
*/
private static int computeNumDocs(LeafReader reader, Query roleQuery, BitSet roleQueryBits) {
private static int computeNumDocs(LeafReader reader, BitSet roleQueryBits) {
final Bits liveDocs = reader.getLiveDocs();
if (roleQueryBits == null) {
return 0;
Expand Down Expand Up @@ -103,7 +104,7 @@ private static int getNumDocs(LeafReader reader, Query roleQuery, BitSet roleQue
throw e;
}
}
return perReaderCache.computeIfAbsent(roleQuery, q -> computeNumDocs(reader, roleQuery, roleQueryBits));
return perReaderCache.computeIfAbsent(roleQuery, q -> computeNumDocs(reader, roleQueryBits));
}

public static final class DocumentSubsetDirectoryReader extends FilterDirectoryReader {
Expand Down Expand Up @@ -152,21 +153,44 @@ public CacheHelper getReaderCacheHelper() {
}
}

private final BitSet roleQueryBits;
private final int numDocs;
private final DocumentSubsetBitsetCache bitsetCache;
private final Query roleQuery;
// we don't use a volatile here because the bitset is resolved before numDocs in the synchronized block
// so any thread that see numDocs != -1 should also see the true value of the roleQueryBits (happens-before).
private BitSet roleQueryBits;
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does this one need to be volatile too?

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I thought it wouldn't be needed since we access the variable after the synchronized block ?

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What about access from getLiveDocs?

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We discussed offline and I added a comment in the code to explain why this is not needed (happens-before):
9e98a69

private volatile int numDocs = -1;

private DocumentSubsetReader(final LeafReader in, DocumentSubsetBitsetCache bitsetCache, final Query roleQuery) throws Exception {
private DocumentSubsetReader(final LeafReader in, DocumentSubsetBitsetCache bitsetCache, final Query roleQuery) {
super(in);
this.roleQueryBits = bitsetCache.getBitSet(roleQuery, in.getContext());
this.numDocs = getNumDocs(in, roleQuery, roleQueryBits);
this.bitsetCache = bitsetCache;
this.roleQuery = roleQuery;
}

/**
* Resolve the role query and the number of docs lazily
*/
private void computeNumDocsIfNeeded() {
if (numDocs == -1) {
synchronized (this) {
if (numDocs == -1) {
try {
roleQueryBits = bitsetCache.getBitSet(roleQuery, in.getContext());
numDocs = getNumDocs(in, roleQuery, roleQueryBits);
} catch (Exception e) {
throw new ElasticsearchException("Failed to load role query", e);
}
}
}
}
}

@Override
public Bits getLiveDocs() {
computeNumDocsIfNeeded();
final Bits actualLiveDocs = in.getLiveDocs();
if (roleQueryBits == null) {
// If we would a <code>null</code> liveDocs then that would mean that no docs are marked as deleted,
// but that isn't the case. No docs match with the role query and therefor all docs are marked as deleted
// If we would return a <code>null</code> liveDocs then that would mean that no docs are marked as deleted,
// but that isn't the case. No docs match with the role query and therefore all docs are marked as deleted
return new Bits.MatchNoBits(in.maxDoc());
} else if (actualLiveDocs == null) {
return roleQueryBits;
Expand All @@ -178,6 +202,7 @@ public Bits getLiveDocs() {

@Override
public int numDocs() {
computeNumDocsIfNeeded();
return numDocs;
}

Expand Down