GH-5148 Introduce "soft fail" for corrupt ValueStore

Author: ebner

core/sail/nativerdf/src/main/java/org/eclipse/rdf4j/sail/nativerdf/ValueStore.java

@@ -33,6 +33,7 @@
 import org.eclipse.rdf4j.model.vocabulary.XSD;
 import org.eclipse.rdf4j.sail.SailException;
 import org.eclipse.rdf4j.sail.nativerdf.datastore.DataStore;
+import org.eclipse.rdf4j.sail.nativerdf.model.CorruptValue;
 import org.eclipse.rdf4j.sail.nativerdf.model.NativeBNode;
 import org.eclipse.rdf4j.sail.nativerdf.model.NativeIRI;
 import org.eclipse.rdf4j.sail.nativerdf.model.NativeLiteral;
@@ -123,6 +124,11 @@ public class ValueStore extends SimpleValueFactory {
 	 */
 	private final ConcurrentCache<String, Integer> namespaceIDCache;
 
+	/**
+	 * Do not throw an exception in case a value cannot be loaded, e.g. due to a corrupt value store.
+	 */
+	private final boolean softFailOnCorruptData;
+
 	/*--------------*
 	 * Constructors *
 	 *--------------*/
@@ -146,6 +152,15 @@ public ValueStore(File dataDir, boolean forceSync, int valueCacheSize, int value
 		namespaceIDCache = new ConcurrentCache<>(namespaceIDCacheSize);
 
 		setNewRevision();
+
+		/*
+		 * Soft failure when a ValueStore is corrupt (i.e., one or more NativeValues cannot be read properly) can be
+		 * enabled using the system property org.eclipse.rdf4j.sail.nativerdf.softFailOnCorruptData (boolean). The
+		 * default behavior is that ValueStore will fail hard with a SailException, whereas softFaileOnCorruptData set
+		 * to true will make ValueStore return instances of CorruptValue if NativeValue cannot be read.
+		 */
+		this.softFailOnCorruptData = "true"
+				.equalsIgnoreCase(System.getProperty("org.eclipse.rdf4j.sail.nativerdf.softFailOnCorruptData"));
 	}
 
 	/*---------*
@@ -526,6 +541,12 @@ private boolean isNamespaceData(byte[] data) {
 	}
 
 	private NativeValue data2value(int id, byte[] data) throws IOException {
+		if (data.length == 0) {
+			if (softFailOnCorruptData) {
+				return new CorruptValue(revision, id);
+			}
+			throw new SailException("Empty data array for value with id " + id);
+		}
 		switch (data[0]) {
 		case URI_VALUE:
 			return data2uri(id, data);
@@ -534,7 +555,10 @@ private NativeValue data2value(int id, byte[] data) throws IOException {
 		case LITERAL_VALUE:
 			return data2literal(id, data);
 		default:
-			throw new IllegalArgumentException("Invalid type " + data[0] + " for value with id " + id);
+			if (softFailOnCorruptData) {
+				return new CorruptValue(revision, id);
+			}
+			throw new SailException("Invalid type " + data[0] + " for value with id " + id);
 		}
 	}
 

core/sail/nativerdf/src/main/java/org/eclipse/rdf4j/sail/nativerdf/model/CorruptValue.java

@@ -0,0 +1,91 @@
+/*******************************************************************************
+ * Copyright (c) 2024 Eclipse RDF4J contributors, Aduna, and others.
+ *
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Distribution License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *******************************************************************************/
+package org.eclipse.rdf4j.sail.nativerdf.model;
+
+import org.eclipse.rdf4j.sail.nativerdf.ValueStoreRevision;
+
+/**
+ * CorruptValue is used when a NativeValue cannot be read from the ValueStore and if soft failure is enabled (see
+ * ValueStore#softFailOnCorruptData).
+ *
+ * There is no method isCorruptValue() is it would exist for a "regular" implementation of NativeValue. Since
+ * CorruptValue is only to be used in exceptional situations, the recommended way of checking for it is using
+ * "instanceof".
+ *
+ * @author Hannes Ebner
+ */
+public class CorruptValue implements NativeValue {
+
+	/*-----------*
+	 * Constants *
+	 *-----------*/
+
+	private static final long serialVersionUID = 8829067881854394802L;
+
+	/*----------*
+	 * Variables *
+	 *----------*/
+
+	private volatile ValueStoreRevision revision;
+
+	private volatile int internalID;
+
+	/*--------------*
+	 * Constructors *
+	 *--------------*/
+
+	public CorruptValue(ValueStoreRevision revision, int internalID) {
+		setInternalID(internalID, revision);
+	}
+
+	/*---------*
+	 * Methods *
+	 *---------*/
+
+	@Override
+	public void setInternalID(int internalID, ValueStoreRevision revision) {
+		this.internalID = internalID;
+		this.revision = revision;
+	}
+
+	@Override
+	public ValueStoreRevision getValueStoreRevision() {
+		return revision;
+	}
+
+	@Override
+	public int getInternalID() {
+		return internalID;
+	}
+
+	public String stringValue() {
+		return Integer.toString(internalID);
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		if (this == o) {
+			return true;
+		}
+
+		if (o instanceof CorruptValue && internalID != NativeValue.UNKNOWN_ID) {
+			CorruptValue otherCorruptValue = (CorruptValue) o;
+
+			if (otherCorruptValue.internalID != NativeValue.UNKNOWN_ID && revision.equals(otherCorruptValue.revision)) {
+				// CorruptValue is from the same revision of the same native store with both IDs set
+				return internalID == otherCorruptValue.internalID;
+			}
+		}
+
+		return super.equals(o);
+	}
+
+}