Add faster scaling composite hash value encoding for remote path

server/src/internalClusterTest/java/org/opensearch/remotestore/RemoteRestoreSnapshotIT.java

@@ -59,7 +59,7 @@
 import static org.opensearch.index.remote.RemoteStoreEnums.DataCategory.TRANSLOG;
 import static org.opensearch.index.remote.RemoteStoreEnums.DataType.DATA;
 import static org.opensearch.index.remote.RemoteStoreEnums.DataType.METADATA;
-import static org.opensearch.indices.IndicesService.CLUSTER_REMOTE_STORE_PATH_PREFIX_TYPE_SETTING;
+import static org.opensearch.indices.IndicesService.CLUSTER_REMOTE_STORE_PATH_TYPE_SETTING;
 import static org.opensearch.test.hamcrest.OpenSearchAssertions.assertAcked;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.greaterThan;
@@ -229,7 +229,7 @@ public void testRemoteStoreCustomDataOnIndexCreationAndRestore() {
         client(clusterManagerNode).admin()
             .cluster()
             .prepareUpdateSettings()
-            .setTransientSettings(Settings.builder().put(CLUSTER_REMOTE_STORE_PATH_PREFIX_TYPE_SETTING.getKey(), PathType.FIXED))
+            .setTransientSettings(Settings.builder().put(CLUSTER_REMOTE_STORE_PATH_TYPE_SETTING.getKey(), PathType.FIXED))
             .get();
         createRepository(snapshotRepoName, "fs", getRepositorySettings(absolutePath1, true));
         Client client = client();
@@ -260,7 +260,7 @@ public void testRemoteStoreCustomDataOnIndexCreationAndRestore() {
         client(clusterManagerNode).admin()
             .cluster()
             .prepareUpdateSettings()
-            .setTransientSettings(Settings.builder().put(CLUSTER_REMOTE_STORE_PATH_PREFIX_TYPE_SETTING.getKey(), PathType.HASHED_PREFIX))
+            .setTransientSettings(Settings.builder().put(CLUSTER_REMOTE_STORE_PATH_TYPE_SETTING.getKey(), PathType.HASHED_PREFIX))
             .get();
 
         restoreSnapshotResponse = client.admin()
@@ -272,13 +272,13 @@ public void testRemoteStoreCustomDataOnIndexCreationAndRestore() {
             .get();
         assertEquals(RestStatus.ACCEPTED, restoreSnapshotResponse.status());
         ensureGreen(restoredIndexName1version2);
-        validatePathType(restoredIndexName1version2, PathType.HASHED_PREFIX, PathHashAlgorithm.FNV_1A);
+        validatePathType(restoredIndexName1version2, PathType.HASHED_PREFIX, PathHashAlgorithm.FNV_1A_COMPOSITE_1);
 
-        // Create index with cluster setting cluster.remote_store.index.path.prefix.type as hashed_prefix.
+        // Create index with cluster setting cluster.remote_store.index.path.type as hashed_prefix.
         indexSettings = getIndexSettings(1, 0).build();
         createIndex(indexName2, indexSettings);
         ensureGreen(indexName2);
-        validatePathType(indexName2, PathType.HASHED_PREFIX, PathHashAlgorithm.FNV_1A);
+        validatePathType(indexName2, PathType.HASHED_PREFIX, PathHashAlgorithm.FNV_1A_COMPOSITE_1);
 
         // Validating that custom data has not changed for indexes which were created before the cluster setting got updated
         validatePathType(indexName1, PathType.FIXED);
@@ -294,7 +294,7 @@ public void testRemoteStoreCustomDataOnIndexCreationAndRestore() {
         client(clusterManagerNode).admin()
             .cluster()
             .prepareUpdateSettings()
-            .setTransientSettings(Settings.builder().put(CLUSTER_REMOTE_STORE_PATH_PREFIX_TYPE_SETTING.getKey(), PathType.FIXED))
+            .setTransientSettings(Settings.builder().put(CLUSTER_REMOTE_STORE_PATH_TYPE_SETTING.getKey(), PathType.FIXED))
             .get();
 
         // Close index 2
@@ -309,7 +309,7 @@ public void testRemoteStoreCustomDataOnIndexCreationAndRestore() {
         ensureGreen(indexName2);
 
         // Validating that custom data has not changed for testindex2 which was created before the cluster setting got updated
-        validatePathType(indexName2, PathType.HASHED_PREFIX, PathHashAlgorithm.FNV_1A);
+        validatePathType(indexName2, PathType.HASHED_PREFIX, PathHashAlgorithm.FNV_1A_COMPOSITE_1);
     }
 
     private void validatePathType(String index, PathType pathType) {

server/src/main/java/org/opensearch/common/settings/ClusterSettings.java

@@ -712,7 +712,8 @@ public void apply(Settings value, Settings current, Settings previous) {
                 RemoteStoreNodeService.MIGRATION_DIRECTION_SETTING,
                 IndicesService.CLUSTER_REMOTE_INDEX_RESTRICT_ASYNC_DURABILITY_SETTING,
                 IndicesService.CLUSTER_INDEX_RESTRICT_REPLICATION_TYPE_SETTING,
-                IndicesService.CLUSTER_REMOTE_STORE_PATH_PREFIX_TYPE_SETTING,
+                IndicesService.CLUSTER_REMOTE_STORE_PATH_TYPE_SETTING,
+                IndicesService.CLUSTER_REMOTE_STORE_PATH_HASH_ALGORITHM_SETTING,
 
                 // Admission Control Settings
                 AdmissionControlSettings.ADMISSION_CONTROL_TRANSPORT_LAYER_MODE,

server/src/main/java/org/opensearch/index/remote/RemoteStoreEnums.java

@@ -23,6 +23,8 @@
 import static java.util.Collections.unmodifiableMap;
 import static org.opensearch.index.remote.RemoteStoreEnums.DataType.DATA;
 import static org.opensearch.index.remote.RemoteStoreEnums.DataType.METADATA;
+import static org.opensearch.index.remote.RemoteStoreUtils.longToCompositeBase64AndBinaryEncoding;
+import static org.opensearch.index.remote.RemoteStoreUtils.longToUrlBase64;
 
 /**
  * This class contains the different enums related to remote store like data categories and types, path types
@@ -216,13 +218,26 @@ public static PathType parseString(String pathType) {
     @PublicApi(since = "2.14.0")
     public enum PathHashAlgorithm {
 
-        FNV_1A(0) {
+        FNV_1A_BASE64(0) {
             @Override
             String hash(PathInput pathInput) {
                 String input = pathInput.indexUUID() + pathInput.shardId() + pathInput.dataCategory().getName() + pathInput.dataType()
                     .getName();
                 long hash = FNV1a.hash64(input);
-                return RemoteStoreUtils.longToUrlBase64(hash);
+                return longToUrlBase64(hash);
+            }
+        },
+        /**
+         * This hash algorithm will generate a hash value which will use 1st 6 bits to create bas64 character and next 14
+         * bits to create binary string.
+         */
+        FNV_1A_COMPOSITE_1(1) {
+            @Override
+            String hash(PathInput pathInput) {
+                String input = pathInput.indexUUID() + pathInput.shardId() + pathInput.dataCategory().getName() + pathInput.dataType()
+                    .getName();
+                long hash = FNV1a.hash64(input);
+                return longToCompositeBase64AndBinaryEncoding(hash, 20);
             }
         };
 

server/src/main/java/org/opensearch/index/remote/RemoteStorePathStrategyResolver.java

@@ -25,12 +25,16 @@ public class RemoteStorePathStrategyResolver {
 
     private volatile PathType type;
 
+    private volatile PathHashAlgorithm hashAlgorithm;
+
     private final Supplier<Version> minNodeVersionSupplier;
 
     public RemoteStorePathStrategyResolver(ClusterSettings clusterSettings, Supplier<Version> minNodeVersionSupplier) {
         this.minNodeVersionSupplier = minNodeVersionSupplier;
-        type = clusterSettings.get(IndicesService.CLUSTER_REMOTE_STORE_PATH_PREFIX_TYPE_SETTING);
-        clusterSettings.addSettingsUpdateConsumer(IndicesService.CLUSTER_REMOTE_STORE_PATH_PREFIX_TYPE_SETTING, this::setType);
+        type = clusterSettings.get(IndicesService.CLUSTER_REMOTE_STORE_PATH_TYPE_SETTING);
+        hashAlgorithm = clusterSettings.get(IndicesService.CLUSTER_REMOTE_STORE_PATH_HASH_ALGORITHM_SETTING);
+        clusterSettings.addSettingsUpdateConsumer(IndicesService.CLUSTER_REMOTE_STORE_PATH_TYPE_SETTING, this::setType);
+        clusterSettings.addSettingsUpdateConsumer(IndicesService.CLUSTER_REMOTE_STORE_PATH_HASH_ALGORITHM_SETTING, this::setHashAlgorithm);
     }
 
     public RemoteStorePathStrategy get() {
@@ -39,11 +43,15 @@ public RemoteStorePathStrategy get() {
         // Min node version check ensures that we are enabling the new prefix type only when all the nodes understand it.
         pathType = Version.CURRENT.compareTo(minNodeVersionSupplier.get()) <= 0 ? type : PathType.FIXED;
         // If the path type is fixed, hash algorithm is not applicable.
-        pathHashAlgorithm = pathType == PathType.FIXED ? null : PathHashAlgorithm.FNV_1A;
+        pathHashAlgorithm = pathType == PathType.FIXED ? null : hashAlgorithm;
         return new RemoteStorePathStrategy(pathType, pathHashAlgorithm);
     }
 
     private void setType(PathType type) {
         this.type = type;
     }
+
+    private void setHashAlgorithm(PathHashAlgorithm hashAlgorithm) {
+        this.hashAlgorithm = hashAlgorithm;
+    }
 }

server/src/main/java/org/opensearch/index/remote/RemoteStoreUtils.java

@@ -15,6 +15,7 @@
 import java.util.Base64;
 import java.util.HashMap;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.function.Function;
 
@@ -26,10 +27,16 @@
 public class RemoteStoreUtils {
     public static final int LONG_MAX_LENGTH = String.valueOf(Long.MAX_VALUE).length();
 
+    /**
+     * URL safe base 64 character set. This must not be changed as this is used in deriving the base64 equivalent of binary.
+     */
+    static final char[] URL_BASE64_CHARSET = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_".toCharArray();
+
     /**
      * This method subtracts given numbers from Long.MAX_VALUE and returns a string representation of the result.
      * The resultant string is guaranteed to be of the same length that of Long.MAX_VALUE. If shorter, we add left padding
      * of 0s to the string.
+     *
      * @param num number to get the inverted long string for
      * @return String value of Long.MAX_VALUE - num
      */
@@ -46,6 +53,7 @@
 
     /**
      * This method converts the given string into long and subtracts it from Long.MAX_VALUE
+     *
      * @param str long in string format to be inverted
      * @return long value of the invert result
      */
@@ -59,6 +67,7 @@
 
     /**
      * Extracts the segment name from the provided segment file name
+     *
      * @param filename Segment file name to parse
      * @return Name of the segment that the segment file belongs to
      */
@@ -79,10 +88,9 @@
     }
 
     /**
-     *
      * @param mdFiles List of segment/translog metadata files
-     * @param fn Function to extract PrimaryTerm_Generation and Node Id from metadata file name .
-     *          fn returns null if node id is not part of the file name
+     * @param fn      Function to extract PrimaryTerm_Generation and Node Id from metadata file name .
+     *                fn returns null if node id is not part of the file name
      */
     public static void verifyNoMultipleWriters(List<String> mdFiles, Function<String, Tuple<String, String>> fn) {
         Map<String, String> nodesByPrimaryTermAndGen = new HashMap<>();
@@ -116,4 +124,26 @@
         String base64Str = Base64.getUrlEncoder().encodeToString(hashBytes);
         return base64Str.substring(0, base64Str.length() - 1);
     }
+
+    static long urlBase64ToLong(String base64Str) {
+        byte[] hashBytes = Base64.getUrlDecoder().decode(base64Str);
+        return ByteBuffer.wrap(hashBytes).getLong();
+    }
+
+    /**
+     * Converts an input hash which occupies 64 bits of memory into a composite encoded string. The string will have 2 parts -
+     * 1. Base 64 string and 2. Binary String. We will use the first 6 bits for creating the base 64 string.
+     * For the second part, the rest of the bits (of length {@code len}-6) will be used as is in string form.
+     */
+    static String longToCompositeBase64AndBinaryEncoding(long value, int len) {
+        if (len < 7 || len > 64) {
+            throw new IllegalArgumentException("In longToCompositeBase64AndBinaryEncoding, len must be between 7 and 64 (both inclusive)");
+        }
+        String binaryEncoding = String.format(Locale.ROOT, "%64s", Long.toBinaryString(value)).replace(' ', '0');
+        String base64Part = binaryEncoding.substring(0, 6);
+        String binaryPart = binaryEncoding.substring(6, len);
+        int base64DecimalValue = Integer.valueOf(base64Part, 2);
+        assert base64DecimalValue >= 0 && base64DecimalValue < 64;
+        return URL_BASE64_CHARSET[base64DecimalValue] + binaryPart;
+    }
 }

server/src/main/java/org/opensearch/indices/IndicesService.java

@@ -124,6 +124,7 @@
 import org.opensearch.index.query.QueryRewriteContext;
 import org.opensearch.index.recovery.RecoveryStats;
 import org.opensearch.index.refresh.RefreshStats;
+import org.opensearch.index.remote.RemoteStoreEnums.PathHashAlgorithm;
 import org.opensearch.index.remote.RemoteStoreEnums.PathType;
 import org.opensearch.index.remote.RemoteStoreStatsTrackerFactory;
 import org.opensearch.index.search.stats.SearchStats;
@@ -307,17 +308,30 @@ public class IndicesService extends AbstractLifecycleComponent
     );
 
     /**
-     * This setting is used to set the remote store blob store path prefix strategy. This setting is effective only for
+     * This setting is used to set the remote store blob store path type strategy. This setting is effective only for
      * remote store enabled cluster.
      */
-    public static final Setting<PathType> CLUSTER_REMOTE_STORE_PATH_PREFIX_TYPE_SETTING = new Setting<>(
-        "cluster.remote_store.index.path.prefix.type",
+    public static final Setting<PathType> CLUSTER_REMOTE_STORE_PATH_TYPE_SETTING = new Setting<>(
+        "cluster.remote_store.index.path.type",
         PathType.FIXED.toString(),
         PathType::parseString,
         Property.NodeScope,
         Property.Dynamic
     );
 
+    /**
+     * This setting is used to set the remote store blob store path hash algorithm strategy. This setting is effective only for
+     * remote store enabled cluster. This setting will come to effect if the {@link #CLUSTER_REMOTE_STORE_PATH_TYPE_SETTING}
+     * is either {@code HASHED_PREFIX} or {@code HASHED_INFIX}.
+     */
+    public static final Setting<PathHashAlgorithm> CLUSTER_REMOTE_STORE_PATH_HASH_ALGORITHM_SETTING = new Setting<>(
+        "cluster.remote_store.index.path.hash_algorithm",
+        PathHashAlgorithm.FNV_1A_COMPOSITE_1.toString(),
+        PathHashAlgorithm::parseString,
+        Property.NodeScope,
+        Property.Dynamic
+    );
+
     /**
      * The node's settings.
      */

server/src/test/java/org/opensearch/cluster/metadata/MetadataCreateIndexServiceTests.java

@@ -1711,7 +1711,7 @@ public void testRemoteCustomData() {
         validateRemoteCustomData(
             indexMetadata.getCustomData(IndexMetadata.REMOTE_STORE_CUSTOM_KEY),
             PathHashAlgorithm.NAME,
-            PathHashAlgorithm.FNV_1A.name()
+            PathHashAlgorithm.FNV_1A_COMPOSITE_1.name()
         );
     }
 
@@ -1720,7 +1720,7 @@ private IndexMetadata testRemoteCustomData(boolean remoteStoreEnabled, PathType
         if (remoteStoreEnabled) {
             settingsBuilder.put(NODE_ATTRIBUTES.getKey() + REMOTE_STORE_SEGMENT_REPOSITORY_NAME_ATTRIBUTE_KEY, "test");
         }
-        settingsBuilder.put(IndicesService.CLUSTER_REMOTE_STORE_PATH_PREFIX_TYPE_SETTING.getKey(), pathType.toString());
+        settingsBuilder.put(IndicesService.CLUSTER_REMOTE_STORE_PATH_TYPE_SETTING.getKey(), pathType.toString());
         Settings settings = settingsBuilder.build();
 
         ClusterService clusterService = mock(ClusterService.class);