[Remote Store] Add implementation for path types and change default p…

…ath type

Signed-off-by: Ashish Singh <ssashish@amazon.com>

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

@@ -103,9 +103,24 @@ boolean requiresHashAlgorithm() {
         HASHED_PREFIX(1) {
             @Override
             public BlobPath generatePath(PathInput pathInput, PathHashAlgorithm hashAlgorithm) {
-                // TODO - We need to implement this, keeping the same path as Fixed for sake of multiple tests that can fail otherwise.
-                // throw new UnsupportedOperationException("Not implemented"); --> Not using this for unblocking couple of tests.
+                assert Objects.nonNull(hashAlgorithm) : "hashAlgorithm is expected to be non-null";
+                return addPrefix(pathInput.basePath(), hashAlgorithm.hash(pathInput)).add(pathInput.indexUUID())
+                    .add(pathInput.shardId())
+                    .add(pathInput.dataCategory().getName())
+                    .add(pathInput.dataType().getName());
+            }
+
+            @Override
+            boolean requiresHashAlgorithm() {
+                return true;
+            }
+        },
+        HASHED_INFIX(2) {
+            @Override
+            public BlobPath generatePath(PathInput pathInput, PathHashAlgorithm hashAlgorithm) {
+                assert Objects.nonNull(hashAlgorithm) : "hashAlgorithm is expected to be non-null";
                 return pathInput.basePath()
+                    .add(hashAlgorithm.hash(pathInput))
                     .add(pathInput.indexUUID())
                     .add(pathInput.shardId())
                     .add(pathInput.dataCategory().getName())
@@ -200,10 +215,11 @@ public enum PathHashAlgorithm {
 
         FNV_1A(0) {
             @Override
-            long hash(PathInput pathInput) {
+            String hash(PathInput pathInput) {
                 String input = pathInput.indexUUID() + pathInput.shardId() + pathInput.dataCategory().getName() + pathInput.dataType()
                     .getName();
-                return FNV1a.hash32(input);
+                long hash = FNV1a.hash64(input);
+                return RemoteStoreUtils.longToBase64(hash);
             }
         };
 
@@ -218,6 +234,7 @@ public int getCode() {
         }
 
         private static final Map<Integer, PathHashAlgorithm> CODE_TO_ENUM;
+
         static {
             PathHashAlgorithm[] values = values();
             Map<Integer, PathHashAlgorithm> codeToStatus = new HashMap<>(values.length);
@@ -240,7 +257,7 @@ public static PathHashAlgorithm fromCode(int code) {
             return CODE_TO_ENUM.get(code);
         }
 
-        abstract long hash(PathInput pathInput);
+        abstract String hash(PathInput pathInput);
 
         public static PathHashAlgorithm parseString(String pathHashAlgorithm) {
             try {
@@ -257,4 +274,13 @@ public static PathHashAlgorithm parseString(String pathHashAlgorithm) {
          */
         public static final String NAME = "path_hash_algorithm";
     }
+
+    static BlobPath addPrefix(BlobPath blobPath, String prefix) {
+        BlobPath updatedPath = BlobPath.cleanPath();
+        updatedPath = updatedPath.add(prefix);
+        for (String path : blobPath) {
+            updatedPath = updatedPath.add(path);
+        }
+        return updatedPath;
+    }
 }

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

@@ -10,7 +10,9 @@
 
 import org.opensearch.common.collect.Tuple;
 
+import java.nio.ByteBuffer;
 import java.util.Arrays;
+import java.util.Base64;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -101,4 +103,26 @@ public static void verifyNoMultipleWriters(List<String> mdFiles, Function<String
         });
     }
 
+    /**
+     * Converts an input hash which occupies 64 bits of space into Base64 (6 bits per character) String. This must not
+     * be changed as it is used for creating path for storing remote store data on the remote store.
+     */
+    static String longToBase64(long value) {
+        byte[] hashBytes = ByteBuffer.allocate(Long.BYTES).putLong(value).array();
+        return base64(hashBytes);
+    }
+
+    /**
+     * This converts the byte array to base 64 string. `/` is replaced with `_`, `+` is replaced with `-` and `=`
+     * which is padded at the last is also removed. These characters are either used as delimiter or special character
+     * requiring special handling in some vendors. The characters present in this base64 version are [A-Za-z0-9_-].
+     * This must not be changed as it is used for creating path for storing remote store data on the remote store.
+     *
+     * @param bytes byte array
+     * @return base 64 string.
+     */
+    private static String base64(byte[] bytes) {
+        String base64 = Base64.getEncoder().encodeToString(bytes);
+        return base64.substring(0, base64.length() - 1).replace('/', '_').replace('+', '-');
+    }
 }

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

@@ -312,7 +312,7 @@ public class IndicesService extends AbstractLifecycleComponent
      */
     public static final Setting<PathType> CLUSTER_REMOTE_STORE_PATH_PREFIX_TYPE_SETTING = new Setting<>(
         "cluster.remote_store.index.path.prefix.type",
-        PathType.FIXED.toString(),
+        PathType.HASHED_PREFIX.toString(),
         PathType::parseString,
         Property.NodeScope,
         Property.Dynamic