[Remote Cluster State] Remote state interfaces (#13785)

* Remote Writable Entity interfaces

Signed-off-by: Sooraj Sinha <soosinha@amazon.com>

server/src/main/java/org/opensearch/common/remote/AbstractRemoteWritableBlobEntity.java

@@ -0,0 +1,91 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.common.remote;
+
+import org.opensearch.common.blobstore.BlobPath;
+import org.opensearch.core.compress.Compressor;
+import org.opensearch.core.xcontent.NamedXContentRegistry;
+import org.opensearch.gateway.remote.ClusterMetadataManifest.UploadedMetadata;
+
+import static org.opensearch.gateway.remote.RemoteClusterStateUtils.PATH_DELIMITER;
+
+/**
+ * An extension of {@link RemoteWriteableEntity} class which caters to the use case of writing to and reading from a blob storage
+ *
+ * @param <T> The class type which can be uploaded to or downloaded from a blob storage.
+ */
+public abstract class AbstractRemoteWritableBlobEntity<T> implements RemoteWriteableEntity<T> {
+
+    protected String blobFileName;
+
+    protected String blobName;
+    private final String clusterUUID;
+    private final Compressor compressor;
+    private final NamedXContentRegistry namedXContentRegistry;
+    private String[] pathTokens;
+
+    public AbstractRemoteWritableBlobEntity(
+        final String clusterUUID,
+        final Compressor compressor,
+        final NamedXContentRegistry namedXContentRegistry
+    ) {
+        this.clusterUUID = clusterUUID;
+        this.compressor = compressor;
+        this.namedXContentRegistry = namedXContentRegistry;
+    }
+
+    public abstract BlobPathParameters getBlobPathParameters();
+
+    public String getFullBlobName() {
+        return blobName;
+    }
+
+    public String getBlobFileName() {
+        if (blobFileName == null) {
+            String[] pathTokens = getBlobPathTokens();
+            if (pathTokens == null || pathTokens.length < 1) {
+                return null;
+            }
+            blobFileName = pathTokens[pathTokens.length - 1];
+        }
+        return blobFileName;
+    }
+
+    public String[] getBlobPathTokens() {
+        if (pathTokens != null) {
+            return pathTokens;
+        }
+        if (blobName == null) {
+            return null;
+        }
+        pathTokens = blobName.split(PATH_DELIMITER);
+        return pathTokens;
+    }
+
+    public abstract String generateBlobFileName();
+
+    public String clusterUUID() {
+        return clusterUUID;
+    }
+
+    public abstract UploadedMetadata getUploadedMetadata();
+
+    public void setFullBlobName(BlobPath blobPath) {
+        this.blobName = blobPath.buildAsString() + blobFileName;
+    }
+
+    public NamedXContentRegistry getNamedXContentRegistry() {
+        return namedXContentRegistry;
+    }
+
+    protected Compressor getCompressor() {
+        return compressor;
+    }
+
+}

server/src/main/java/org/opensearch/common/remote/BlobPathParameters.java

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+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.common.remote;
+
+import java.util.List;
+
+/**
+ * Parameters which can be used to construct a blob path
+ *
+ */
+public class BlobPathParameters {
+
+    private final List<String> pathTokens;
+    private final String filePrefix;
+
+    public BlobPathParameters(final List<String> pathTokens, final String filePrefix) {
+        this.pathTokens = pathTokens;
+        this.filePrefix = filePrefix;
+    }
+
+    public List<String> getPathTokens() {
+        return pathTokens;
+    }
+
+    public String getFilePrefix() {
+        return filePrefix;
+    }
+}

server/src/main/java/org/opensearch/common/remote/RemoteWritableEntityStore.java

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+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.common.remote;
+
+import org.opensearch.core.action.ActionListener;
+
+import java.io.IOException;
+
+/**
+ * An interface to read/write an object from/to a remote storage. This interface is agnostic of the remote storage type.
+ *
+ * @param <T> The object type which can be uploaded to or downloaded from remote storage.
+ * @param <U> The wrapper entity which provides methods for serializing/deserializing entity T.
+ */
+public interface RemoteWritableEntityStore<T, U extends RemoteWriteableEntity<T>> {
+
+    public void writeAsync(U entity, ActionListener<Void> listener);
+
+    public T read(U entity) throws IOException;
+
+    public void readAsync(U entity, ActionListener<T> listener);
+}

server/src/main/java/org/opensearch/common/remote/RemoteWriteableEntity.java

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+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.common.remote;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+/**
+ * An interface to which provides defines the serialization/deserialization methods for objects to be uploaded to or downloaded from remote store.
+ * This interface is agnostic of the remote storage type.
+ *
+ * @param <T> The object type which can be uploaded to or downloaded from remote storage.
+ */
+public interface RemoteWriteableEntity<T> {
+    /**
+     * @return An InputStream created by serializing the entity T
+     * @throws IOException Exception encountered while serialization
+     */
+    public InputStream serialize() throws IOException;
+
+    /**
+     * @param inputStream The InputStream which is used to read the serialized entity
+     * @return The entity T after deserialization
+     * @throws IOException Exception encountered while deserialization
+     */
+    public T deserialize(InputStream inputStream) throws IOException;
+
+}

server/src/main/java/org/opensearch/common/remote/package-info.java

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+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+/**
+ * Common remote store package
+ */
+package org.opensearch.common.remote;

server/src/main/java/org/opensearch/gateway/remote/RemoteClusterStateUtils.java

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+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.gateway.remote;
+
+import java.nio.charset.StandardCharsets;
+import java.util.Base64;
+
+/**
+ * Utility class for Remote Cluster State
+ */
+public class RemoteClusterStateUtils {
+    public static final String PATH_DELIMITER = "/";
+
+    public static String encodeString(String content) {
+        return Base64.getUrlEncoder().withoutPadding().encodeToString(content.getBytes(StandardCharsets.UTF_8));
+    }
+}

server/src/main/java/org/opensearch/gateway/remote/model/RemoteClusterStateBlobStore.java

@@ -0,0 +1,107 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.gateway.remote.model;
+
+import org.opensearch.common.blobstore.BlobPath;
+import org.opensearch.common.remote.AbstractRemoteWritableBlobEntity;
+import org.opensearch.common.remote.RemoteWritableEntityStore;
+import org.opensearch.common.remote.RemoteWriteableEntity;
+import org.opensearch.core.action.ActionListener;
+import org.opensearch.gateway.remote.RemoteClusterStateUtils;
+import org.opensearch.index.translog.transfer.BlobStoreTransferService;
+import org.opensearch.repositories.blobstore.BlobStoreRepository;
+import org.opensearch.threadpool.ThreadPool;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.concurrent.ExecutorService;
+
+/**
+ * Abstract class for a blob type storage
+ *
+ * @param <T> The entity which can be uploaded to / downloaded from blob store
+ * @param <U> The concrete class implementing {@link RemoteWriteableEntity} which is used as a wrapper for T entity.
+ */
+public class RemoteClusterStateBlobStore<T, U extends AbstractRemoteWritableBlobEntity<T>> implements RemoteWritableEntityStore<T, U> {
+
+    private final BlobStoreTransferService transferService;
+    private final BlobStoreRepository blobStoreRepository;
+    private final String clusterName;
+    private final ExecutorService executorService;
+
+    public RemoteClusterStateBlobStore(
+        final BlobStoreTransferService blobStoreTransferService,
+        final BlobStoreRepository blobStoreRepository,
+        final String clusterName,
+        final ThreadPool threadPool,
+        final String executor
+    ) {
+        this.transferService = blobStoreTransferService;
+        this.blobStoreRepository = blobStoreRepository;
+        this.clusterName = clusterName;
+        this.executorService = threadPool.executor(executor);
+    }
+
+    @Override
+    public void writeAsync(final U entity, final ActionListener<Void> listener) {
+        try {
+            try (InputStream inputStream = entity.serialize()) {
+                BlobPath blobPath = getBlobPathForUpload(entity);
+                entity.setFullBlobName(blobPath);
+                // TODO uncomment below logic after merging PR https://github.com/opensearch-project/OpenSearch/pull/13836
+                // transferService.uploadBlob(inputStream, getBlobPathForUpload(entity), entity.getBlobFileName(), WritePriority.URGENT,
+                // listener);
+            }
+        } catch (Exception e) {
+            listener.onFailure(e);
+        }
+    }
+
+    public T read(final U entity) throws IOException {
+        // TODO Add timing logs and tracing
+        assert entity.getFullBlobName() != null;
+        return entity.deserialize(transferService.downloadBlob(getBlobPathForDownload(entity), entity.getBlobFileName()));
+    }
+
+    @Override
+    public void readAsync(final U entity, final ActionListener<T> listener) {
+        executorService.execute(() -> {
+            try {
+                listener.onResponse(read(entity));
+            } catch (Exception e) {
+                listener.onFailure(e);
+            }
+        });
+    }
+
+    private BlobPath getBlobPathForUpload(final AbstractRemoteWritableBlobEntity<T> obj) {
+        BlobPath blobPath = blobStoreRepository.basePath()
+            .add(RemoteClusterStateUtils.encodeString(clusterName))
+            .add("cluster-state")
+            .add(obj.clusterUUID());
+        for (String token : obj.getBlobPathParameters().getPathTokens()) {
+            blobPath = blobPath.add(token);
+        }
+        return blobPath;
+    }
+
+    private BlobPath getBlobPathForDownload(final AbstractRemoteWritableBlobEntity<T> obj) {
+        String[] pathTokens = obj.getBlobPathTokens();
+        BlobPath blobPath = new BlobPath();
+        if (pathTokens == null || pathTokens.length < 1) {
+            return blobPath;
+        }
+        // Iterate till second last path token to get the blob folder
+        for (int i = 0; i < pathTokens.length - 1; i++) {
+            blobPath = blobPath.add(pathTokens[i]);
+        }
+        return blobPath;
+    }
+
+}

server/src/main/java/org/opensearch/gateway/remote/model/package-info.java

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+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+/**
+ * Package containing models for remote cluster state
+ */
+package org.opensearch.gateway.remote.model;