[Remote Store] Add Lock Manager in Remote Segment Store to persist data (#6787)

Signed-off-by: Harish Bhakuni <hbhakuni@amazon.com>

Author: harishbhakuni

server/src/main/java/org/opensearch/index/store/RemoteBufferedIndexOutput.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.index.store;
+
+import org.apache.lucene.store.DataInput;
+import org.apache.lucene.store.OutputStreamIndexOutput;
+import org.opensearch.common.blobstore.BlobContainer;
+import org.opensearch.common.io.stream.BytesStreamOutput;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+/**
+ * Class for output to a file in a {@link RemoteBufferedOutputDirectory}. This is right now used only for writing locks
+ * in remote store. in the future, we can use it for other operations as well.
+ * The current limitation of this is we keep all the file content in memory till we call close(),
+ * So this class should be used to write small files (in MBs).
+ * TODO: extend the class to continously write to the store if content size in buffer gets higher than a specific size.
+ * @see RemoteBufferedOutputDirectory
+ *
+ * @opensearch.internal
+ */
+public class RemoteBufferedIndexOutput extends RemoteIndexOutput {
+    private final BytesStreamOutput out;
+    private final OutputStreamIndexOutput indexOutputBuffer;
+    // visible for testing
+    static final int BUFFER_SIZE = 4096;
+
+    public RemoteBufferedIndexOutput(String name, BlobContainer blobContainer, int bufferSize) {
+        super(name, blobContainer);
+        out = new BytesStreamOutput();
+        indexOutputBuffer = new OutputStreamIndexOutput(name, name, out, bufferSize);
+    }
+
+    public RemoteBufferedIndexOutput(String name, BlobContainer blobContainer) {
+        this(name, blobContainer, BUFFER_SIZE);
+    }
+
+    // Visible for testing
+    RemoteBufferedIndexOutput(String name, BlobContainer blobContainer, BytesStreamOutput out, OutputStreamIndexOutput indexOutputBuffer) {
+        super(name, blobContainer);
+        this.out = out;
+        this.indexOutputBuffer = indexOutputBuffer;
+    }
+
+    @Override
+    public void copyBytes(DataInput input, long numBytes) throws IOException {
+        indexOutputBuffer.copyBytes(input, numBytes);
+    }
+
+    /**
+     * when we trigger close() to close the stream, we will first flush the buffer to output stream and then write all
+     * data to blob container and close the output stream.
+     *
+     */
+    @Override
+    public void close() throws IOException {
+
+        try (final BytesStreamOutput outStream = out; InputStream stream = out.bytes().streamInput()) {
+            indexOutputBuffer.close();
+            blobContainer.writeBlob(getName(), stream, out.bytes().length(), false);
+        }
+
+    }
+
+    /**
+     * This method will write Bytes to the stream we are maintaining.
+     *
+     */
+    @Override
+    public void writeByte(byte b) throws IOException {
+        indexOutputBuffer.writeByte(b);
+    }
+
+    /**
+     * This method will write a byte array to the stream we are maintaining.
+     *
+     */
+    @Override
+    public void writeBytes(byte[] byteArray, int offset, int length) throws IOException {
+        indexOutputBuffer.writeBytes(byteArray, offset, length);
+    }
+
+    /**
+     * This method will return the file pointer to the current position in the stream.
+     *
+     */
+    @Override
+    public long getFilePointer() {
+        return indexOutputBuffer.getFilePointer();
+    }
+
+    /**
+     * This method will return checksum
+     *
+     */
+    @Override
+    public long getChecksum() throws IOException {
+        return indexOutputBuffer.getChecksum();
+    }
+}

server/src/main/java/org/opensearch/index/store/RemoteBufferedOutputDirectory.java

@@ -0,0 +1,32 @@
+/*
+ * 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.index.store;
+
+import org.apache.lucene.store.IOContext;
+import org.apache.lucene.store.IndexOutput;
+import org.opensearch.common.blobstore.BlobContainer;
+
+/**
+ * A {@code RemoteBufferedOutputDirectory} is an extension of RemoteDirectory which also provides an abstraction layer
+ * for storing a list of files to a remote store.
+ * Additionally, with this implementation, creation of new files is also allowed.
+ * A remoteDirectory contains only files (no sub-folder hierarchy).
+ *
+ * @opensearch.internal
+ */
+public class RemoteBufferedOutputDirectory extends RemoteDirectory {
+    public RemoteBufferedOutputDirectory(BlobContainer blobContainer) {
+        super(blobContainer);
+    }
+
+    @Override
+    public IndexOutput createOutput(String name, IOContext context) {
+        return new RemoteBufferedIndexOutput(name, this.blobContainer);
+    }
+}

server/src/main/java/org/opensearch/index/store/RemoteDirectory.java

@@ -35,7 +35,7 @@
  */
 public class RemoteDirectory extends Directory {
 
-    private final BlobContainer blobContainer;
+    protected final BlobContainer blobContainer;
 
     public RemoteDirectory(BlobContainer blobContainer) {
         this.blobContainer = blobContainer;

server/src/main/java/org/opensearch/index/store/RemoteIndexOutput.java

@@ -28,7 +28,7 @@
  */
 public class RemoteIndexOutput extends IndexOutput {
 
-    private final BlobContainer blobContainer;
+    protected final BlobContainer blobContainer;
 
     public RemoteIndexOutput(String name, BlobContainer blobContainer) {
         super(name, name);