Use stronger write-once semantics for Azure repository (#30437)

There's no need for an extra blobExists() call when writing a blob to the Azure service. Azure
provides an option (with stronger consistency guarantees) on the upload method that guarantees
that the blob that's uploaded does not already exist. This saves one network roundtrip.

Relates to #19749

Author: ywelsch

plugins/repository-azure/qa/microsoft-azure-storage/src/test/java/org/elasticsearch/repositories/azure/AzureStorageTestServer.java

@@ -164,7 +164,12 @@ private static PathTrie<RequestHandler> defaultHandlers(final String endpoint, f
                 if (destContainer == null) {
                     return newContainerNotFoundError(requestId);
                 }
-                destContainer.objects.put(destBlobName, body);
+
+                byte[] existingBytes = destContainer.objects.putIfAbsent(destBlobName, body);
+                if (existingBytes != null) {
+                    return newBlobAlreadyExistsError(requestId);
+                }
+
                 return new Response(RestStatus.CREATED, emptyMap(), "text/plain", EMPTY_BYTE);
             })
         );
@@ -363,6 +368,10 @@ private static Response newBlobNotFoundError(final long requestId) {
         return newError(requestId, RestStatus.NOT_FOUND, "BlobNotFound", "The specified blob does not exist");
     }
 
+    private static Response newBlobAlreadyExistsError(final long requestId) {
+        return newError(requestId, RestStatus.CONFLICT, "BlobAlreadyExists", "The specified blob already exists");
+    }
+
     private static Response newInternalError(final long requestId) {
         return newError(requestId, RestStatus.INTERNAL_SERVER_ERROR, "InternalError", "The server encountered an internal error");
     }

plugins/repository-azure/src/main/java/org/elasticsearch/cloud/azure/blobstore/AzureBlobContainer.java

@@ -88,10 +88,8 @@ public InputStream readBlob(String blobName) throws IOException {
 
     @Override
     public void writeBlob(String blobName, InputStream inputStream, long blobSize) throws IOException {
-        if (blobExists(blobName)) {
-            throw new FileAlreadyExistsException("blob [" + blobName + "] already exists, cannot overwrite");
-        }
         logger.trace("writeBlob({}, stream, {})", buildKey(blobName), blobSize);
+
         try {
             blobStore.writeBlob(buildKey(blobName), inputStream, blobSize);
         } catch (URISyntaxException|StorageException e) {

plugins/repository-azure/src/main/java/org/elasticsearch/cloud/azure/blobstore/AzureBlobStore.java

@@ -34,6 +34,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.net.URISyntaxException;
+import java.nio.file.FileAlreadyExistsException;
 import java.util.Locale;
 import java.util.Map;
 
@@ -115,7 +116,8 @@ public Map<String, BlobMetaData> listBlobsByPrefix(String keyPath, String prefix
         return this.client.listBlobsByPrefix(this.clientName, this.locMode, container, keyPath, prefix);
     }
 
-    public void writeBlob(String blobName, InputStream inputStream, long blobSize) throws URISyntaxException, StorageException {
+    public void writeBlob(String blobName, InputStream inputStream, long blobSize) throws URISyntaxException, StorageException,
+        FileAlreadyExistsException {
         this.client.writeBlob(this.clientName, this.locMode, container, blobName, inputStream, blobSize);
     }
 }

plugins/repository-azure/src/main/java/org/elasticsearch/cloud/azure/storage/AzureStorageService.java

@@ -33,6 +33,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.net.URISyntaxException;
+import java.nio.file.FileAlreadyExistsException;
 import java.util.Map;
 
 /**
@@ -79,7 +80,7 @@ Map<String,BlobMetaData> listBlobsByPrefix(String account, LocationMode mode, St
         throws URISyntaxException, StorageException;
 
     void writeBlob(String account, LocationMode mode, String container, String blobName, InputStream inputStream, long blobSize) throws
-        URISyntaxException, StorageException;
+        URISyntaxException, StorageException, FileAlreadyExistsException;
 
     static InputStream giveSocketPermissionsToStream(InputStream stream) {
         return new InputStream() {

plugins/repository-azure/src/main/java/org/elasticsearch/cloud/azure/storage/AzureStorageServiceImpl.java

@@ -19,11 +19,13 @@
 
 package org.elasticsearch.cloud.azure.storage;
 
+import com.microsoft.azure.storage.AccessCondition;
 import com.microsoft.azure.storage.CloudStorageAccount;
 import com.microsoft.azure.storage.LocationMode;
 import com.microsoft.azure.storage.OperationContext;
 import com.microsoft.azure.storage.RetryExponentialRetry;
 import com.microsoft.azure.storage.RetryPolicy;
+import com.microsoft.azure.storage.StorageErrorCodeStrings;
 import com.microsoft.azure.storage.StorageException;
 import com.microsoft.azure.storage.blob.BlobInputStream;
 import com.microsoft.azure.storage.blob.BlobListingDetails;
@@ -46,8 +48,10 @@
 import org.elasticsearch.repositories.RepositoryException;
 
 import java.io.InputStream;
+import java.net.HttpURLConnection;
 import java.net.URI;
 import java.net.URISyntaxException;
+import java.nio.file.FileAlreadyExistsException;
 import java.util.EnumSet;
 import java.util.HashMap;
 import java.util.Map;
@@ -327,12 +331,21 @@ enumBlobListingDetails, null, generateOperationContext(account))) {
 
     @Override
     public void writeBlob(String account, LocationMode mode, String container, String blobName, InputStream inputStream, long blobSize)
-        throws URISyntaxException, StorageException {
+        throws URISyntaxException, StorageException, FileAlreadyExistsException {
         logger.trace("writeBlob({}, stream, {})", blobName, blobSize);
         CloudBlobClient client = this.getSelectedClient(account, mode);
         CloudBlobContainer blobContainer = client.getContainerReference(container);
         CloudBlockBlob blob = blobContainer.getBlockBlobReference(blobName);
-        SocketAccess.doPrivilegedVoidException(() -> blob.upload(inputStream, blobSize, null, null, generateOperationContext(account)));
+        try {
+            SocketAccess.doPrivilegedVoidException(() -> blob.upload(inputStream, blobSize, AccessCondition.generateIfNotExistsCondition(),
+                null, generateOperationContext(account)));
+        } catch (StorageException se) {
+            if (se.getHttpStatusCode() == HttpURLConnection.HTTP_CONFLICT &&
+                StorageErrorCodeStrings.BLOB_ALREADY_EXISTS.equals(se.getErrorCode())) {
+                throw new FileAlreadyExistsException(blobName, null, se.getMessage());
+            }
+            throw se;
+        }
         logger.trace("writeBlob({}, stream, {}) - done", blobName, blobSize);
     }
 }

plugins/repository-azure/src/test/java/org/elasticsearch/cloud/azure/storage/AzureStorageServiceMock.java

@@ -34,6 +34,7 @@
 import java.io.InputStream;
 import java.net.SocketPermission;
 import java.net.URISyntaxException;
+import java.nio.file.FileAlreadyExistsException;
 import java.nio.file.NoSuchFileException;
 import java.security.AccessController;
 import java.util.Locale;
@@ -106,7 +107,10 @@ public Map<String, BlobMetaData> listBlobsByPrefix(String account, LocationMode
 
     @Override
     public void writeBlob(String account, LocationMode mode, String container, String blobName, InputStream inputStream, long blobSize)
-        throws URISyntaxException, StorageException {
+        throws URISyntaxException, StorageException, FileAlreadyExistsException {
+        if (blobs.containsKey(blobName)) {
+            throw new FileAlreadyExistsException(blobName);
+        }
         try (ByteArrayOutputStream outputStream = new ByteArrayOutputStream()) {
             blobs.put(blobName, outputStream);
             Streams.copy(inputStream, outputStream);