turcsanyip commented on code in PR #6319:
URL: https://github.com/apache/nifi/pull/6319#discussion_r981666699


##########
nifi-nar-bundles/nifi-azure-bundle/nifi-azure-processors/src/main/java/org/apache/nifi/processors/azure/eventhub/position/LegacyBlobStorageEventPositionProvider.java:
##########
@@ -0,0 +1,154 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.nifi.processors.azure.eventhub.position;
+
+import com.azure.core.util.BinaryData;
+import com.azure.messaging.eventhubs.models.EventPosition;
+import com.azure.storage.blob.BlobAsyncClient;
+import com.azure.storage.blob.BlobContainerAsyncClient;
+import com.azure.storage.blob.models.BlobItem;
+import com.azure.storage.blob.models.BlobListDetails;
+import com.azure.storage.blob.models.ListBlobsOptions;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.Objects;
+
+/**
+ * Event Position Provider using Azure Blob Storage implemented in Azure Event 
Hubs SDK Version 3
+ */
+public class LegacyBlobStorageEventPositionProvider implements 
EventPositionProvider {
+    private static final String LEASE_SEQUENCE_NUMBER_FIELD = "sequenceNumber";
+
+    private static final Logger logger = 
LoggerFactory.getLogger(LegacyBlobStorageEventPositionProvider.class);
+
+    private static final ObjectMapper objectMapper = new ObjectMapper();
+
+    private final BlobContainerAsyncClient blobContainerAsyncClient;
+
+    private final String consumerGroup;
+
+    public LegacyBlobStorageEventPositionProvider(
+            final BlobContainerAsyncClient blobContainerAsyncClient,
+            final String consumerGroup
+    ) {
+        this.blobContainerAsyncClient = 
Objects.requireNonNull(blobContainerAsyncClient, "Client required");
+        this.consumerGroup = Objects.requireNonNull(consumerGroup, "Consumer 
Group required");
+    }
+
+    /**
+     * Get Initial Partition Event Position using Azure Blob Storage as 
persisted in
+     * 
com.microsoft.azure.eventprocessorhost.AzureStorageCheckpointLeaseManager
+     *
+     * @return Map of Partition and Event Position or empty when no 
checkpoints found
+     */
+    @Override
+    public Map<String, EventPosition> getInitialPartitionEventPosition() {
+        final Map<String, EventPosition> partitionEventPosition;
+
+        if (containerExists()) {
+            final BlobListDetails blobListDetails = new 
BlobListDetails().setRetrieveMetadata(true);
+            final ListBlobsOptions listBlobsOptions = new 
ListBlobsOptions().setPrefix(consumerGroup).setDetails(blobListDetails);
+            final Iterable<BlobItem> blobItems = 
blobContainerAsyncClient.listBlobs(listBlobsOptions).toIterable();
+            partitionEventPosition = getPartitionEventPosition(blobItems);
+        } else {
+            partitionEventPosition = Collections.emptyMap();
+        }
+
+        return partitionEventPosition;
+    }
+
+    private Map<String, EventPosition> getPartitionEventPosition(final 
Iterable<BlobItem> blobItems) {
+        final Map<String, EventPosition> partitionEventPosition = new 
LinkedHashMap<>();
+
+        for (final BlobItem blobItem : blobItems) {
+            if (Boolean.TRUE.equals(blobItem.isPrefix())) {
+                continue;
+            }
+
+            final String partitionId = getPartitionId(blobItem);
+            final EventPosition eventPosition = getEventPosition(blobItem);
+            if (eventPosition == null) {
+                logger.info("Legacy Event Position not found for Partition 
[{}] Blob [{}]", partitionId, blobItem.getName());
+            } else {
+                partitionEventPosition.put(partitionId, eventPosition);
+            }
+        }
+
+        return partitionEventPosition;
+    }
+
+    private String getPartitionId(final BlobItem blobItem) {
+        final String blobItemName = blobItem.getName();
+        final Path blobItemPath = Paths.get(blobItemName);
+        final Path blobItemFileName = blobItemPath.getFileName();
+        return blobItemFileName.toString();
+    }
+
+    private EventPosition getEventPosition(final BlobItem blobItem) {
+        final EventPosition eventPosition;
+
+        final String blobName = blobItem.getName();
+        final BlobAsyncClient blobAsyncClient = 
blobContainerAsyncClient.getBlobAsyncClient(blobName);
+
+        if (itemExists(blobAsyncClient)) {
+            final BinaryData content = 
blobAsyncClient.downloadContent().block();
+            if (content == null) {
+                throw new IllegalStateException(String.format("Legacy Event 
Position content not found [%s]", blobName));
+            }
+
+            try {
+                // Read com.microsoft.azure.eventprocessorhost.AzureBlobLease 
from JSON
+                final JsonNode lease = 
objectMapper.readTree(content.toBytes());
+                if (lease.hasNonNull(LEASE_SEQUENCE_NUMBER_FIELD)) {
+                    final JsonNode sequenceNumberField = 
lease.get(LEASE_SEQUENCE_NUMBER_FIELD);
+                    final long sequenceNumber = sequenceNumberField.asLong();
+                    eventPosition = 
EventPosition.fromSequenceNumber(sequenceNumber);
+
+                    blobAsyncClient.delete().block();

Review Comment:
   I'm afraid we cannot delete the old storage because in a clustered 
environment the "first" Consume processor instance (on the fastest node) reads 
all partition positions and then deletes all the files, but the others would 
need the info for their partitions too.
   I got this error:
   ```
   com.azure.storage.blob.models.BlobStorageException: Status code 404, 
"<U+FEFF><?xml version="1.0" 
encoding="utf-8"?><Error><Code>BlobNotFound</Code><Message>The specified blob 
does not exist.
   ```
   And the "second" consumer could not migrate the offsets for its partitions.
   
   As far as I can see, the consumers need to have the initial positions before 
we know which partitions belong to them so it is not possible to read/delete 
only specific files (each consumer its own files).
   
   



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