From ec9f6657fe774a5995f976c90ded362ee47c2ebb Mon Sep 17 00:00:00 2001
From: kamil-di <149760741+kamil-di@users.noreply.github.com>
Date: Fri, 19 Sep 2025 09:45:38 +0200
Subject: [PATCH] #46752: Fix missing offset assignment logic in checkpoint
 store

---
 .../CHANGELOG.md                                  |  3 ++-
 .../checkpointstore/blob/BlobCheckpointStore.java | 15 ++++++++++++---
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/sdk/eventhubs/azure-messaging-eventhubs-checkpointstore-blob/CHANGELOG.md b/sdk/eventhubs/azure-messaging-eventhubs-checkpointstore-blob/CHANGELOG.md
index 43714c5039d1..ee6360e48b19 100644
--- a/sdk/eventhubs/azure-messaging-eventhubs-checkpointstore-blob/CHANGELOG.md
+++ b/sdk/eventhubs/azure-messaging-eventhubs-checkpointstore-blob/CHANGELOG.md
@@ -8,6 +8,8 @@
 
 ### Bugs Fixed
 
+- Fixed `updateCheckpoint` to properly handle checkpoints when `offsetString` is available but `offset` is null, preventing potential data loss during checkpoint updates.
+
 ### Other Changes
 
 ## 1.21.2 (2025-10-27)
@@ -617,4 +619,3 @@ store checkpoints and balance partition load among all instances of Event Proces
 
 - Initial offset provider for each partition is not implemented.
 - Interoperability with Event Processors of other language SDKs like Python is not supported.
-
diff --git a/sdk/eventhubs/azure-messaging-eventhubs-checkpointstore-blob/src/main/java/com/azure/messaging/eventhubs/checkpointstore/blob/BlobCheckpointStore.java b/sdk/eventhubs/azure-messaging-eventhubs-checkpointstore-blob/src/main/java/com/azure/messaging/eventhubs/checkpointstore/blob/BlobCheckpointStore.java
index 2e5818c031c9..e30fb9b7a3c1 100644
--- a/sdk/eventhubs/azure-messaging-eventhubs-checkpointstore-blob/src/main/java/com/azure/messaging/eventhubs/checkpointstore/blob/BlobCheckpointStore.java
+++ b/sdk/eventhubs/azure-messaging-eventhubs-checkpointstore-blob/src/main/java/com/azure/messaging/eventhubs/checkpointstore/blob/BlobCheckpointStore.java
@@ -243,9 +243,12 @@ private Mono<PartitionOwnership> updateOwnershipETag(Response<?> response, Parti
      */
     @Override
     public Mono<Void> updateCheckpoint(Checkpoint checkpoint) {
-        if (checkpoint == null || (checkpoint.getSequenceNumber() == null && checkpoint.getOffset() == null)) {
+        if (checkpoint == null
+            || (checkpoint.getSequenceNumber() == null
+                && checkpoint.getOffset() == null
+                && CoreUtils.isNullOrEmpty(checkpoint.getOffsetString()))) {
             throw LOGGER.logExceptionAsWarning(Exceptions.propagate(new IllegalStateException(
-                "Both sequence number and offset cannot be null when updating a checkpoint")));
+                "At least one of sequence number or offset information (offset or offsetString) must be provided when updating a checkpoint")));
         }
 
         String partitionId = checkpoint.getPartitionId();
@@ -259,8 +262,14 @@ public Mono<Void> updateCheckpoint(Checkpoint checkpoint) {
         String sequenceNumber
             = checkpoint.getSequenceNumber() == null ? null : String.valueOf(checkpoint.getSequenceNumber());
 
+        String offset;
+        if (CoreUtils.isNullOrEmpty(checkpoint.getOffsetString())) {
+            offset = Objects.toString(checkpoint.getOffset(), null);
+        } else {
+            offset = checkpoint.getOffsetString();
+        }
         metadata.put(SEQUENCE_NUMBER, sequenceNumber);
-        metadata.put(OFFSET, checkpoint.getOffsetString());
+        metadata.put(OFFSET, offset);
         BlobAsyncClient blobAsyncClient = blobClients.get(blobName);
 
         return blobAsyncClient.exists().flatMap(exists -> {