fix: dynamodb big-segments treats absent synchronizedOn as never-synced, not error

Author: beekld

libs/server-sdk-dynamodb-source/src/dynamodb_big_segment_store.cpp

@@ -137,8 +137,10 @@ IBigSegmentStore::GetMetadataResult DynamoDBBigSegmentStore::GetMetadata()
 
     auto const it = item.find(kBigSegmentsSyncTimeAttribute);
     if (it == item.end()) {
-        return tl::make_unexpected(
-            "DynamoDB Big Segments metadata row missing 'synchronizedOn'");
+        // "absent" sync time is treated as never synchronized rather than
+        // an error; the wrapper marks the store stale based on the
+        // resulting nullopt.
+        return std::nullopt;
     }
 
     auto const& raw = it->second.GetN();

libs/server-sdk-dynamodb-source/tests/dynamodb_big_segment_store_test.cpp

@@ -185,6 +185,15 @@ TEST_F(DynamoDBBigSegmentTests, GetMetadataReturnsSyncTime) {
               std::chrono::milliseconds{1700000000000LL});
 }
 
+TEST_F(DynamoDBBigSegmentTests, GetMetadataAbsentSyncTimeReturnsNoMetadata) {
+    PrefixedDynamoDBClient(*client_, prefix_, table_name_)
+        .PutBigSegmentMetadataWithoutSyncTime();
+
+    auto const result = store_->GetMetadata();
+    ASSERT_TRUE(result);
+    ASSERT_FALSE(result->has_value());
+}
+
 TEST_F(DynamoDBBigSegmentTests, GetMetadataRejectsMalformedSyncTime) {
     PrefixedDynamoDBClient(*client_, prefix_, table_name_)
         .PutMalformedBigSegmentSyncTime();

libs/server-sdk-dynamodb-source/tests/prefixed_dynamodb_client.hpp

@@ -224,6 +224,24 @@ class PrefixedDynamoDBClient {
         }
     }
 
+    // Writes a metadata row that has no `synchronizedOn` attribute at all.
+    // The metadata row exists but is incomplete; the spec treats absent
+    // sync-time as "never synchronized" rather than an error.
+    void PutBigSegmentMetadataWithoutSyncTime() const {
+        std::string const ns = Prefixed("big_segments_metadata");
+        Aws::DynamoDB::Model::PutItemRequest request;
+        request.SetTableName(table_name_);
+        request.AddItem("namespace", Aws::DynamoDB::Model::AttributeValue{ns});
+        request.AddItem("key", Aws::DynamoDB::Model::AttributeValue{ns});
+
+        auto outcome = client_.PutItem(request);
+        if (!outcome.IsSuccess()) {
+            FAIL() << "couldn't put DynamoDB big-segments metadata without "
+                      "sync time: "
+                   << outcome.GetError().GetMessage();
+        }
+    }
+
     // Writes a metadata row whose `synchronizedOn` is stored as a String
     // instead of a Number. DynamoDB does not enforce non-key attribute types,
     // so a non-Relay writer can produce this shape; we want the store to