Eventhubs: Refactor Destination Table Semantics (#1200)

The destination table name in table mapping of Create CDC Mirror now
expected to look like:
```
<eventhub_name>.<eventhub_namespace>.<unique_identifier>.<partition_key>
```
This is to allow multiple source tables to be mapped to same eventhub
partition.
`unique identifier` can be the source table name or anything else. It's
purely to distinguish destination table names

flow/connectors/eventhub/eventhub.go

@@ -267,11 +267,18 @@ func (c *EventHubConnector) SyncRecords(req *model.SyncRecordsRequest) (*model.S
 	}, nil
 }
 
+func (c *EventHubConnector) GetPeerOfEventhubNamespace(eventhubNamespace string) string {
+	for peerName, config := range c.config.Eventhubs {
+		if config.Namespace == eventhubNamespace {
+			return peerName
+		}
+	}
+	return ""
+}
+
 func (c *EventHubConnector) CreateRawTable(req *protos.CreateRawTableInput) (*protos.CreateRawTableOutput, error) {
 	// create topics for each table
-	// key is the source table and value is the "eh_peer.eh_topic" that ought to be used.
 	tableMap := req.GetTableNameMapping()
-
 	for _, destinationTable := range tableMap {
 		// parse peer name and topic name.
 		name, err := NewScopedEventhub(destinationTable)
@@ -281,7 +288,8 @@ func (c *EventHubConnector) CreateRawTable(req *protos.CreateRawTableInput) (*pr
 			return nil, err
 		}
 
-		err = c.hubManager.EnsureEventHubExists(c.ctx, name)
+		peerName := c.GetPeerOfEventhubNamespace(name.EventhubNamespace)
+		err = c.hubManager.EnsureEventHubExists(c.ctx, name, peerName)
 		if err != nil {
 			c.logger.Error("failed to ensure eventhub exists",
 				slog.Any("error", err), slog.String("destinationTable", destinationTable))

flow/connectors/eventhub/hubmanager.go

@@ -68,12 +68,7 @@ func (m *EventHubManager) GetNumPartitions(ctx context.Context, name ScopedEvent
 func (m *EventHubManager) GetOrCreateHubClient(ctx context.Context, name ScopedEventhub) (
 	*azeventhubs.ProducerClient, error,
 ) {
-	ehConfig, ok := m.peerConfig.Get(name.PeerName)
-	if !ok {
-		return nil, fmt.Errorf("eventhub '%s' not configured", name.Eventhub)
-	}
-
-	namespace := ehConfig.Namespace
+	namespace := name.EventhubNamespace
 	// if the namespace isn't fully qualified, add the `.servicebus.windows.net`
 	// check by counting the number of '.' in the namespace
 	if strings.Count(namespace, ".") < 2 {
@@ -164,10 +159,10 @@ func (m *EventHubManager) CreateEventDataBatch(ctx context.Context, destination
 }
 
 // EnsureEventHubExists ensures that the eventhub exists.
-func (m *EventHubManager) EnsureEventHubExists(ctx context.Context, name ScopedEventhub) error {
-	cfg, ok := m.peerConfig.Get(name.PeerName)
+func (m *EventHubManager) EnsureEventHubExists(ctx context.Context, name ScopedEventhub, peerName string) error {
+	cfg, ok := m.peerConfig.Get(peerName)
 	if !ok {
-		return fmt.Errorf("eventhub peer '%s' not configured", name.PeerName)
+		return fmt.Errorf("eventhub peer '%s' not configured", peerName)
 	}
 
 	hubClient, err := m.getEventHubMgmtClient(cfg.SubscriptionId)

flow/connectors/eventhub/scoped_eventhub.go

@@ -9,25 +9,30 @@ import (
 // partition_column is the column in the table that is used to determine
 // the partition key for the eventhub. Partition value is one such value of that column.
 type ScopedEventhub struct {
-	PeerName           string
+	EventhubNamespace  string
 	Eventhub           string
 	PartitionKeyColumn string
 	PartitionKeyValue  string
 }
 
 func NewScopedEventhub(dstTableName string) (ScopedEventhub, error) {
-	// split by dot, the model is peername.eventhub.partition_key_column
+	// split by dot, the model is eventhub.eventhub_namespace.table_name.partition_key_column
 	parts := strings.Split(dstTableName, ".")
 
-	if len(parts) != 3 {
+	if len(parts) != 4 {
 		return ScopedEventhub{}, fmt.Errorf("invalid scoped eventhub '%s'", dstTableName)
 	}
 
-	// support eventhub name and partition key with hyphens etc.
-	eventhubPart := strings.Trim(parts[1], `"`)
-	partitionPart := strings.Trim(parts[2], `"`)
+	// support eventhub namespace, eventhub name, partition key with hyphens etc.
+	// part[2] will be some table identifier.
+	// It's just so that we have distinct destination table names
+	// in create mirror's table mapping.
+	// We can ignore it.
+	eventhubPart := strings.Trim(parts[0], `"`)
+	namespacePart := strings.Trim(parts[1], `"`)
+	partitionPart := strings.Trim(parts[3], `"`)
 	return ScopedEventhub{
-		PeerName:           parts[0],
+		EventhubNamespace:  namespacePart,
 		Eventhub:           eventhubPart,
 		PartitionKeyColumn: partitionPart,
 	}, nil
@@ -37,14 +42,7 @@ func (s *ScopedEventhub) SetPartitionValue(value string) {
 	s.PartitionKeyValue = value
 }
 
-func (s ScopedEventhub) Equals(other ScopedEventhub) bool {
-	return s.PeerName == other.PeerName &&
-		s.Eventhub == other.Eventhub &&
-		s.PartitionKeyColumn == other.PartitionKeyColumn &&
-		s.PartitionKeyValue == other.PartitionKeyValue
-}
-
 // ToString returns the string representation of the ScopedEventhub
 func (s ScopedEventhub) ToString() string {
-	return fmt.Sprintf("%s.%s.%s.%s", s.PeerName, s.Eventhub, s.PartitionKeyColumn, s.PartitionKeyValue)
+	return fmt.Sprintf("%s.%s.%s.%s", s.EventhubNamespace, s.Eventhub, s.PartitionKeyColumn, s.PartitionKeyValue)
 }