Validate offset topic

src/main/java/com/bakdata/kafka/KafkaConnectorSourceResetter.java

@@ -80,9 +80,9 @@
  * }</pre>
  *
  * Kafka Connect stores offsets for source connectors in a dedicated topic. The key of such an offset consists of the
- * connector name and a connector specific partition name, e.g., {@code ["connector-name", { some-source-specific
- * -data... }] }. This tool finds all partitions belonging to the connector that should be reset and deletes the
- * corresponding offsets.
+ * connector name and a connector specific partition name, e.g.,
+ * {@code ["connector-name", { some-source-specific -data... }] }. This tool finds all partitions belonging to the
+ * connector that should be reset and deletes the corresponding offsets.
  */
 
 @Slf4j
@@ -124,6 +124,9 @@ private static Converter createConverter(final Map<String, Object> kafkaConfig)
 
     @Override
     public void run() {
+        if (this.offsetTopic.isBlank()) {
+            throw new IllegalArgumentException("--offset-topic should be set and cannot be blank.");
+        }
         final String id = this.createId();
         final Map<String, Object> kafkaConfig = this.sharedOptions.createKafkaConfig();
         kafkaConfig.put(ConsumerConfig.CLIENT_ID_CONFIG, id);
@@ -180,6 +183,13 @@ private Consumer<byte[], byte[]> createConsumer(final Map<String, Object> kafkaC
         final Consumer<byte[], byte[]> consumer =
                 new KafkaConsumer<>(kafkaConfig, byteArrayDeserializer, byteArrayDeserializer);
         final List<PartitionInfo> partitions = consumer.partitionsFor(this.offsetTopic);
+        if (partitions.isEmpty()) {
+            final String message = String.format(
+                    "Could not fetch partitions from the offset topic '%s'. Check if the offset topic name is set "
+                            + "correctly.",
+                    this.offsetTopic);
+            throw new IllegalArgumentException(message);
+        }
         final List<TopicPartition> topicPartitions = partitions.stream()
                 .map(KafkaConnectorSourceResetter::toTopicPartition)
                 .collect(Collectors.toList());