Allow kafka group.id to be configured (Graylog2#5867)

Signed-off-by: Pierre De Paepe <[email protected]>

Closes Graylog2#3976

Author: pdepaepe

graylog2-server/src/main/java/org/graylog2/inputs/transports/KafkaTransport.java

@@ -72,13 +72,13 @@
 import static com.codahale.metrics.MetricRegistry.name;
 
 public class KafkaTransport extends ThrottleableTransport {
-    public static final String GROUP_ID = "graylog2";
     public static final String CK_FETCH_MIN_BYTES = "fetch_min_bytes";
     public static final String CK_FETCH_WAIT_MAX = "fetch_wait_max";
     public static final String CK_ZOOKEEPER = "zookeeper";
     public static final String CK_TOPIC_FILTER = "topic_filter";
     public static final String CK_THREADS = "threads";
     public static final String CK_OFFSET_RESET = "offset_reset";
+    public static final String CK_GROUP_ID = "group_id";
 
     // See https://kafka.apache.org/090/documentation.html for available values for "auto.offset.reset".
     private static final ImmutableMap<String, String> OFFSET_RESET_VALUES = ImmutableMap.of(
@@ -87,6 +87,7 @@ public class KafkaTransport extends ThrottleableTransport {
     );
 
     private static final String DEFAULT_OFFSET_RESET = "largest";
+    private static final String DEFAULT_GROUP_ID = "graylog2";
 
     private static final Logger LOG = LoggerFactory.getLogger(KafkaTransport.class);
 
@@ -185,7 +186,7 @@ public void run() {
 
         final Properties props = new Properties();
 
-        props.put("group.id", GROUP_ID);
+        props.put("group.id", configuration.getString(CK_GROUP_ID, DEFAULT_GROUP_ID));
         props.put("client.id", "gl2-" + nodeId + "-" + input.getId());
 
         props.put("fetch.min.bytes", String.valueOf(configuration.getInt(CK_FETCH_MIN_BYTES)));
@@ -382,6 +383,13 @@ public ConfigurationRequest getRequestedConfiguration() {
                     "What to do when there is no initial offset in ZooKeeper or if an offset is out of range",
                     ConfigurationField.Optional.OPTIONAL));
 
+            cr.addField(new TextField(
+                    CK_GROUP_ID,
+                    "Consumer group id",
+                    DEFAULT_GROUP_ID,
+                    "Name of the consumer group the Kafka input belongs to",
+                    ConfigurationField.Optional.OPTIONAL));
+
             return cr;
         }
     }