Compiled against Kafka 0.10

The 2.* releases compile against Kafka 0.10 based on the respective for-0.10 branch. It is no longer able to connect to a 0.9 broker. The master branch keeps 0.9 compatibility.

Improved handling when Kafka offline

Closed issues: #8, #9, #10, #11, #12 most of which are improvements to the behavior when Kafka is down.

Implemented #4 and #5

In the Offsets view, the lag total for a topic is now shown (#4) and big numbers are formatted with a locale specific group separator (#5) for better readability.

Proper thread safe use of KafkaConsumer

Fixes issues #1, #2 and #3

Fix release for an NPE

Fixes an NPE when initially reading __consumer_offsets.

Group state kept internally

Previously a request for the group state rewound the offsets in __consumer_offsets by an arbitrary number of records and started reading from there, putting together the current state of consumer groups. Now a consumer continuously polls __consumer_offsets and always has the most recent state in memory. In addition, group members are now decoded. Further, groups and offsets are shown in separate tables.

Better groups metadata handling

Improved handling and display of the consumer groups metadata.

Back to Java 1.7 compatibility

Moved back to Java 7. Have sites that cannot yet upgrade to Java 8.

Rudimentary but working

This is still compiled against the 0.9.0 kafka client library. It works with brokers of 0.10.0 too, but does not show extended information like time stamps in messages.