* fixed message enqueue exception in v2.2

* add log to samples

* Improved log output.  #114

* add default timeout configuration for kafka client.

* fixed retry processor bugs.

* Fixed kafka producer exception log without logging when publish message.

* update version num to 2.2.2

* rename configuration options FailedCallback to FailedThresholdCallback

* rename files name.

* remove unused files.

* modify the error comments.

* update samples.

* add logs.