* 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.

* Improve the implementation mechanism of queue mode. #96

* refactor the code .

* add Copyright & License description into header text of code files.

* refactor

* set version to 2.2.0

* update unit tests.

* add exception class to process the publish send and subscriber exectution exception

* modify first retry time to three.

* code refactor.

* add retry mechanism

* code refactor

* refactor consumer execution

* fix spell error

* remove dashboard  `processing ` content.

* Modify the retry to retry the message only 4 minutes ago.

* update samples

* update ci configuration.