A test of lettuce client for redis. The test is used for integration redis as a type of block store in Spark.
In this test, data is stored in an asynchronous steaming fashion and retrieved with synchronous operation.
An additional K-V codec for String key and ByteBuffer value is also defined.
The test result has shown that Java's WritableByteChannelImpl is buffered and not applicable for the type of
output streams that do not flush immediately in a write operation. Therefore, we have reimplemented a new WritableByteChannel with neither buffer nor additional data copy.