HADOOP-19098. Vector IO: Specify and validate ranges consistently. #6604



Clarifies behaviour of VectorIO methods with contract tests as well as
specification.

* Add precondition range checks to all implementations
* Identify and fix bug where direct buffer reads was broken
  (HADOOP-19101; this surfaced in ABFS contract tests)
* Logging in VectoredReadUtils.
* TestVectoredReadUtils verifies validation logic.
* FileRangeImpl toString() improvements
* CombinedFileRange tracks bytes in range which are wanted;
   toString() output logs this.

HDFS
* Add test TestHDFSContractVectoredRead

ABFS
* Add test ITestAbfsFileSystemContractVectoredRead

S3A
* checks for vector IO being stopped in all iterative
  vector operations, including draining
* maps read() returning -1 to failure
* passes in file length to validation
* Error reporting to only completeExceptionally() those ranges
  which had not yet read data in.
* Improved logging.

readVectored()
* made synchronized. This is only for the invocation;
  the actual async retrieves are unsynchronized.
* closes input stream on invocation
* switches to random IO, so avoids keeping any long-lived connection around.

+ AbstractSTestS3AHugeFiles enhancements.
+ ADDENDUM: test fix in ITestS3AContractVectoredRead
+ ADDENDUM: HADOOP-19098. Vector IO: test failure followup (#6701)

Contains: HADOOP-19101. Vectored Read into off-heap buffer broken in fallback
implementation

Contributed by Steve Loughran
22 files changed