[HADOOP-13017] Implementations of InputStream.read(buffer, offset, bytes) to exit 0 if bytes==0

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.8.0
• Fix Version/s: 2.8.0
• Component/s: fs, io
• Assignee: Steve Loughran
• Reporter: Steve Loughran
• Created: 11/Apr/16 21:39
• Updated: 28/Feb/17 17:25
• Resolved: 27/Oct/16 06:57

Description

HDFS-10277 showed that HDFS was return -1 on read(buf[], 0, 0) when there was no data left in the stream; Java IO says

If len is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read at least one byte.

Review the implementations of {{IOStream.(buffer, offset, bytes)} and, where necessary and considered safe, add a fast exit if the length is 0.

Issue Links

• breaks: HADOOP-13798 TestHadoopArchives times out
• is depended upon by: HADOOP-11694 Über-jira: S3a phase II: robustness, scale and performance
• relates to: HDFS-10277 PositionedReadable test testReadFullyZeroByteFile failing in HDFS
• relates to: HADOOP-12994 Specify PositionedReadable, add contract tests, fix problems