Chris Nauroth created HADOOP-19389:
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Summary: Optimize shell -text command I/O with multi-byte read.
Key: HADOOP-19389
URL: https://issues.apache.org/jira/browse/HADOOP-19389
Project: Hadoop Common
Issue Type: Improvement
Components: fs
Reporter: Chris Nauroth
Assignee: Chris Nauroth
{{hadoop fs -text}} reads Avro files and sequence files by internally wrapping
the stream in
[{{AvroFileInputStream}}|https://github.com/apache/hadoop/blob/rel/release-3.4.1/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/shell/Display.java#L270]
or
[{{TextRecordInputStream}}|https://github.com/apache/hadoop/blob/rel/release-3.4.1/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/shell/Display.java#L217].
These classes implement the required single-byte
[{{read()}}|https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/io/InputStream.html#read()],
but not the optional multi-byte buffered [{{read(byte[], int,
int)}}|https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/io/InputStream.html#read(byte%5B%5D,int,int)].
The default implementation in the JDK is a [loop over single-byte
read|https://github.com/openjdk/jdk11u-dev/blob/a47c72fad455bfdf9053cb8e94c99e73965ab50d/src/java.base/share/classes/java/io/InputStream.java#L280],
which causes sub-optimal I/O and method call overhead. We can optimize this by
overriding the multi-byte read method.
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