sarkaramrit1993 opened a new pull request, #29390:
URL: https://github.com/apache/flink/pull/29390
## What is the purpose of the change
`CompressibleFSDataInputStream` only overrode `read()`. Bulk reads fell back
to `InputStream#read(byte[], int, int)`, which loops over `read()`, so the
wrapped stream got hit one byte at a time. Operator state restore (list, union
and broadcast state, including source split state) reads through this class, so
restoring large operator state was very slow. The JIRA has numbers: 120 MB took
~44s before and ~136ms with bulk reads.
## Brief change log
- Override `read(byte[], int, int)` in `CompressibleFSDataInputStream` to
delegate to the (possibly compressing) wrapped stream.
## Verifying this change
This change added tests and can be verified as follows:
- Added
`CompressibleFSDataInputStreamTest#testBulkReadIsForwardedToDelegate`, run with
and without Snappy. It writes 64 KiB, reads it back with bulk reads, checks the
bytes, and asserts the underlying stream saw no single-byte `read()` calls.
Without the fix the uncompressed case makes 65,536 single-byte reads and fails.
- `OperatorStateBackendTest` and `StateSnapshotCompressionTest` still pass.
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): no
- The public API, i.e., is any changed class annotated with
`@Public(Evolving)`: no
- The serializers: no
- The runtime per-record code paths (performance sensitive): no
- Anything that affects deployment or recovery: JobManager (and its
components), Checkpointing, Kubernetes/Yarn, ZooKeeper: yes (faster operator
state restore, no behavior change)
- The S3 file system connector: no
## Documentation
- Does this pull request introduce a new feature? no
- If yes, how is the feature documented? not applicable
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