rohangarg opened a new pull request, #13741:
URL: https://github.com/apache/druid/pull/13741
Many MSQ jobs start failing with `Premature EOF` / `SDKException` errors
when `faultTolerance` and `durableShuffleStorage` context params are enabled.
After adding some logging, it was found that these exceptions are preceded
by `ConnectionReset` exceptions which might happen from S3 server side incase
we open an S3 request for very long time. Trying out a change where we first
download the file on s3 to local disk and then read fixed the issue for the
jobs - but the caveat was that multiple threads downloading the files
concurrently might put pressure on disks.
So, the current change downloads the file chunk-by-chunk locally at runtime
and then stitch the chunks together under a SequenceInputStream for upstream
MSQ processing engine. Each chunk is currently of size 100MB and is downloaded
eagerly to a local file. When that chunk is consumed, the local file is deleted
and the next chunk is queue is processed.
This PR has:
- [x] been self-reviewed.
- [ ] using the [concurrency
checklist](https://github.com/apache/druid/blob/master/dev/code-review/concurrency.md)
(Remove this item if the PR doesn't have any relation to concurrency.)
- [ ] added documentation for new or modified features or behaviors.
- [ ] a release note entry in the PR description.
- [ ] added Javadocs for most classes and all non-trivial methods. Linked
related entities via Javadoc links.
- [ ] added or updated version, license, or notice information in
[licenses.yaml](https://github.com/apache/druid/blob/master/dev/license.md)
- [ ] added comments explaining the "why" and the intent of the code
wherever would not be obvious for an unfamiliar reader.
- [ ] added unit tests or modified existing tests to cover new code paths,
ensuring the threshold for [code
coverage](https://github.com/apache/druid/blob/master/dev/code-review/code-coverage.md)
is met.
- [ ] added integration tests.
- [x] been tested in a test Druid cluster.
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