IMPALA-5378: Disk IO manager needs to understand ADLS

The Disk IO Manager had customized support for S3 and remote HDFS that
allows for these to use a separate queue and have a customized number
of IO threads. ADLS did not have this support.

Based on the code in DiskIoMgr::Init and DiskIoMgr::AssignQueue, IOs
for ADLS were previously put in local disk queues. Since local disks
are considered rotational unless we can confirm otherwise by looking at
the /sys filesystem, this means that THREADS_PER_ROTATIONAL_DISK=1 was
being applied as the thread count.

This patch adds customized support for ADLS, similar to how it was done
for S3. We set 16 threads as the default number of IO threads for ADLS.
For smaller clusters, setting a higher number like 64 would work better.
We keep the thread count to a lower default of 16 since there is an
undocumented concurrency limit for clusters, which is around 500-700
connections, which means we would hurt node level parallelism if we
have higher thread level parallelism, for larger clusters.

We also set the default maximum chunk size for ADLS as 128k. This is due
to the fact that direct reads aren't supported for ADLS, which means that
the JNI array allocation and the memcpy adds significant overhead for
larger buffers. 128k was chosen emperically for S3 for the same reason.
Since this reason also holds for ADLS, we keep the same value. A new
flag called FLAGS_adls_read_chunk_size is used to control this value.

TODO: Settle on a buffer size with the most optimal buffer size
emperically.

Change-Id: I067f053fec941e3631610c5cc89a384f257ba906
Reviewed-on: http://gerrit.cloudera.org:8080/7033
Reviewed-by: Sailesh Mukil <sailesh@cloudera.com>
Tested-by: Impala Public Jenkins
3 files changed
tree: 93a1ac914dab21c4e08c630178aa6f8235f2d6f6
  1. .clang-format
  2. .clang-tidy
  3. .gitignore
  4. CMakeLists.txt
  5. DISCLAIMER
  6. EXPORT_CONTROL.md
  7. LICENSE.txt
  8. LOGS.md
  9. NOTICE.txt
  10. README.md
  11. be/
  12. bin/
  13. buildall.sh
  14. cmake_modules/
  15. common/
  16. docs/
  17. ext-data-source/
  18. fe/
  19. infra/
  20. shell/
  21. ssh_keys/
  22. testdata/
  23. tests/
  24. www/
README.md

Welcome to Impala

Lightning-fast, distributed SQL queries for petabytes of data stored in Apache Hadoop clusters.

Impala is a modern, massively-distributed, massively-parallel, C++ query engine that lets you analyze, transform and combine data from a variety of data sources:

  • Best of breed performance and scalability.
  • Support for data stored in HDFS, Apache HBase and Amazon S3.
  • Wide analytic SQL support, including window functions and subqueries.
  • On-the-fly code generation using LLVM to generate CPU-efficient code tailored specifically to each individual query.
  • Support for the most commonly-used Hadoop file formats, including the Apache Parquet (incubating) project.
  • Apache-licensed, 100% open source.

More about Impala

To learn more about Impala as a business user, or to try Impala live or in a VM, please visit the Impala homepage.

If you are interested in contributing to Impala as a developer, or learning more about Impala's internals and architecture, visit the Impala wiki.

Supported Platforms

Impala only supports Linux at the moment.

Build Instructions

See bin/bootstrap_build.sh.

Export Control Notice

This distribution uses cryptographic software and may be subject to export controls. Please refer to EXPORT_CONTROL.md for more information.