[HADOOP-18528] Disable abfs prefetching by default - ASF JIRA

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Details

Type: Bug
Status: Resolved
Priority: Major
Resolution: Fixed
Affects Version/s: 3.3.4
Fix Version/s: 3.4.0, 3.3.5
Component/s: fs/azure
Labels:
- pull-request-available

Target Version/s:

3.3.5
Hadoop Flags:

Reviewed
Release Note:

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ABFS block prefetching has been disabled to avoid ~~HADOOP-18521~~ and buffer sharing on multithreaded processes (Hive, Spark etc). This will have little/no performance impact on queries against Parquet or ORC data, but can slow down sequential stream processing, including CSV files -however, the read data will be correct.
It may slow down distcp downloads, where the race condition does not arise. For maximum distcp performance re-enable the readahead by setting fs.abfs.enable.readahead to true.

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ABFS block prefetching has been disabled to avoid HADOOP-18521 and buffer sharing on multithreaded processes (Hive, Spark etc). This will have little/no performance impact on queries against Parquet or ORC data, but can slow down sequential stream processing, including CSV files -however, the read data will be correct. It may slow down distcp downloads, where the race condition does not arise. For maximum distcp performance re-enable the readahead by setting fs.abfs.enable.readahead to true.

Description

After the addition of ~~HADOOP-18517~~, we should disable readAhead by default to mitigate inconsistent read results caused by ABFS prefetching, ~~HADOOP-18521~~.

As an urgent fix: Disable readAhead/prefetch, tracked for 3.3.5.
Long-term fix: ~~HADOOP-18521~~, tracked for 3.3.6.