Laszlo Gaal has uploaded this change for review. ( 
http://gerrit.cloudera.org:8080/21510


Change subject: IMPALA-13156: Investigation: Set explicit credential provider 
for S3 builds
......................................................................

IMPALA-13156: Investigation: Set explicit credential provider for S3 builds

Lately we have seen several failures during S3 builds that relied on AWS
EC2 IAM instances roles for S3 bucket access credentials.
The failure mode was a spurious failure for the s3a IAM Instance
Credential Provider to actually provide the credentials.

This patch is an attempt to extract more debugging information from such
a failure: according to Hadoop-AWS developers, "Unable to load
credentials from system settings..." is a generic error message from the
Hadoop credential providers when they operate in a chained fashion. This
happens when there is no explicit credetial provider specified in
core-site.xml, and the credential providers are tried in sequence.

The patch specifies the Hadoop s3a IAM Instance Credential Provider
when the default file system is S3, the minicluster is running on and
AWS EC2 VM, and AWS credentials are provided by an IAM instance role
attached to the VM.
This is detected by following the rule matrix set up in
bin/impala-config.sh; the same rule set is evaluated in
core-site.xml.py, the Python script that set up the working copy of
core-site.xml.

The patch also XFAILs test_keys_do_not_work() in test_s3_access.py in
custom cluster tests, because the test assumes the default chain of
Hadoop AWS credential providers being available. This patch restricts
the credential provider set to the IAM Instance Credential Provider
only, which breaks the test mechanism.
The test will be reinstated when a suitable workaround mechanism is
found, but at this stage the extended diagnostic provided by this patch
for investigating the credential provider flakiness is considered more
valuable.

Tests:
- private build on S3 for the positive case
- regression tested on a HDFS private build
- in both cases the generated core-site.xml file was inspected during
  the test run.

Change-Id: Ia8c09f8d042a69c5d3227398c720ea38e1c7e12f
---
M testdata/cluster/node_templates/common/etc/hadoop/conf/core-site.xml.py
M tests/custom_cluster/test_s3a_access.py
2 files changed, 10 insertions(+), 0 deletions(-)



  git pull ssh://gerrit.cloudera.org:29418/Impala-ASF refs/changes/10/21510/1
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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: newchange
Gerrit-Change-Id: Ia8c09f8d042a69c5d3227398c720ea38e1c7e12f
Gerrit-Change-Number: 21510
Gerrit-PatchSet: 1
Gerrit-Owner: Laszlo Gaal <[email protected]>

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