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# Testing the S3A filesystem client and its features

<!-- MACRO{toc|fromDepth=0|toDepth=3} -->

This module includes both unit tests, which can run in isolation without
connecting to the S3 service, and integration tests, which require a working
connection to S3 to interact with a bucket.  Unit test suites follow the naming
convention `Test*.java`.  Integration tests follow the naming convention
`ITest*.java`.


## <a name="policy"></a> Policy for submitting patches which affect the `hadoop-aws` module.

The Apache Jenkins infrastructure does not run any S3 integration tests,
due to the need to keep credentials secure.

### The submitter of any patch is required to run all the integration tests and declare which S3 region/implementation they used.

This is important: **patches which do not include this declaration will be ignored**

This policy has proven to be the only mechanism to guarantee full regression
testing of code changes. Why the declaration of region? Two reasons

1. It helps us identify regressions which only surface against specific endpoints
or third-party implementations of the S3 protocol.
1. It forces the submitters to be more honest about their testing. It's easy
to lie, "yes, I tested this". To say "yes, I tested this against S3 US-west"
is a more specific lie and harder to make. And, if you get caught out: you
lose all credibility with the project.

You don't need to test from a VM within the AWS infrastructure; with the
`-Dparallel-tests` option the non-scale tests complete in under twenty minutes.
Because the tests clean up after themselves, they are also designed to be low
cost. It's neither hard nor expensive to run the tests; if you can't,
there's no guarantee your patch works. The reviewers have enough to do, and
don't have the time to do these tests, especially as every failure will simply
make for a slow iterative development.

Please: run the tests. And if you don't, we are sorry for declining your
patch, but we have to.

### What if there's an intermittent failure of a test?

Some of the tests do fail intermittently, especially in parallel runs.
If this happens, try to run the test on its own to see if the test succeeds.

If it still fails, include this fact in your declaration. We know some tests
are intermittently unreliable.

### What if the tests are timing out or failing over my network connection?

The tests and the S3A client are designed to be configurable for different
timeouts. If you are seeing problems and this configuration isn't working,
that's a sign of the configuration mechanism isn't complete. If it's happening
in the production code, that could be a sign of a problem which may surface
over long-haul connections. Please help us identify and fix these problems
&mdash; especially as you are the one best placed to verify the fixes work.

## <a name="setting-up"></a> Setting up the tests

To integration test the S3* filesystem clients, you need to provide
`auth-keys.xml` which passes in authentication details to the test runner.

It is a Hadoop XML configuration file, which must be placed into
`hadoop-tools/hadoop-aws/src/test/resources`.

### File `core-site.xml`

This file pre-exists and sources the configurations created
under `auth-keys.xml`.

For most purposes you will not need to edit this file unless you
need to apply a specific, non-default property change during the tests.

### File `auth-keys.xml`

The presence of this file triggers the testing of the S3 classes.

Without this file, *none of the integration tests in this module will be
executed*.

The XML file must contain all the ID/key information needed to connect
each of the filesystem clients to the object stores, and a URL for
each filesystem for its testing.

1. `test.fs.s3a.name` : the URL of the bucket for S3a tests
1. `fs.contract.test.fs.s3a` : the URL of the bucket for S3a filesystem contract tests


The contents of the bucket will be destroyed during the test process:
do not use the bucket for any purpose other than testing. Furthermore, for
s3a, all in-progress multi-part uploads to the bucket will be aborted at the
start of a test (by forcing `fs.s3a.multipart.purge=true`) to clean up the
temporary state of previously failed tests.

Example:

```xml
<configuration>

  <property>
    <name>test.fs.s3a.name</name>
    <value>s3a://test-aws-s3a/</value>
  </property>

  <property>
    <name>fs.contract.test.fs.s3a</name>
    <value>${test.fs.s3a.name}</value>
  </property>

  <property>
    <name>fs.s3a.access.key</name>
    <description>AWS access key ID. Omit for IAM role-based authentication.</description>
    <value>DONOTCOMMITTHISKEYTOSCM</value>
  </property>

  <property>
    <name>fs.s3a.secret.key</name>
    <description>AWS secret key. Omit for IAM role-based authentication.</description>
    <value>DONOTEVERSHARETHISSECRETKEY!</value>
  </property>

  <property>
    <name>test.sts.endpoint</name>
    <description>Specific endpoint to use for STS requests.</description>
    <value>sts.amazonaws.com</value>
  </property>

</configuration>
```

## <a name="encryption"></a> Configuring S3a Encryption

For S3a encryption tests to run correctly, the
`fs.s3a.encryption.key` must be configured in the s3a contract xml
file or `auth-keys.xml` file with a AWS KMS encryption key arn as this value is
different for each AWS KMS. Please note this KMS key should be created in the
same region as your S3 bucket. Otherwise, you may get `KMS.NotFoundException`.

Example:

```xml
<property>
  <name>fs.s3a.encryption.key</name>
  <value>arn:aws:kms:us-west-2:360379543683:key/071a86ff-8881-4ba0-9230-95af6d01ca01</value>
</property>
```

You can also force all the tests to run with a specific SSE encryption method
by configuring the property `fs.s3a.encryption.algorithm` in the s3a
contract file.

### <a name="default_encyption"></a> Default Encryption

Buckets can be configured with [default encryption](https://docs.aws.amazon.com/AmazonS3/latest/dev/bucket-encryption.html)
on the AWS side. Some S3AFileSystem tests are skipped when default encryption is
enabled due to unpredictability in how [ETags](https://docs.aws.amazon.com/AmazonS3/latest/API/RESTCommonResponseHeaders.html)
are generated.

### Disabling the encryption tests

If the S3 store/storage class doesn't support server-side-encryption, these will fail. They
can be turned off.

```xml
<property>
  <name>test.fs.s3a.encryption.enabled</name>
  <value>false</value>
</property>
```

Encryption is only used for those specific test suites with `Encryption` in
their classname.

## <a name="running"></a> Running the Tests

After completing the configuration, execute the test run through Maven.

```bash
mvn clean verify
```

It's also possible to execute multiple test suites in parallel by passing the
`parallel-tests` property on the command line.  The tests spend most of their
time blocked on network I/O with the S3 service, so running in parallel tends to
complete full test runs faster.

```bash
mvn -Dparallel-tests clean verify
```

Some tests must run with exclusive access to the S3 bucket, so even with the
`parallel-tests` property, several test suites will run in serial in a separate
Maven execution step after the parallel tests.

By default, `parallel-tests` runs 4 test suites concurrently.  This can be tuned
by passing the `testsThreadCount` property.

```bash
mvn -Dparallel-tests -DtestsThreadCount=8 clean verify
```

To run just unit tests, which do not require S3 connectivity or AWS credentials,
use any of the above invocations, but switch the goal to `test` instead of
`verify`.

```bash
mvn clean test

mvn -Dparallel-tests clean test

mvn -Dparallel-tests -DtestsThreadCount=8 clean test
```

To run only a specific named subset of tests, pass the `test` property for unit
tests or the `it.test` property for integration tests.

```bash
mvn clean test -Dtest=TestS3AInputPolicies

mvn clean verify -Dit.test=ITestS3AFileContextStatistics -Dtest=none

mvn clean verify -Dtest=TestS3A* -Dit.test=ITestS3A*
```

Note that when running a specific subset of tests, the patterns passed in `test`
and `it.test` override the configuration of which tests need to run in isolation
in a separate serial phase (mentioned above).  This can cause unpredictable
results, so the recommendation is to avoid passing `parallel-tests` in
combination with `test` or `it.test`.  If you know that you are specifying only
tests that can run safely in parallel, then it will work.  For wide patterns,
like `ITestS3A*` shown above, it may cause unpredictable test failures.

### <a name="regions"></a> Testing against different regions

S3A can connect to different regions —the tests support this. Simply
define the target region in `auth-keys.xml`.

```xml
<property>
  <name>fs.s3a.endpoint.region</name>
  <value>eu-central-1</value>
</property>
```

### <a name="csv"></a> CSV Data Tests

The `TestS3AInputStreamPerformance` tests require read access to a multi-MB
text file. The default file for these tests is a public one.
`s3a://noaa-cors-pds/raw/2023/001/akse/AKSE001a.23_.gz`
from the [NOAA Continuously Operating Reference Stations (CORS) Network (NCN)](https://registry.opendata.aws/noaa-ncn/)

Historically it was required to be a `csv.gz` file to validate S3 Select
support. Now that S3 Select support has been removed, other large files
may be used instead.

The path to this object is set in the option `fs.s3a.scale.test.csvfile`,

```xml
<property>
  <name>fs.s3a.scale.test.csvfile</name>
  <value>s3a://noaa-cors-pds/raw/2023/001/akse/AKSE001a.23_.gz</value>
</property>
```

1. If the option is not overridden, the default value is used. This
is hosted in Amazon's US-east datacenter.
1. If `fs.s3a.scale.test.csvfile` is empty, tests which require it will be skipped.
1. If the data cannot be read for any reason then the test will fail.
1. If the property is set to a different path, then that data must be readable
and "sufficiently" large.
1. If a `.gz` file, expect decompression-related test failures.

(the reason the space or newline is needed is to add "an empty entry"; an empty
`<value/>` would be considered undefined and pick up the default)


If using a test file in a different AWS S3 region then
a bucket-specific region must be defined.
For the default test dataset, hosted in the `noaa-cors-pds` bucket, this is:

```xml
  <property>
    <name>fs.s3a.bucket.noaa-cors-pds.endpoint.region</name>
    <value>us-east-1</value>
  </property>
```

### <a name="access"></a> Testing Access Point Integration

S3a supports using Access Point ARNs to access data in S3. If you think your changes affect VPC
integration, request signing, ARN manipulation, or any code path that deals with the actual
sending and retrieving of data to/from S3, make sure you run the entire integration test suite with
this feature enabled.

Check out [our documentation](./index.html#accesspoints) for steps on how to enable this feature. To
create access points for your S3 bucket you can use the AWS Console or CLI.

## <a name="reporting"></a> Viewing Integration Test Reports


Integration test results and logs are stored in `target/failsafe-reports/`.
An HTML report can be generated during site generation, or with the `surefire-report`
plugin:

```bash
mvn surefire-report:failsafe-report-only
```
## <a name="versioning"></a> Testing Versioned Stores

Some tests (specifically some in `ITestS3ARemoteFileChanged`) require
a versioned bucket for full test coverage.

To enable versioning in a bucket.

1. In the AWS S3 Management console find and select the bucket.
1. In the Properties "tab", set it as versioned.
1. <i>Important</i> Create a lifecycle rule to automatically clean up old versions
after 24h. This avoids running up bills for objects which tests runs create and
then delete.
1. Run the tests again.

Once a bucket is converted to being versioned, it cannot be converted back
to being unversioned.

## <a name="enabling-prefetch"></a> Enabling prefetch for all tests

The tests are run with prefetch if the `prefetch` property is set in the
maven build. This can be combined with the scale tests as well.

```bash
mvn verify -Dprefetch

mvn verify -Dparallel-tests -Dprefetch -DtestsThreadCount=8

mvn verify -Dparallel-tests -Dprefetch -Dscale -DtestsThreadCount=8
```

## <a name="scale"></a> Scale Tests

There are a set of tests designed to measure the scalability and performance
at scale of the S3A tests, *Scale Tests*. Tests include: creating
and traversing directory trees, uploading large files, renaming them,
deleting them, seeking through the files, performing random IO, and others.
This makes them a foundational part of the benchmarking.

By their very nature they are slow. And, as their execution time is often
limited by bandwidth between the computer running the tests and the S3 endpoint,
parallel execution does not speed these tests up.

### <a name="enabling-scale"></a> Enabling the Scale Tests

The tests are enabled if the `scale` property is set in the maven build
this can be done regardless of whether or not the parallel test profile
is used

```bash
mvn verify -Dscale

mvn verify -Dparallel-tests -Dscale -DtestsThreadCount=8
```

The most bandwidth intensive tests (those which upload data) always run
sequentially; those which are slow due to HTTPS setup costs or server-side
actions are included in the set of parallelized tests.


### <a name="tuning_scale"></a> Tuning scale options from Maven


Some of the tests can be tuned from the maven build or from the
configuration file used to run the tests.

```bash
mvn verify -Dparallel-tests -Dscale -DtestsThreadCount=8 -Dfs.s3a.scale.test.huge.filesize=128M
```

The algorithm is

1. The value is queried from the configuration file, using a default value if
it is not set.
1. The value is queried from the JVM System Properties, where it is passed
down by maven.
1. If the system property is null, an empty string, or it has the value `unset`,
then the configuration value is used. The `unset` option is used to
[work round a quirk in maven property propagation](http://stackoverflow.com/questions/7773134/null-versus-empty-arguments-in-maven).

Only a few properties can be set this way; more will be added.

| Property | Meaning |
|-----------|-------------|
| `fs.s3a.scale.test.timeout`| Timeout in seconds for scale tests |
| `fs.s3a.scale.test.huge.filesize`| Size for huge file uploads |
| `fs.s3a.scale.test.huge.huge.partitionsize`| Size for partitions in huge file uploads |

The file and partition sizes are numeric values with a k/m/g/t/p suffix depending
on the desired size. For example: 128M, 128m, 2G, 2G, 4T or even 1P.

### <a name="scale-config"></a> Scale test configuration options

Some scale tests perform multiple operations (such as creating many directories).

The exact number of operations to perform is configurable in the option
`scale.test.operation.count`

```xml
<property>
  <name>scale.test.operation.count</name>
  <value>10</value>
</property>
```

Larger values generate more load, and are recommended when testing locally,
or in batch runs.

Smaller values results in faster test runs, especially when the object
store is a long way away.

Operations which work on directories have a separate option: this controls
the width and depth of tests creating recursive directories. Larger
values create exponentially more directories, with consequent performance
impact.

```xml
<property>
  <name>scale.test.directory.count</name>
  <value>2</value>
</property>
```

DistCp tests targeting S3A support a configurable file size.  The default is
10 MB, but the configuration value is expressed in KB so that it can be tuned
smaller to achieve faster test runs.

```xml
<property>
  <name>scale.test.distcp.file.size.kb</name>
  <value>10240</value>
</property>
```

S3A specific scale test properties are

*`fs.s3a.scale.test.huge.filesize`: size in MB for "Huge file tests".*

The Huge File tests validate S3A's ability to handle large files —the property
`fs.s3a.scale.test.huge.filesize` declares the file size to use.

```xml
<property>
  <name>fs.s3a.scale.test.huge.filesize</name>
  <value>200M</value>
</property>
```

Amazon S3 handles files larger than 5GB differently than smaller ones.
Setting the huge filesize to a number greater than that) validates support
for huge files.

```xml
<property>
  <name>fs.s3a.scale.test.huge.filesize</name>
  <value>6G</value>
</property>
```

Tests at this scale are slow: they are best executed from hosts running in
the cloud infrastructure where the S3 endpoint is based.
Otherwise, set a large timeout in `fs.s3a.scale.test.timeout`

```xml
<property>
  <name>fs.s3a.scale.test.timeout</name>
  <value>432000</value>
</property>
```

The tests are executed in an order to only clean up created files after
the end of all the tests. If the tests are interrupted, the test data will remain.

## <a name="CI"/> Testing through continuous integration

### Parallel CI builds.
For CI testing of the module, including the integration tests,
it is generally necessary to support testing multiple PRs simultaneously.

To do this
1. A job ID must be supplied in the `job.id` property, so each job works on an isolated directory
   tree. This should be a number or unique string, which will be used within a path element, so
   must only contain characters valid in an S3/hadoop path element.
2. Root directory tests need to be disabled by setting `fs.s3a.root.tests.enabled` to
   `false`, either in the command line to maven or in the XML configurations.

```
mvn verify -T 1C -Dparallel-tests -DtestsThreadCount=14 -Dscale -Dfs.s3a.root.tests.enabled=false -Djob.id=001
```

This parallel execution feature is only for isolated builds sharing a single S3 bucket; it does
not support parallel builds and tests from the same local source tree.

Without the root tests being executed, set up a scheduled job to purge the test bucket of all
data on a regular basis, to keep costs down.
The easiest way to do this is to have a bucket lifecycle rule for the bucket to delete all files more than a few days old,
alongside one to abort all pending uploads more than 24h old.


### Securing CI builds

It's clearly unsafe to have CI infrastructure testing PRs submitted to apache github account
with AWS credentials -which is why it isn't done by the Yetus-initiated builds.

Anyone doing this privately should:
* Review incoming patches before triggering the tests.
* Have a dedicated IAM role with restricted access to the test bucket, any KMS keys used, and the
  external bucket containing the CSV test file.
* Have a build process which generates short-lived session credentials for this role.
* Run the tests in an EC2 VM/container which collects the restricted IAM credentials
  from the IAM instance/container credentials provider.

## <a name="load"></a> Load tests.

Some tests are designed to overload AWS services with more
requests per second than an AWS account is permitted.

The operation of these tests may be observable to other users of the same
account -especially if they are working in the AWS region to which the
tests are targeted.

There may also run up larger bills.

These tests all have the prefix `ILoadTest`

They do not run automatically: they must be explicitly run from the command line or an IDE.

Look in the source for these and reads the Javadocs before executing.

Note: one fear here was that asking for two many session/role credentials in a short period
of time would actually lock an account out of a region. It doesn't: it simply triggers
throttling of STS requests.

## <a name="alternate_s3"></a> Testing against non-AWS S3 Stores.

The S3A filesystem is designed to work with S3 stores which implement
the S3 protocols to the extent that the amazon S3 SDK is capable of talking
to it. We encourage testing against other filesystems and submissions of patches
which address issues. In particular, we encourage testing of Hadoop release
candidates, as these third-party endpoints get even less testing than the
S3 endpoint itself.

The core XML settings to turn off tests of features unavailable
on third party stores.

```xml
  <property>
    <name>test.fs.s3a.encryption.enabled</name>
    <value>false</value>
  </property>
  <property>
    <name>test.fs.s3a.create.storage.class.enabled</name>
    <value>false</value>
  </property>
  <property>
    <name>test.fs.s3a.sts.enabled</name>
    <value>false</value>
  </property>
  <property>
    <name>test.fs.s3a.create.create.acl.enabled</name>
    <value>false</value>
  </property>
  <property>
    <name>test.fs.s3a.performance.enabled</name>
    <value>false</value>
  </property>

  <!--
   If the store reports errors when trying to list/abort completed multipart uploads,
   expect failures in ITestUploadRecovery and ITestS3AContractMultipartUploader.
   The tests can be reconfigured to expect failure.
   Note how this can be set as a per-bucket option.
  -->
  <property>
    <name>fs.s3a.ext.test.multipart.commit.consumes.upload.id</name>
    <value>true</value>
  </property>
```

See [Third Party Stores](third_party_stores.html) for more on this topic.

### Public datasets used in tests

Some tests rely on the presence of existing public datasets available on Amazon S3.
You may find a number of these in `org.apache.hadoop.fs.s3a.test.PublicDatasetTestUtils`.

When testing against an endpoint which is not part of Amazon S3's standard commercial partition
(`aws`) such as third-party implementations or AWS's China regions, you should replace these
configurations with an empty space (` `) to disable the tests or an existing path in your object
store that supports these tests.

An example of this might be the MarkerTools tests which require a bucket with a large number of
objects or the requester pays tests that require requester pays to be enabled for the bucket.


### Disabling the storage class tests

When running storage class tests against third party object store that doesn't support
S3 storage class, these tests might fail. They can be disabled.

```xml
<property>
  <name>test.fs.s3a.create.storage.class.enabled</name>
  <value>false</value>
</property>
```

### Configuring the CSV file read tests

To test on alternate infrastructures supporting
the same APIs, the option `fs.s3a.scale.test.csvfile` must either be
set to " ", or an object of at least 10MB is uploaded to the object store, and
the `fs.s3a.scale.test.csvfile` option set to its path.

```xml
<property>
  <name>fs.s3a.scale.test.csvfile</name>
  <value> </value>
</property>
```

(yes, the space is necessary. The Hadoop `Configuration` class treats an empty
value as "do not override the default").

### <a name="enabling-prefetch"></a> Enabling prefetch for all tests

The tests are run with prefetch if the `prefetch` property is set in the
maven build. This can be combined with the scale tests as well.


If `ITestS3AContractGetFileStatusV1List` fails with any error about unsupported API.
```xml
  <property>
    <name>test.fs.s3a.list.v1.enabled</name>
    <value>false</value>
  </property>
```

Note: there's no equivalent for turning off v2 listing API, which all stores are now
required to support.


### Testing Requester Pays

By default, the requester pays tests will look for a bucket that exists on Amazon S3
in us-east-1.

If the endpoint does support requester pays, you can specify an alternative object.
The test only requires an object of at least a few bytes in order
to check that lists and basic reads work.

```xml
<property>
  <name>test.fs.s3a.requester.pays.file</name>
  <value>s3a://my-req-pays-enabled-bucket/on-another-endpoint.json</value>
</property>
```

If the endpoint does not support requester pays, you can also disable the tests by configuring
the test URI as a single space.

```xml
<property>
  <name>test.fs.s3a.requester.pays.file</name>
  <value> </value>
</property>
```

### Testing Session Credentials

Some tests requests a session credentials and assumed role credentials from the
AWS Secure Token Service, then use them to authenticate with S3 either directly
or via delegation tokens.

If an S3 implementation does not support STS, then these functional test
cases must be disabled:

```xml
<property>
  <name>test.fs.s3a.sts.enabled</name>
  <value>false</value>
</property>

```
These tests request a temporary set of credentials from the STS service endpoint.
An alternate endpoint may be defined in `fs.s3a.assumed.role.sts.endpoint`.
If this is set, a delegation token region must also be defined:
in `fs.s3a.assumed.role.sts.endpoint.region`.
This is useful not just for testing alternative infrastructures,
but to reduce latency on tests executed away from the central
service.

```xml
<property>
  <name>fs.s3a.delegation.token.endpoint</name>
  <value>fs.s3a.assumed.role.sts.endpoint</value>
</property>
<property>
  <name>fs.s3a.assumed.role.sts.endpoint.region</name>
  <value>eu-west-2</value>
</property>
```
The default is ""; meaning "use the amazon default endpoint" (`sts.amazonaws.com`).

Consult the [AWS documentation](https://docs.aws.amazon.com/general/latest/gr/rande.html#sts_region)
for the full list of locations.

### Disabling Content Encoding tests

Tests in `ITestS3AContentEncoding` may need disabling
```xml
  <property>
    <name>test.fs.s3a.content.encoding.enabled</name>
    <value>false</value>
  </property>
```

### Disabling tests running in performance mode

Some tests running in performance mode turn off the safety checks. They expect operations which break POSIX semantics to succeed.
For stores with stricter semantics, these test cases must be disabled.
```xml
  <property>
    <name>test.fs.s3a.performance.enabled</name>
    <value>false</value>
  </property>
```

### Changing expectations on multipart upload retries: `ITestS3AContractMultipartUploader` and `ITestUploadRecovery`

If the store reports errors when trying to list/abort completed multipart uploads,
expect failures in `ITestUploadRecovery` and `ITestS3AContractMultipartUploader`.
The tests can be reconfigured to expect failure by setting the option
`fs.s3a.ext.test.multipart.commit.consumes.upload.id` to true.

Note how this can be set as a per-bucket option.

```xml
  <property>
    <name>fs.s3a.ext.test.multipart.commit.consumes.upload.id</name>
    <value>true</value>
  </property>
```
### Tests which may fail (and which you can ignore)

* `ITestS3AMiscOperations.testEmptyFileChecksums`: if the FS encrypts data always.

## <a name="debugging"></a> Debugging Test failures

Logging at debug level is the standard way to provide more diagnostics output;
after setting this rerun the tests

```properties
log4j.logger.org.apache.hadoop.fs.s3a=DEBUG
```

There are also some logging options for debug logging of the AWS client;
consult the file.

There is also the option of enabling logging on a bucket; this could perhaps
be used to diagnose problems from that end. This isn't something actively
used, but remains an option. If you are forced to debug this way, consider
setting the `fs.s3a.user.agent.prefix` to a unique prefix for a specific
test run, which will enable the specific log entries to be more easily
located.

## <a name="new_tests"></a> Adding new tests

New tests are always welcome. Bear in mind that we need to keep costs
and test time down, which is done by

* Not duplicating tests.
* Being efficient in your use of Hadoop API calls.
* Isolating large/slow tests into the "scale" test group.
* Designing all tests to execute in parallel (where possible).
* Adding new probes and predicates into existing tests, albeit carefully.

*No duplication*: if an operation is tested elsewhere, don't repeat it. This
applies as much for metadata operations as it does for bulk IO. If a new
test case is added which completely obsoletes an existing test, it is OK
to cut the previous one —after showing that coverage is not worsened.

*Efficient*: prefer the `getFileStatus()` and examining the results, rather than
call to `exists()`, `isFile()`, etc.

*Isolating Scale tests*. Any S3A test doing large amounts of IO MUST extend the
class `S3AScaleTestBase`, so only running if `scale` is defined on a build,
supporting test timeouts configurable by the user. Scale tests should also
support configurability as to the actual size of objects/number of operations,
so that behavior at different scale can be verified.

*Designed for parallel execution*. A key need here is for each test suite to work
on isolated parts of the filesystem. Subclasses of `AbstractS3ATestBase`
SHOULD use the `path()` method, with a base path of the test suite name, to
build isolated paths. Tests MUST NOT assume that they have exclusive access
to a bucket.

*Extending existing tests where appropriate*. This recommendation goes
against normal testing best practise of "test one thing per method".
Because it is so slow to create directory trees or upload large files, we do
not have that luxury. All the tests against real S3 endpoints are integration
tests where sharing test setup and teardown saves time and money.

A standard way to do this is to extend existing tests with some extra predicates,
rather than write new tests. When doing this, make sure that the new predicates
fail with meaningful diagnostics, so any new problems can be easily debugged
from test logs.

***Effective use of FS instances during S3A integration tests.*** Tests using
`FileSystem` instances are fastest if they can recycle the existing FS
instance from the same JVM.

If you do that, you MUST NOT close or do unique configuration on them.
If you want a guarantee of 100% isolation or an instance with unique config,
create a new instance which you MUST close in the teardown to avoid leakage
of resources.

Do NOT add `FileSystem` instances manually
(with e.g `org.apache.hadoop.fs.FileSystem#addFileSystemForTesting`) to the
cache that will be modified or closed during the test runs. This can cause
other tests to fail when using the same modified or closed FS instance.
For more details see HADOOP-15819.

## <a name="requirements"></a> Requirements of new Tests

This is what we expect from new tests; they're an extension of the normal
Hadoop requirements, based on the need to work with remote servers whose
use requires the presence of secret credentials, where tests may be slow,
and where finding out why something failed from nothing but the test output
is critical.

### Subclasses Existing Shared Base Classes

Extend `AbstractS3ATestBase` or `AbstractSTestS3AHugeFiles` unless justifiable.
These set things up for testing against the object stores, provide good threadnames,
help generate isolated paths, and for `AbstractSTestS3AHugeFiles` subclasses,
only run if `-Dscale` is set.

Key features of `AbstractS3ATestBase`

* `getFileSystem()` returns the S3A Filesystem bonded to the contract test Filesystem
defined in `fs.s3a.contract.test`
* will automatically skip all tests if that URL is unset.
* Extends  `AbstractFSContractTestBase`
* Uses AssertJ for all assertions, _not_ those of JUnit5.

Having shared base classes may help reduce future maintenance too. Please
use them.

We adopted AssertJ assertions long before the move to JUnit5.
While there are still many tests with legacy JUnit 1.x assertions, all new test cases
should use AssertJ assertions and MUST NOT use JUnit5.

### Secure

Don't ever log credentials. The credential tests go out of their way to
not provide meaningful logs or assertion messages precisely to avoid this.

### Efficient of Time and Money

This means efficient in test setup/teardown, and, ideally, making use of
existing public datasets to save setup time and tester cost.

Strategies of particular note are:

1. `ITestS3ADirectoryPerformance`: a single test case sets up the directory
tree then performs different list operations, measuring the time taken.
1. `AbstractSTestS3AHugeFiles`: marks the test suite as
`@FixMethodOrder(MethodSorters.NAME_ASCENDING)` then orders the test cases such
that each test case expects the previous test to have completed (here: uploaded a file,
renamed a file, ...). This provides for independent tests in the reports, yet still
permits an ordered sequence of operations. Do note the use of `Assume.assume()`
to detect when the preconditions for a single test case are not met, hence,
the tests become skipped, rather than fail with a trace which is really a false alarm.

The ordered test case mechanism of `AbstractSTestS3AHugeFiles` is probably
the most elegant way of chaining test setup/teardown.

Regarding reusing existing data, we tend to use the noaa-cors-pds archive of
AWS US-East for our testing of input stream operations. This doesn't work
against other regions, or with third party S3 implementations. Thus the
URL can be overridden for testing elsewhere.


### Works With Other S3 Stores

Don't assume AWS S3 US-East only, do allow for working with external S3 implementations.
Those may be behind the latest S3 API features, not support encryption, session
APIs, etc.

They won't have the same CSV/large test files as some of the input tests rely on.
Look at `ITestS3AInputStreamPerformance` to see how tests can be written
to support the declaration of a specific large test file on alternate filesystems.


### Works Over Long-haul Links

As well as making file size and operation counts scalable, this includes
making test timeouts adequate. The Scale tests make this configurable; it's
hard coded to ten minutes in `AbstractS3ATestBase()`; subclasses can
change this by overriding `getTestTimeoutMillis()`.

Equally importantly: support proxies, as some testers need them.


### Provides Diagnostics and timing information

1. Give threads useful names.
1. Create logs, log things. Know that the `S3AFileSystem` and its input
and output streams *all* provide useful statistics in their {{toString()}}
calls; logging them is useful on its own.
1. you can use `AbstractS3ATestBase.describe(format-stringm, args)` here.; it
adds some newlines so as to be easier to spot.
1. Use `ContractTestUtils.NanoTimer` to measure the duration of operations,
and log the output.

### Fails Meaningfully

The `ContractTestUtils` class contains a whole set of assertions for making
statements about the expected state of a filesystem, e.g.
`assertPathExists(FS, path)`, `assertPathDoesNotExists(FS, path)`, and others.
These do their best to provide meaningful diagnostics on failures (e.g. directory
listings, file status, ...), so help make failures easier to understand.

At the very least, do not use `assertTrue()` or `assertFalse()` without
including error messages.

### Sets up its filesystem and checks for those settings

Tests can overrun `createConfiguration()` to add new options to the configuration
file for the S3A Filesystem instance used in their tests.

However, filesystem caching may mean that a test suite may get a cached
instance created with an different configuration. For tests which don't need
specific configurations caching is good: it reduces test setup time.

For those tests which do need unique options (encryption, magic files),
things can break, and they will do so in hard-to-replicate ways.

Use `S3ATestUtils.disableFilesystemCaching(conf)` to disable caching when
modifying the config. As an example from `AbstractTestS3AEncryption`:

```java
@Override
protected Configuration createConfiguration() {
  Configuration conf = super.createConfiguration();
  S3ATestUtils.disableFilesystemCaching(conf);
  removeBaseAndBucketOverrides(conf,
      SERVER_SIDE_ENCRYPTION_ALGORITHM);  
  conf.set(Constants.SERVER_SIDE_ENCRYPTION_ALGORITHM,
          getSSEAlgorithm().getMethod());
  return conf;
}
```

Then verify in the setup method or test cases that their filesystem actually has
the desired feature (`fs.getConf().getProperty(...)`). This not only
catches filesystem reuse problems, it catches the situation where the
filesystem configuration in `auth-keys.xml` has explicit per-bucket settings
which override the test suite's general option settings.

### Cleans Up Afterwards

Keeps costs down.

1. Do not only cleanup if a test case completes successfully; test suite
teardown must do it.
1. That teardown code must check for the filesystem and other fields being
null before the cleanup. Why? If test setup fails, the teardown methods still
get called.

### Works Reliably

We really appreciate this &mdash; you will too.

### Runs in parallel unless this is unworkable.

Tests must be designed to run in parallel with other tests, all working
with the same shared S3 bucket. This means

* Uses relative and JVM-fork-unique paths provided by the method
  `AbstractFSContractTestBase.path(String filepath)`.
* Doesn't manipulate the root directory or make assertions about its contents
(for example: delete its contents and assert that it is now empty).
* Doesn't have a specific requirement of all active clients of the bucket
(example: SSE-C tests which require all files, even directory markers,
to be encrypted with the same key).
* Doesn't use so much bandwidth that all other tests will be starved of IO and
start timing out (e.g. the scale tests).

Tests such as these can only be run as sequential tests. When adding one,
exclude it in the POM file. from the parallel failsafe run and add to the
sequential one afterwards. The IO heavy ones must also be subclasses of
`S3AScaleTestBase` and so only run if the system/maven property
`fs.s3a.scale.test.enabled` is true.

### Individual test cases can be run in an IDE

This is invaluable for debugging test failures.

How to set test options in your hadoop configuration rather
than on the maven command line:

### Keeping AWS Costs down

Most of the base S3 tests are designed delete files after test runs,
so you don't have to pay for storage costs. The scale tests do work with more data
so will cost more as well as generally take more time to execute.

You are however billed for

1. Data left in S3 after test runs.
3. HTTP operations on files (HEAD, LIST, GET).
4. In-progress multipart uploads from bulk IO or S3A committer tests.
5. Encryption/decryption using AWS KMS keys.

The GET/decrypt costs are incurred on each partial read of a file,
so random IO can cost more than sequential IO; the speedup of queries with
columnar data usually justifies this.

How to keep costs down

* Don't run the scale tests with large datasets; keep `fs.s3a.scale.test.huge.filesize` unset, or a few MB (minimum: 5).
* Remove all files in the filesystem. The root tests usually do this, but
it can be manually done:

      hadoop fs -rm -r -f -skipTrash s3a://test-bucket/\*
* Abort all outstanding uploads:

      hadoop s3guard uploads -abort -force s3a://test-bucket/


## <a name="tips"></a> Tips

### How to keep your credentials really safe

Although the `auth-keys.xml` file is marked as ignored in git and subversion,
it is still in your source tree, and there's always that risk that it may
creep out.

You can avoid this by keeping your keys outside the source tree and
using an absolute XInclude reference to it.

```xml
<configuration>

  <include xmlns="http://www.w3.org/2001/XInclude"
    href="file:///users/ubuntu/.auth-keys.xml" />

</configuration>
```

## <a name="failure-injection"></a>Failure Injection

S3A provides an "Inconsistent S3 Client Factory" that can be used to
simulate throttling by injecting random failures on S3 client requests.


**Note**

In previous releases, this factory could also be used to simulate
inconsistencies during testing of S3Guard. Now that S3 is consistent,
injecting inconsistency is no longer needed during testing.



## <a name="assumed_roles"></a> Testing Assumed Roles

Tests for the AWS Assumed Role credential provider require an assumed
role to request.

If this role is not declared in `fs.s3a.assumed.role.arn`,
the tests which require it will be skipped.

The specific tests an Assumed Role ARN is required for are

- `ITestAssumeRole`.
- `ITestRoleDelegationTokens`.
- One of the parameterized test cases in `ITestDelegatedMRJob`.

To run these tests you need:

1. A role in your AWS account will full read and write access rights to
the S3 bucket used in the tests, and KMS for any SSE-KMS or DSSE-KMS tests.


1. Your IAM User to have the permissions to "assume" that role.

1. The role ARN must be set in `fs.s3a.assumed.role.arn`.

```xml
<property>
  <name>fs.s3a.assumed.role.arn</name>
  <value>arn:aws:iam::9878543210123:role/role-s3-restricted</value>
</property>
```

The tests assume the role with different subsets of permissions and verify
that the S3A client (mostly) works when the caller has only write access
to part of the directory tree.

You can also run the entire test suite in an assumed role, a more
thorough test, by switching to the credentials provider.

```xml
<property>
  <name>fs.s3a.aws.credentials.provider</name>
  <value>org.apache.hadoop.fs.s3a.auth.AssumedRoleCredentialProvider</value>
</property>
```

The usual credentials needed to log in to the bucket will be used, but now
the credentials used to interact with S3 will be temporary
role credentials, rather than the full credentials.

## <a name="qualifying_sdk_updates"></a> Qualifying an AWS SDK Update

Updating the AWS SDK is something which does need to be done regularly,
but is rarely without complications, major or minor.

Assume that the version of the SDK will remain constant for an X.Y release,
excluding security fixes, so it's good to have an update before each release
&mdash; as long as that update works doesn't trigger any regressions.


1. Don't make this a last minute action.
1. The upgrade patch should focus purely on the SDK update, so it can be cherry
picked and reverted easily.
1. Do not mix in an SDK update with any other piece of work, for the same reason.
1. Plan for an afternoon's work, including before/after testing, log analysis
and any manual tests.
1. Make sure all the integration tests are running (including ARN, encryption, scale)
  *before you start the upgrade*.
1. Create a JIRA for updating the SDK. Don't include the version (yet),
as it may take a couple of SDK updates before it is ready.
1. Identify the latest AWS SDK [available for download](https://aws.amazon.com/sdk-for-java/).
1. Create a private git branch of trunk for JIRA, and in
  `hadoop-project/pom.xml` update the `aws-java-sdk.version` to the new SDK version.
1. Update AWS SDK versions in NOTICE.txt and LICENSE.binary
1. Do a clean build and rerun all the `hadoop-aws` tests.
  This includes the `-Pscale` set, with a role defined for the assumed role tests.
  in `fs.s3a.assumed.role.arn` for testing assumed roles,
  and `fs.s3a.encryption.key` for encryption, for full coverage.
  If you can, scale up the scale tests.
1. Create an Access Point for your bucket (using the AWS Console or CLI), update S3a configuration
to use it ([docs for help](./index.html#accesspoints)) and re-run the `ITest*` integration tests from
your IDE or via maven.
1. Run the `ILoadTest*` load tests from your IDE or via maven through
      `mvn verify -Dtest=skip -Dit.test=ILoadTest\*`  ; look for regressions in performance
      as much as failures.
1. Create the site with `mvn site -DskipTests`; look in `target/site` for the report.
1. Review *every single `-output.txt` file in `hadoop-tools/hadoop-aws/target/failsafe-reports`,
  paying particular attention to
  `org.apache.hadoop.fs.s3a.scale.ITestS3AInputStreamPerformance-output.txt`,
  as that is where changes in stream close/abort logic will surface.
1. Run `mvn install` to install the artifacts, then in
  `hadoop-cloud-storage-project/hadoop-cloud-storage` run
  `mvn dependency:tree -Dverbose > target/dependencies.txt`.
  Examine the `target/dependencies.txt` file to verify that no new
  artifacts have unintentionally been declared as dependencies
  of the shaded `software.amazon.awssdk:bundle:jar` artifact.
1. Run a full AWS-test suite with S3 client-side encryption enabled by
 setting `fs.s3a.encryption.algorithm` to 'CSE-KMS' and setting up AWS-KMS
  Key ID in `fs.s3a.encryption.key`.
2. Verify that the output of test `TestAWSV2SDK` doesn't contain any unshaded classes.

The dependency chain of the `hadoop-aws` module should be similar to this, albeit
with different version numbers:
```
[INFO] +- org.apache.hadoop:hadoop-aws:jar:3.4.0-SNAPSHOT:compile
[INFO] |  +- software.amazon.awssdk:bundle:jar:2.23.5:compile
[INFO] |  \- org.wildfly.openssl:wildfly-openssl:jar:1.1.3.Final:compile
```
### Basic command line regression testing

We need a run through of the CLI to see if there have been changes there
which cause problems, especially whether new log messages have surfaced,
or whether some packaging change breaks that CLI.

It is always interesting when doing this to enable IOStatistics reporting
```xml
<property>
  <name>fs.iostatistics.logging.level</name>
  <value>info</value>
</property>
```

From the root of the project, create a command line release `mvn package -Pdist -DskipTests -Dmaven.javadoc.skip=true  -DskipShade`;

1. Change into the `hadoop-dist/target/hadoop-x.y.z-SNAPSHOT` dir.
1. Copy a `core-site.xml` file into `etc/hadoop`.
1. Set the `HADOOP_OPTIONAL_TOOLS` env var on the command line or `~/.hadoop-env`.

```bash
export HADOOP_OPTIONAL_TOOLS="hadoop-aws"
```

Run some basic s3guard CLI as well as file operations.

```bash
export BUCKETNAME=example-bucket-name
export BUCKET=s3a://$BUCKETNAME

bin/hadoop s3guard bucket-info $BUCKET

bin/hadoop s3guard uploads $BUCKET
# repeat twice, once with "no" and once with "yes" as responses
bin/hadoop s3guard uploads -abort $BUCKET

# ---------------------------------------------------
# root filesystem operatios
# ---------------------------------------------------

bin/hadoop fs -ls $BUCKET/
# assuming file is not yet created, expect error and status code of 1
bin/hadoop fs -ls $BUCKET/file

# exit code of 0 even when path doesn't exist
bin/hadoop fs -rm -R -f $BUCKET/dir-no-trailing
bin/hadoop fs -rm -R -f $BUCKET/dir-trailing/

# error because it is a directory
bin/hadoop fs -rm $BUCKET/

bin/hadoop fs -touchz $BUCKET/file
# expect I/O error as it is the root directory
bin/hadoop fs -rm -r $BUCKET/

# succeeds
bin/hadoop fs -rm -r $BUCKET/\*

# ---------------------------------------------------
# File operations
# ---------------------------------------------------

bin/hadoop fs -mkdir $BUCKET/dir-no-trailing
bin/hadoop fs -mkdir $BUCKET/dir-trailing/
bin/hadoop fs -touchz $BUCKET/file
bin/hadoop fs -ls $BUCKET/
bin/hadoop fs -mv $BUCKET/file $BUCKET/file2
# expect "No such file or directory"
bin/hadoop fs -stat $BUCKET/file

# expect success
bin/hadoop fs -stat $BUCKET/file2

# expect "file exists"
bin/hadoop fs -mkdir $BUCKET/dir-no-trailing
bin/hadoop fs -mv $BUCKET/file2 $BUCKET/dir-no-trailing
bin/hadoop fs -stat $BUCKET/dir-no-trailing/file2
# treated the same as the file stat
bin/hadoop fs -stat $BUCKET/dir-no-trailing/file2/
bin/hadoop fs -ls $BUCKET/dir-no-trailing/file2/
bin/hadoop fs -ls $BUCKET/dir-no-trailing
# expect a "0" here:
bin/hadoop fs -test -d  $BUCKET/dir-no-trailing ; echo $?
# expect a "1" here:
bin/hadoop fs -test -d  $BUCKET/dir-no-trailing/file2 ; echo $?
# will return NONE unless bucket has checksums enabled
bin/hadoop fs -checksum $BUCKET/dir-no-trailing/file2
# expect "etag" + a long string
bin/hadoop fs -D fs.s3a.etag.checksum.enabled=true -checksum $BUCKET/dir-no-trailing/file2
bin/hadoop fs -expunge -immediate -fs $BUCKET

# ---------------------------------------------------
# Delegation Token support
# ---------------------------------------------------

# failure unless delegation tokens are enabled
bin/hdfs fetchdt --webservice $BUCKET secrets.bin
# success
bin/hdfs fetchdt -D fs.s3a.delegation.token.binding=org.apache.hadoop.fs.s3a.auth.delegation.SessionTokenBinding --webservice $BUCKET secrets.bin
bin/hdfs fetchdt -print secrets.bin

# expect warning "No TokenRenewer defined for token kind S3ADelegationToken/Session"
bin/hdfs fetchdt -renew secrets.bin


# ---------------------------------------------------
# Copy to from local
# ---------------------------------------------------

time bin/hadoop fs -copyFromLocal -t 10  share/hadoop/tools/lib/*aws*jar $BUCKET/

# expect the iostatistics object_list_request value to be O(directories)
bin/hadoop fs -ls -R $BUCKET/

# expect the iostatistics object_list_request and op_get_content_summary values to be 1
bin/hadoop fs -du -h -s $BUCKET/

mkdir tmp
time bin/hadoop fs -copyToLocal -t 10  $BUCKET/\*aws\* tmp

# ---------------------------------------------------
# Cloudstore
# check out and build https://github.com/steveloughran/cloudstore
# then for these tests, set CLOUDSTORE env var to point to the JAR
# ---------------------------------------------------

bin/hadoop jar $CLOUDSTORE storediag $BUCKET

time bin/hadoop jar $CLOUDSTORE bandwidth 64M $BUCKET/testfile

```

### Other tests

* Whatever applications you have which use S3A: build and run them before the upgrade,
Then see if complete successfully in roughly the same time once the upgrade is applied.
* Test any third-party endpoints you have access to.
* Try different regions (especially a v4 only region), and encryption settings.
* Any performance tests you have can identify slowdowns, which can be a sign
  of changed behavior in the SDK (especially on stream reads and writes).
* If you can, try to test in an environment where a proxy is needed to talk
to AWS services.
* Try and get other people, especially anyone with their own endpoints,
  apps or different deployment environments, to run their own tests.
* Run the load tests, especially `ILoadTestS3ABulkDeleteThrottling`.
* Checkout cloudstore, build it against your version of hadoop, then use its CLI to run some commands (`storediag` etc)

### Dealing with Deprecated APIs and New Features

A Jenkins run should tell you if there are new deprecations.
If so, you should think about how to deal with them.

Moving to methods and APIs which weren't in the previous SDK release makes it
harder to roll back if there is a problem; but there may be good reasons
for the deprecation.

At the same time, there may be good reasons for staying with the old code.

* AWS have embraced the builder pattern for new operations; note that objects
constructed this way often have their (existing) setter methods disabled; this
may break existing code.
* New versions of S3 calls (list v2, bucket existence checks, bulk operations)
may be better than the previous HTTP operations & APIs, but they may not work with
third-party endpoints, so can only be adopted if made optional, which then
adds a new configuration option (with docs, testing, ...). A change like that
must be done in its own patch, with its new tests which compare the old
vs new operations.

### Committing the patch

When the patch is committed: update the JIRA to the version number actually
used; use that title in the commit message.

Be prepared to roll-back, re-iterate or code your way out of a regression.

There may be some problem which surfaces with wider use, which can get
fixed in a new AWS release, rolling back to an older one,
or just worked around [HADOOP-14596](https://issues.apache.org/jira/browse/HADOOP-14596).

Don't be surprised if this happens, don't worry too much, and,
while that rollback option is there to be used, ideally try to work forwards.

If the problem is with the SDK, file issues with the
 [AWS V2 SDK Bug tracker](https://github.com/aws/aws-sdk-java-v2/issues).
If the problem can be fixed or worked around in the Hadoop code, do it there too.
