Followup to HADOOP-13327, which changed S3A output stream hsync/hflush calls
to raise an exception.
Adds a new option fs.s3a.downgrade.syncable.exceptions
When true, calls to Syncable hsync/hflush on S3A output streams will
log once at warn (for entire process life, not just the stream), then
increment IOStats with the relevant operation counter
With the downgrade option false (default)
* IOStats are incremented
* The UnsupportedOperationException current raised includes a link to the
JIRA.
Contributed by Steve Loughran.
Moves to the builder API for AWS S3 client creation, and
offers a similar style of API to the S3A FileSystem and tests, hiding
the details of which options are client, which are in AWS Conf,
and doing the wiring up of S3A statistics interfaces to the AWS
SDK internals. S3A Statistics, including IOStatistics, should now
count throttling events handled in the AWS SDK itself.
This patch restores endpoint determination by probes to US-East-1
if the client isn't configured with fs.s3a.endpoint.
Explicitly setting the endpoint will save the cost of these probe
HTTP requests.
Contributed by Steve Loughran.
The S3A connector's rename() operation now raises FileNotFoundException if
the source doesn't exist; a FileAlreadyExistsException if the destination
exists and is unsuitable for the source file/directory.
When renaming to a path which does not exist, the connector no longer checks
for the destination parent directory existing -instead it simply verifies
that there is no file immediately above the destination path.
This is needed to avoid race conditions with delete() and rename()
calls working on adjacent subdirectories.
Contributed by Steve Loughran.
Removed findbugs from the hadoop build images and added spotbugs instead.
Upgraded SpotBugs to 4.2.2 and spotbugs-maven-plugin to 4.2.0.
Reviewed-by: Masatake Iwasaki <iwasakims@apache.org>
Use spotbugs instead of findbugs. Removed findbugs from the hadoop build images,
and added spotbugs in the images instead.
Reviewed-by: Masatake Iwasaki <iwasakims@apache.org>
Reviewed-by: Inigo Goiri <inigoiri@apache.org>
Reviewed-by: Dinesh Chitlangia <dineshc@apache.org>
Adds an Abortable.abort() interface for streams to enable output streams to be terminated; this
is implemented by the S3A connector's output stream. It allows for commit protocols
to be implemented which commit/abort work by writing to the final destination and
using the abort() call to cancel any write which is not intended to be committed.
Consult the specification document for information about the interface and its use.
Contributed by Jungtaek Lim and Steve Loughran.
This defines what output streams and especially those which implement
Syncable are meant to do, and documents where implementations (HDFS; S3)
don't. With tests.
The file:// FileSystem now supports Syncable if an application calls
FileSystem.setWriteChecksum(false) before creating a file -checksumming
and Syncable.hsync() are incompatible.
Contributed by Steve Loughran.
* core-default.xml updated so that fs.s3a.committer.magic.enabled = true
* CommitConstants updated to match
* All tests which previously enabled the magic committer now rely on
default settings. This helps make sure it is enabled.
* Docs cover the switch, mention its enabled and explain why you may
want to disable it.
Note: this doesn't switch to using the committer -it just enables the path
rewriting magic which it depends on.
Contributed by Steve Loughran.
Caused by HADOOP-16830 and HADOOP-17271.
Fixes tests which fail intermittently based on configs and
in the case of the HugeFile tests, bulk runs with existing
FS instances meant statistic probes sometimes ended up probing those
of a previous FS.
Contributed by Steve Loughran.
Change-Id: I65ba3f44444e59d298df25ac5c8dc5a8781dfb7d
Caused by HADOOP-16380 and HADOOP-17271.
Fixes tests which fail intermittently based on configs and
in the case of the HugeFile tests, bulk runs with existing
FS instances meant statistic probes sometimes ended up probing those
of a previous FS.
Contributed by Steve Loughran.
Also fixes HADOOP-16995. ITestS3AConfiguration proxy tests failures when bucket probes == 0
The improvement should include the fix, ebcause the test would fail by default otherwise.
Change-Id: I9a7e4b5e6d4391ebba096c15e84461c038a2ec59
S3A connector to support the IOStatistics API of HADOOP-16830,
This is a major rework of the S3A Statistics collection to
* Embrace the IOStatistics APIs
* Move from direct references of S3AInstrumention statistics
collectors to interface/implementation classes in new packages.
* Ubiquitous support of IOStatistics, including:
S3AFileSystem, input and output streams, RemoteIterator instances
provided in list calls.
* Adoption of new statistic names from hadoop-common
Regarding statistic collection, as well as all existing
statistics, the connector now records min/max/mean durations
of HTTP GET and HEAD requests, and those of LIST operations.
Contributed by Steve Loughran.
The addition of deprecated S3A configuration options in HADOOP-17318
triggered a reload of default (xml resource) configurations, which breaks
tests which fail if there's a per-bucket setting inconsistent with test
setup.
Creating an S3AFS instance before creating the Configuration() instance
for test runs gets that reload out the way before test setup takes
place.
Along with the fix, extra changes in the failing test suite to fail
fast when marker policy isn't as expected, and to log FS state better.
Rather than create and discard an instance, add a new static method
to S3AFS and invoke it in test setup. This forces the load
Change-Id: Id52b1c46912c6fedd2ae270e2b1eb2222a360329
This adds a semaphore to throttle the number of FileSystem instances which
can be created simultaneously, set in "fs.creation.parallel.count".
This is designed to reduce the impact of many threads in an application calling
FileSystem.get() on a filesystem which takes time to instantiate -for example
to an object where HTTPS connections are set up during initialization.
Many threads trying to do this may create spurious delays by conflicting
for access to synchronized blocks, when simply limiting the parallelism
diminishes the conflict, so speeds up all threads trying to access
the store.
The default value, 64, is larger than is likely to deliver any speedup -but
it does mean that there should be no adverse effects from the change.
If a service appears to be blocking on all threads initializing connections to
abfs, s3a or store, try a smaller (possibly significantly smaller) value.
Contributed by Steve Loughran.
This patch
* fixes the inversion
* adds a precondition check
* if the commands are supplied inverted, swaps them with a warning.
This is to stop breaking any tests written to cope with the existing
behavior.
Contributed by Steve Loughran
See also [SPARK-33402]: Jobs launched in same second have duplicate MapReduce JobIDs
Contributed by Steve Loughran.
Change-Id: Iae65333cddc84692997aae5d902ad8765b45772a
This fixes the S3Guard/Directory Marker Retention integration so that when
fs.s3a.directory.marker.retention=keep, failures during multipart delete
are handled correctly, as are incremental deletes during
directory tree operations.
In both cases, when a directory marker with children is deleted from
S3, the directory entry in S3Guard is not deleted, because it is still
critical to representing the structure of the store.
Contributed by Steve Loughran.
Change-Id: I4ca133a23ea582cd42ec35dbf2dc85b286297d2f
Unless you explicitly set it, the issue date of a delegation token identifier is 0, which confuses spark renewal (SPARK-33440). This patch makes sure that all S3A DT identifiers have the current time as issue date, fixing the problem as far as S3A tokens are concerned.
Contributed by Jungtaek Lim.
This reverts changes in HADOOP-13230 to use S3Guard TTL in choosing when
to issue a HEAD request; fixing tests to compensate.
New org.apache.hadoop.fs.s3a.performance.OperationCost cost,
S3GUARD_NONAUTH_FILE_STATUS_PROBE for use in cost tests.
Contributed by Steve Loughran.
Change-Id: I418d55d2d2562a48b2a14ec7dee369db49b4e29e
S3AFileSystem.listStatus() is optimized for invocations
where the path supplied is a non-empty directory.
The number of S3 requests is significantly reduced, saving
time, money, and reducing the risk of S3 throttling.
Contributed by Mukund Thakur.
This changes directory tree deletion so that only files are incrementally deleted
from S3Guard after the objects are deleted; the directories are left alone
until metadataStore.deleteSubtree(path) is invoke.
This avoids directory tombstones being added above files/child directories,
which stop the treewalk and delete phase from working.
Also:
* Callback to delete objects splits files and dirs so that
any problems deleting the dirs doesn't trigger s3guard updates
* New statistic to measure #of objects deleted, alongside request count.
* Callback listFilesAndEmptyDirectories renamed listFilesAndDirectoryMarkers
to clarify behavior.
* Test enhancements to replicate the failure and verify the fix
Contributed by Steve Loughran
Now skips ITestS3AEncryptionWithDefaultS3Settings.testEncryptionOverRename
when server side encryption is not set to sse:kms
Contributed by Mukund Thakur
This adds an option to disable "empty directory" marker deletion,
so avoid throttling and other scale problems.
This feature is *not* backwards compatible.
Consult the documentation and use with care.
Contributed by Steve Loughran.
Change-Id: I69a61e7584dc36e485d5e39ff25b1e3e559a1958
Contributed by Steve Loughran.
Fixes a condition which can cause job commit to fail if a task was
aborted < 60s before the job commit commenced: the task abort
will shut down the thread pool with a hard exit after 60s; the
job commit POST requests would be scheduled through the same pool,
so be interrupted and fail. At present the access is synchronized,
but presumably the executor shutdown code is calling wait() and releasing
locks.
Task abort is triggered from the AM when task attempts succeed but
there are still active speculative task attempts running. Thus it
only surfaces when speculation is enabled and the final tasks are
speculating, which, given they are the stragglers, is not unheard of.
Note: this problem has never been seen in production; it has surfaced
in the hadoop-aws tests on a heavily overloaded desktop
Contributed by Steve Loughran.
S3A delegation token providers will be asked for any additional
token issuers, an array can be returned,
each one will be asked for tokens when DelegationTokenIssuer collects
all the tokens for a filesystem.
Contributed by Mukund Thakur and Steve Loughran.
This patch ensures that writes to S3A fail when more than 10,000 blocks are
written. That upper bound still exists. To write massive files, make sure
that the value of fs.s3a.multipart.size is set to a size which is large
enough to upload the files in fewer than 10,000 blocks.
Change-Id: Icec604e2a357ffd38d7ae7bc3f887ff55f2d721a
Contributed by Steve Loughran.
The S3Guard absence warning of HADOOP-16484 has been changed
so that by default the S3A connector only logs at debug
when the connection to the S3 Store does not have S3Guard
enabled.
The option to control this log level is now
fs.s3a.s3guard.disabled.warn.level
and can be one of: silent, inform, warn, fail.
On a failure, an ExitException is raised with exit code 49.
For details on this safety feature, consult the s3guard documentation.
HADOOP-16986. S3A to not need wildfly JAR on its classpath.
Contributed by Steve Loughran
This is a successor to HADOOP-16346, which enabled the S3A connector
to load the native openssl SSL libraries for better HTTPS performance.
That patch required wildfly.jar to be on the classpath. This
update:
* Makes wildfly.jar optional except in the special case that
"fs.s3a.ssl.channel.mode" is set to "openssl"
* Retains the declaration of wildfly.jar as a compile-time
dependency in the hadoop-aws POM. This means that unless
explicitly excluded, applications importing that published
maven artifact will, transitively, add the specified
wildfly JAR into their classpath for compilation/testing/
distribution.
This is done for packaging and to offer that optional
speedup. It is not mandatory: applications importing
the hadoop-aws POM can exclude it if they choose.
Contributed by Mukund Thakur.
If you set the log org.apache.hadoop.fs.s3a.impl.NetworkBinding
to DEBUG, then when the S3A bucket probe is made -the DNS address
of the S3 endpoint is calculated and printed.
This is useful to see if a large set of processes are all using
the same IP address from the pool of load balancers to which AWS
directs clients when an AWS S3 endpoint is resolved.
This can have implications for performance: if all clients
access the same load balancer performance may be suboptimal.
Note: if bucket probes are disabled, fs.s3a.bucket.probe = 0,
the DNS logging does not take place.
Change-Id: I21b3ac429dc0b543f03e357fdeb94c2d2a328dd8
add unit test, new ITest and then fix the issue: different schema, bucket == skip
factored out the underlying logic for unit testing; also moved
maybeAddTrailingSlash to S3AUtils (while retaining/forwarnding existing method
in S3AFS).
tested: london, sole failure is
testListingDelete[auth=true](org.apache.hadoop.fs.s3a.ITestS3GuardOutOfBandOperations)
filed HADOOP-16853
Change-Id: I4b8d0024469551eda0ec70b4968cba4abed405ed
Contributed by Ben Roling.
ETag values are unpredictable with some S3 encryption algorithms.
Skip ITestS3AMiscOperations tests which make assertions about etags
when default encryption on a bucket is enabled.
When testing with an AWS an account which lacks the privilege
for a call to getBucketEncryption(), we don't skip the tests.
In the event of failure, developers get to expand the
permissions of the account or relax default encryption settings.
Contributed by Steve Loughran
* move qualify logic to S3AFileSystem.makeQualified()
* make S3AFileSystem.qualify() a private redirect to that
* ITestS3GuardFsShell turned off
Contributed by Steve Loughran.
Not all stores do complete validation here; in particular the S3A
Connector does not: checking up the entire directory tree to see if a path matches
is a file significantly slows things down.
This check does take place in S3A mkdirs(), which walks backwards up the list of
parent paths until it finds a directory (success) or a file (failure).
In practice production applications invariably create destination directories
before writing 1+ file into them -restricting check purely to the mkdirs()
call deliver significant speed up while implicitly including the checks.
Change-Id: I2c9df748e92b5655232e7d888d896f1868806eb0
AreContributed by Mukund Thakur.
This addresses an issue which surfaced with KMS encryption: the wrong
KMS key could be picked up in the S3 COPY operation, so
renamed files, while encrypted, would end up with the
bucket default key.
As well as adding tests in the new suite
ITestS3AEncryptionWithDefaultS3Settings,
AbstractSTestS3AHugeFiles has a new test method to
verify that the encryption settings also work
for large files copied via multipart operations.
Contributed by Sergei Poganshev.
Catches Exception instead of IOException in closeStream()
and so handle exceptions such as SdkClientException by
aborting the wrapped stream. This will increase resilience
to failures, as any which occuring during stream closure
will be caught. Furthermore, because the
underlying HTTP connection is aborted, rather than closed,
it will not be recycled to cause problems on subsequent
operations.
This adds a new option fs.s3a.bucket.probe, range (0-2) to
control which probe for a bucket existence to perform on startup.
0: no checks
1: v1 check (as has been performend until now)
2: v2 bucket check, which also incudes a permission check. Default.
When set to 0, bucket existence checks won't be done
during initialization thus making it faster.
When the bucket is not available in S3,
or if fs.s3a.endpoint points to the wrong instance of a private S3 store
consecutive calls like listing, read, write etc. will fail with
an UnknownStoreException.
Contributed by:
* Mukund Thakur (main patch and tests)
* Rajesh Balamohan (v0 list and performance tests)
* lqjacklee (HADOOP-15990/v2 list)
* Steve Loughran (UnknownStoreException support)
modified: hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/Constants.java
modified: hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AFileSystem.java
modified: hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3ARetryPolicy.java
modified: hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AUtils.java
new file: hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/UnknownStoreException.java
new file: hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/impl/ErrorTranslation.java
modified: hadoop-tools/hadoop-aws/src/site/markdown/tools/hadoop-aws/index.md
modified: hadoop-tools/hadoop-aws/src/site/markdown/tools/hadoop-aws/performance.md
modified: hadoop-tools/hadoop-aws/src/site/markdown/tools/hadoop-aws/troubleshooting_s3a.md
modified: hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/AbstractS3AMockTest.java
new file: hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/ITestS3ABucketExistence.java
modified: hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/MockS3ClientFactory.java
modified: hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/TestS3AExceptionTranslation.java
modified: hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/s3guard/AbstractS3GuardToolTestBase.java
modified: hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/s3guard/ITestS3GuardToolDynamoDB.java
modified: hadoop-tools/hadoop-aws/src/test/resources/core-site.xml
Change-Id: Ic174f803e655af172d81c1274ed92b51bdceb384
Contributed by Steve Loughran.
During S3A rename() and delete() calls, the list of objects delete is
built up into batches of a thousand and then POSTed in a single large
DeleteObjects request.
But as the IO capacity allowed on an S3 partition may only be 3500 writes
per second *and* each entry in that POST counts as a single write, then
one of those posts alone can trigger throttling on an already loaded
S3 directory tree. Which can trigger backoff and retry, with the same
thousand entry post, and so recreate the exact same problem.
Fixes
* Page size for delete object requests is set in
fs.s3a.bulk.delete.page.size; the default is 250.
* The property fs.s3a.experimental.aws.s3.throttling (default=true)
can be set to false to disable throttle retry logic in the AWS
client SDK -it is all handled in the S3A client. This
gives more visibility in to when operations are being throttled
* Bulk delete throttling events are logged to the log
org.apache.hadoop.fs.s3a.throttled log at INFO; if this appears
often then choose a smaller page size.
* The metric "store_io_throttled" adds the entire count of delete
requests when a single DeleteObjects request is throttled.
* A new quantile, "store_io_throttle_rate" can track throttling
load over time.
* DynamoDB metastore throttle resilience issues have also been
identified and fixed. Note: the fs.s3a.experimental.aws.s3.throttling
flag does not apply to DDB IO precisely because there may still be
lurking issues there and it safest to rely on the DynamoDB client
SDK.
Change-Id: I00f85cdd94fc008864d060533f6bd4870263fd84
Contributed by Steve Loughran.
This fixes two problems with S3Guard authoritative mode and
the auth directory flags which are stored in DynamoDB.
1. mkdirs was creating dir markers without the auth bit,
forcing needless scans on newly created directories and
files subsequently added; it was only with the first listStatus call
on that directory that the dir would be marked as authoritative -even
though it would be complete already.
2. listStatus(path) would reset the authoritative status bit of all
child directories even if they were already marked as authoritative.
Issue #2 is possibly the most expensive, as any treewalk using listStatus
(e.g globfiles) would clear the auth bit for all child directories before
listing them. And this would happen every single time...
essentially you weren't getting authoritative directory listings.
For the curious, that the major bug was actually found during testing
-we'd all missed it during reviews.
A lesson there: the better the tests the fewer the bugs.
Maybe also: something obvious and significant can get by code reviews.
modified: hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AFileSystem.java
modified: hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/s3guard/BulkOperationState.java
modified: hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/s3guard/DynamoDBMetadataStore.java
modified: hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/s3guard/LocalMetadataStore.java
modified: hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/s3guard/MetadataStore.java
modified: hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/s3guard/NullMetadataStore.java
modified: hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/s3guard/S3Guard.java
modified: hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/ITestS3GuardWriteBack.java
modified: hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/auth/ITestRestrictedReadAccess.java
modified: hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/impl/TestPartialDeleteFailures.java
modified: hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/s3guard/ITestDynamoDBMetadataStore.java
modified: hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/s3guard/ITestDynamoDBMetadataStoreAuthoritativeMode.java
modified: hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/s3guard/ITestDynamoDBMetadataStoreScale.java
modified: hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/s3guard/ITestS3GuardFsck.java
modified: hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/s3guard/MetadataStoreTestBase.java
modified: hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/s3guard/TestS3Guard.java
Change-Id: Ic3ffda13f2af2430afedd50fd657b595c83e90a7
Contributed by Mustafa Iman.
This adds a new configuration option fs.s3a.connection.request.timeout
to declare the time out on HTTP requests to the AWS service;
0 means no timeout.
Measured in seconds; the usual time suffixes are all supported
Important: this is the maximum duration of any AWS service call,
including upload and copy operations. If non-zero, it must be larger
than the time to upload multi-megabyte blocks to S3 from the client,
and to rename many-GB files. Use with care.
Change-Id: I407745341068b702bf8f401fb96450a9f987c51c
* Enhanced builder + FS spec
* s3a FS to use this to skip HEAD on open
* and to use version/etag when opening the file
works with S3AFileStatus FS and S3ALocatedFileStatus
Introduces `openssl` as an option for `fs.s3a.ssl.channel.mode`.
The new option is documented and marked as experimental.
For details on how to use this, consult the peformance document
in the s3a documentation.
This patch is the successor to HADOOP-16050 "S3A SSL connections
should use OpenSSL" -which was reverted because of
incompatibilities between the wildfly OpenSSL client and the AWS
HTTPS servers (HADOOP-16347). With the Wildfly release moved up
to 1.0.7.Final (HADOOP-16405) everything should now work.
Related issues:
* HADOOP-15669. ABFS: Improve HTTPS Performance
* HADOOP-16050: S3A SSL connections should use OpenSSL
* HADOOP-16371: Option to disable GCM for SSL connections when running on Java 8
* HADOOP-16405: Upgrade Wildfly Openssl version to 1.0.7.Final
Contributed by Sahil Takiar
Change-Id: I80a4bc5051519f186b7383b2c1cea140be42444e
Contains:
HADOOP-16474. S3Guard ProgressiveRenameTracker to mark destination
dirirectory as authoritative on success.
HADOOP-16684. S3guard bucket info to list a bit more about
authoritative paths.
HADOOP-16722. S3GuardTool to support FilterFileSystem.
This patch improves the marking of newly created/import directory
trees in S3Guard DynamoDB tables as authoritative.
Specific changes:
* Renamed directories are marked as authoritative if the entire
operation succeeded (HADOOP-16474).
* When updating parent table entries as part of any table write,
there's no overwriting of their authoritative flag.
s3guard import changes:
* new -verbose flag to print out what is going on.
* The "s3guard import" command lets you declare that a directory tree
is to be marked as authoritative
hadoop s3guard import -authoritative -verbose s3a://bucket/path
When importing a listing and a file is found, the import tool queries
the metastore and only updates the entry if the file is different from
before, where different == new timestamp, etag, or length. S3Guard can get
timestamp differences due to clock skew in PUT operations.
As the recursive list performed by the import command doesn't retrieve the
versionID, the existing entry may in fact be more complete.
When updating an existing due to clock skew the existing version ID
is propagated to the new entry (note: the etags must match; this is needed
to deal with inconsistent listings).
There is a new s3guard command to audit a s3guard bucket/path's
authoritative state:
hadoop s3guard authoritative -check-config s3a://bucket/path
This is primarily for testing/auditing.
The s3guard bucket-info command also provides some more details on the
authoritative state of a store (HADOOP-16684).
Change-Id: I58001341c04f6f3597fcb4fcb1581ccefeb77d91
Contributed by Steve Loughran.
This is part of the ongoing refactoring of the S3A codebase, with the
delegation token support (HADOOP-14556) no longer given a direct reference
to the owning S3AFileSystem. Instead it gets a StoreContext and a new
interface, DelegationOperations, to access those operations offered by S3AFS
which are specifically needed by the DT bindings.
The sole operation needed is listAWSPolicyRules(), which is used to allow
S3A FS and the S3Guard metastore to return the AWS policy rules needed to
access their specific services/buckets/tables, allowing the AssumedRole
delegation token to be locked down.
As further restructuring takes place, that interface's implementation
can be moved to wherever the new home for those operations ends up.
Although it changes the API of an extension point, that feature (S3
Delegation Tokens) has not shipped; backwards compatibility is not a
problem except for anyone who has implemented DT support against trunk.
To those developers: sorry.
Change-Id: I770f58b49ff7634a34875ba37b7d51c94d7c21da