org.apache.hadoop.fs.s3a.impl

Class S3AStoreImpl

java.lang.Object

org.apache.hadoop.service.AbstractService

org.apache.hadoop.service.CompositeService

org.apache.hadoop.fs.s3a.impl.S3AStoreImpl

All Implemented Interfaces:

Closeable, AutoCloseable, org.apache.hadoop.fs.PathCapabilities, ClientManager, ObjectInputStreamFactory, S3AStore, org.apache.hadoop.fs.statistics.IOStatisticsSource, org.apache.hadoop.fs.StreamCapabilities, org.apache.hadoop.service.Service

public class S3AStoreImpl
extends org.apache.hadoop.service.CompositeService
implements S3AStore, ObjectInputStreamFactory

Store Layer. This is where lower level storage operations are intended to move.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.hadoop.service.CompositeService

org.apache.hadoop.service.CompositeService.CompositeServiceShutdownHook

Nested classes/interfaces inherited from interface org.apache.hadoop.fs.s3a.impl.streams.ObjectInputStreamFactory

ObjectInputStreamFactory.StreamFactoryCallbacks

Nested classes/interfaces inherited from interface org.apache.hadoop.service.Service

org.apache.hadoop.service.Service.STATE

Nested classes/interfaces inherited from interface org.apache.hadoop.fs.StreamCapabilities

org.apache.hadoop.fs.StreamCapabilities.StreamCapability

Field Summary

Fields inherited from class org.apache.hadoop.service.CompositeService

STOP_ONLY_STARTED_SERVICES

Fields inherited from interface org.apache.hadoop.fs.StreamCapabilities

ABORTABLE_STREAM, DROPBEHIND, HFLUSH, HSYNC, IOSTATISTICS, IOSTATISTICS_CONTEXT, PREADBYTEBUFFER, READAHEAD, READBYTEBUFFER, UNBUFFER, VECTOREDIO, VECTOREDIO_BUFFERS_SLICED

Method Summary

Modifier and Type	Method and Description
Duration	acquireReadCapacity(int capacity) Acquire read capacity for rate limiting Acquire read capacity for operations..
Duration	acquireWriteCapacity(int capacity) Acquire write capacity for rate limiting Acquire write capacity for operations..
void	bind(FactoryBindingParameters factoryBindingParameters) This operation is not implemented, as is this class which invokes it on the actual factory.
ClientManager	clientManager() Get the client manager.
software.amazon.awssdk.services.s3.model.CompleteMultipartUploadResponse	completeMultipartUpload(software.amazon.awssdk.services.s3.model.CompleteMultipartUploadRequest request) Complete a multipart upload.
AuditSpanS3A	createSpan(String operation, String path1, String path2) Start an operation; this informs the audit service of the event and then sets it as the active span.
File	createTemporaryFileForWriting(String pathStr, long size, org.apache.hadoop.conf.Configuration conf) Demand create the directory allocator, then create a temporary file.
protected void	decrementGauge(Statistic statistic, long count) Decrement a gauge by a specific value.
Map.Entry<Duration,Optional<software.amazon.awssdk.services.s3.model.DeleteObjectResponse>>	deleteObject(software.amazon.awssdk.services.s3.model.DeleteObjectRequest request) Delete an object.
Map.Entry<Duration,software.amazon.awssdk.services.s3.model.DeleteObjectsResponse>	deleteObjects(software.amazon.awssdk.services.s3.model.DeleteObjectsRequest deleteRequest) Perform a bulk object delete operation against S3.
StreamFactoryRequirements	factoryRequirements() Get requirements from the factory which then tune behavior elsewhere in the system.
org.apache.hadoop.fs.LocalDirAllocator	getDirectoryAllocator() Get the directory allocator.
org.apache.hadoop.fs.statistics.DurationTrackerFactory	getDurationTrackerFactory()
org.apache.hadoop.fs.statistics.IOStatistics	getIOStatistics() Get the instrumentation's IOStatistics.
software.amazon.awssdk.services.s3.S3AsyncClient	getOrCreateAsyncClient() Get the Async S3Client,raising a failure to create as an IOException.
software.amazon.awssdk.services.s3.S3Client	getOrCreateAsyncS3ClientUnchecked() Get the AsyncS3Client, raising a failure to create as an UncheckedIOException.
software.amazon.awssdk.services.s3.S3Client	getOrCreateS3Client() Get the S3Client, raising a failure to create as an IOException.
software.amazon.awssdk.services.s3.S3Client	getOrCreateS3ClientUnchecked() Get the S3Client, raising a failure to create as an UncheckedIOException.
software.amazon.awssdk.transfer.s3.S3TransferManager	getOrCreateTransferManager() Get the transfer manager, creating it and any dependencies if needed.
software.amazon.awssdk.services.s3.S3Client	getOrCreateUnencryptedS3Client() Get or create an unencrypted S3 client.
software.amazon.awssdk.core.ResponseInputStream<software.amazon.awssdk.services.s3.model.GetObjectResponse>	getRangedS3Object(String key, long start, long end) Retrieves a specific byte range of an S3 object as a stream.
RequestFactory	getRequestFactory()
S3AStatisticsContext	getStatisticsContext()
StoreContext	getStoreContext()
boolean	hasPathCapability(org.apache.hadoop.fs.Path path, String capability) Return the store path capabilities.
software.amazon.awssdk.services.s3.model.HeadObjectResponse	headObject(String key, ChangeTracker changeTracker, Invoker changeInvoker, S3AFileSystemOperations fsHandler, String operation) Performs a HEAD request on an S3 object to retrieve its metadata.
protected void	incrementGauge(Statistic statistic, long count) Increment a gauge by a specific value.
void	incrementPutCompletedStatistics(boolean success, long bytes) At the end of a put/multipart upload operation, update the relevant counters and gauges.
void	incrementPutProgressStatistics(String key, long bytes) Callback for use in progress callbacks from put/multipart upload events.
void	incrementPutStartStatistics(long bytes) At the start of a put/multipart upload operation, update the relevant counters.
void	incrementReadOperations() Increment read operations.
protected void	incrementStatistic(Statistic statistic) Increment a statistic by 1.
protected void	incrementStatistic(Statistic statistic, long count) Increment a statistic by a specific value.
void	incrementWriteOperations() Increment the write operation counter.
boolean	inputStreamHasCapability(String capability) Return the capabilities of input streams created through the store.
org.apache.hadoop.fs.statistics.DurationTrackerFactory	nonNullDurationTrackerFactory(org.apache.hadoop.fs.statistics.DurationTrackerFactory factory) Given a possibly null duration tracker factory, return a non-null one for use in tracking durations -either that or the FS tracker itself.
void	operationRetried(Exception ex) Callback when an operation was retried.
void	operationRetried(String text, Exception ex, int retries, boolean idempotent) Callback from Invoker when an operation is retried.
UploadInfo	putObject(software.amazon.awssdk.services.s3.model.PutObjectRequest putObjectRequest, File file, ProgressableProgressListener listener) Start a transfer-manager managed async PUT of an object, incrementing the put requests and put bytes counters.
ObjectInputStream	readObject(ObjectReadParameters parameters) Create a new input stream.
protected void	serviceInit(org.apache.hadoop.conf.Configuration conf) Create and initialize any subsidiary services, including the input stream factory.
protected void	serviceStart()
InputStreamType	streamType() Get the input stream type.
software.amazon.awssdk.services.s3.model.UploadPartResponse	uploadPart(software.amazon.awssdk.services.s3.model.UploadPartRequest request, software.amazon.awssdk.core.sync.RequestBody body, org.apache.hadoop.fs.statistics.DurationTrackerFactory trackerFactory) Upload part of a multi-partition file.
software.amazon.awssdk.transfer.s3.model.CompletedFileUpload	waitForUploadCompletion(String key, UploadInfo uploadInfo) Wait for an upload to complete.

Methods inherited from class org.apache.hadoop.service.CompositeService

addIfService, addService, getServices, removeService, serviceStop

Methods inherited from class org.apache.hadoop.service.AbstractService

close, getBlockers, getConfig, getFailureCause, getFailureState, getLifecycleHistory, getName, getServiceState, getStartTime, init, isInState, noteFailure, putBlocker, registerGlobalListener, registerServiceListener, removeBlocker, setConfig, start, stop, toString, unregisterGlobalListener, unregisterServiceListener, waitForServiceToStop

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.apache.hadoop.fs.s3a.S3AStore

hasCapability

Methods inherited from interface org.apache.hadoop.service.Service

close, getBlockers, getConfig, getFailureCause, getFailureState, getLifecycleHistory, getName, getServiceState, getStartTime, init, isInState, registerServiceListener, start, stop, unregisterServiceListener, waitForServiceToStop

Method Detail

serviceInit

protected void serviceInit(org.apache.hadoop.conf.Configuration conf)
                    throws Exception

Create and initialize any subsidiary services, including the input stream factory.

Overrides:

serviceInit in class org.apache.hadoop.service.CompositeService

Parameters:

conf - configuration

Throws:

Exception

serviceStart

protected void serviceStart()
                     throws Exception

Overrides:

serviceStart in class org.apache.hadoop.service.CompositeService

Throws:

Exception

hasPathCapability

public boolean hasPathCapability(org.apache.hadoop.fs.Path path,
                                 String capability)

Return the store path capabilities. If the object stream factory is non-null, hands off the query to that factory if not handled here.

Specified by:

hasPathCapability in interface org.apache.hadoop.fs.PathCapabilities

Parameters:

path - path to query the capability of.

capability - non-null, non-empty string to query the path for support.

Returns:

known capabilities

inputStreamHasCapability

public boolean inputStreamHasCapability(String capability)

Return the capabilities of input streams created through the store.

Specified by:

inputStreamHasCapability in interface S3AStore

Parameters:

capability - string to query the stream support for.

Returns:

capabilities declared supported in streams.

acquireWriteCapacity

public Duration acquireWriteCapacity(int capacity)

Acquire write capacity for rate limiting Acquire write capacity for operations. This should be done within retry loops..

Specified by:

acquireWriteCapacity in interface S3AStore

Parameters:

capacity - capacity to acquire.

Returns:

time spent waiting for output.

acquireReadCapacity

public Duration acquireReadCapacity(int capacity)

Acquire read capacity for rate limiting Acquire read capacity for operations. This should be done within retry loops..

Specified by:

acquireReadCapacity in interface S3AStore

Parameters:

capacity - capacity to acquire.

Returns:

time spent waiting for output.

getStoreContext

public StoreContext getStoreContext()

Specified by:

getStoreContext in interface S3AStore

getOrCreateTransferManager

public software.amazon.awssdk.transfer.s3.S3TransferManager getOrCreateTransferManager()
                                                                                throws IOException

Description copied from interface: ClientManager

Get the transfer manager, creating it and any dependencies if needed.

Specified by:

getOrCreateTransferManager in interface ClientManager

Returns:

a transfer manager

Throws:

IOException - on any failure to create the manager

getOrCreateS3Client

public software.amazon.awssdk.services.s3.S3Client getOrCreateS3Client()
                                                                throws IOException

Description copied from interface: ClientManager

Get the S3Client, raising a failure to create as an IOException.

Specified by:

getOrCreateS3Client in interface ClientManager

Returns:

the S3 client

Throws:

IOException - failure to create the client.

getOrCreateAsyncClient

public software.amazon.awssdk.services.s3.S3AsyncClient getOrCreateAsyncClient()
                                                                        throws IOException

Description copied from interface: ClientManager

Get the Async S3Client,raising a failure to create as an IOException.

Specified by:

getOrCreateAsyncClient in interface ClientManager

Returns:

the Async S3 client

Throws:

IOException - failure to create the client.

getOrCreateS3ClientUnchecked

public software.amazon.awssdk.services.s3.S3Client getOrCreateS3ClientUnchecked()
                                                                         throws UncheckedIOException

Description copied from interface: ClientManager

Get the S3Client, raising a failure to create as an UncheckedIOException.

Specified by:

getOrCreateS3ClientUnchecked in interface ClientManager

Returns:

the S3 client

Throws:

UncheckedIOException - failure to create the client.

getOrCreateAsyncS3ClientUnchecked

public software.amazon.awssdk.services.s3.S3Client getOrCreateAsyncS3ClientUnchecked()
                                                                              throws UncheckedIOException

Description copied from interface: ClientManager

Get the AsyncS3Client, raising a failure to create as an UncheckedIOException.

Specified by:

getOrCreateAsyncS3ClientUnchecked in interface ClientManager

Returns:

the S3 client

Throws:

UncheckedIOException - failure to create the client.

getOrCreateUnencryptedS3Client

public software.amazon.awssdk.services.s3.S3Client getOrCreateUnencryptedS3Client()
                                                                           throws IOException

Description copied from interface: ClientManager

Get or create an unencrypted S3 client. This is used for unencrypted operations when CSE is enabled with V1 compatibility.

Specified by:

getOrCreateUnencryptedS3Client in interface ClientManager

Returns:

unencrypted S3 client

Throws:

IOException - on any failure

getDurationTrackerFactory

public org.apache.hadoop.fs.statistics.DurationTrackerFactory getDurationTrackerFactory()

Specified by:

getDurationTrackerFactory in interface S3AStore

getStatisticsContext

public S3AStatisticsContext getStatisticsContext()

Specified by:

getStatisticsContext in interface S3AStore

getRequestFactory

public RequestFactory getRequestFactory()

Specified by:

getRequestFactory in interface S3AStore

clientManager

public ClientManager clientManager()

Get the client manager.

Specified by:

clientManager in interface S3AStore

Returns:

the client manager.

incrementStatistic

protected void incrementStatistic(Statistic statistic)

Increment a statistic by 1. This increments both the instrumentation and storage statistics.

Parameters:

statistic - The operation to increment

incrementStatistic

protected void incrementStatistic(Statistic statistic,
                                  long count)

Increment a statistic by a specific value. This increments both the instrumentation and storage statistics.

Parameters:

statistic - The operation to increment

count - the count to increment

decrementGauge

protected void decrementGauge(Statistic statistic,
                              long count)

Decrement a gauge by a specific value.

Parameters:

statistic - The operation to decrement

count - the count to decrement

incrementGauge

protected void incrementGauge(Statistic statistic,
                              long count)

Increment a gauge by a specific value.

Parameters:

statistic - The operation to increment

count - the count to increment

operationRetried

public void operationRetried(Exception ex)

Callback when an operation was retried. Increments the statistics of ignored errors or throttled requests, depending up on the exception class.

Parameters:

ex - exception.

operationRetried

public void operationRetried(String text,
                             Exception ex,
                             int retries,
                             boolean idempotent)

Callback from Invoker when an operation is retried.

Parameters:

text - text of the operation

ex - exception

retries - number of retries

idempotent - is the method idempotent

getIOStatistics

public org.apache.hadoop.fs.statistics.IOStatistics getIOStatistics()

Get the instrumentation's IOStatistics.

Specified by:

getIOStatistics in interface org.apache.hadoop.fs.statistics.IOStatisticsSource

Returns:

statistics

incrementReadOperations

public void incrementReadOperations()

Increment read operations.

Specified by:

incrementReadOperations in interface S3AStore

incrementWriteOperations

public void incrementWriteOperations()

Increment the write operation counter. This is somewhat inaccurate, as it appears to be invoked more often than needed in progress callbacks.

Specified by:

incrementWriteOperations in interface S3AStore

incrementPutStartStatistics

public void incrementPutStartStatistics(long bytes)

At the start of a put/multipart upload operation, update the relevant counters.

Specified by:

incrementPutStartStatistics in interface S3AStore

Parameters:

bytes - bytes in the request.

incrementPutCompletedStatistics

public void incrementPutCompletedStatistics(boolean success,
                                            long bytes)

At the end of a put/multipart upload operation, update the relevant counters and gauges.

Specified by:

incrementPutCompletedStatistics in interface S3AStore

Parameters:

success - did the operation succeed?

bytes - bytes in the request.

incrementPutProgressStatistics

public void incrementPutProgressStatistics(String key,
                                           long bytes)

Callback for use in progress callbacks from put/multipart upload events. Increments those statistics which are expected to be updated during the ongoing upload operation.

Specified by:

incrementPutProgressStatistics in interface S3AStore

Parameters:

key - key to file that is being written (for logging)

bytes - bytes successfully uploaded.

nonNullDurationTrackerFactory

public org.apache.hadoop.fs.statistics.DurationTrackerFactory nonNullDurationTrackerFactory(org.apache.hadoop.fs.statistics.DurationTrackerFactory factory)

Given a possibly null duration tracker factory, return a non-null one for use in tracking durations -either that or the FS tracker itself.

Specified by:

nonNullDurationTrackerFactory in interface S3AStore

Parameters:

factory - factory.

Returns:

a non-null factory.

createSpan

public AuditSpanS3A createSpan(String operation,
                               @Nullable
                               String path1,
                               @Nullable
                               String path2)
                        throws IOException

Start an operation; this informs the audit service of the event and then sets it as the active span.

Parameters:

operation - operation name.

path1 - first path of operation

path2 - second path of operation

Returns:

a span for the audit

Throws:

IOException - failure

deleteObjects

@Retries.RetryRaw
public Map.Entry<Duration,software.amazon.awssdk.services.s3.model.DeleteObjectsResponse> deleteObjects(software.amazon.awssdk.services.s3.model.DeleteObjectsRequest deleteRequest)
                                                                                                                   throws software.amazon.awssdk.core.exception.SdkException

Perform a bulk object delete operation against S3. Increments the OBJECT_DELETE_REQUESTS and write operation statistics

OBJECT_DELETE_OBJECTS is updated with the actual number of objects deleted in the request.

Retry policy: retry untranslated; delete considered idempotent. If the request is throttled, this is logged in the throttle statistics, with the counter set to the number of keys, rather than the number of invocations of the delete operation. This is because S3 considers each key as one mutating operation on the store when updating its load counters on a specific partition of an S3 bucket. If only the request was measured, this operation would under-report. A write capacity will be requested proportional to the number of keys preset in the request and will be re-requested during retries such that retries throttle better. If the request is throttled, the time spent is recorded in a duration IOStat named STORE_IO_RATE_LIMITED_DURATION..

Specified by:

deleteObjects in interface S3AStore

Parameters:

deleteRequest - keys to delete on the s3-backend

Returns:

the AWS response

Throws:

MultiObjectDeleteException - one or more of the keys could not be deleted.

software.amazon.awssdk.core.exception.SdkException - amazon-layer failure.

headObject

@Retries.RetryRaw
public software.amazon.awssdk.services.s3.model.HeadObjectResponse headObject(String key,
                                                                                                ChangeTracker changeTracker,
                                                                                                Invoker changeInvoker,
                                                                                                S3AFileSystemOperations fsHandler,
                                                                                                String operation)
                                                                                         throws IOException

Performs a HEAD request on an S3 object to retrieve its metadata.

Specified by:

headObject in interface S3AStore

Parameters:

key - The S3 object key to perform the HEAD operation on

changeTracker - Tracks changes to the object's metadata across operations

changeInvoker - The invoker responsible for executing the HEAD request with retries

fsHandler - Handler for filesystem-level operations and configurations

operation - Description of the operation being performed for tracking purposes

Returns:

HeadObjectResponse containing the object's metadata

Throws:

IOException - If the HEAD request fails, object doesn't exist, or other I/O errors occur

getRangedS3Object

@Retries.RetryRaw
public software.amazon.awssdk.core.ResponseInputStream<software.amazon.awssdk.services.s3.model.GetObjectResponse> getRangedS3Object(String key,
                                                                                                                                                       long start,
                                                                                                                                                       long end)
                                                                                                                                                throws IOException

Retrieves a specific byte range of an S3 object as a stream.

Specified by:

getRangedS3Object in interface S3AStore

Parameters:

key - The S3 object key to retrieve

start - The starting byte position (inclusive) of the range to retrieve

end - The ending byte position (inclusive) of the range to retrieve

Returns:

A ResponseInputStream containing the requested byte range of the S3 object

Throws:

IOException - If the object cannot be retrieved other I/O errors occur

See Also:

For additional metadata about the retrieved object

deleteObject

@Retries.RetryRaw
public Map.Entry<Duration,Optional<software.amazon.awssdk.services.s3.model.DeleteObjectResponse>> deleteObject(software.amazon.awssdk.services.s3.model.DeleteObjectRequest request)
                                                                                                                           throws software.amazon.awssdk.core.exception.SdkException

Delete an object. Increments the OBJECT_DELETE_REQUESTS statistics.

Retry policy: retry untranslated; delete considered idempotent. 404 errors other than bucket not found are swallowed; this can be raised by third party stores (GCS).

A write capacity of 1 ( as it is signle object delete) will be requested before the delete call and will be re-requested during retries such that retries throttle better. If the request is throttled, the time spent is recorded in a duration IOStat named STORE_IO_RATE_LIMITED_DURATION. If an exception is caught and swallowed, the response will be empty; otherwise it will be the response from the delete operation..

Specified by:

deleteObject in interface S3AStore

Parameters:

request - request to make

Returns:

the total duration and response.

Throws:

software.amazon.awssdk.core.exception.SdkException - problems working with S3

uploadPart

@Retries.OnceRaw
public software.amazon.awssdk.services.s3.model.UploadPartResponse uploadPart(software.amazon.awssdk.services.s3.model.UploadPartRequest request,
                                                                                               software.amazon.awssdk.core.sync.RequestBody body,
                                                                                               @Nullable
                                                                                               org.apache.hadoop.fs.statistics.DurationTrackerFactory trackerFactory)
                                                                                        throws software.amazon.awssdk.awscore.exception.AwsServiceException,
                                                                                               UncheckedIOException

Upload part of a multi-partition file. Increments the write and put counters. Important: this call does not close any input stream in the body.

Retry Policy: none.

Specified by:

uploadPart in interface S3AStore

Parameters:

trackerFactory - duration tracker factory for operation

request - the upload part request.

body - the request body.

Returns:

the result of the operation.

Throws:

software.amazon.awssdk.awscore.exception.AwsServiceException - on problems

UncheckedIOException - failure to instantiate the s3 client

putObject

@Retries.OnceRaw
public UploadInfo putObject(software.amazon.awssdk.services.s3.model.PutObjectRequest putObjectRequest,
                                             File file,
                                             ProgressableProgressListener listener)
                                      throws IOException

Start a transfer-manager managed async PUT of an object, incrementing the put requests and put bytes counters.

It does not update the other counters, as existing code does that as progress callbacks come in. Byte length is calculated from the file length, or, if there is no file, from the content length of the header.

Because the operation is async, any stream supplied in the request must reference data (files, buffers) which stay valid until the upload completes. Retry policy: N/A: the transfer manager is performing the upload. Auditing: must be inside an audit span.

Specified by:

putObject in interface S3AStore

Parameters:

putObjectRequest - the request

file - the file to be uploaded

listener - the progress listener for the request

Returns:

the upload initiated

Throws:

IOException - if transfer manager creation failed.

waitForUploadCompletion

@Retries.OnceTranslated
public software.amazon.awssdk.transfer.s3.model.CompletedFileUpload waitForUploadCompletion(String key,
                                                                                                                    UploadInfo uploadInfo)
                                                                                                             throws IOException

Wait for an upload to complete. If the upload (or its result collection) failed, this is where the failure is raised as an AWS exception. Calls S3AStore.incrementPutCompletedStatistics(boolean, long) to update the statistics.

Specified by:

waitForUploadCompletion in interface S3AStore

Parameters:

key - destination key

uploadInfo - upload to wait for

Returns:

the upload result

Throws:

IOException - IO failure

CancellationException - if the wait() was cancelled

completeMultipartUpload

@Retries.OnceRaw
public software.amazon.awssdk.services.s3.model.CompleteMultipartUploadResponse completeMultipartUpload(software.amazon.awssdk.services.s3.model.CompleteMultipartUploadRequest request)

Complete a multipart upload.

Specified by:

completeMultipartUpload in interface S3AStore

Parameters:

request - request

Returns:

the response

getDirectoryAllocator

public org.apache.hadoop.fs.LocalDirAllocator getDirectoryAllocator()

Get the directory allocator.

Specified by:

getDirectoryAllocator in interface S3AStore

Returns:

the directory allocator

createTemporaryFileForWriting

public File createTemporaryFileForWriting(String pathStr,
                                          long size,
                                          org.apache.hadoop.conf.Configuration conf)
                                   throws IOException

Demand create the directory allocator, then create a temporary file. This does not mark the file for deletion when a process exits. Pass in a file size of LocalDirAllocator.SIZE_UNKNOWN if the size is unknown. LocalDirAllocator.createTmpFileForWrite(String, long, Configuration).

Specified by:

createTemporaryFileForWriting in interface S3AStore

Parameters:

pathStr - prefix for the temporary file

size - the size of the file that is going to be written

conf - the Configuration object

Returns:

a unique temporary file

Throws:

IOException - IO problems

readObject

public ObjectInputStream readObject(ObjectReadParameters parameters)
                             throws IOException

Description copied from interface: ObjectInputStreamFactory

Create a new input stream. There is no requirement to actually contact the store; this is generally done lazily.

Specified by:

readObject in interface ObjectInputStreamFactory

Parameters:

parameters - parameters.

Returns:

the input stream

Throws:

IOException - problem creating the stream.

factoryRequirements

public StreamFactoryRequirements factoryRequirements()

Description copied from interface: ObjectInputStreamFactory

Get requirements from the factory which then tune behavior elsewhere in the system.

Specified by:

factoryRequirements in interface ObjectInputStreamFactory

Returns:

the count of background threads.

bind

public void bind(FactoryBindingParameters factoryBindingParameters)

This operation is not implemented, as is this class which invokes it on the actual factory.

Specified by:

bind in interface ObjectInputStreamFactory

Parameters:

factoryBindingParameters - ignored

Throws:

UnsupportedOperationException - always

streamType

public InputStreamType streamType()

Description copied from interface: ObjectInputStreamFactory

Get the input stream type.

Specified by:

streamType in interface ObjectInputStreamFactory

Returns:

the specific stream type this factory produces.