FlowFileQueue (nifi-api 0.7.4 API)

```
public interface FlowFileQueue
```

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method and Description
`void`	`acknowledge(Collection<FlowFileRecord> flowFiles)`
`void`	`acknowledge(FlowFileRecord flowFile)`
`DropFlowFileStatus`	`cancelDropFlowFileRequest(String requestIdentifier)` Cancels the request to drop FlowFiles that has the given identifier.
`ListFlowFileStatus`	`cancelListFlowFileRequest(String requestIdentifier)` Cancels the request to list FlowFiles that has the given identifier.
`long`	`drainQueue(Queue<FlowFileRecord> sourceQueue, List<FlowFileRecord> destination, int maxResults, Set<FlowFileRecord> expiredRecords)` Drains flow files from the given source queue into the given destination list.
`DropFlowFileStatus`	`dropFlowFiles(String requestIdentifier, String requestor)` Initiates a request to drop all FlowFiles in this queue.
`String`	`getBackPressureDataSizeThreshold()`
`long`	`getBackPressureObjectThreshold()`
`DropFlowFileStatus`	`getDropFlowFileStatus(String requestIdentifier)` Returns the current status of a Drop FlowFile Request that was initiated via the `#dropFlowFiles()` method that has the given identifier
`FlowFileRecord`	`getFlowFile(String flowFileUuid)` Returns the FlowFile with the given UUID or `null` if no FlowFile can be found in this queue with the given UUID
`String`	`getFlowFileExpiration()`
`int`	`getFlowFileExpiration(TimeUnit timeUnit)`
`String`	`getIdentifier()`
`ListFlowFileStatus`	`getListFlowFileStatus(String requestIdentifier)` Returns the current status of a List FlowFile Request that was initiated via the `#listFlowFiles(String)` method that has the given identifier
`List<FlowFilePrioritizer>`	`getPriorities()`
`QueueSize`	`getUnacknowledgedQueueSize()` Returns a QueueSize that represents all FlowFiles that are 'unacknowledged'.
`boolean`	`isActiveQueueEmpty()`
`boolean`	`isEmpty()`
`boolean`	`isFull()`
`ListFlowFileStatus`	`listFlowFiles(String requestIdentifier, int maxResults)` Initiates a request to obtain a listing of FlowFiles in this queue.
`List<FlowFileRecord>`	`poll(FlowFileFilter filter, Set<FlowFileRecord> expiredRecords)`
`List<FlowFileRecord>`	`poll(int maxResults, Set<FlowFileRecord> expiredRecords)`
`FlowFileRecord`	`poll(Set<FlowFileRecord> expiredRecords)`
`void`	`purgeSwapFiles()` Destroys any Swap Files that exist for this queue without updating the FlowFile Repository or Provenance Repository.
`void`	`put(FlowFileRecord file)` places the given file into the queue
`void`	`putAll(Collection<FlowFileRecord> files)` places the given files into the queue
`SwapSummary`	`recoverSwappedFlowFiles()` Reads any Swap Files that belong to this queue and returns a summary of what is swapped out.
`void`	`setBackPressureDataSizeThreshold(String maxDataSize)`
`void`	`setBackPressureObjectThreshold(long maxQueueSize)` Establishes this queue's preferred maximum work load.
`void`	`setFlowFileExpiration(String flowExpirationPeriod)`
`void`	`setPriorities(List<FlowFilePrioritizer> newPriorities)` Resets the comparator used by this queue to maintain order.
`QueueSize`	`size()`
`void`	`verifyCanList()` Ensures that a listing can be performed on the queue

- Method Detail
  - getIdentifier
```
String getIdentifier()
```
    Returns:
    
    the unique identifier for this FlowFileQueue
  - getPriorities
```
List<FlowFilePrioritizer> getPriorities()
```
    Returns:
    
    list of processing priorities for this queue
  - recoverSwappedFlowFiles
```
SwapSummary recoverSwappedFlowFiles()
```
    Reads any Swap Files that belong to this queue and returns a summary of what is swapped out. This will be called only during NiFi startup as an initialization step. This method is then responsible for returning a FlowFileSummary of the FlowFiles that are swapped out, or null if no FlowFiles are swapped out for this queue.
    
    Returns:
    
    a SwapSummary that describes the FlowFiles that exist in the queue but are swapped out.
  - purgeSwapFiles
```
void purgeSwapFiles()
```
    Destroys any Swap Files that exist for this queue without updating the FlowFile Repository or Provenance Repository. This is done only on startup in the case of non-persistent repositories. In the case of non-persistent repositories, we may still have Swap Files because we may still need to overflow the FlowFiles from heap onto disk, even though we don't want to keep the FlowFiles on restart.
  - setPriorities
```
void setPriorities(List<FlowFilePrioritizer> newPriorities)
```
    Resets the comparator used by this queue to maintain order.
    
    Parameters:
    
    newPriorities - the ordered list of prioritizers to use to determine order within this queue.
    
    Throws:
    
    NullPointerException - if arg is null
  - setBackPressureObjectThreshold
```
void setBackPressureObjectThreshold(long maxQueueSize)
```
    Establishes this queue's preferred maximum work load.
    
    Parameters:
    
    maxQueueSize - the maximum number of flow files this processor recommends having in its work queue at any one time
  - getBackPressureObjectThreshold
```
long getBackPressureObjectThreshold()
```
    Returns:
    
    maximum number of flow files that should be queued up at any one time
  - setBackPressureDataSizeThreshold
```
void setBackPressureDataSizeThreshold(String maxDataSize)
```
    Parameters:
    
    maxDataSize - Establishes this queue's preferred maximum data size.
  - getBackPressureDataSizeThreshold
```
String getBackPressureDataSizeThreshold()
```
    Returns:
    
    maximum data size that should be queued up at any one time
  - size
```
QueueSize size()
```
  - isEmpty
```
boolean isEmpty()
```
    Returns:
    
    true if no items queue; false otherwise
  - isActiveQueueEmpty
```
boolean isActiveQueueEmpty()
```
    Returns:
    
    true if the queue is empty or contains only FlowFiles that already are being processed by others, false if the queue contains at least one FlowFile that is available for processing, regardless of whether that FlowFile(s) is in-memory or swapped out.
  - getUnacknowledgedQueueSize
```
QueueSize getUnacknowledgedQueueSize()
```
    Returns a QueueSize that represents all FlowFiles that are 'unacknowledged'. A FlowFile is considered to be unacknowledged if it has been pulled from the queue by some component but the session that pulled the FlowFile has not yet been committed or rolled back.
    
    Returns:
    
    a QueueSize that represents all FlowFiles that are 'unacknowledged'.
  - acknowledge
```
void acknowledge(FlowFileRecord flowFile)
```
  - acknowledge
```
void acknowledge(Collection<FlowFileRecord> flowFiles)
```
  - isFull
```
boolean isFull()
```
    Returns:
    
    true if maximum queue size has been reached or exceeded; false otherwise
  - put
```
void put(FlowFileRecord file)
```
    places the given file into the queue
    
    Parameters:
    
    file - to place into queue
  - putAll
```
void putAll(Collection<FlowFileRecord> files)
```
    places the given files into the queue
    
    Parameters:
    
    files - to place into queue
  - poll
```
FlowFileRecord poll(Set<FlowFileRecord> expiredRecords)
```
    Parameters:
    
    expiredRecords - expired records
    
    Returns:
    
    the next flow file on the queue; null if empty
  - poll
```
List<FlowFileRecord> poll(int maxResults,
                          Set<FlowFileRecord> expiredRecords)
```
    Parameters:
    
    maxResults - limits how many results can be polled
    
    expiredRecords - for expired records
    
    Returns:
    
    the next flow files on the queue up to the max results; null if empty
  - drainQueue
```
long drainQueue(Queue<FlowFileRecord> sourceQueue,
                List<FlowFileRecord> destination,
                int maxResults,
                Set<FlowFileRecord> expiredRecords)
```
    Drains flow files from the given source queue into the given destination list.
    
    Parameters:
    
    sourceQueue - queue to drain from
    
    destination - Collection to drain to
    
    maxResults - max number to drain
    
    expiredRecords - for expired records
    
    Returns:
    
    size (bytes) of flow files drained from queue
  - poll
```
List<FlowFileRecord> poll(FlowFileFilter filter,
                          Set<FlowFileRecord> expiredRecords)
```
  - getFlowFileExpiration
```
String getFlowFileExpiration()
```
  - getFlowFileExpiration
```
int getFlowFileExpiration(TimeUnit timeUnit)
```
  - setFlowFileExpiration
```
void setFlowFileExpiration(String flowExpirationPeriod)
```
  - dropFlowFiles
```
DropFlowFileStatus dropFlowFiles(String requestIdentifier,
                                 String requestor)
```
    Initiates a request to drop all FlowFiles in this queue. This method returns a DropFlowFileStatus that can be used to determine the current state of the request. Additionally, the DropFlowFileStatus provides a request identifier that can then be passed to the getDropFlowFileStatus(String) and #cancelDropFlowFileStatus(String) methods in order to obtain the status later or cancel a request
    
    Parameters:
    
    requestIdentifier - the identifier of the Drop FlowFile Request
    
    requestor - the entity that is requesting that the FlowFiles be dropped; this will be included in the Provenance Events that are generated.
    
    Returns:
    
    the status of the drop request.
  - getDropFlowFileStatus
```
DropFlowFileStatus getDropFlowFileStatus(String requestIdentifier)
```
    Returns the current status of a Drop FlowFile Request that was initiated via the #dropFlowFiles() method that has the given identifier
    
    Parameters:
    
    requestIdentifier - the identifier of the Drop FlowFile Request
    
    Returns:
    
    the status for the request with the given identifier, or null if no request status exists with that identifier
  - cancelDropFlowFileRequest
```
DropFlowFileStatus cancelDropFlowFileRequest(String requestIdentifier)
```
    Cancels the request to drop FlowFiles that has the given identifier. After this method is called, the request will no longer be known by this queue, so subsequent calls to getDropFlowFileStatus(String) or cancelDropFlowFileRequest(String) will return null
    
    Parameters:
    
    requestIdentifier - the identifier of the Drop FlowFile Request
    
    Returns:
    
    the status for the request with the given identifier after it has been canceled, or null if no request status exists with that identifier
  - listFlowFiles
```
ListFlowFileStatus listFlowFiles(String requestIdentifier,
                                 int maxResults)
```
    Initiates a request to obtain a listing of FlowFiles in this queue. This method returns a ListFlowFileStatus that can be used to obtain information about the FlowFiles that exist within the queue. Additionally, the ListFlowFileStatus provides a request identifier that can then be passed to the getListFlowFileStatus(String). The listing of FlowFiles will be returned ordered by the position of the FlowFile in the queue.
    
    Note that if maxResults is larger than the size of the "active queue" (i.e., the un-swapped queued, FlowFiles that are swapped out will not be returned.)
    
    Parameters:
    
    requestIdentifier - the identifier of the List FlowFile Request
    
    maxResults - the maximum number of FlowFileSummary objects to add to the ListFlowFileStatus
    
    Returns:
    
    the status for the request
    
    Throws:
    
    IllegalStateException - if either the source or the destination of the connection to which this queue belongs is currently running.
  - getListFlowFileStatus
```
ListFlowFileStatus getListFlowFileStatus(String requestIdentifier)
```
    Returns the current status of a List FlowFile Request that was initiated via the #listFlowFiles(String) method that has the given identifier
    
    Parameters:
    
    requestIdentifier - the identifier of the Drop FlowFile Request
    
    Returns:
    
    the current status of the List FlowFile Request with the given identifier or null if no request status exists with that identifier
  - cancelListFlowFileRequest
```
ListFlowFileStatus cancelListFlowFileRequest(String requestIdentifier)
```
    Cancels the request to list FlowFiles that has the given identifier. After this method is called, the request will no longer be known by this queue, so subsequent calls to getListFlowFileStatus(String) or cancelListFlowFileRequest(String) will return null
    
    Parameters:
    
    requestIdentifier - the identifier of the Drop FlowFile Request
    
    Returns:
    
    the current status of the List FlowFile Request with the given identifier or null if no request status exists with that identifier
  - getFlowFile
```
FlowFileRecord getFlowFile(String flowFileUuid)
                    throws IOException
```
    Returns the FlowFile with the given UUID or null if no FlowFile can be found in this queue with the given UUID
    
    Parameters:
    
    flowFileUuid - the UUID of the FlowFile to retrieve
    
    Returns:
    
    the FlowFile with the given UUID or null if no FlowFile can be found in this queue with the given UUID
    
    Throws:
    
    IOException - if unable to read FlowFiles that are stored on some external device
  - verifyCanList
```
void verifyCanList()
            throws IllegalStateException
```
    Ensures that a listing can be performed on the queue
    
    Throws:
    
    IllegalStateException - if the queue is not in a state in which a listing can be performed

Interface FlowFileQueue

Method Summary

Method Detail

getIdentifier

getPriorities

recoverSwappedFlowFiles

purgeSwapFiles

setPriorities

setBackPressureObjectThreshold

getBackPressureObjectThreshold

setBackPressureDataSizeThreshold

getBackPressureDataSizeThreshold

size

isEmpty

isActiveQueueEmpty

getUnacknowledgedQueueSize

acknowledge

acknowledge

isFull

put

putAll

poll

poll

drainQueue

poll

getFlowFileExpiration

getFlowFileExpiration

setFlowFileExpiration

dropFlowFiles

getDropFlowFileStatus

cancelDropFlowFileRequest

listFlowFiles

getListFlowFileStatus

cancelListFlowFileRequest

getFlowFile

verifyCanList