org.apache.nifi.controller.repository.claim

Interface ContentClaimManager

public interface ContentClaimManager

Responsible for managing all ContentClaims that are used in the application

Method Summary

Methods

Modifier and Type	Method and Description
int	decrementClaimantCount(ContentClaim claim) Decreases by 1 the count of how many FlowFiles hold a claim to a particular piece of FlowFile content and returns the new count
void	drainDestructableClaims(Collection<ContentClaim> destination, int maxElements) Drains up to maxElements Content Claims from the internal queue of destructable content claims to the given destination so that they can be destroyed.
void	drainDestructableClaims(Collection<ContentClaim> destination, int maxElements, long timeout, TimeUnit unit) Drains up to maxElements Content Claims from the internal queue of destructable content claims to the given destination so that they can be destroyed.
int	getClaimantCount(ContentClaim claim) Returns the number of FlowFiles that hold a claim to a particular piece of FlowFile content
int	incrementClaimantCount(ContentClaim claim) Increases by 1 the count of how many FlowFiles hold a claim to a particular piece of FlowFile content and returns the new count
int	incrementClaimantCount(ContentClaim claim, boolean newClaim) Increases by 1 the count of how many FlowFiles hold a claim to a particular piece of FlowFile content and returns the new count.
void	markDestructable(ContentClaim claim) Indicates that the given ContentClaim can now be destroyed by the appropriate Content Repository.
ContentClaim	newContentClaim(String container, String section, String id, boolean lossTolerant) Creates a new Content Claim with the given id, container, section, and loss tolerance.
void	purge() Clears the manager's memory of any and all ContentClaims that it knows about

Method Detail

newContentClaim

ContentClaim newContentClaim(String container,
                           String section,
                           String id,
                           boolean lossTolerant)

Creates a new Content Claim with the given id, container, section, and loss tolerance.

Parameters:

id -

container -

section -

lossTolerant -

Returns:

getClaimantCount

int getClaimantCount(ContentClaim claim)

Returns the number of FlowFiles that hold a claim to a particular piece of FlowFile content

Parameters:

claim -

Returns:

decrementClaimantCount

int decrementClaimantCount(ContentClaim claim)

Decreases by 1 the count of how many FlowFiles hold a claim to a particular piece of FlowFile content and returns the new count

Parameters:

claim -

Returns:

incrementClaimantCount

int incrementClaimantCount(ContentClaim claim)

Increases by 1 the count of how many FlowFiles hold a claim to a particular piece of FlowFile content and returns the new count

Parameters:

claim -

Returns:

incrementClaimantCount

int incrementClaimantCount(ContentClaim claim,
                         boolean newClaim)

Increases by 1 the count of how many FlowFiles hold a claim to a particular piece of FlowFile content and returns the new count. If it is known that the Content Claim whose count is being incremented is a newly created ContentClaim, this method should be called with a value of true as the second argument, as it may allow the manager to optimize its tasks, knowing that the Content Claim cannot be referenced by any other component

Parameters:

claim -

newClaim -

Returns:

markDestructable

void markDestructable(ContentClaim claim)

Indicates that the given ContentClaim can now be destroyed by the appropriate Content Repository. This should be done only after it is guaranteed that the FlowFile Repository has been synchronized with its underlying storage component. This way, we avoid the following sequence of events:

• FlowFile Repository is updated to indicate that FlowFile F no longer depends on ContentClaim C
• ContentClaim C is no longer needed and is destroyed
• The Operating System crashes or there is a power failure
• Upon restart, the FlowFile Repository was not synchronized with its underlying storage mechanism and as such indicates that FlowFile F needs ContentClaim C.
• Since ContentClaim C has already been destroyed, it is inaccessible, and FlowFile F's Content is not found, so the FlowFile is removed, resulting in data loss.

Using this method of marking the ContentClaim as destructable only when the FlowFile repository has been synced with the underlying storage mechanism, we can ensure that on restart, we will not point to this unneeded claim. As such, it is now safe to destroy the contents.

Parameters:

claim -

drainDestructableClaims

void drainDestructableClaims(Collection<ContentClaim> destination,
                           int maxElements)

Drains up to maxElements Content Claims from the internal queue of destructable content claims to the given destination so that they can be destroyed.

Parameters:

destination -

maxElements -

drainDestructableClaims

void drainDestructableClaims(Collection<ContentClaim> destination,
                           int maxElements,
                           long timeout,
                           TimeUnit unit)

Drains up to maxElements Content Claims from the internal queue of destructable content claims to the given destination so that they can be destroyed. If no ContentClaim is ready to be destroyed at this time, will wait up to the specified amount of time before returning. If, after the specified amount of time, there is still no ContentClaim ready to be destroyed, the method will return without having added anything to the given destination.

Parameters:

destination -

maxElements -

timeout -

unit -

purge

void purge()

Clears the manager's memory of any and all ContentClaims that it knows about