org.microbean.kubernetes.controller

Interface EventCache<T extends HasMetadata>

Type Parameters:

T - a type of Kubernetes resource

All Known Implementing Classes:

EventQueueCollection

public interface EventCache<T extends HasMetadata>

A minimalistic interface indicating that its implementations cache Events representing Kubernetes resources.

Thread Safety

Instances of implementations of this interface must be safe for concurrent usage by multiple Threads.

Author:

Laird Nelson

See Also:

Event, EventQueueCollection

Method Summary

Modifier and Type	Method and Description
Event<T>	add(Object source, AbstractEvent.Type eventType, T resource) Adds a new Event constructed out of the parameters supplied to this method to this EventCache implementation and returns the Event that was added.
void	replace(Collection<? extends T> incomingResources, Object resourceVersion) A "full replace" operation that atomically replaces all internal state with new state derived from the supplied Collection of resources.
void	synchronize() Synchronizes this EventCache implementation's state with its downstream consumers, if any.

Method Detail

add

Event<T> add(Object source,
             AbstractEvent.Type eventType,
             T resource)

Adds a new Event constructed out of the parameters supplied to this method to this EventCache implementation and returns the Event that was added.

Implementations of this method may return null to indicate that for whatever reason no Event was actually added.

Parameters:

source - the source of the Event that will be created and added; must not be null

eventType - the type of Event that will be created and added; must not be null

resource - the resource of the Event that will be created and added must not be null

Returns:

the Event that was created and added, or null if no Event was actually added as a result of this method's invocation

Throws:

NullPointerException - if any of the parameters is null

See Also:

Event

replace

void replace(Collection<? extends T> incomingResources,
             Object resourceVersion)

A "full replace" operation that atomically replaces all internal state with new state derived from the supplied Collection of resources.

Parameters:

incomingResources - the resources comprising the new state; must not be null; must be synchronized on when accessing

resourceVersion - the notional version of the supplied Collection; may be null; often ignored by implementations

Throws:

NullPointerException - if incomingResources is null

synchronize

void synchronize()

Synchronizes this EventCache implementation's state with its downstream consumers, if any.

Not all EventCache implementations need support synchronization. An implementation of this method that does nothing is explicitly permitted.

Implementations of this method must expect to be called on a fixed schedule.

Design Notes

This method emulates the Resync function in the Go code's DeltaFifo construct Specifically, it is anticipated that an implementation of this method that does not simply return will go through the internal resources that this EventCache knows about, and, for each that does not have an event queue set up for it already—i.e. for each that is not currently being processed— will fire a SynchronizationEvent. This will have the effect of "heartbeating" the current desired state of the system "downstream" to processors that may wish to alter the actual state of the system to conform to it.

See Also:

SynchronizationEvent