org.apache.beam.sdk.transforms

Interface Watch.Growth.TerminationCondition<InputT,StateT>

All Superinterfaces:

java.io.Serializable

Enclosing class:

Watch.Growth<InputT,OutputT,KeyT>

public static interface Watch.Growth.TerminationCondition<InputT,StateT>
extends java.io.Serializable

A strategy for determining whether it is time to stop polling the current input regardless of whether its output is complete or not.

Some built-in termination conditions are Watch.Growth.never(), Watch.Growth.afterTotalOf(org.joda.time.ReadableDuration) and Watch.Growth.afterTimeSinceNewOutput(org.joda.time.ReadableDuration). Conditions can be combined using Watch.Growth.eitherOf(org.apache.beam.sdk.transforms.Watch.Growth.TerminationCondition<InputT, FirstStateT>, org.apache.beam.sdk.transforms.Watch.Growth.TerminationCondition<InputT, SecondStateT>) and Watch.Growth.allOf(org.apache.beam.sdk.transforms.Watch.Growth.TerminationCondition<InputT, FirstStateT>, org.apache.beam.sdk.transforms.Watch.Growth.TerminationCondition<InputT, SecondStateT>). Users can also develop custom termination conditions, for example, one might imagine a condition that terminates after a given time after the first output appears for the input (unlike Watch.Growth.afterTotalOf(org.joda.time.ReadableDuration) which operates relative to when the input itself arrives).

A Watch.Growth.TerminationCondition is provided to Watch.Growth.withTerminationPerInput(TerminationCondition) and is used to maintain an independent state of the termination condition for every input, represented as StateT which must be immutable, non-null, and encodable via getStateCoder().

All functions take the wall-clock timestamp as Instant for convenience of unit-testing custom termination conditions.

Method Summary

Modifier and Type	Method and Description
boolean	canStopPolling(Instant now, StateT state) Called by the Watch transform to determine whether the given termination state signals that Watch should stop calling Watch.Growth.PollFn for the current input, regardless of whether the last Watch.Growth.PollResult was complete or incomplete.
StateT	forNewInput(Instant now, InputT input) Called by the Watch transform to create a new independent termination state for a newly arrived InputT.
Coder<StateT>	getStateCoder() Used to encode the state of this Watch.Growth.TerminationCondition.
StateT	onSeenNewOutput(Instant now, StateT state) Called by the Watch transform to compute a new termination state, in case after calling the Watch.Growth.PollFn for the current input, the Watch.Growth.PollResult included a previously unseen OutputT.
java.lang.String	toString(StateT state) Creates a human-readable representation of the given state of this condition.

Method Detail

getStateCoder

Coder<StateT> getStateCoder()

Used to encode the state of this Watch.Growth.TerminationCondition.

forNewInput

StateT forNewInput(Instant now,
                   @Nullable
                   InputT input)

Called by the Watch transform to create a new independent termination state for a newly arrived InputT.

onSeenNewOutput

StateT onSeenNewOutput(Instant now,
                       StateT state)

Called by the Watch transform to compute a new termination state, in case after calling the Watch.Growth.PollFn for the current input, the Watch.Growth.PollResult included a previously unseen OutputT.

canStopPolling

boolean canStopPolling(Instant now,
                       StateT state)

Called by the Watch transform to determine whether the given termination state signals that Watch should stop calling Watch.Growth.PollFn for the current input, regardless of whether the last Watch.Growth.PollResult was complete or incomplete.

toString

java.lang.String toString(StateT state)

Creates a human-readable representation of the given state of this condition.