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Version: v2.0.0-...-974d4e3 Latest Latest
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Published: Sep 25, 2021 License: Apache-2.0, BSD-3-Clause, MIT Imports: 1 Imported by: 0

Documentation

Overview

Package contains interfaces used specifically for splittable DoFns.

Warning: Splittable DoFns are still experimental, largely untested, and likely to have bugs.

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

This section is empty.

Types

type LockRTracker

type LockRTracker struct {
	Mu sync.Mutex // Lock on accessing underlying tracker.
	// The underlying tracker. If accessing directly, consider thread safety.
	// Lock the mutex if thread safety is needed.
	Rt RTracker
}

LockRTracker is a restriction tracker that wraps another restriction tracker and adds thread safety to it by locking a mutex in each method, before delegating to the underlying tracker.

func NewLockRTracker

func NewLockRTracker(rt RTracker) *LockRTracker

NewLockRTracker creates a LockRTracker initialized with the specified restriction tracker as its underlying restriction tracker.

func (*LockRTracker) GetError

func (rt *LockRTracker) GetError() error

GetError locks a mutex for thread safety, and then delegates to the underlying tracker's GetError.

func (*LockRTracker) GetProgress

func (rt *LockRTracker) GetProgress() (float64, float64)

GetProgress locks a mutex for thread safety, and then delegates to the underlying tracker's GetProgress.

func (*LockRTracker) GetRestriction

func (rt *LockRTracker) GetRestriction() interface{}

GetRestriction locks a mutex for thread safety, and then delegates to the underlying tracker's GetRestriction.

func (*LockRTracker) IsDone

func (rt *LockRTracker) IsDone() bool

IsDone locks a mutex for thread safety, and then delegates to the underlying tracker's IsDone.

func (*LockRTracker) TryClaim

func (rt *LockRTracker) TryClaim(pos interface{}) (ok bool)

TryClaim locks a mutex for thread safety, and then delegates to the underlying tracker's TryClaim.

func (*LockRTracker) TrySplit

func (rt *LockRTracker) TrySplit(fraction float64) (interface{}, interface{}, error)

TrySplit locks a mutex for thread safety, and then delegates to the underlying tracker's TrySplit.

type RTracker

type RTracker interface {
	// TryClaim attempts to claim the block of work located in the given position of the
	// restriction. This method must be called in ProcessElement to claim work before it can be
	// processed. Processing work without claiming it first can lead to incorrect output.
	//
	// The position type is up to individual implementations, and will usually be related to the
	// kind of restriction used. For example, a simple restriction representing a numeric range
	// might use an int64. A more complex restriction, such as one representing a multidimensional
	// space, might use a more complex type.
	//
	// If the claim is successful, the DoFn must process the entire block. If the claim is
	// unsuccessful ProcessElement method of the DoFn must return without performing
	// any additional work or emitting any outputs.
	//
	// If the claim fails due to an error, that error is stored and will be automatically emitted
	// when the RTracker is validated, or can be manually retrieved with GetError.
	//
	// This pseudocode example illustrates the typical usage of TryClaim:
	//
	// 	pos = position of first block within the restriction
	// 	for TryClaim(pos) == true {
	// 		// Do all work in the claimed block and emit outputs.
	// 		pos = position of next block within the restriction
	// 	}
	// 	return
	TryClaim(pos interface{}) (ok bool)

	// GetError returns the error that made this RTracker stop executing, and returns nil if no
	// error occurred. This is the error that is emitted if automated validation fails.
	GetError() error

	// TrySplit splits the current restriction into a primary (currently executing work) and
	// residual (work to be split off) based on a fraction of work remaining. The split is performed
	// at the first valid split point located after the given fraction of remaining work.
	//
	// For example, a fraction of 0.5 means to split at the halfway point of remaining work only. If
	// 50% of work is done and 50% remaining, then a fraction of 0.5 would split after 75% of work.
	//
	// This method modifies the underlying restriction in the RTracker to reflect the primary. It
	// then returns a copy of the newly modified restriction as a primary, and returns a new
	// restriction for the residual. If the split would produce an empty residual (either because
	// the only split point is the end of the restriction, or the split failed for some recoverable
	// reason), then this function returns nil as the residual.
	//
	// If an error is returned, some catastrophic failure occurred and the entire bundle will fail.
	TrySplit(fraction float64) (primary, residual interface{}, err error)

	// GetProgress returns two abstract scalars representing the amount of done and remaining work.
	// These values have no specific units, but are used to estimate work in relation to each other
	// and should be self-consistent.
	GetProgress() (done float64, remaining float64)

	// IsDone returns a boolean indicating whether all blocks inside the restriction have been
	// claimed. This method is called by the SDK Harness to validate that a splittable DoFn has
	// correctly processed all work in a restriction before finishing. If this method still returns
	// false after processing, then GetError is expected to return a non-nil error.
	IsDone() bool

	// GetRestriction returns the restriction this tracker is tracking, or nil if the restriction
	// is unavailable for some reason.
	GetRestriction() interface{}
}

RTracker is an interface used to interact with restrictions while processing elements in splittable DoFns (specifically, in the ProcessElement method). Each RTracker tracks the progress of a single restriction.

All RTracker methods should be thread-safe for dynamic splits to function correctly.

Source Files

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