1. Elegantní dataflow pomocí TPL
TPL Dataflow Is The Best Library You're Not Using

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Motivation
lightweight actor library on top of TPL
messages passed from a producer to a consumer
consists of built-in blocks used for composing your dataflow
you don’t have to care about synchronization
no lock, Manual/AutoResetEvent etc
single responsibility
reusability – blocks might appear in multiple dataflows
parallel out of the box
TPL = API v Threading/Threading.Tasks namespace
Paralelismus, threading thread pool, cancellation support, async/await
Klasický scénář – zpracováváte příchozí data, něco s nimi uděláte a pak je třeba pošlete dál. Task, ContinueWith atd. Co když ale musíte mít omezení na počet souběžně běžících tasků?
© 2018 SolarWinds Worldwide, LLC. All rights reserved.

3. © 2018 SolarWinds Worldwide, LLC. All rights reserved.
How to get started
nuget
System.Threading.Tasks.Dataflow
DO NOT USE Microsoft.Tpl.Dataflow nuget
GitHub:
dotnet/corefx/tree/master/src/System.Threading.Tasks.Dataflow
used to be part of .NET Framework till 4.5
funny issue - build vs runtime
© 2018 SolarWinds Worldwide, LLC. All rights reserved.

4. © 2018 SolarWinds Worldwide, LLC. All rights reserved.
Contents
9 default data blocks
execution – ActionBlock, TransformBlock, TransformManyBlock
buffering – BufferBlock, BroadcastBlock, WriteOnceBlock
grouping – BatchBlock, JoinBlock, BatchedJoinBlock
SolarWinds
ExpiringBatchBlock – BatchBlock + Timer
© 2018 SolarWinds Worldwide, LLC. All rights reserved.

5. Creating a dataflow – i.e. linking blocks together
ISourceBlock<T>.LinkTo(ITargetBlock<T>)
source.LinkTo(target, options, criteria)
options
append (default: true)
whether a new link is appended or set as first
propagation (default: false)
criteria
disposable
disposable - compare with unsubscribing from .NET events
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6. © 2018 SolarWinds Worldwide, LLC. All rights reserved.
Block options
MaxDegreeOfParallelism (default: 1)
EnsureOrdered (default: true)
BoundedCapacity (default: max)
max number of messages that a block might hold
if reached, block rejects messages
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7. © 2018 SolarWinds Worldwide, LLC. All rights reserved.
DEMO
source:
© 2018 SolarWinds Worldwide, LLC. All rights reserved.

8. Additional topics to cover
completion
cancellation support
encapsulation
task schedulers
Completion - manual or by exception
© 2018 SolarWinds Worldwide, LLC. All rights reserved.

9. © 2018 SolarWinds Worldwide, LLC. All rights reserved.
Recommendations
use read-only or immutable types for data being passed around
nuget System.Collections.Immutable
handle exceptions properly
use Rx for async errors -
use functional Either<TResult, TException>
consider Akka.net in cross-computer scenarios
© 2018 SolarWinds Worldwide, LLC. All rights reserved.

10. Required last page sample