Akka streams
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The document presents an overview of Akka Streams, describing it as a toolkit for processing streams addressing issues like blocking and back pressure. It outlines key components such as sources, flows, and sinks, as well as fan-in and fan-out junctions, which facilitate data processing efficiency. The document also covers error handling strategies and testing methods relevant to stream processing.
![Fan-out Junctions
Fan-out operations give us the ability to split a stream
into sub-streams.
●
Broadcast[T] – (1 input, N outputs)
Ingests elements from one input and emits duplicated
events across more than one output.
●
Balance[T] – (1 input, N outputs)
Ingests elements from one input and emits to the first
available output port.](https://image.slidesharecdn.com/akka-streams1-160822100124/85/Akka-streams-9-320.jpg)
![Fan-in Junctions
Fan-in operations give us the ability to join multiple streams into a single
output stream.
●
Merge[In] – (N inputs , 1 output)
Picks randomly from inputs pushing them one by one to its output.
●
MergePreferred[In]
Similar to Merge but if elements are available on preferred port, it picks
from it, otherwise randomly from others.
●
Concat[A] – (2 inputs, 1 output)
Concatenates two streams (first consume one, then the second one)](https://image.slidesharecdn.com/akka-streams1-160822100124/85/Akka-streams-10-320.jpg)
![References
[1] Akka Streams Documentation
[2] Lightbend Activator
[3] Opencredo Blog](https://image.slidesharecdn.com/akka-streams1-160822100124/85/Akka-streams-13-320.jpg)
Akka streams
- 1. Akka Stream Sonu Mehrotra Software Consultant Knoldus Software LLP
- 2. Agenda 1) What is Akka Stream ? 2) Components of Akka Stream. 3) Working with Graphs. 4) Error handling. 5) Testing Streams.
- 3. Akka Stream There are two basic problems with data processing - 1) Blocking (Pull Based System) 2) Back Pressure (Push Based System) Akka Streams is a toolkit for processing of streams. It is an implementation of Reactive Streams Specification. Its purpose is to “formulate stream processing setups such that we can then execute them efficiently and with bounded resource usage.”
- 4. Components of Akka Streams There are three main components of Akka Streams - 1) Source 2) Flow 3) Sink
- 5. Source Source is a “processing stage with exactly one output, emitting data elements whenever downstream processing stages are ready to receive them.” ● Various Sources -
- 6. Sink Sink is a “processing stage with exactly one input, requesting and accepting data elements possibly slowing down the upstream producer of elements.” Various Sinks -
- 7. Flow Flow is a “processing stage which has exactly one input and output, which connects its up- and down streams by transforming the data elements flowing through it.” Various Flows -
- 8. Working with Graphs Graphs are built from simple Flows which serve as the linear connections within the graphs as well as junctions which serve as fan-in and fan-out points for Flows. Various Junctions provided by Akka Streams - ● Fan-out Junctions ● Fan-in Junctions
- 9. Fan-out Junctions Fan-out operations give us the ability to split a stream into sub-streams. ● Broadcast[T] – (1 input, N outputs) Ingests elements from one input and emits duplicated events across more than one output. ● Balance[T] – (1 input, N outputs) Ingests elements from one input and emits to the first available output port.
- 10. Fan-in Junctions Fan-in operations give us the ability to join multiple streams into a single output stream. ● Merge[In] – (N inputs , 1 output) Picks randomly from inputs pushing them one by one to its output. ● MergePreferred[In] Similar to Merge but if elements are available on preferred port, it picks from it, otherwise randomly from others. ● Concat[A] – (2 inputs, 1 output) Concatenates two streams (first consume one, then the second one)
- 11. Error Handling Strategies for how to handle exceptions from processing stream elements can be defined when materializing the stream. There are three ways to handle Exceptions - ● Stop – The stream is completed with failure. ● Resume – The element is dropped and the stream continues. ● Restart - The element is dropped and the stream continues after restarting the stage. Restarting a stage means that any accumulated state is cleared.
- 12. Testing Streams There are 3 ways to test the stream - ● Simple sources, sinks and flows. ● Sources and Sinks in combination with TestProbe from the akka-testkit module. ● Sources and Sinks specifically crafted for writing tests from the akka-stream-testkit module.
- 13. References [1] Akka Streams Documentation [2] Lightbend Activator [3] Opencredo Blog
- 14. Thank you !