Fleam

Fleam is a library designed to help create disjunctive (Eithers) and more generally monadic streams using Cats and Akka Streams.

In the disjunctive case this means that as data flows through the stream if it becomes a Left it will no longer be processed by the disjunctive stages and will pass through continuing further down stream.

Getting Started

Add a dependency in your build.sbt.

val fleamVersion = "7.0.0"
...
libraryDependencies ++= Seq(
  "com.nike.fleam" %% "fleam" % fleamVersion,
  "com.nike.fleam" %% "fleam-aws-sqs" % fleamVersion,
  "com.nike.fleam" %% "fleam-aws-cloudwatch" % fleamVersion)

Either Stream enhancements

• eitherMap - Applies a function to items that are Right where only the right-hand value is passed and the result is placed back into the Either R => R1
• eitherFlatMap - Applies a function to items that are Right where only the right-hand value is passed and the result is a new either. R => Either[L, R1]
• eitherMapAsync, eitherMapAsyncUnordered, eitherFlatMapAsync, eitherFlatMapAsyncUnordered, eitherFlatMapAsyncUnordered - Future based versions of eitherMap and eitherFlatMap that preserve item order or not.
• flatten - On an Either turns a Right Iterable into individual Rights
• flatMapConcat - Takes a function from Either[L, R] that creates a Source of eithers to be introduced into the stream.
• broadcastMerge - process an item through a collection of flows in parallel and merge the results back into the stream
• joinRight - Join nested eithers to the right a stream of Either[L, [Either[L, R]] becomes Either[L, R]
• joinLeft - Join nested eithers to the left a stream of Either[Either[L, R], R] becomes Either[L, R]
• viaRight - eitherMap, but takes a flow instead of a function
• viaLeft - process left values through a flow
• biVia - Process Lefts and Rights through different flow and merge the results back into the stream

General Stream enhancements

• StreamDaemon a class that manages starting and cleanly stopping a stream.
• Type classes for stream based metrics logging whereby data is created as part of the stream.
• tickingGroupedWithin - Like a normal groupedWithin except will emit an empty Seq after the elapsed within duration even if nothing has been received.
• SerializedByKeyBidi - a BidiFlow that limits items by a key to serial processing. For example an items of key A will while have to complete processing before another item of key A will be processed. This helps prevent concurrent operations for a key.
• Valve - Slows processing during failed downstream services instead of failing fast.
• ContainsCount - typeclass to require the ability to extract a count for an item. Used to track repeated trips through a processing stream.
• Case class based configuration for common parameters, GroupedWithinConfiguration, ThrottleConfiguration, CircuitBreakerConfiguration
• Enrichments to convert a function that returns a future into a flow
• Enrichments to help with processing tuples through flows

Fleam SQS

Fleam SQS is a library of classes to aid in processing AWS SQS messages in a functional manner. In practice this means providing operations that are complete and explicitly handling retry and dead-letter scenarios instead of relying on message timeouts.

• ContainsRetrievedMessage - typeclass to require an SQS message is extractable in an item
• ToMessage - typeclass to turn an object into a new SQS Message
• MessageAttributes - provides an instance of ContainsCount that stores a count in an SQS message's messageAttributes
• RetrievedTime - typeclass which requires a retrieved time for the message and calculates the elapsed time.
• SqsSource - throttlable Source for reading messages from an SQS Queue.
• SqsDelete - flow to delete SQS message individually or in batches.
• SqsEnqueue - flow to enqueue SQS messages individually or in batches.
• SqsReduce - combines messages within a grouping window with the same key into a single message and deletes the duplicate messages.
• SqsRetry - explicit handling of retry and dead-letters. Takes two partial functions to define each group. Provides options for back-off, retry count, timeout, error inclusion in the message, and message duplication id modification.
• Case class based Configuration
• toMessageAttributes - extension on tuples to create maps of MessageAttributeValue
• Cats' Show instances for logging SqsRetry Errors

Fleam Cloudwatch

Provides a class to create a flow which logs a count to Cloudwatch as part of the stream. Often used to create a metric of items processed.

Getting Started

Enhancements to streams can be imported using import com.nike.fleam.implicits._

SQS specific enhancements can be imported using import com.nike.fleam.sqs.implicits._

Docs

• Turning Async Function into Flows
• Using Tuple-2 Flow Helpers
• Using Valves to slow processing when external system are unavailable
• Processing SQS pipelines
• Logging stream metrics
• Logging with disjunction flows
• Using SqsRetry to manage your retry and dead-letter policies

Contributing

See our Contributing guidelines.

Developing

sbt ~test

Running the Checks

sbt check