Effective Akka by Allen, Jamie -- Read -- Imperial Library of Trantor

Index

Effective Akka Preface

Who This Book Is For What Problems Are We Solving with Akka?

Distributed Asynchronous High Performance

Reactive Applications Use Case for This Book: Banking Service for Account Data Conventions Used in This Book Using Code Examples Safari® Books Online How to Contact Us Acknowledgments

1. Actor Application Types

Domain-driven

Domain-driven Messages Are “Facts”

Work Distribution

Routers and Routees

Random Round robin Smallest mailbox Broadcast ScatterGatherFirstCompletedOf Consistent hash routing

BalancingDispatcher Will Be Deprecated Soon! Work Distribution Messages Are “Commands”

2. Patterns of Actor Usage

The Extra Pattern

The Problem Avoiding Ask Capturing Context Sending Yourself a Timeout Message

Why not use a promise? How to test this logic

The Cameo Pattern

The Companion Object Factory Method How to Test This Logic

3. Best Practices

Actors Should Do Only One Thing

Single Responsibility Principle Create Specific Supervisors Keep the Error Kernel Simple Failure Zones

Avoid Blocking

Futures Delegation Example

Java futures are blocking!

Pre-defining Parallel Futures Parallel Futures with the zip() Method Sequential Futures Callbacks versus Monadic Handling Futures and ExecutionContext Push, Don’t Pull When You Must Block Managed Blocking in Scala

Avoid Premature Optimization

Start Simple

Deterministic Declarative Immutable Functional

Layer in Complexity via Indeterminism Optimize with Mutability

Add mutability with compare and swap (CAS) Compose CAS with Software Transactional Memory Add locks as a last resort

Prepare for Race Conditions

Avoid coding in a way where timing matters Tell, don’t ask

Be Explicit

Name Actors and ActorSystem Instances Create Specialized Messages Create Specialized Exceptions Beware the “Thundering Herd”

Dampen message overload Use circuit breakers for failure overload

Don’t Expose Actors

Avoid Using this The Companion Object Factory Method Never Use Direct References Don’t Close Over Variables Use Immutable Messages with Immutable Data

Help Yourself in Production

Make Debugging Easier Add Metrics Externalize Business Logic Use Semantically Useful Logging Aggregate Your Logs with a Tool Like Flume Use Unique IDs for Messages

Tune Akka Applications with the Typesafe Console

Fixing Starvation

How do you fix it? Does PinnedDispatcher help? Failure zones Routers

Sizing Dispatchers The Parallelism-Factor Setting Actor Mailbox Size Throughput Setting Edge Cases

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