Worker Threads Tamar Twena-Stern 

Tamar Twena-Stern • Software Engineer - manager and architect • Backend Manager @XM Cyber • Was a CTO of my own startup • Passionate about Node.js ! • Twitter: @SternTwena 

Tamar Twena-Stern • On Maternity Leave • Have 3 kids • Loves to play my violin • Javascript Israel community leader 

Introduction 

Traditional Approach - Blocking IO Client Server Thread Thread Thread Request Request Request 

Problems •The system allocates CPU and memory resources for every new thread •When the system is stressed – overhead of thread scheduling and context switching •The system waste resources for allocating threads instead of doing actual work 

Node.js Architecture 

Node.js Architecture - High Level 

• One Process • One Thread • One Event Loop • One JS Engine Instance • One Node.js Instance Node.js Process 

Demo - CPU Intensive Operation 

Lets Deep Dive Into The CPU Intensive Problem 

Blocking & Non Blocking Functions • Blocking Function - Main event loop must wait until it has finished to execute the next command. • Non-Blocking Function - • Main event loop will continue as soon as the function begins • Alerts the main loop once it has finished by calling a “callback”. 

Why CPU Intensive Operations Don’t Shine In Node • Non Blocking IO + Event Loop • Constant amount of threads • CPU Intensive operation will block the event loop • CPU intensive operation that will be off loaded to the worker thread pool will make one of the threads busy for long 

CPU Intensive Operations Synchrones Operations 

Brilliant Idea :Let’s Add Threads To Node.js Core ! 

Why It Will Not Work ? • Theoretically simple - add Libraries to Node core to enable threads • Adding threads will change the nature of JavaScript • No synchronise mechanism • JavaScript basic types are not atomic, for example numerics 

Worker Threads 

Worker Threads - Definition • Applications use multiple isolated JavaScript workers • Main worker and child workers • Communication provided by Node.js • Separate instances of V8 and Event Loop • Shared memory 

Worker Threads - Components • One process • Multiple threads • One event loop per thread • One JS Engine Instance per thread • One Node.js Instance per thread 

From One Process To Worker Threads 

How Is It Work ? • Worker executes a script provided by the parent worker • The worker runs in Isolation from other workers • Ability to pass messages between the worker and the parent • Parallelism - V8 Isolate 

How Is It Work ? 

Demo - CPU Intensive Operations With Worker Threads 

Why The Improvement Is Not Enough ? 

Our Mistake : Opening Worker On Each Request 

Guidelines For Writing Production Worker Threads Applications : • For production - use worker threads pool • If you can - use asynchronous operations, it is much faster • Don’t use Worker Thread for IO operations - Node.js built in mechanisms are much faster 

Demo - Creating Worker Threads Pool 

• Twitter: @SternTwena