Skip to main content

Memory Leaks

JavaScript / NodeJS​

V8 handles 2 main memory categories​

  1. Stack - it stores the primitive data types: Number, String, boolean, Null, Undefined, Symbol and references to non-primitive data types Object
  2. Heap
    • stores the non-primitive data types: Object

V8 has a garbage collector runs mainly Mark and Sweep algorithm​

  • It checks for all objects' reference paths to the root node, which is the global or window object
  • If any reference has no path to the root node, it will be marked as garbage and will be swept later
  • Important Note: When the Garbage Collector runs, it pauses your application entirely until it finishes its work
    • so you need to minimize its work by taking care of your objects' references

Global Variables​

  • As they have a direct path to the root node, they will stay in memory as long as the application is running
  • so you need to be careful when setting global variables and the amount of data you’ll set to them

Multiple References​

  • Setting multiple references to the same object may cause a problem
  • also as you may remove one ref and forget the other which will keep your object still exists in the Heap

Closures​

  • In closures simply you keep references to objects to be used later
  • this feature has many advantages but if it’s used without caution
    • it may cause big issues as these references will keep objects in heap and these objects might be large ones, not just simple objects

Run app with garbage collector attach to chrome debugger options​

node --expose-gc --inspect=9222 app.js