Run A Function Right Before Nodejs Crashes Due to OOM

Question

Is it possible to force a Node.js app to run a function (i.e. send an API call) right before it crashes due to OOM?

I am trying to log the timestamps of OOM crashes, but this requires the ability to run a function right before the process gets killed. PM2 is currently being used to manage this Node.js process.

Answer 1

Medium: Detect heap overflow on Node.js: JavaScript heap out of memory

Uses the cluster module. Forks a worker that on exit event forks another worker that logs:

total_heap_size: The size V8 has allocated for the heap. This can grow if used_heap_size needs more. heap_size_limit: The absolute size limit the heap cannot exceed. e.g.: max_old_space_size

It then exits and spawns a new worker and runs the main function again. This prevents crashing on out of memory, since it exits before the out of memory error is triggered and spawns a new worker. If you still want it to crash you can remove process.exit().

heavyHeapConsumer is a demo function that consumes a large amount of memory.

const cluster = require('cluster');
const v8 = require('v8');

let heavyHeapConsumer = () => {
  let arrays = [];
  setInterval(() => {
    arrays.push(new Array(1000000));
  }, 100);
};

if (cluster.isMaster) {
  cluster.fork();
  cluster.on('exit', (deadWorker, code, signal) => {
    // Restart the worker
    let worker = cluster.fork();
    
    // Note the process IDs
    let newPID = worker.process.pid;
    let oldPID = deadWorker.process.pid;
    
    // Log the event
    console.log('worker ' + oldPID + ' died.');
    console.log('worker ' + newPID + ' born.');
  });
} else { // worker
  const initialStats = v8.getHeapStatistics();
  
  const totalHeapSizeThreshold = 
    initialStats.heap_size_limit * 85 / 100;
  console.log("totalHeapSizeThreshold: " + totalHeapSizeThreshold);
  
  let detectHeapOverflow = () => {
    let stats = v8.getHeapStatistics();
    
    console.log("total_heap_size: " + (stats.total_heap_size));
    
    if ((stats.total_heap_size) > totalHeapSizeThreshold) {
      process.exit();
    }
  };
  setInterval(detectHeapOverflow, 1000);
  
  // here goes the main logic
  heavyHeapConsumer();
}