FATAL ERROR: CALL_AND_RETRY_LAST Allocation failed - JavaScript heap out of memory
java.lang.OutOfMemoryError: Java heap space
MemoryError

Your application ran out of available memory. Either you’re processing too much data at once, or you have a memory leak.

Fix 1: Increase Memory Limit

# Node.js
node --max-old-space-size=4096 app.js  # 4GB

# Java
java -Xmx4g -Xms2g MyApp

# Python — no direct limit, but check system RAM

Fix 2: Process Data in Chunks

// ❌ Loading entire file into memory
const data = fs.readFileSync('huge-file.csv', 'utf8');

// ✅ Stream it
const stream = fs.createReadStream('huge-file.csv');
stream.on('data', (chunk) => {
    processChunk(chunk);
});

# ❌ Loading all rows at once
rows = cursor.fetchall()  # Millions of rows

# ✅ Fetch in batches
while True:
    rows = cursor.fetchmany(1000)
    if not rows:
        break
    process(rows)

Fix 3: Memory Leak — Event Listeners

// ❌ Adding listeners without removing them
setInterval(() => {
    emitter.on('data', handler);  // Leak: new listener every interval
}, 1000);

// ✅ Remove listeners when done
emitter.on('data', handler);
// Later:
emitter.removeListener('data', handler);

Fix 4: Memory Leak — Growing Arrays

// ❌ Array grows forever
const cache = [];
app.get('/data', (req, res) => {
    cache.push(req.body);  // Never cleared
    res.json({ ok: true });
});

// ✅ Use a bounded cache
const LRU = require('lru-cache');
const cache = new LRU({ max: 500 });

Fix 5: Large JSON Parsing

// ❌ Parsing a 2GB JSON file
const data = JSON.parse(fs.readFileSync('huge.json'));

// ✅ Use a streaming JSON parser
const JSONStream = require('JSONStream');
fs.createReadStream('huge.json')
    .pipe(JSONStream.parse('*'))
    .on('data', (item) => process(item));

Fix 6: Docker Memory Limits

# docker-compose.yml — container hits memory limit
services:
  app:
    deploy:
      resources:
        limits:
          memory: 2G  # Increase if needed

Debugging

# Node.js — track memory usage
node --inspect app.js
# Open chrome://inspect and use Memory tab

# Java — heap dump
jmap -dump:format=b,file=heap.hprof <pid>

# Linux — check system memory
free -h

Related resources

• Node.js heap out of memory fix
• Java OutOfMemoryError fix
• Docker ENOMEM fix

Related: JavaScript Array Methods Cheat Sheet · Java Cheat Sheet · Python Cheat Sheet · Pip Install Error Fix