Work with V8 memory leaks

Transcript

• 1. Work with leaks Roman Krivtsov
• 2. Leaks in js: Easy to create 
 (timers, closures, 
 listeners) Difficult to find out Critical in long-live apps — — — 2
• 3. 3 Gmail 
 with leaks
• 4. 3:00 4 Server programmer’s life
• 5. V8 GARBAGE COLLECTOR 5
• 6. — Concept of reachability — Blocked event-loop — Totally optimising 
 (partions, dynamic intervals) — New space (1-8Mb) 
 & Old space (512Mb-1.7Gb) 6 GC
• 7. — max-old-space-size 
 limit for old-space GC — nouse-idle-notification 
 prevent running GC constantly — expose-gc 
 global.gc() — trace-gc 
 logging — trace-gc-verbose 
 extended logging Flags 7
• 8. 8 PATTERNS 
 AND ANTIPATTERNS
• 9. var latestNews = function (html) { var container = document.getElementById("news"); container.innerHTML = html; container.addEventListener("click", function click() { showFullItem(); }); } setInterval(XHR.bind(null, "/get_news", latestNews), 1000); 9 Latest news
• 10. 10
• 11. container DOM Window click listener click listener click listener click listener click listener
• 12. 12 var latestNews = function (html) { var container = document.getElementById("news"); container.innerHTML = html; container.addEventListener("click", function click() { showFullItem(html); }); } setInterval(XHR.bind(null, "/get_news", latestNews), 1000); Variable usage
• 13. 13
• 14. 14 Scopes clickhtml latestNews html clickhtml clickhtml clickhtml
• 15. 15 var latestNews = function (html) { var container = document.getElementById("news"); container.innerHTML = html; container.addEventListener("click", function click() { showFullItem(); }); var unused = function () { if (html) console.log("never"); } } setInterval(XHR.bind(null, "/get_news", latestNews), 1000); Deeper down the rabbit hole
• 16. 16
• 17. 17 Scopes click latestNews html unusedhtmlhtml =
• 18. 18 var latestNews = function (html) { var container = document.getElementById("news"); container.innerHTML = html; html = null; container.addEventListener("click", function click() { showFullItem(html); }); } setInterval(XHR.bind(null, "/get_news", latestNews), 1000);
• 19. var job = function () { mysql.query("select * from tasks order by ts desc", function (err, res) { use(res); }); } setInterval(job, 1000); 19 Long responses mysql.query({ sql: 'select * from tasks order by ts', timeout: 1000 });
• 20. TOOLS 20
• 21. Events CPU Memory Force GC Timeline
• 22. Rule of 3 snapshots Profiling Retained sizeShallow sizeDistance
• 23. — node-heapdump — node-memwatch — REPL — dynamic tracing frameworks 23 Node.js
• 24. --abort-on-uncaught-exception 24 — production MDB and DTrace (dynamic tracing frameworks)
• 25. — Timers — Frequent events — Listeners — Parent scope — Give names — Clear big variables — Databases Conclusions 25
• 26. Good luck and don’t leak! 26
• 27. 27 Code and links