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