Neflix makes this: https://github.com/restify/node-restify
Linux perf command: https://perf.wiki.kernel.org/index.php/Main_Page
- Doesn't show our JS frames
- V8 places symbols JIT
- use
node --perf_basic_prof_only_functions, woo - Can run in prod, negligble impact on perf
- in v5, coming to v4
Now we've got a full stack trace with all the frames!
aaaand now we've got a bazillion traces/frames
- Flame graphs! Yeah!
- https://github.com/brendangregg/FlameGraph
- http://www.brendangregg.com/flamegraphs.html
- (x is depth of stack, y is time (length of time on CPU)
Things go wrong
- Restart app, it keeps going
- You now can take the coredump and debug
- Node flag:
--abort_on_uncaught_exception
tool: mdb (has JS plugins w/ mdb_v8, only works on Solaris)
Where (what code caused the crash) Why (did the project crash)
Need to name your functions shows you function name, file, line number can even pull out source code
Can pull out JS vars from memory
Core dumps give you complete process state
Step 1: call Reed Hastings
Can generate core dump whenever you want: gcore
$gcore pgrep node<- backticks part of command (markdown ate 'em)
Can find all JS objs on heap with ::findjsobjects
So, take successive core dumps and compare object counts
Look for growing things
Find root obj
(remember, can inspect actual objects via objhash::jsprint)
LOTTA OBJECTS can pipe & stuff
The whole goal of digging through memory leaks is to find the root object
objhash::findjsobjects -r <- finds objs with references to the hash
Tools to diff flame graphs