The document discusses debugging node.js performance. It recommends starting by measuring how slow an application is, then using tools like perf to identify bottlenecks. Common bottlenecks include synchronous operations, unoptimized code, databases, and network calls. The document demonstrates using perf to generate flamegraphs to visualize slow functions. Improving involves steps like migrating from Express to Fastify, using node-bottleneck, and remeasuring performance.

2. Node Performance Debug
@rafaelgss
https://blog.rafaelgss.com.br/node-cpu-profiler

3. Performance is a big area
Everything can be improved!
The tests depends of hardware!

4. What part is the bottleneck?
The bottleneck is internal
E.g:
● Synchronous operation
● Non-optimized operation
The bottleneck is external
E.g:
● Database
● External API
● Socket communication

5. Baby Steps
1 How slow is it?
2 Where is the slowness at?
3 Why is slow?
4 Improve
How slow
is it?
Where are
the slow?
Improve
5 Repeat

6. How slow is it?

7. To know if we reach our goals we
need metrics!
● Wrk
● Apache Benchmark (ab)
● ...

8. ● KafkaMeter
● Kafka-load-consumer - made with
in Jacareí
● Function-perf - made with in Jacareí
Event-Driven applications?

9. Test on node-bottleneck!
https://github.com/rafaelgss/node-bottleneck

10. Endpoint

11. Autocannon
How slow is it?

13. Our metrics
Http Router Requests/(10~12sec) Throughput(MB)
Express 148k 18.5

14. Where is the slowness at?

15. We need tools!
● 0x
● Clinic Js
● CDT (Chrome Dev Tools)
● Perf

16. About perf_events
● Profiling tool available only kernel linux, and can be used with eBPF
tools: kprobes, uprobes, etc.
● Measure how many CPU instructions happens in your
application/command. Try: “sudo perf stat ls”

17. Let’s check

18. Getting output by perf
root$ perf record …. write on /tmp/$PID.map (JIT)
root$ chown root /tmp/perf-3870.map // doesn’t exists
root$ perf script > output-perf

19. Node Profiling Options
--perf-basic-prof and --perf-basic-prof-only-function
replace most of functions V8::Function::Call to real
javascript function
Output the files in a format that existing perf tools can
consume.
Here you can see this flag on NodeJs world

20. Let’s check (again)
term1: root$ node --perf-basic-prof-only-functions index.js &
[1] 3870
term1:root$ perf record -F 99 -p 3870 -g -- sleep 20
term2:root$ autocannon -c 10 -d 10 http://localhost:3000/
term1:root$ chown root /tmp/perf-3870.map
term1:root$ perf script > output-perf
root$ cat output-perf

21. We have javascript functions!
But still hard to check

22. Too many traces

23. Solution: FlameGraphs

24. Generating FlameGraph
root$ google-chrome flame.svg
root$ git clone --depth 1
https://github.com/brendangregg/FlameGraph
root$ cd FlameGraph/
root$ ./stackcollapse-perf.pl < ../$PROJECT/output-
perf | ./flamegraph.pl --colors js > flame.svg

25. flame.svg

26. Why is slow?

27. Function that use most time of CPU
express
more than 60% from express

28. Understanding one line
● LazyCompile is an event generated by V8 Compiler, meaning that your
function is being compiled and optimized on-demand.
● Asterisk* This is good news meaning that your code was successfully
compiled to native code (fast) if you see a tilde (~) that means your code is
being interpreted (slow).
● Path & Line - This tells file and line.

29. Improve

30. Improving
Moving from express to fastify as HTTP Router
node-bottleneck-v2

31. Results on V2

32. Our metrics
Http Router Requests/(10~12sec) Throughput(MB)
Express 148k 18.5
Fastify 210k 30.8> 40%

33. What next?

34. Repeat!

35. References
- https://github.com/RafaelGSS/node-bottleneck
- https://github.com/RafaelGSS/kafka-load-consumer
- https://github.com/RafaelGSS/function-perf
- http://www.brendangregg.com/flamegraphs.html
- http://fastify.io/
- https://expressjs.com/
- https://perf.wiki.kernel.org/index.php/Main_Page
- https://github.com/mcollina/autocannon