Node.js Question:

There's a few tools and ways out there:
Interactive Stack Traces with traceGL - Shareware

Guide here

Profiling with Profiler

Install globally npm install -g profiler
Start your process with node --prof this will create a v8.log file
Build nprof by running ~/.nvm/v0.8.22/lib/node_modules/profiler/tools/build-nprof
Run ~/.nvm/v0.8.22/lib/node_modules/profiler/nprof this will read the v8.log profile and give you nice ouput

CPU and Memory Profiling with NodeTime

Install to your app npm install nodetime
Include in your app require('nodetime').profile()
Follow the instructions it will output to console

Alternatively, you may want to use look, which is based on nodetime but doesn't send data to nodetime.com.
Blink (formerly Webkit) Developer Tools Debugging with Node Inspector

Install it globally: npm install -g node-inspector
Run your app in debug mode: node --debug-brk your/node/program.js (or attach to a running process: kill -s USR1 <your node process id>)
In another terminal window run node-inspector: node-inspector
Open http://127.0.0.1:8080/debug?port=5858 (or debug remotely by replacing 127.0.0.1 with your host; make sure port 8080 is open)

Webkit Developer Tools Profiling with Node Webkit Agent

Install to your app npm install webkit-devtools-agent
Include in your app agent = require('webkit-devtools-agent')
Activate the agent: kill -SIGUSR2 <your node process id>
Access the agent via the appropriate link

Interactive Cloud9 Debugging

Guide here

Heapdumps to Webkit Developer Tools

Tool and guide here

Logging Libraries that output Debugging Information

Caterpillar
Tracer

Flamegraphs with Dtrace and StackVis

Only supported on SmartOS

Flamegraphs with Chrome Developer Tools

Coming soon

Benchmark

with Apache Bench: ab -n 100000 -c 1 http://127.0.0.1:9778/
with wrk