Application Profiling

Node.js Profiling

CPU Profiling with clinic.js

# Install
npm install -g clinic

# CPU profiling
clinic doctor -- node app.js

# Flame graph
clinic flame -- node app.js

# Bubble profiling
clinic bubbleprof -- node app.js

# Generate report
clinic doctor --collect-only -- node app.js
clinic doctor --visualize-only PID.clinic-doctor

Built-in Node.js Profiler

// Start profiling
node --prof app.js

# Process the output
node --prof-process isolate-0x*.log > processed.txt

# Chrome DevTools
node --inspect app.js
# Open chrome://inspect

Memory Profiling

// Heap snapshot
const snapshot = v8.writeHeapSnapshot();
console.log('Snapshot written to:', snapshot);

// Memory usage
const usage = process.memoryUsage();
console.log({
  rss: `${Math.round(usage.rss / 1024 / 1024)}MB`,
  heapTotal: `${Math.round(usage.heapTotal / 1024 / 1024)}MB`,
  heapUsed: `${Math.round(usage.heapUsed / 1024 / 1024)}MB`,
  external: `${Math.round(usage.external / 1024 / 1024)}MB`,
});

Custom Performance Marks

// Mark start
performance.mark('operation-start');

// ... do work ...
await processOrder(orderId);

// Mark end
performance.mark('operation-end');

// Measure
performance.measure('operation', 'operation-start', 'operation-end');

// Observer
const obs = new PerformanceObserver((items) => {
  items.getEntries().forEach((entry) => {
    console.log(`${entry.name}: ${entry.duration}ms`);
  });
});
obs.observe({ entryTypes: ['measure'] });

Python Profiling

cProfile

# Profile a function
def main():
    # Your code here
    process_data()

if __name__ == '__main__':
    profiler = cProfile.Profile()
    profiler.enable()

    main()

    profiler.disable()
    stats = pstats.Stats(profiler)
    stats.sort_stats('cumulative')
    stats.print_stats(20)  # Top 20 functions

Line Profiler

from line_profiler import LineProfiler

@profile
def expensive_function():
    # Code to profile
    result = []
    for i in range(10000):
        result.append(i ** 2)
    return result

# Run with: kernprof -l -v script.py

Memory Profiler

from memory_profiler import profile

@profile
def process_large_data():
    data = [i for i in range(1000000)]
    result = [x * 2 for x in data]
    return result

# Run with: python -m memory_profiler script.py

py-spy

# CPU sampling (live process)
py-spy top --pid 12345

# Generate flame graph
py-spy record -o profile.svg --pid 12345

# Record for duration
py-spy record -o profile.svg --duration 60 -- python app.py

Go Profiling

pprof

    "net/http"
    _ "net/http/pprof"
    "runtime"
)

func main() {
    // Enable profiling endpoint
    go func() {
        http.ListenAndServe("localhost:6060", nil)
    }()

    // Your application code
}

# CPU profile
curl http://localhost:6060/debug/pprof/profile?seconds=30 > cpu.prof
go tool pprof cpu.prof

# Memory profile
curl http://localhost:6060/debug/pprof/heap > heap.prof
go tool pprof heap.prof

# Goroutine profile
curl http://localhost:6060/debug/pprof/goroutine > goroutine.prof
go tool pprof goroutine.prof

# Web interface
go tool pprof -http=:8080 cpu.prof

Java Profiling

VisualVM

# Start application with JMX
java -Dcom.sun.management.jmxremote \\
     -Dcom.sun.management.jmxremote.port=9010 \\
     -Dcom.sun.management.jmxremote.authenticate=false \\
     -Dcom.sun.management.jmxremote.ssl=false \\
     -jar app.jar

# Connect with VisualVM
jvisualvm

async-profiler

# CPU profiling
./profiler.sh -d 30 -f cpu.html <pid>

# Allocation profiling
./profiler.sh -d 30 -e alloc -f alloc.html <pid>

# Flame graph
./profiler.sh -d 30 -f flamegraph.svg <pid>

Database Query Profiling

PostgreSQL

-- Enable query logging
ALTER SYSTEM SET log_min_duration_statement = 100;  -- Log queries > 100ms
SELECT pg_reload_conf();

-- Explain analyze
EXPLAIN ANALYZE
SELECT * FROM orders
WHERE user_id = 123
AND created_at > NOW() - INTERVAL '30 days';

-- Track slow queries
SELECT query, calls, total_time, mean_time
FROM pg_stat_statements
ORDER BY mean_time DESC
LIMIT 10;

MySQL

-- Enable slow query log
SET GLOBAL slow_query_log = 'ON';
SET GLOBAL long_query_time = 0.1;  -- 100ms

-- Explain query
EXPLAIN ANALYZE
SELECT * FROM orders
WHERE user_id = 123;

-- Performance schema
SELECT * FROM performance_schema.events_statements_summary_by_digest
ORDER BY SUM_TIMER_WAIT DESC
LIMIT 10;

APM Integration

New Relic

// Custom transaction
newrelic.startBackgroundTransaction('process-orders', async () => {
  const orders = await getOrders();

  // Custom segment
  await newrelic.startSegment('validate-orders', true, async () => {
    return validateOrders(orders);
  });
});

// Custom metrics
newrelic.recordMetric('Custom/OrderValue', orderTotal);

DataDog APM

tracer.init();

// Custom span
const span = tracer.startSpan('process.order', {
  resource: orderId,
  tags: {
    'order.total': orderTotal,
    'user.id': userId,
  },
});

try {
  await processOrder(orderId);
  span.setTag('status', 'success');
} catch (err) {
  span.setTag('error', err);
} finally {
  span.finish();
}

Quick Reference