Function: createUpDownCounter()

@arolariu/website

---

@arolariu/website / instrumentation.server / createUpDownCounter

Function: createUpDownCounter()

createUpDownCounter(name, description?, unit?): UpDownCounter<Attributes>

Defined in: instrumentation.server.ts:1248

Create an up-down counter metric instrument.

Up-down counters track values that can increase or decrease. Use for gauges like active connections, queue depth, or resource utilization.

Parameters

name

MetricName

Metric name following semantic conventions (e.g., "http.server.active_requests")

description?

string

Human-readable description of what the metric measures

unit?

string

Optional unit of measurement (e.g., "1", "connections", "bytes")

Returns

UpDownCounter<Attributes>

UpDownCounter instrument for recording values with type-safe attributes

Remarks

• Values can increase or decrease (unlike regular counters)
• Use add() with positive or negative values
• Ideal for tracking current state or active resources
• Backends typically report the current sum
• Not suitable for rates or totals (use counter instead)

Examples

const activeConnections = createUpDownCounter(
  'http.server.active_requests',
  'Number of active HTTP requests being processed',
  '1'
);

// Request starts
activeConnections.add(1, {
  'http.method': 'GET',
  'next.render_context': 'api',
});

// ... process request

// Request completes
activeConnections.add(-1, {
  'http.method': 'GET',
  'next.render_context': 'api',
});

// Cache size tracking
const cacheSize = createUpDownCounter('cache.size.bytes', 'Current cache size in bytes', 'bytes');
cacheSize.add(1024, { 'cache.system': 'redis' }); // Item cached
cacheSize.add(-1024, { 'cache.system': 'redis' }); // Item evicted

See

https://opentelemetry.io/docs/specs/otel/metrics/api/#updowncounter