Custom Metrics Endpoint

Expose Prometheus metrics from any application and forward them to xScaler. Use the official Prometheus client libraries to instrument your code with counters, gauges, histograms, and summaries.

Pattern: Custom /metrics endpoint → Prometheus scrape → xScaler remote_write

---

Prerequisites

• Any language runtime
• xScaler tenant credentials (token + tenant ID)

---

Instrument Your Application

Python

pip install prometheus-client

from prometheus_client import Counter, Histogram, start_http_server
import time

REQUEST_COUNT = Counter('myapp_requests_total', 'Total requests', ['method', 'endpoint'])
REQUEST_LATENCY = Histogram('myapp_request_duration_seconds', 'Request latency')

# Expose /metrics on port 8000
start_http_server(8000)

# In your handler:
REQUEST_COUNT.labels(method='GET', endpoint='/api').inc()
with REQUEST_LATENCY.time():
    handle_request()

Node.js

npm install prom-client

const client = require('prom-client');
const express = require('express');

const app = express();
const register = new client.Registry();
client.collectDefaultMetrics({ register });

const httpRequests = new client.Counter({
  name: 'myapp_requests_total',
  help: 'Total HTTP requests',
  labelNames: ['method', 'status'],
  registers: [register],
});

app.get('/metrics', async (req, res) => {
  res.set('Content-Type', register.contentType);
  res.send(await register.metrics());
});

Go

go get github.com/prometheus/client_golang/prometheus

import (
  "github.com/prometheus/client_golang/prometheus"
  "github.com/prometheus/client_golang/prometheus/promhttp"
)

var requestCount = prometheus.NewCounterVec(
  prometheus.CounterOpts{Name: "myapp_requests_total"},
  []string{"method"},
)

func main() {
  prometheus.MustRegister(requestCount)
  http.Handle("/metrics", promhttp.Handler())
  http.ListenAndServe(":8080", nil)
}

---

Option A — Prometheus

scrape_configs:
  - job_name: my_app
    static_configs:
      - targets: ['localhost:8080']

remote_write:
  - url: https://euw1-01.m.xscalerlabs.com/api/v1/push
    authorization:
      credentials: <token>
    headers:
      X-Scope-OrgID: <tenant-id>

---

Option B — Grafana Alloy

prometheus.scrape "my_app" {
  targets    = [{"__address__" = "localhost:8080"}]
  forward_to = [prometheus.remote_write.xscaler.receiver]
}

prometheus.remote_write "xscaler" {
  endpoint {
    url = "https://euw1-01.m.xscalerlabs.com/api/v1/push"
    authorization {
      type        = "Bearer"
      credentials = "<token>"
    }
    headers = { "X-Scope-OrgID" = "<tenant-id>" }
  }
}

---

Option C — OpenTelemetry Collector

receivers:
  prometheus:
    config:
      scrape_configs:
        - job_name: my_app
          static_configs:
            - targets: ['localhost:8080']

processors:
  batch:
    timeout: 10s

exporters:
  otlphttp/xscaler:
    endpoint: https://euw1-01.m.xscalerlabs.com
    headers:
      Authorization: "Bearer <token>"
      X-Scope-OrgID: "<tenant-id>"
    compression: gzip

service:
  pipelines:
    metrics:
      receivers:  [prometheus]
      processors: [batch]
      exporters:  [otlphttp/xscaler]

---

Metric types

Type	Use for
Counter	Things that only increase: requests, errors, bytes
Gauge	Values that go up and down: queue depth, memory, active connections
Histogram	Measured distributions: request duration, payload size
Summary	Quantiles over a sliding window: p50, p95, p99 latency

Logs

Collect application log — tail the log file for the service exposing the /metrics endpoint. Add the following to your Alloy config, adjusting __path__ to match your application's log file location:

local.file_match "metrics_endpoint_logs" {
  path_targets = [{
    __address__ = "localhost",
    __path__    = "/var/log/metrics_endpoint/app.log",
    instance    = constants.hostname,
    job         = "integrations/metrics_endpoint",
  }]
}

loki.source.file "metrics_endpoint_logs" {
  targets    = local.file_match.metrics_endpoint_logs.targets
  forward_to = [loki.write.xscaler.receiver]
}

loki.write "xscaler" {
  endpoint {
    url = "https://euw1-01.l.xscalerlabs.com/api/v1/logs/push"

    http_client_config {
      authorization {
        type        = "Bearer"
        credentials = env("XSCALER_TOKEN")
      }
    }

    headers = { "X-Scope-OrgID" = env("XSCALER_TENANT_ID") }
  }
}