Counter Issue not working with example code in opentelemetry docs

❗ Metrics not pushed to Prometheus from PHP SDK (Counter not working)

We are working on a legacy CRM system, and we’re adding full observability using OpenTelemetry, Grafana Alloy, and Prometheus.

• ✅ Traces and logs are working via Alloy and OTLP
• ✅ Metrics using ObservableGauge are working
• ❌ Metrics using Counter::add() are collected by Alloy, but do not show up in Prometheus

---

✅ Environment

Component	Version / Details
PHP	8.2.28
OpenTelemetry PHP SDK	1.2.4
Alloy	Latest (May 2025)
Prometheus	v2.51+
Export Protocol	OTLP over HTTP (x-protobuf)
Prometheus remote_write	Enabled (/api/v1/write)

---

📜 Sample Code

require_once 'vendor/autoload.php';

use OpenTelemetry\Contrib\Otlp\MetricExporter;
use OpenTelemetry\Contrib\Otlp\OtlpHttpTransportFactory;
use OpenTelemetry\SDK\Metrics\MeterProvider;
use OpenTelemetry\SDK\Metrics\MetricReader\ExportingReader;
use OpenTelemetry\SDK\Resource\ResourceInfo;
use OpenTelemetry\SemConv\ResourceAttributes;
use OpenTelemetry\SDK\Common\Attribute\Attributes;
use OpenTelemetry\SDK\Common\Time\ClockFactory;
use OpenTelemetry\SDK\Resource\ResourceInfoFactory;
use OpenTelemetry\SDK\Common\Instrumentation\InstrumentationScopeFactory;
use OpenTelemetry\SDK\Metrics\StalenessHandler\ImmediateStalenessHandlerFactory;
use OpenTelemetry\SDK\Metrics\Exemplar\ExemplarFilter\WithSampledTraceExemplarFilter;
use OpenTelemetry\SDK\Metrics\View\CriteriaViewRegistry;

$transport = (new OtlpHttpTransportFactory())->create(
    'http://localhost:4318/v1/metrics',
    'application/x-protobuf'
);

$reader = new ExportingReader(new MetricExporter($transport), ClockFactory::getDefault());

$resource = ResourceInfo::create(Attributes::create([
    ResourceAttributes::SERVICE_NAME => 'counter-test',
]));

$provider = new MeterProvider(
    null,
    ResourceInfoFactory::emptyResource(),
    ClockFactory::getDefault(),
    Attributes::factory(),
    new InstrumentationScopeFactory(Attributes::factory()),
    [$reader],
    new CriteriaViewRegistry(),
    new WithSampledTraceExemplarFilter(),
    new ImmediateStalenessHandlerFactory(),
);

$meter = $provider->getMeter('io.opentelemetry.contrib.php');

$counter = $meter->createCounter('test.counter.total', 'ms', 'A simple counter.');
$counter->add(1, ['label' => 'test']);

$reader->collect();
$provider->forceFlush();

---

📦 Alloy Log Output

Alloy successfully logs this:

Metric #0
-> Name: test.counter.total
-> DataType: Sum
-> IsMonotonic: true
-> AggregationTemporality: Delta
-> Value: 1

---

❌ Problem

Prometheus only shows:

sample: ts=..., labels={__name__="target_info"}, value=1.0

No counter metric appears.

---

✅ Comparison with Python SDK

Using Python with:

meter.create_counter("test.counter.total").add(1)

✅ Metric appears in Prometheus immediately.

---

✅ ObservableGauge Works in PHP

If we simulate the counter like this:

$meter->createObservableGauge('test.counter.total')
    ->observe(fn($observer) => $observer->observe(1, ['label' => 'test']));

✅ It appears in Prometheus without issue.

---

❓ Expected Behavior

• Counter::add() should produce a flushable metric
• It should show up in Prometheus after collect() + forceFlush()

---

❓ Actual Behavior

• Metric is collected by Alloy and logged
• Prometheus drops or does not store the sample
• Same metric works from Python, not from PHP

---

🔍 Hypothesis

1. PHP SDK uses AggregationTemporality = Delta, while Prometheus prefers CUMULATIVE
2. StartTimestamp may reset or be incomplete for Prometheus to stitch time series
3. Prometheus silently drops delta counters that do not follow its expectations

---

✅ Alloy Configuration Used

otelcol.receiver.otlp "default" {
  http {
    endpoint = "0.0.0.0:4318"
  }
  output {
    metrics = [otelcol.processor.batch.default.input]
  }
}

otelcol.processor.batch "default" {
  output {
    metrics = [otelcol.exporter.prometheus.default.input]
  }
}

otelcol.exporter.prometheus "default" {
  forward_to = [prometheus.remote_write.default.receiver]
}

prometheus.remote_write "default" {
  endpoint {
    url = "http://localhost:9090/api/v1/write"
  }
}

---

No repository files or tests are named. Start by tracing the PHP SDK metrics path from Counter::add() through collect(), forceFlush(), and the OTLP MetricExporter, then compare the emitted data with the Alloy and Prometheus configuration shown here. Done means the counter appears in Prometheus after the documented flush sequence, with a regression test if the relevant test location can be identified.