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Manuel Raynaud
70102aad83
We want to export metrics to prometheus. We install for this django-prometheus. By default the feature is disabled and must be explicitly enabled. A complete documentation is available in documentation/metrics.md
59 lines
2.3 KiB
Python
59 lines
2.3 KiB
Python
"""Prometheus metrics of the application, as served on /metrics.
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Enabled by PROMETHEUS_METRICS_ENABLED and protected by
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`core.middleware.PrometheusAuthMiddleware` — see documentation/metrics.md.
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"""
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import socket
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from django.http import HttpResponse
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from django.views.decorators.http import require_safe
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from prometheus_client import CONTENT_TYPE_LATEST, CollectorRegistry, generate_latest
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from prometheus_client.core import Metric
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from prometheus_client.multiprocess import MultiProcessCollector
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HOSTNAME_LABEL = "hostname"
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class HostnameLabelCollector:
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"""
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The metrics of every worker process of this host, labelled with its name.
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uvicorn runs several workers and the scrape is answered by one of them: the
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multiprocess collector reads what they all wrote to PROMETHEUS_MULTIPROC_DIR
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and adds it up, instead of reporting the numbers of that worker alone.
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The label is for a scraper that goes through a load balancer (an ingress in
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front of several replicas): each scrape is then answered by a different
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replica, and without it their counters would land in the same series, which
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would jump from the numbers of one replica to those of another. With it,
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each replica has its own series, sampled whenever it happens to answer.
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"""
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def __init__(self):
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self.hostname = socket.gethostname()
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def collect(self):
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"""Yield the aggregated metrics with the hostname added to every sample."""
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# a registry of its own: the collector registers itself in the one it is given
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for metric in MultiProcessCollector(CollectorRegistry()).collect():
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labelled = Metric(metric.name, metric.documentation, metric.type)
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for sample in metric.samples:
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labelled.add_sample(
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sample.name,
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{**sample.labels, HOSTNAME_LABEL: self.hostname},
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sample.value,
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sample.timestamp,
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sample.exemplar,
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)
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yield labelled
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@require_safe
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def metrics_view(request):
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"""Serve the metrics in the Prometheus text format."""
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registry = CollectorRegistry()
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registry.register(HostnameLabelCollector())
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return HttpResponse(generate_latest(registry), content_type=CONTENT_TYPE_LATEST)
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