OpenTelemetry source

Receives metrics pushed with OTLP over HTTP, from an OpenTelemetry Collector or directly from an instrumented application. Gauges, sums and histograms are stored as series, graphed in the explorer and usable in threshold rules. Logs sent to the same endpoint are stored in VictoriaLogs when it is enabled.

DumbMonit does not poll anything here: the data comes in.

Endpoints

Route	Purpose
POST /api/otlp/v1/metrics	Metrics, application/x-protobuf or application/json, plain or Content-Encoding: gzip.
POST /api/otlp/v1/logs	Logs, relayed unchanged to VictoriaLogs (503 while it is disabled).

OTLP over gRPC is not supported: the HTTP exporter of the OpenTelemetry Collector (otlphttp) and of every SDK does the same job on the same port as the web interface, with no extra listener.

Setup

1. In Settings, API & assistants, create a token with the write scope. Restrict it to the network of your collector and give it an expiry date.
2. Add an OpenTelemetry source monitor and note its number: it ends the address of its page, /devices/<number>.
3. Point the exporter at DumbMonit with the token and the number.

OpenTelemetry Collector:

receivers:
  otlp:
    protocols:
      http:
      grpc:

processors:
  # Counters and histograms must be cumulative; this turns delta ones into
  # cumulative ones. Not needed with the defaults of most SDKs.
  deltatocumulative:
  batch:

exporters:
  otlphttp/dumbmonit:
    endpoint: https://monit.example.com/api/otlp
    headers:
      Authorization: Bearer dmt_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
      X-DumbMonit-Target: "12"

service:
  pipelines:
    metrics:
      receivers: [otlp]
      processors: [deltatocumulative, batch]
      exporters: [otlphttp/dumbmonit]
    logs:
      receivers: [otlp]
      processors: [batch]
      exporters: [otlphttp/dumbmonit]

An SDK reads the same settings from its environment:

OTEL_EXPORTER_OTLP_ENDPOINT=https://monit.example.com/api/otlp
OTEL_EXPORTER_OTLP_PROTOCOL=http/protobuf
OTEL_EXPORTER_OTLP_HEADERS=Authorization=Bearer dmt_xxx,X-DumbMonit-Target=12

The target can also be given as ?target=<number> on the URL.

How points become series

Names are written with underscores (http.server.duration becomes dumbmonit_http_server_duration). Point attributes become labels, as do the resource attributes service.name, service.namespace and service.instance.id (service_name, …). The labels target and host are always the monitor’s own; the sender’s are kept as exported_target and exported_host.

OTLP	Series
Gauge	Gauge.
Sum, monotonic, cumulative	Counter, named …_total.
Sum, not monotonic	Gauge.
Histogram, cumulative	Counters …_bucket{le} (cumulated), …_sum, …_count.
Summary	Counters …_sum, …_count and a gauge with quantile.

Not stored, and counted as rejected in the response (partialSuccess): delta temporality, exponential histograms, and points dated more than 30 days back or one hour ahead. Traces are not accepted.

Limits

• 8 MiB per request (32 MiB once decompressed), 50 000 series per request.
• 120 requests per minute per token (the limit of every API token); the response carries RateLimit-* headers and a 429 tells the exporter to retry.
• Labels are limited to 32 per series and 256 characters per value.

Activity and alerts

The monitor publishes dumbmonit_otlp_last_receive_seconds (age of the last accepted request), dumbmonit_otlp_points_received_total and dumbmonit_otlp_points_rejected_total. They live in memory: after a restart of the server nothing is published until the next request. Create a threshold rule on dumbmonit_otlp_last_receive_seconds to be told when an exporter goes quiet, and others on the metrics you send, for example dumbmonit_queue_depth > 1000.

Security

The write scope also opens the write half of the REST API: keep the token in the secrets of the collector, restrict it by network and set an expiry date.