Many metrics are provided by the Collector for its monitoring. Below some key recommendations for alerting and monitoring are listed.
Use rate of otelcol_processor_dropped_spans > 0 and
otelcol_processor_dropped_metric_points > 0 to detect data loss, depending on
the requirements set up a minimal time window before alerting, avoiding
notifications for small losses that are not considered outages or within the
desired reliability level.
This depends on the CPU metrics available on the deployment, eg.:
kube_pod_container_resource_limits{resource="cpu", unit="core"} for Kubernetes. Let's call it
available_cores below. The idea here is to have an upper bound of the number
of available cores, and the maximum expected ingestion rate considered safe,
let's call it safe_rate, per core. This should trigger increase of resources/
instances (or raise an alert as appropriate) whenever
(actual_rate/available_cores) < safe_rate.
The safe_rate depends on the specific configuration being used.
// TODO: Provide reference safe_rate for a few selected configurations.
Most exporters offer a queue/retry mechanism that is recommended as the retry mechanism for the Collector and as such should be used in any production deployment.
The otelcol_exporter_queue_capacity indicates the capacity of the retry queue (in batches). The otelcol_exporter_queue_size indicates the current size of retry queue. So you can use these two metrics to check if the queue capacity is enough for your workload.
The otelcol_exporter_enqueue_failed_spans, otelcol_exporter_enqueue_failed_metric_points and otelcol_exporter_enqueue_failed_log_records indicate the number of span/metric points/log records failed to be added to the sending queue. This may be cause by a queue full of unsettled elements, so you may need to decrease your sending rate or horizontally scale collectors.
The queue/retry mechanism also supports logging for monitoring. Check
the logs for messages like "Dropping data because sending_queue is full".
Sustained rates of otelcol_receiver_refused_spans and
otelcol_receiver_refused_metric_points indicate too many errors returned to
clients. Depending on the deployment and the client’s resilience this may
indicate data loss at the clients.
Sustained rates of otelcol_exporter_send_failed_spans and
otelcol_exporter_send_failed_metric_points indicate that the Collector is not
able to export data as expected.
It doesn't imply data loss per se since there could be retries but a high rate
of failures could indicate issues with the network or backend receiving the
data.
The otelcol_receiver_accepted_spans and
otelcol_receiver_accepted_metric_points metrics provide information about
the data ingested by the Collector.
The otecol_exporter_sent_spans and
otelcol_exporter_sent_metric_pointsmetrics provide information about
the data exported by the Collector.