Documentation for PR #797 in demo app - Collector Data Flow Dashboard

content/en/docs/demo/collector-data-flow-dashboard/index.md

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+---
+title: Collector Data Flow Dashboard
+---
+
+Monitoring data flow through the OpenTelemetry Collector is crucial for several
+reasons. Gaining a macro-level perspective on incoming data, such as sample
+counts and cardinality, is essential for comprehending the collector's internal
+dynamics. However, when delving into the details, the interconnections can
+become complex. The Collector Data Flow Dashboard aims to demonstrate the
+capabilities of the OpenTelemetry demo application, offering a solid foundation
+for users to build upon. Collector Data Flow Dashboard provides valuable
+guidance on which metrics to monitor. Users can tailor their own dashboard
+variations by adding necessary metrics specific to their use cases, such as
+memory_delimiter processor or other data flow indicators. This demo dashboard
+serves as a starting point, enabling users to explore diverse usage scenarios
+and adapt the tool to their unique monitoring needs.
+
+## Data Flow Overview
+
+The diagram below provides an overview of the system components, showcasing the
+configuration derived from the OpenTelemetry Collector (otelcol) configuration
+file utilized by the OpenTelemetry demo application. Additionally, it highlights
+the observability data (traces and metrics) flow within the system.
+
+![OpenTelemetry Collector Data Flow Overview](otelcol-data-flow-overview.png)
+
+## Ingress/Egress Metrics
+
+The metrics depicted in the diagram below are employed to monitor both egress
+and ingress data flows. These metrics are generated by the otelcol process,
+exported on port 8888, and subsequently scraped by Prometheus. The namespace
+associated with these metrics is "otelcol," and the job name is labeled as
+"otel."
+
+![OpenTelemetry Collector Ingress and Egress Metrics](otelcol-data-flow-metrics.png)
+
+Labels serve as a valuable tool for identifying specific metric sets (such as
+exporter, receiver, or job), enabling differentiation among metric sets within
+the overall namespace. It is important to note that you will only encounter
+refused metrics if the memory limits, as defined in the memory delimiter
+processor, are exceeded.
+
+### Ingress Traces Pipeline
+
+- `otelcol_receiver_accepted_spans`
+- `otelcol_receiver_refused_spans`
+- `by (receiver,transport)`
+
+### Ingress Metrics Pipeline
+
+- `otelcol_receiver_accepted_metric_points`
+- `otelcol_receiver_refused_metric_points`
+- `by (receiver,transport)`
+
+### Processor
+
+Currently, the only processor present in the demo application is a batch
+processor, which is used by both traces and metrics pipelines.
+
+- `otelcol_processor_batch_batch_send_size_sum`
+
+### Egress Traces Pipeline
+
+- `otelcol_exporter_sent_spans`
+- `otelcol_exporter_send_failed_spans`
+- `by (exporter)`
+
+### Egress Metrics Pipeline
+
+- `otelcol_exporter_sent_metric_points`
+- `otelcol_exporter_send_failed_metric_points`
+- `by (exporter)`
+
+### Prometheus Scraping
+
+- `scrape_samples_scraped`
+- `by (job)`
+
+## Dashboard
+
+You can access the dashboard by navigating to the Grafana UI, selecting the
+**OpenTelemetry Collector Data Flow** dashboard under browse icon on the
+left-hand side of the screen.
+
+![OpenTelemetry Collector Data Flow dashboard](otelcol-data-flow-dashboard.png)
+
+The dashboard has four main sections:
+
+1. Process Metrics
+2. Traces Pipeline
+3. Metrics Pipeline
+4. Prometheus Scraping
+
+Sections 2,3 and 4 represent overall data flow using the metrics mentioned
+above. Additionally, export ratio is calculated for each pipeline to understand
+the data flow.
+
+### Export Ratio
+
+Export ratio is basically the ratio between receiver and exporter metrics. You
+can notice over the dashboard screenshot above that the export ratio on metrics
+is way too high than the received metrics. This is because the demo application
+is configured to generate spanmetrics which is a processor that generates
+metrics from spans inside collector as illustrated in overview diagram.
+
+### Process Metrics
+
+Very limited but informative process metrics are added to dashboard. For
+example, you might observe more than one instance of otelcol running on the
+system during restarts or similar. This can be useful for understanding spikes
+on dataflow.
+
+![OpenTelemetry Collector Process Metrics](otelcol-dashbord-process-metrics.png)