6. Clone the demo app

yarn add @opentelemetry/api @opentelemetry/auto-instrumentations-node @opentelemetry/exporter-trace-otlp-proto @opentelemetry/sdk-node

9. How Distributed traces are made

OpenTelemetry (OTEL) context is sent in HTTP headers

• Span ID
• Parent Span ID
  • If not defined, then the root id is used
• Trace ID

10. Adding Metrics

Follow steps in the link below:

https://github.com/habmic/opentelemetry-101/blob/main/docs/adding-metrics.md

Notes:

– Add the ‘Running Prometheus’ code to the docker-compose.yml file and not prometheus.yml as hinted by the online doc!

– sleep command does not exist. Add the following line before app.get (all one line)

const sleep = (time: number) => { return new Promise((resolve) => { setTimeout(resolve, time) }) };

– fail fails! Something about cannot send headers after … (

if (req.query['fail']){
    console.error('Really bad error!');
    res.sendStatus(500);
    return;
}

Prometheus

• Prometheus is an open-source time-series database
  • Also provided by the CNCF Cloud Native Computing Foundation
• Prometheus ‘scrapes’ for metrics.
  • The targets are noted in the prometheus.yml file, hitting the source files on their assigned ports.

Verify

• API Calls
  • http://localhost:8081/todos?slow=1
  • http://localhost:8081/todos?fail=1
• Jaeger
• Prometheus
  • histogram_quantile(0.95, sum(rate(http_calls_bucket[1m])) by (le, route))

11. Correlating logs with traces

12. Creating manual spans

13. Creating span attributes (tags)

• Key: Value pairs
• Can be used to search in Jaeger
• Custom tags can be added
  • i.e. User ID

opentelemetry.trace.getActiveSpan()?.setAttribute('userId',123);
opentelemetry.trace.getActiveSpan()?.setAttributes({'userId',123});