hotrod

README

Hot R.O.D. - Rides on Demand

This is a demo application that consists of several microservices and illustrates the use of the OpenTracing API. It can be run standalone, but requires Jaeger backend to view the traces. A tutorial / walkthrough is available:

• as a blog post Take OpenTracing for a HotROD ride,
• as a video OpenShift Commons Briefing: Distributed Tracing with Jaeger & Prometheus on Kubernetes.

Features

• Discover architecture of the whole system via data-driven dependency diagram
• View request timeline & errors, understand how the app works
• Find sources of latency, lack of concurrency
• Highly contextualized logging
• Use baggage propagation to
  • Diagnose inter-request contention (queueing)
  • Attribute time spent in a service
• Use open source libraries with OpenTracing integration to get vendor-neutral instrumentation for free

Running

Run everything via docker-compose

• Download docker-compose.yml from https://github.com/jaegertracing/jaeger/blob/main/examples/hotrod/docker-compose.yml
• Run Jaeger backend and HotROD demo with docker-compose -f path-to-yml-file up
• Access Jaeger UI at http://localhost:16686 and HotROD app at http://localhost:8080
• Shutdown / cleanup with docker-compose -f path-to-yml-file down

Alternatively, you can run each component separately as described below.

Run Jaeger backend

An all-in-one Jaeger backend is packaged as a Docker container with in-memory storage.

docker run \
  --rm \
  --name jaeger \
  -p6831:6831/udp \
  -p16686:16686 \
  jaegertracing/all-in-one:latest

Jaeger UI can be accessed at http://localhost:16686.

Run HotROD from source

git clone git@github.com:jaegertracing/jaeger.git jaeger
cd jaeger
go run ./examples/hotrod/main.go all

Run HotROD from docker

docker run \
  --rm \
  --link jaeger \
  --env JAEGER_AGENT_HOST=jaeger \
  --env JAEGER_AGENT_PORT=6831 \
  -p8080-8083:8080-8083 \
  jaegertracing/example-hotrod:latest \
  all

Then open http://127.0.0.1:8080

Metrics

The app exposes metrics in either Go's expvar format (by default) or in Prometheus format (enabled via -m prometheus flag).

• expvar: curl http://127.0.0.1:8083/debug/vars
• Prometheus: curl http://127.0.0.1:8083/metrics

Linking to traces

The HotROD UI can generate links to the Jaeger UI to find traces corresponding to each executed request. By default it uses the standard Jaeger UI address http://localhost:16686, but if your Jaeger UI is running at a different address, it can be customized via -j <address> flag passed to HotROD, e.g.

go run ./examples/hotrod/main.go all -j http://jaeger-ui:16686