The purpose of this project to provide an example application that demonstrates the basics of OpenTelemetry. The project provides an example for creating a simple trace with spans among HTTP requests between two servers.
The demonstration project is made up of two HTTP servers, HTTP SERVER 1 and HTTP SERVER 2. HTTP SERVER 1 creates a random string that gets passed down stream as an HTTP POST request to HTTP SERVER 2. HTTP SERVER 2 repeats the randon string and pass the result back as a response to HTTP SERVER 1.
The string is repeated according to the HTTP SERVER 2 environment variable, REPEATER_REPEATS. If the environment variable REPEATER_REPEATS is not set, the server process, the number of repeats will be 3, the default value as defined here.
This example application uses OpenTelemetry to implement tracing. Also, the application uses the Jaeger all-in-one executable to collect the trace informatoin.
The application uses OpenTelementy's default request/response tracing. In addition, the application implements custom spans to report the contents of the various HTTP requests and responses instigates by HTTP SERVER 1 and HTTP SERVER 2.
Once the application is up and running, you can view the Jeager UI on port 16686.
If you are not running the application under Docker Compose, make sure that the Jaeger executable is running as a Docker container. To run Jaeger as a Docker container, invoke the following command:
docker run -d --name jaeger \
-e COLLECTOR_ZIPKIN_HTTP_PORT=9411 \
-p 5775:5775/udp \
-p 6831:6831/udp \
-p 6832:6832/udp \
-p 5778:5778 \
-p 16686:16686 \
-p 14268:14268 \
-p 14250:14250 \
-p 9411:9411 \
jaegertracing/all-in-one:1.19
If you are not on Katacoda go here:
https://katacoda.com/courses/ubuntu/playground
Get the code from GitHub:
git clone https://github.com/reselbob/simpletracing.git
cd simpletracing/
This application run under Docker Compose.
To get the application up and running under Docker Compose execute the following command from the project's root directory:
docker-compose up
To stop the application and remove the docker images created according to the Docker Compose file execute the following command:
docker-compose down --rmi all
You can view the example Docker-Compose that ships with the code here.
The way to invoke a trace is to run a curl command against HTTP SERVER 1. A call to HTTP SERVER 1 will create a ran string in which is then passed to HTTP SERVER 2 for repeating. The repeated string is passed back from HTTP SERVER 2 to HTTP SERVER 1.
Assuing you are up and running under Docker Compose, execute the following curl command to invoke a trace;
curl localhost:3000
You will get a response similar to the following. (The actual repeated string will be different in your response.)
["CONSECTETUR UT UT QUO INVENTORE","CONSECTETUR UT UT QUO INVENTORE","CONSECTETUR UT UT QUO INVENTORE"]
Once you've run the curl command, you can view the Jeager UI at the following URL: http://localhost:16686.
NOTE: If you are running on a Katacoda virtual machine, you will need to use Katacoda's mechanism for a browser against port, 16686 as shown in the animated GIF below.
