Instrumentation Demo App

This is a demo app that we will use to complete challenges for the software instrumentation course.

About this project

This project is a gRPC server, written in Go, that provides few endpoints to manage courses catalog and bookings for a fake online course marketplace. This project uses library named gRPC-gateway which provide a RESTful API endpoints proxy. So, while the implementation is actually a gRPC server, you can also access it by using curl or any other way you used to.

Getting Started

Pre-setup

I have prepared some basic setup here including the following:

Docker compose file to start few dependencies.
Logger initialization which will write the logs to stdout and file located on logs/app.log. Thus, you can just directly use zerolog to log your application. You can find the initialization on server.go.

Running the application

Make sure you have terminated all running containers from other projects if any. Run docker compose down on the other project if necessary.
Set these environment variable in your profile (e.g. ~/.bashrc):
```
export REDIS_PASSWORD=<set to password you like>
```
From this project directory, start all dependencies with docker compose for this project:
```
make bootstrap
docker compose up -d
```
Make sure you have make installed. If not, run apt install make or whatever you need to do to install make on your machine.

If you get error when running make bootstrap because some dependencies are missing, just install them. For instance, if you got this following errors:
```
no required module provides package google.golang.org/grpc/cmd/protoc-gen-go-grpc; to add it:
    go get google.golang.org/grpc/cmd/protoc-gen-go-grpc
```
In this case, run go get google.golang.org/grpc/cmd/protoc-gen-go-grpc.

Please check the docker-compose.yml file to see what services are started.
To start this API server, run:
```
make course/server
```
You should see that HTTP server starts at port 8800 and gRPC server starts at port 9900.
Seed the database by running the following command from this project directory
```
make course/seed
```
If necessary, you may update the data after it is seeded to database. Or you can truncate the database and re-seed it if necessary.
Check out list of available APIs from the swagger docs. Go to http://localhost:8800/swagger. You can try out the API from there as well if you want.

Running load generator

Load generator here is used to test your implementation.

While you may see the implementation of the load generator, I suggest you to not do that. Instead, you should treat the load generator as a black box so that you can fully understand how the API clients interacting with your API only by using instrumentation you set.

Make sure you have python 3.x installed.
Install virtualenv
```
pip install virtualenv
```
Go to locust directory under scripts directory. Crete and activate a virtual environment
```
cd scripts/locust
virtualenv .venv
source .venv/bin/activate
```
Install the required dependencies for the load generator
```
pip install -r requirements.txt
```

Run the load generator

locust -f locustfiles --class-picker --modern-ui -H http://localhost:8800