Troubleshooting

Common error messages

Cannot connect to the Docker daemon

The Docker daemon is required for running any docker container. If you get the following error,

docker: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?.
See ‘docker run –help’.

try starting the Docker daemon with the dockerd command:

sudo dockerd

or with your service manager:

systemctl start docker # for systemd, or
sudo service docker start # for open-rc

Error 403 on the dashboard

You are not authorized. This is likely because you restarted the frontend/backend process(es) and lost the authorized session, but your browser cached the dashboard pages. Try to log in again. See login credentials at the Project setup page.

Port 5000 is already in use

The backend is hard-coded to use port 5000 and would not start if the port is already in use. Try to kill the process that is currently using port 5000 before re-running. You can find the process using the port with lsof -i :5000, which will give a pid. Kill the process with kill -9 <pid>.

⚠️ Double check the pid before running kill -9 <pid>, since killing the wrong process may cause unwanted side effects to the system.

On MacOS, this process could be an AirPlay server that respawns immediately after getting killed. To disable it, uncheck "AirPlay Receiver" in System Preferences → Sharing.

ECONNREFUSED when starting backend or GraphDB exceptions with no GraphDB messages

There might be a conflict with the definition of localhost in IPv4 and IPv6. Replace localhost with 127.0.0.1 in backend/config/index.js, for the graphdb field:

const config = {
  graphdb: {
    addr: isProduction ? 'http://127.0.0.1:7200' : `http://${isDocker ? 'host.docker.internal' : '127.0.0.1'}:7200`,
  },
  ...

Module not found

Usually due to outdated dependencies, which can be resolved by re-running yarn install.

Inconsistent data across pages

For example, if the deleted data entries still show up somewhere, or if the dropdown menus don't list all entries.

This is a bug. To work around it, clear both GraphDB and MongoDB.

• GraphDB: Go to http://localhost:7200 in your browser and clear repository.
• MongoDB: One way is to re-create the entire docker container:

docker remove mongo
docker run --name mongo -p 27017:27017 --restart unless-stopped -d mongo:latest

where mongos (not mongo:latest) are replaced with the name of your docker container.

Tips and tricks

• Open the console in your browser to see the error messages
• Ask for help if you get stuck

Finding out which frontend component triggers which API/query

Open the web client and the terminal window where you ran yarn start in backend/ side by side. Interact with the frontend and observe the logs being printed in the terminal. If the API calls a SPARQL query, it will also log the exact query.