Add execution metrics

[antho1404]

I needed to add some stats in order to debug #1570.

This is not a final version, let's discuss first what and how we need to implements metrics but this is a way to start.

To test

Start prometheus and grafana

docker service create -p 3001:3000 --network=engine grafana/grafana
docker service create -p 9090:9090 --network=engine --name=prometheus --mount type=bind,source=$(pwd)/prometheus.yml,destination=/etc/prometheus/prometheus.yml prom/prometheus

Configure grafana

• go to http://localhost:3001/
• add a datasource with the url http://prometheus:9090
• create a dashboard with 4 different metrics
  • mesg_execution_created
  • mesg_execution_signed
  • mesg_execution_in_progress
  • mesg_execution_completed

Then you can create an execution the way you want and you will see the 4 different steps of the lifecycle of an execution

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Prometheus config > https://github.com/mesg-foundation/engine/blob/f54c8633e59268bdb72af4b3f5501b11418e1d5f/prometheus.yml