Update grafana_agent/agent.yaml.example

[Diego Mascialino]

The current example for agent configuration file has deprecated fields.

More information in:
https://grafana.com/docs/agent/latest/upgrade-guide/#deprecation-on-yaml-fields-in-server-block-that-have-flags

We need to update our example, and our guide to set up metrics ( https://maas.io/docs/how-to-set-up-maas-metrics ) with new command.

Example, using:
agent-linux-amd64_0_28_0

root@diego-maas-ss:~# head /opt/agent/agent.yml
server:
  http_listen_address: 0.0.0.0
  http_listen_port: 3100
  grpc_listen_address: 0.0.0.0
  grpc_listen_port: 9095
  log_level: info

metrics:
  wal_directory: ${AGENT_WAL_DIR}
  global:
root@diego-maas-ss:~# HOSTNAME="maas-system-maas" AGENT_WAL_DIR="/var/lib/grafana-agent/wal" AGENT_POS_DIR="/var/lib/grafana-agent/positions" PROMETHEUS_REMOTE_WRITE_URL="http://10.245.136.5:9090/api/v1/write" LOKI_API_URL="http://10.245.136.5:3100/loki/api/v1/push" MAAS_LOGS="/var/snap/maas/common/log/" MAAS_IS_REGION="true" MAAS_IS_RACK="true" MAAS_AZ="default" /opt/agent/agent-linux-amd64 -config.expand-env -config.file=/opt/agent/agent.yml
2022-11-25 13:54:14.895144 I | error loading config file /opt/agent/agent.yml: yaml: unmarshal errors:
  line 2: field http_listen_address not found in type server.config
  line 3: field http_listen_port not found in type server.config
  line 4: field grpc_listen_address not found in type server.config
  line 5: field grpc_listen_port not found in type server.config

[Diego Mascialino (dmascialino)]

new flags are:
- server.http.address
- server.grpc.address

So we have to remove: http_listen_address, http_listen_port, grpc_listen_address and grpc_listen_port fields from config file.

And execute this line:

HOSTNAME="maas-system-maas" AGENT_WAL_DIR="/var/lib/grafana-agent/wal" AGENT_POS_DIR="/var/lib/grafana-agent/positions" PROMETHEUS_REMOTE_WRITE_URL="http://10.245.136.5:9090/api/v1/write" LOKI_API_URL="http://10.245.136.5:3100/loki/api/v1/push" MAAS_LOGS="/var/snap/maas/common/log/" MAAS_IS_REGION="true" MAAS_IS_RACK="true" MAAS_AZ="default"
/opt/agent/agent-linux-amd64 -config.expand-env -config.file=/opt/agent/agent.yml -server.http.address="0.0.0.0:3100" -server.grpc.address="0.0.0.0:9095"