Both, local and global nodes, exposes an API which lets operators disable the service so load balancers will not send queries to these ones.

This is based on the status API method (see REST API: status resource section)

If the operator needs to work on a machine, he first should disable the service sending the correct command to the service:

curl -d 'enable=false' -k --key test_ca/TEST_CERTIFICATES/client.key --cert test_ca/TEST_CERTIFICATES/client.crt https://[SERVER]/status

After maintainment is finished, the operator will reenable the service again with this other command:

curl -d 'enable=true' -k --key test_ca/TEST_CERTIFICATES/client.key --cert test_ca/TEST_CERTIFICATES/client.crt https://[SERVER]/status

Load balancers will check the response of the GET query to the status URL (https://[SERVER]/status/). If the HTTP status is 200 (OK) the service is enabled. If the response is 503 (Under maintanance) the service is disabled