Why is Prometheus not running on 9090

[srajappa]

Description

On deploying Prometheus 0.1.2-2.3.2 on DC/OS v2.1.0 we are seeing the following behavior.

The Prometheus instance i.e. Prometheus-server is running on one of the Private agents and exposed at PORT 1031.

The information is as below:

Address: <PRIVATE_AGENT_IP>:1031
DNS: prometheus-0-server.prometheus.autoip.dcos.thisdcos.directory:1031
VIP: prometheus.prometheus.l4lb.thisdcos.directory:9090

Expected Behavior

On deploying we should have Prometheus workload running on the host and exposing the service at port: 9090.

Question

Is this behavior intentional ? Even other units of this package i.e. alertManager and PushGateway are exposed in other ports eg.

AlertManager
Address: <PRIVATE_AGENT_IP>:1026
DNS: alertmanager-0-server.prometheus.autoip.dcos.thisdcos.directory:1026
VIP: alertmanager.infraprometheus.l4lb.thisdcos.directory:9093