Enabling the NGINX monitoring interface

If you want to use the NGINX monitoring by deploying the Unified Agent, you must confirm that the NGINX monitoring interface is enabled.

Procedure

Run the following command on the machine where you want to deploy the Unified Agent:
```
http://pod_ip_or_nginx_host:18080/nginx_status
```
where pod_ip_or_nginx_host is the fully qualified host name of the NGINX server.
If no status is returned, the NGINX monitoring interface is not enabled.
The NGINX monitoring interface requires loading the ngx_http_stub_status_module module. This module helps in collecting basic performance metrics. IBM® Cloud Private provides the NGINX Docker image ibmcom/nginx-ingress-controller, which has ngx_http_stub_status module enabled. If the workloads are using this image, there is no need to do any further configuration. You need only to get the Kubernetes SERVICE or POD IP and verify that the management interface is enabled. For example, http://NGINX_service_or_node_or_pod_ip:18080/nginx_status. Some command examples are shown below to help you determine if NGINX workloads are running and to confirm that their management interfaces are enabled.
Note: Log into IBM Cloud Private to continue with the following section:
```
> cloudctl login -a <cluster> -u <username> 
> kubectl get po -n kube-system -o wide |grep nginx

The command returns output similar to the following

nginx-ingress-controller-jx8vb      1/1     Running   0     5h   
10.1.253.201   9.42.75.39

Verify the NGINX management interface status

> curl http://10.1.253.201:18080/nginx_status

Active connections: 9
server accepts handled requests
 5372 5372 22532
Reading: 0 Writing: 2 Waiting: 7
```
Because the pod IP address can change, you can optionally create a service that points to the POD to get a static IP address. The following commands help create a service configuration:
```
> kubectl describe po nginx-ingress-controller-jx8vb -n kube-system 

Name:              nginx-ingress-controller-jx8vb 
Namespace:         kube-system 
Priority:          0 
PriorityClassName: <none> 
Node:              9.42.75.39/9.42.75.39 
Start Time:        Fri, 28 Sep 2018 23:46:39 -0400 
Labels:            app=nginx-ingress-controller
```
Note: Here the selector is app=nginx-ingress-controller. It may differ in your IBM Cloud Private environment
Create a service resource file (nginx-status.yaml) as shown here:
```
{
  "apiVersion": "v1",
  "kind": "Service",
  "metadata": {
    "name": "nginx-status",
    "namespace": "kube-system",
    "labels": {
      "app": "nginx-status"
    }
  },
  "spec": {
    "ports": [
      {
        "name": "nginx-status",
        "protocol": "TCP",
        "port": 18080,
        "targetPort": 18080
      }
    ],
    "selector": {
      "app": "nginx-ingress-controller"
    },
    "type": "ClusterIP",
    "sessionAffinity": "None"
  }
}
```
Note: Open port 18080 for NGINX status access.
Create the Kubernetes service resource using the file that you created above and obtain the service ip
```
> kubectl create -f nginx-status.yaml
> kubectl describe svc nginx-status -n kube-system

Name:              nginx-status
Namespace:         kube-system
Labels:            app=nginx-status
Annotations:       <none>
Selector:          name=nginx-ingress-controller
Type:              ClusterIP
IP:                10.0.0.243
Port:              nginx-status  18080/TCP
TargetPort:        18080/TCP
Endpoints:         9.37.22.210:18080
Session Affinity:  None
Events:            <none>
```
```
 curl http://10.0.0.243:18080/nginx_status 
```
You can give the NGINX management interface URL http://10.0.0.243:18080/nginx_status to the Helm Chart configuration. In on-premises installations, this module is not enabled by default. It must first be built and then enabled with the configuration parameter --with-http_stub_status_module. Please see the NGINX documentation for enablement.

If you want to monitor NGINX in IBM Cloud Private 3.2.0 or 3.2.1, you need to do extra steps to ensure NGINX monitoring can run successfully.

Find the NGINX pod on IBM Cloud Private.

# kubectl get po -n kube-system|grep nginx
nginx-ingress-controller-ph8t6                                 1/1     Running     0          18m

Export nginx.tmpl.

# kubectl cp kube-system/nginx-ingress-controller-ph8t6:template/nginx.tmpl nginx.tmpl

Remove the line deny all in nginx.tmpl.

location /nginx_status {
            {{ if $all.Cfg.EnableOpentracing }}
            opentracing off;
            {{ end }}

            {{ range $v := $all.NginxStatusIpv4Whitelist }}
            allow {{ $v }};
            {{ end }}
            {{ if $all.IsIPV6Enabled -}}
            {{ range $v := $all.NginxStatusIpv6Whitelist }}
            allow {{ $v }};
            {{ end }}
            {{ end -}}
###This line should be removed , or comment out
            deny all;
###End
            access_log off;
            stub_status on;
        }

Create nginx template configmap.

kubectl create configmap nginx-template -n kube-system --from-file=nginx.tmpl

Modify nginx daemonset to use this configmap.

kubectl edit daemonset nginx-ingress-controller -n kube-system

Snippet to add to here:

spec:
      containers:
      - args:
        ...
        ...
### Here begin the config map setting to copy ###
        volumeMounts:
        - mountPath: /etc/nginx/template
          name: nginx-template-volume
          readOnly: true
      volumes:
      - name: nginx-template-volume
        configMap:
          name: nginx-template
          items:
          - key: nginx.tmpl
            path: nginx.tmpl
### End ###

Do the verification. After finishing the daemonset edit, the Nginx controller pod will be automatically restarted. If not, manually delete it to take effect.

# kubectl get po -n kube-system -o wide|grep nginx
nginx-ingress-controller-ph8t6                                 1/1     Running     0          3m    10.1.13.68     9.46.67.224   <none>           <none>

The nginx status is exposed on port 80 according to the nginx config. So, curl this url for verification:

#curl http://10.1.13.68/nginx_status
Active connections: 48
server accepts handled requests
 729017 729017 896362
Reading: 0 Writing: 14 Waiting: 33