nginx

Nginx Ingress Controller

This is a nginx Ingress controller that uses ConfigMap to store the nginx configuration. See Ingress controller documentation for details on how it works.

What it provides?

• Ingress controller
• nginx 1.9.x with
• SSL support
• custom ssl_dhparam (optional). Just mount a secret with a file named dhparam.pem.
• support for TCP services (flag --tcp-services-configmap)
• custom nginx configuration using ConfigMap
• custom error pages. Using the flag --custom-error-service is possible to use a custom compatible 404-server image

Requirements

• default backend 404-server

Dry running the Ingress controller

Before deploying the controller to production you might want to run it outside the cluster and observe it.

$ make controller
$ mkdir /etc/nginx-ssl
$ ./nginx-ingress-controller --running-in-cluster=false --default-backend-service=kube-system/default-http-backend

Deploy the Ingress controller

First create a default backend:

$ kubectl create -f examples/default-backend.yaml
$ kubectl expose rc default-http-backend --port=80 --target-port=8080 --name=default-http-backend

Loadbalancers are created via a ReplicationController or Daemonset:

$ kubectl create -f examples/default/rc-default.yaml

HTTP

First we need to deploy some application to publish. To keep this simple we will use the echoheaders app that just returns information about the http request as output

kubectl run echoheaders --image=gcr.io/google_containers/echoserver:1.3 --replicas=1 --port=8080

Now we expose the same application in two different services (so we can create different Ingress rules)

kubectl expose deployment echoheaders --port=80 --target-port=8080 --name=echoheaders-x
kubectl expose deployment echoheaders --port=80 --target-port=8080 --name=echoheaders-y

Next we create a couple of Ingress rules

kubectl create -f examples/ingress.yaml

we check that ingress rules are defined:

$ kubectl get ing
NAME      RULE          BACKEND   ADDRESS
echomap   -
          foo.bar.com
          /foo          echoheaders-x:80
          bar.baz.com
          /bar          echoheaders-y:80
          /foo          echoheaders-x:80

Before the deploy of the Ingress controller we need a default backend 404-server

kubectl create -f examples/default-backend.yaml
kubectl expose rc default-http-backend --port=80 --target-port=8080 --name=default-http-backend

Check NGINX it is running with the defined Ingress rules:

$ LBIP=$(kubectl get node `kubectl get po -l name=nginx-ingress-lb --template '{{range .items}}{{.spec.nodeName}}{{end}}'` --template '{{range $i, $n := .status.addresses}}{{if eq $n.type "ExternalIP"}}{{$n.address}}{{end}}{{end}}')
$ curl $LBIP/foo -H 'Host: foo.bar.com'

TLS

You can secure an Ingress by specifying a secret that contains a TLS private key and certificate. Currently the Ingress only supports a single TLS port, 443, and assumes TLS termination. This controller supports SNI. The TLS secret must contain keys named tls.crt and tls.key that contain the certificate and private key to use for TLS, eg:

apiVersion: v1
data:
  tls.crt: base64 encoded cert
  tls.key: base64 encoded key
kind: Secret
metadata:
  name: testsecret
  namespace: default
type: Opaque

Referencing this secret in an Ingress will tell the Ingress controller to secure the channel from the client to the loadbalancer using TLS:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: no-rules-map
spec:
  tls:
    secretName: testsecret
  backend:
    serviceName: s1
    servicePort: 80

Please follow test.sh as a guide on how to generate secrets containing SSL certificates. The name of the secret can be different than the name of the certificate.

Check the example

Optimizing TLS Time To First Byte (TTTFB)

NGINX provides the configuration option ssl_buffer_size to allow the optimization of the TLS record size. This improves the Time To First Byte (TTTFB). The default value in the Ingress controller is 4k (nginx default is 16k);

Exposing TCP services

Ingress does not support TCP services (yet). For this reason this Ingress controller uses a ConfigMap where the key is the external port to use and the value is <namespace/service name>:<service port> It is possible to use a number or the name of the port.

The next example shows how to expose the service example-go running in the namespace default in the port 8080 using the port 9000

apiVersion: v1
kind: ConfigMap
metadata:
  name: tcp-configmap-example
data:
  9000: "default/example-go:8080"

Please check the tcp services example

Exposing UDP services

Since 1.9.13 NGINX provides UDP Load Balancing.

Ingress does not support UDP services (yet). For this reason this Ingress controller uses a ConfigMap where the key is the external port to use and the value is <namespace/service name>:<service port> It is possible to use a number or the name of the port.

The next example shows how to expose the service kube-dns running in the namespace kube-system in the port 53 using the port 53

apiVersion: v1
kind: ConfigMap
metadata:
  name: udp-configmap-example
data:
  53: "kube-system/kube-dns:53"

Please check the udp services example

Custom NGINX configuration

Using a ConfigMap it is possible to customize the defaults in nginx.

Please check the tcp services example

NGINX status page

The ngx_http_stub_status_module module provides access to basic status information. This is the default module active in the url /nginx_status. This controller provides an alternitive to this module using nginx-module-vts third party module. To use this module just provide a ConfigMap with the key enable-vts-status=true. The URL is exposed in the port 8080. Please check the example example/rc-default.yaml

To extract the information in JSON format the module provides a custom URL: /nginx_status/format/json

Troubleshooting

Problems encountered during 1.2.0-alpha7 deployment:

• make setup-files.sh file in hypercube does not provide 10.0.0.1 IP to make-ca-certs, resulting in CA certs that are issued to the external cluster IP address rather then 10.0.0.1 -> this results in nginx-third-party-lb appearing to get stuck at "Utils.go:177 - Waiting for default/default-http-backend" in the docker logs. Kubernetes will eventually kill the container before nginx-third-party-lb times out with a message indicating that the CA certificate issuer is invalid (wrong ip), to verify this add zeros to the end of initialDelaySeconds and timeoutSeconds and reload the RC, and docker will log this error before kubernetes kills the container.
  • To fix the above, setup-files.sh must be patched before the cluster is inited (refer to https://github.com/kubernetes/kubernetes/pull/21504)

Custom errors

The default backend provides a way to customize the default 404 page. This helps but sometimes is not enough. Using the flag --custom-error-service is possible to use an image that must be 404 compatible and provide the route /error Here there is an example of the the image

The route /error expects two arguments: code and format

• code defines the wich error code is expected to be returned (502,503,etc.)
• format the format that should be returned For instance /error?code=504&format=json or /error?code=502&format=html

Using a volume pointing to /var/www/html directory is possible to use a custom error

Debug

Using the flag --v=XX it is possible to increase the level of logging. In particular:

• --v=2 shows details using diff about the changes in the configuration in nginx

I0316 12:24:37.581267       1 utils.go:148] NGINX configuration diff a//etc/nginx/nginx.conf b//etc/nginx/nginx.conf
I0316 12:24:37.581356       1 utils.go:149] --- /tmp/922554809  2016-03-16 12:24:37.000000000 +0000
+++ /tmp/079811012  2016-03-16 12:24:37.000000000 +0000
@@ -235,7 +235,6 @@

     upstream default-echoheadersx {
         least_conn;
-        server 10.2.112.124:5000;
         server 10.2.208.50:5000;

     }
I0316 12:24:37.610073       1 command.go:69] change in configuration detected. Reloading...

• --v=3 shows details about the service, Ingress rule, endpoint changes and it dumps the nginx configuration in JSON format
• --v=5 configures NGINX in debug mode

Retries in no idempotent methods

Since 1.9.13 NGINX will not retry non-idempotent requests (POST, LOCK, PATCH) in case of an error. The previous behavior can be restored using retry-non-idempotent=true in the configuration ConfigMap

Limitations

• Ingress rules for TLS require the definition of the field host