Chapter 5. Accessing an FTP server using Skupper

Prerequisites

• The kubectl command-line tool, version 1.15 or later (installation guide)
• Access to at least one Kubernetes cluster, from any provider you choose

Procedure

• Clone the repo for this example.
• Install the Skupper command-line tool
• Set up your namespaces
• Deploy the FTP server
• Create your sites
• Link your sites
• Expose the FTP server

• Run the FTP client

  1. Clone the repo for this example. Navigate to the appropriate GitHub repository from https://skupper.io/examples/index.html and clone the repository.

  2. Install the Skupper command-line tool

     This example uses the Skupper command-line tool to deploy Skupper. You need to install the skupper command only once for each development environment.

     See the Installation for details about installing the CLI. For configured systems, use the following command:

     sudo dnf install skupper-cli

  3. Set up your namespaces

     Skupper is designed for use with multiple Kubernetes namespaces, usually on different clusters. The skupper and kubectl commands use your kubeconfig and current context to select the namespace where they operate.

     Your kubeconfig is stored in a file in your home directory. The skupper and kubectl commands use the KUBECONFIG environment variable to locate it.

     A single kubeconfig supports only one active context per user. Since you will be using multiple contexts at once in this exercise, you need to create distinct kubeconfigs.

     For each namespace, open a new terminal window. In each terminal, set the KUBECONFIG environment variable to a different path and log in to your cluster. Then create the namespace you wish to use and set the namespace on your current context.

     Note

     The login procedure varies by provider. See the documentation for yours:

     • Amazon Elastic Kubernetes Service (EKS)
     • Azure Kubernetes Service (AKS)
     • Google Kubernetes Engine (GKE)
     • IBM Kubernetes Service
     • OpenShift

     Public:

     export KUBECONFIG=~/.kube/config-public
     # Enter your provider-specific login command
     kubectl create namespace public
     kubectl config set-context --current --namespace public

     Private:

     export KUBECONFIG=~/.kube/config-private
     # Enter your provider-specific login command
     kubectl create namespace private
     kubectl config set-context --current --namespace private

  4. Deploy the FTP server

     In Private, use kubectl apply to deploy the FTP server.

     Private:

     kubectl apply -f server

     Sample output:

     $ kubectl apply -f server
     deployment.apps/ftp-server created

  5. Create your sites

     A Skupper site is a location where components of your application are running. Sites are linked together to form a network for your application. In Kubernetes, a site is associated with a namespace.

     For each namespace, use skupper init to create a site. This deploys the Skupper router and controller. Then use skupper status to see the outcome.

     Public:

     skupper init
     skupper status

     Sample output:

     $ skupper init
     Waiting for LoadBalancer IP or hostname...
     Waiting for status...
     Skupper is now installed in namespace 'public'.  Use 'skupper status' to get more information.
     
     $ skupper status
     Skupper is enabled for namespace "public". It is not connected to any other sites. It has no exposed services.

     Private:

     skupper init
     skupper status

     Sample output:

     $ skupper init
     Waiting for LoadBalancer IP or hostname...
     Waiting for status...
     Skupper is now installed in namespace 'private'.  Use 'skupper status' to get more information.
     
     $ skupper status
     Skupper is enabled for namespace "private". It is not connected to any other sites. It has no exposed services.

     As you move through the steps below, you can use skupper status at any time to check your progress.

  6. Link your sites

     A Skupper link is a channel for communication between two sites. Links serve as a transport for application connections and requests.

     Creating a link requires use of two skupper commands in conjunction, skupper token create and skupper link create.

     The skupper token create command generates a secret token that signifies permission to create a link. The token also carries the link details. Then, in a remote site, The skupper link create command uses the token to create a link to the site that generated it.

     Note

     The link token is truly a secret. Anyone who has the token can link to your site. Make sure that only those you trust have access to it.

     First, use skupper token create in site Public to generate the token. Then, use skupper link create in site Private to link the sites.

     Public:

     skupper token create ~/secret.token

     Sample output:

     $ skupper token create ~/secret.token
     Token written to ~/secret.token

     Private:

     skupper link create ~/secret.token

     Sample output:

     $ skupper link create ~/secret.token
     Site configured to link to https://10.105.193.154:8081/ed9c37f6-d78a-11ec-a8c7-04421a4c5042 (name=link1)
     Check the status of the link using 'skupper link status'.

     If your terminal sessions are on different machines, you may need to use scp or a similar tool to transfer the token securely. By default, tokens expire after a single use or 15 minutes after creation.

  7. Expose the FTP server

     In Private, use skupper expose to expose the FTP server on all linked sites.

     Private:

     skupper expose deployment/ftp-server --port 21100 --port 21

     Sample output:

     $ skupper expose deployment/ftp-server --port 21100 --port 21
     deployment ftp-server exposed as ftp-server

  8. Run the FTP client

     In Public, use kubectl run and the curl image to perform FTP put and get operations.

     Public:

     echo "Hello!" | kubectl run ftp-client --stdin --rm --image=docker.io/curlimages/curl --restart=Never -- -s -T - ftp://example:example@ftp-server/greeting
     kubectl run ftp-client --attach --rm --image=docker.io/curlimages/curl --restart=Never -- -s ftp://example:example@ftp-server/greeting

     Sample output:

     $ echo "Hello!" | kubectl run ftp-client --stdin --rm --image=docker.io/curlimages/curl --restart=Never -- -s -T - ftp://example:example@ftp-server/greeting
     pod "ftp-client" deleted
     
     $ kubectl run ftp-client --attach --rm --image=docker.io/curlimages/curl --restart=Never -- -s ftp://example:example@ftp-server/greeting
     Hello!
     pod "ftp-client" deleted