This example is part of a suite of examples showing the different ways you can use Skupper to connect services across cloud providers, data centers, and edge sites.
- Overview
- Prerequisites
- Step 1: Install the Skupper command-line tool
- Step 2: Set up your namespaces
- Step 3: Deploy the TCP server
- Step 4: Create your sites
- Step 5: Link your sites
- Step 6: Expose the TCP server
- Step 7: Run the TCP client
- Cleaning up
- Summary
- Next steps
- About this example
This example shows you how you can use Skupper to connect a TCP client on one Kubernetes cluster to a TCP server on another.
-
The
kubectl
command-line tool, version 1.15 or later (installation guide) -
Access to at least one Kubernetes cluster, from any provider you choose
This example uses the Skupper command-line tool to deploy Skupper.
You need to install the skupper
command only once for each
development environment.
On Linux or Mac, you can use the install script (inspect it here) to download and extract the command:
curl https://skupper.io/install.sh | sh
The script installs the command under your home directory. It prompts you to add the command to your path if necessary.
For Windows and other installation options, see Installing Skupper.
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:
- Minikube
- 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
In Private, use kubectl create deployment
to deploy the TCP
server.
Private:
kubectl create deployment tcp-server --image quay.io/skupper/tcp-example-server
Sample output:
$ kubectl create deployment tcp-server --image quay.io/skupper/tcp-example-server
deployment.apps/tcp-server created
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.
Note: If you are using Minikube, you need to start minikube
tunnel before you run skupper init
.
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.
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.
In Private, use skupper expose
to expose the TCP server on all
linked sites.
Private:
skupper expose deployment/tcp-server --port 9090
Sample output:
$ skupper expose deployment/tcp-server --port 9090
deployment tcp-server exposed as tcp-server
In Public, use kubectl run
to run the TCP client. Here we
send "hello" and get "HELLO" echoed back from the server.
Public:
echo "hello" | kubectl run tcp-client --stdin --rm --image=quay.io/skupper/tcp-example-client --restart=Never -- tcp-server 9090
Sample output:
$ echo "hello" | kubectl run tcp-client --stdin --rm --image=quay.io/skupper/tcp-example-client --restart=Never -- tcp-server 9090
tcp-server-54c997c697-7ql7r: HELLO
pod "tcp-client" deleted
To remove Skupper and the other resources from this exercise, use the following commands.
Public:
skupper delete
Private:
skupper delete
kubectl delete deployment/tcp-server
Check out the other examples on the Skupper website.
This example was produced using Skewer, a library for documenting and testing Skupper examples.
Skewer provides utility functions for generating the README and
running the example steps. Use the ./plano
command in the project
root to see what is available.
To quickly stand up the example using Minikube, try the ./plano demo
command.