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132 lines
2.9 KiB
Markdown
132 lines
2.9 KiB
Markdown
# Accessing internal services
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- When we are logged in on a cluster node, we can access internal services
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(by virtue of the Kubernetes network model: all nodes can reach all pods and services)
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- When we are accessing a remote cluster, things are different
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(generally, our local machine won't have access to the cluster's internal subnet)
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- How can we temporarily access a service without exposing it to everyone?
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--
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- `kubectl proxy`: gives us access to the API, which includes a proxy for HTTP resources
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- `kubectl port-forward`: allows forwarding of TCP ports to arbitrary pods, services, ...
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---
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## Suspension of disbelief
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The exercises in this section assume that we have set up `kubectl` on our
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local machine in order to access a remote cluster.
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We will therefore show how to access services and pods of the remote cluster,
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from our local machine.
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You can also run these exercises directly on the cluster (if you haven't
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installed and set up `kubectl` locally).
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Running commands locally will be less useful
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(since you could access services and pods directly),
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but keep in mind that these commands will work anywhere as long as you have
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installed and set up `kubectl` to communicate with your cluster.
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---
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## `kubectl proxy` in theory
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- Running `kubectl proxy` gives us access to the entire Kubernetes API
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- The API includes routes to proxy HTTP traffic
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- These routes look like the following:
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`/api/v1/namespaces/<namespace>/services/<service>/proxy`
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- We just add the URI to the end of the request, for instance:
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`/api/v1/namespaces/<namespace>/services/<service>/proxy/index.html`
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- We can access `services` and `pods` this way
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---
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## `kubectl proxy` in practice
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- Let's access the `webui` service through `kubectl proxy`
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.exercise[
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- Run an API proxy in the background:
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```bash
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kubectl proxy &
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```
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- Access the `webui` service:
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```bash
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curl localhost:8001/api/v1/namespaces/default/services/webui/proxy/index.html
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```
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- Terminate the proxy:
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```bash
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kill %1
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```
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]
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---
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## `kubectl port-forward` in theory
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- What if we want to access a TCP service?
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- We can use `kubectl port-forward` instead
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- It will create a TCP relay to forward connections to a specific port
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(of a pod, service, deployment...)
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- The syntax is:
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`kubectl port-forward service/name_of_service local_port:remote_port`
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- If only one port number is specified, it is used for both local and remote ports
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---
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## `kubectl port-forward` in practice
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- Let's access our remote Redis server
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.exercise[
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- Forward connections from local port 10000 to remote port 6379:
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```bash
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kubectl port-forward svc/redis 10000:6379 &
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```
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- Connect to the Redis server:
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```bash
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telnet localhost 10000
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```
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- Issue a few commands, e.g. `INFO server` then `QUIT`
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<!--
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```wait Connected to localhost```
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```keys INFO server```
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```key ^J```
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```keys QUIT```
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```key ^J```
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-->
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- Terminate the port forwarder:
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```bash
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kill %1
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```
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]
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