Categories
Kubernetes

Kubernetes Service names in HELM templates

Based on my previous post, here comes a snippet that will correctly produce a full DNS name of a service in the cluster from the same namespace.

{{/*
Makes a full hostname from the given string if it's not one already or an IP address.
Attaches ".<namespace>.svc.cluster.local" to the end and includes the release name if required.
Please note that you need to call this template with (dict "Context" . "Value" "your-value")
*/}}
{{- define "prefix.serviceName" -}}
{{- if include "prefix.isIpAddress" .Value }}
    {{- print .Value }}
{{- else -}}
    {{- $parts := splitList "." .Value -}}
    {{- if gt (len $parts) 1 -}}
        {{- print .Value }}
    {{- else -}}
        {{- if eq .Context.Chart.Name .Context.Release.Name -}}
            {{- printf "%s.%s.svc.cluster.local" .Value .Context.Release.Namespace }}
        {{- else -}}
            {{- printf "%s-%s.%s.svc.cluster.local" .Context.Release.Name .Value .Context.Release.Namespace }}
        {{- end -}}

    {{- end -}}
{{- end -}}
{{- end -}}

Please note that using the template is a bit more cumbersome due to some Go language issues:

serviceName-anIpAddress:  {{ include "prefix.serviceName" (dict "Context" . "Value" "1.2.3.4") }}
serviceName-anIpAddress2: {{ include "prefix.serviceName" (dict "Context" . "Value" "1.0.3.4") }}
serviceName-NoIpAddress:  {{ include "prefix.serviceName" (dict "Context" . "Value" "1.2.3.4.5") }}
serviceName-NoIpAddress2: {{ include "prefix.serviceName" (dict "Context" . "Value" "hello") }}
serviceName-NoIpAddress3: {{ include "prefix.serviceName" (dict "Context" . "Value" "hello.svc") }}
serviceName-NoIpAddress4: {{ include "prefix.serviceName" (dict "Context" . "Value" "hello.svc.cluster.local") }}
serviceName-NoIpAddress5: {{ include "prefix.serviceName" (dict "Context" . "Value" "1") }}

The template needs access to the root context. So the dict function is used to pass the context and the actual, simple service name.

Feel free to adjust the function when you need another namespace as an argument.

Categories
Kubernetes

HELM template to detect IP address

I was in a need to detect whether the content of a variable is an IP address or not. I guess the function is not perfect, but it fulfills the basic need:

{{/*
Test if the given value is an IP address
*/}}
{{- define "prefix.isIpAddress" -}}
{{- $rc := . -}}
{{- $parts := splitList "." . -}}
{{- if eq (len $parts) 4 -}}
    {{- range $parts -}}
        {{- if and (not (atoi .)) (ne . "0") -}}
            {{- $rc = "" -}}
        {{- end -}}
    {{- end -}}
{{- else -}}
    {{- $rc = "" -}}
{{- end -}}
{{- print $rc }}
{{- end -}}

The function at least detects these values correctly:

{{ include "prefix.isIpAddress" "1.2.3.4" }}
{{ include "prefix.isIpAddress" "1.0.3.4" }}
{{ include "prefix.isIpAddress" "1.2.3.4.5" }}
{{ include "prefix.isIpAddress" "hello" }}
{{ include "prefix.isIpAddress" "hello.svc" }}
{{ include "prefix.isIpAddress" "hello.svc.tld.com" }}
Categories
Kubernetes

IPv6 with Kubernetes

Awwww – so much work I had put into setting up a Kubernetes cluster (this blog will run there in a few days). I set up the pods and containers, cron jobs, services, and, and, and. Then I started renewing my SSL certificates from LetsEncrypt. This renewal failed hilariously, but with a weird error message:

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Timeout

What? I can reach my websites. Did I miss something? I checked connectivity. The IP addresses were right, the ACME challenge directory was available as required by LetsEncrypt, the DNS was working properly. Why couldn’t LetsEncrypt servers not reach my cluster? I soon found out that they prefer IPv6 over IPv4 which I had both enabled. But the IPv6 connection failed. From everywhere. Ping6 though succeeded.

Further analysis revealed that Kubernetes is not able to expose IPv6 services at all (or at least at now, so I researched). What shall I do now? All my work was based on the assumption that IPv4 and IPv6 will be there. But it’s not with Kubernetes. Of course I could move my reverse proxy out of Kubernetes and put it in front of it. But that would require more work as all the automation scripts for LetsEncrypt would need to be rebased. Testing again and again. Let aside the disadvantage of not having it all self-contained in containers anymore. Another solution must be there.

Luckily there was an easy solution: socat. It’s a small Linux tool that can copy network traffic from one socket to another. So that was setup easily with a systemd script (sock_80.service):

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[Unit]
 Description=socat Service 80
 After=network.target
 
[Service]
 Type=simple
 User=root
 ExecStart=/usr/bin/socat -lf /var/log/socat80.log TCP6-LISTEN:80,reuseaddr,fork,bind=[ip6-address-goes-here] TCP4:ip4-address-goes-here:80
 Restart=on-abort
 
[Install]
 WantedBy=multi-user.target

That’s it. Enabled it (systemctl enable sock_80.service), reloaded systemd (systemctl daemon-reload), and started the service (systemctl start sock_80). Voilá! Here we go. IPv6 traffic is now routed to IPv4. I repeated it with port 443 and the setup is done. And LetsEncrypt servers are happy too 🙂