I'm very new to k8s and the related stuff, so this may be a stupid question: How to change the pod name?
I am aware the pod name seems set in the helm file, in my values.yaml, I have this:
...
hosts:
- host: staging.application.com
paths:
...
- fullName: application
svcPort: 80
path: /*
...
Since the application is running in the prod and staging environment, and the pod name is just something like application-695496ec7d-94ct9, I can't tell which pod is for prod or staging and can't tell if a request if come from the prod or not. So I changed it to:
hosts:
- host: staging.application.com
paths:
...
- fullName: application-staging
svcPort: 80
path: /*
I deployed it to staging, pod updated/recreated automatically but the pod name still remains the same. I was confused about that, and I don't know what is missing. I'm not sure if it is related to the fullnameOverride, but it's empty so it should be fine.
...the pod name still remains the same
The code snippet in your question likely the helm values for Ingress. In this case not related to Deployment of Pod.
Look into your helm template that define the Deployment spec for the pod, search for the name and see which helm value was assigned to it:
apiVersion: apps/v1
kind: Deployment
metadata:
name: busybox # <-- change & you will see the pod name change along. the helm syntax surrounding this field will tell you how the name is construct/assign
labels:
app: busybox
spec:
replicas: 1
selector:
matchLabels:
app: busybox
template:
metadata:
labels:
app: busybox
spec:
containers:
- name: busybox
image: busybox
imagePullPolicy: IfNotPresent
command: ["ash","-c","sleep 3600"]
Save the spec and apply, check with kubectl get pods --selector app=busybox. You should see 1 pod with name busybox prefix. Now if you open the file and change the name to custom and re-apply and get again, you will see 2 pods with different name prefix. Clean up with kubectl delete deployment busybox custom.
This example shows how the name of the Deployment is used for pod(s) underneath. You can paste your helm template surrounding the name field to your question for further examination if you like.
I would like to deploy a bunch of yaml files https://github.com/quay/quay/tree/master/deploy/k8s on my kubernetes cluster and would like to know, what is the best approach to deploy these at once.
You can directly apply folder
kubectl create -f ./<foldername>
kubectl apply -f ./<foldername>
You can also add mutiliple files in one command
kubectl apply -f test.yaml,test-1.yaml
You can also merge all YAML files into a single file and manage it further.
Marge YAML file using ---
For example :
apiVersion: v1
kind: Service
metadata:
name: test-data
labels:
app: test-data
spec:
ports:
- name: http
port: 80
targetPort: 9595
- name: https
port: 9595
targetPort: 9595
selector:
app: test-data
tier: frontend
---
apiVersion: v1
kind: Service
metadata:
name: test-app
labels:
app: test-app
spec:
ports:
- name: http
port: 80
targetPort: 9595
- name: https
port: 9595
targetPort: 9595
selector:
app: test-app
tier: frontend
kubectl apply -f <folder-name>
A simple way to deploy all files in a given folder.
You may consider using Helm (The package manager for Kubernetes). Just like we use yum or apt-get for Linux, we use helm for k8s.
Using Helm, you can deploy multiple resources (bunch of YAMLs) in one go. Helm Charts help you define, install, and upgrade even the most complex Kubernetes application. Helm uses a packaging format called charts. A chart is a collection of files that describe a related set of Kubernetes resources. A single chart might be used to deploy something simple, like a memcached pod, or something complex, like a full web app stack with HTTP servers, databases, caches, and so on. Also, you don't need to combine all your YAMLs; they can remain separate as part of a given chart. Besides, if one chart depends on another, you can use the helm dependency feature.
The reason why i use Helm is because whenever i deploy a chart, helm tracks it as a release. Any change to a chart get a new release version. This way, upgrade (or rollback) becomes very easy and you can confidently say what went as part of a given release.
Also, if you have different microservices that have stuff in common, then helm provides a feature called Library Chart using which you can create definitions that can be re-used across charts, thus keeping your charts DRY.
Have a look at this introductory video: https://www.youtube.com/watch?v=Zzwq9FmZdsU&t=2s
I would advise linking the yaml's into one. The purpose of a deployment and service yaml is to deploy your application onto the cluster in one fell swoop. You can define many deployments and services within the one file. In your case, a tool such as Kustomize will help you combine them. Kustomize comes preinstalled with kubectl.
You can combine your yamls called a Multi-Resource yaml into one file using the --- operator. i.e.
apiVersion: v1
kind: Service
metadata:
name: foo
spec:
...
---
apiVersion: v1
kind: Service
metadata:
name: bar
spec:
...
Then make a kustomization.yaml which combines all your multi-resource yamls. There is a good guide on this here: https://levelup.gitconnected.com/kubernetes-merge-multiple-yaml-into-one-e8844479a73a
The documentation from k8 is here: https://kubernetes.io/docs/tasks/manage-kubernetes-objects/kustomization/
I have a pod that is defined by a deployment, and the yaml definition is stored in my codebase. There are time when I'd like to have a volume mount configured for the pod/container, so it would be great to have a script that could enable this. I know I can use kubectl edit to open up an editor and do this (then restart the pod), but it would be more applicable if our devs could simply do something like ./our_scripts/enable_mount.sh.
One option would be to simply have a copy of the YAML definition and create/apply that while deleting the other, but it would be nicer to modify the existing one in place.
Is there a way to achieve this? Does kubectl edit have any flags that I'm missing to achieve this?
Use Declarative Management of Kubernetes Objects Using Kustomize. You already have a deployment.yaml manifest in your codebase. Now, move that to base/deployment.yaml and also create a overlays/with-mount/deployment-with-mount.yaml that overrides with an mount when you want.
To deploy the base, you use
kubectl apply -k base/deployment.yaml
and when you want to deploy and also override so you get a mount, you use
kubectl apply -k overlays/with-mount/deployment-with-mount.yaml
You want to deploy pod differently on different conditions on environment. Helm allows you do it. You could have one template for the pod and then pass in values that change based on environment or conditions you want to run.
helm install --values ./k8s/charts/values1.yaml <chartname>
or
helm install --values ./k8s/charts/values2.yaml <chartname>
If this only need for templating then using helm may seem more involved. Potentially other solution could be to use a python script that manipulates yaml
Below is quick sample that works for python 2.7
import yaml
document = """
apiVersion: v1
kind: Pod
metadata:
name: myapp
labels:
name: myapp
spec:
containers:
- name: myapp
image: nginx
"""
volumemount = True
podSpec = yaml.load(document)
if volumemount:
volumeSpecDoc = """
volumes:
- configMap:
name: app-config
name : app-config-volume
"""
volumeSpec = yaml.load(volumeSpecDoc, Loader=yaml.FullLoader)
podSpec['spec'].update(volumeSpec)
containerVolumeMountDoc = """
volumeMounts:
- name: app-config-volume
mountPath: /etc/config
"""
containerVolumeMount = yaml.load(containerVolumeMountDoc,Loader=yaml.FullLoader)
original = podSpec['spec']['containers'][0]
original.update(containerVolumeMount)
podSpec['spec']['containers'][0] = original
print yaml.dump(podSpec)
I'd like to elaborate on reply made by #jonas .
One of the "advanced" commands for kubectl is kustomize.
It builds a kustomization target from a directory or a remote url.
Available from v1.14
it supports a few types of functionality
generating resources from other sources
setting cross-cutting fields for resources
composing and customizing collections of resources
I know I can use kubectl edit to open up an editor and do this (then restart the pod), but it would be more applicable if our devs could simply do something like ./our_scripts/enable_mount.sh.
"composing and customizing collections of resources" feature looks like the one you may consider in this context.
it may be an overkill if you like to bring up single pod (single yaml file); however it is useful if you need to do something that is a bit more complex :)
$ ls -go
total 28
-rw-r--r-- 1 49 Dec 17 13:23 kustomization.yaml
-rw-r--r-- 1 119 Dec 17 13:22 pod_no_volume.yaml
-rw-r--r-- 1 275 Dec 17 13:22 pod_with_volume.yaml
-rw-r--r-- 1 160 Dec 17 13:19 service.yaml
$ cat kustomization.yaml
resources:
- pod_with_volume.yaml
- service.yaml
If you run kubectl kustomize <dir> (here dir stands for the directory, your kustomization.yaml sits in and in my example it's just a . ) ,you can see that kubectl come up with the new objects to be applied:
$ kubectl kustomize .
apiVersion: v1
kind: Service
metadata:
labels:
run: my-nginx
name: my-nginx
spec:
ports:
- port: 80
protocol: TCP
selector:
run: my-nginx
---
apiVersion: v1
kind: Pod
metadata:
name: test-nginx-with-volume
spec:
containers:
- image: nginx
name: nginx
volumeMounts:
- mountPath: /etc/nginx/conf.d/
name: nginx-path
volumes:
- hostPath:
path: /tmp/somePath/conf.d
name: nginx-path
As you can guess it is merely a "concat" of
pod_with_volume.yaml
service.yaml
The only peculiarity of this method is that the file you are referring to shall be in or below the directory the kustomization.yaml sits in.
As you can see, ./our_scripts/enable_mount.sh can merely call properly formatted kubectl kustomize <dir> command
Hope you'll find this answer useful :)
I've found a documentation about how to configure your NginX ingress controller using ConfigMap: https://kubernetes.github.io/ingress-nginx/user-guide/nginx-configuration/configmap/
Unfortunately I've no idea and couldn't find it anywhere how to load that ConfigMap from my Ingress controller.
My ingress controller:
helm install --name ingress --namespace ingress-nginx --set rbac.create=true,controller.kind=DaemonSet,controller.service.type=ClusterIP,controller.hostNetwork=true stable/nginx-ingress
My config map:
kind: ConfigMap
apiVersion: v1
metadata:
name: ingress-configmap
data:
proxy-read-timeout: "86400s"
client-max-body-size: "2g"
use-http2: "false"
My ingress:
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: ingress
annotations:
nginx.ingress.kubernetes.io/backend-protocol: "HTTPS"
spec:
tls:
- hosts:
- my.endpoint.net
secretName: ingress-tls
rules:
- host: my.endpoint.net
http:
paths:
- path: /
backend:
serviceName: web
servicePort: 443
- path: /api
backend:
serviceName: api
servicePort: 443
How do I make my Ingress to load the configuration from the ConfigMap?
I've managed to display what YAML gets executed by Helm using the: --dry-run --debug options at the end of helm install command. Then I've noticed that there controller is executed with the: --configmap={namespace-where-the-nginx-ingress-is-deployed}/{name-of-the-helm-chart}-nginx-ingress-controller.
In order to load your ConfigMap you need to override it with your own (check out the namespace).
kind: ConfigMap
apiVersion: v1
metadata:
name: {name-of-the-helm-chart}-nginx-ingress-controller
namespace: {namespace-where-the-nginx-ingress-is-deployed}
data:
proxy-read-timeout: "86400"
proxy-body-size: "2g"
use-http2: "false"
The list of config properties can be found here.
One can pass config mag properties at the time of installation too:
helm install stable/nginx-ingress --name nginx-ingress --set controller.config.use-forwarded-headers='"true"'
NOTE: for non-string values had to use single quotes around double quotes to get it working.
If you used helm install to install the ingress-nginx, if no explicit value for which ConfigMap the nginx controller should look at was passed, the default value seems like it is {namespace}/{release-name}-nginx-ingress-controller. This is generated by https://github.com/helm/charts/blob/1e074fc79d0f2ee085ea75bf9bacca9115633fa9/stable/nginx-ingress/templates/controller-deployment.yaml#L67. (See similar if it's a dead link).
To verify for yourself, try to find your command that you installed the ingress-nginx chart with, and add --dry-run --debug to the command. This will show you the yaml files generated by Tiller to be applied to the cluster. The line # Source: nginx-ingress/templates/controller-deployment.yaml begins the controller deployment which has an arg of --configmap=. The value of this arg is what needs to be the name of the ConfigMap for the controller to sense, and use to update its own .conf file. This could be passed explicitly, but if it is not, it will have a default value.
If a ConfigMap is created with the RIGHT name, the controller's logs will show that it picked up the configuration change and reloaded itself.
This can be verified with kubectl logs <pod-name-of-controller> -n <namespace-arg-if-not-in-default-namespace>. My log messages contained the text Configuration changes detected, backend reload required. These log messages will not be present if the ConfigMap name was wrong.
I believe the official documentation for this is unnecessarily lacking, but maybe I'm incorrect? I will try to submit a PR with these details. Someone who knows more should help flesh them out so people don't need to stumble on this unnecessarily.
Cheers, thanks for your post.
If you want to give your own configuration while deploying nginx-ingress-controller, you can have a wrapper Helm chart over the original nginx-ingress Helm chart and provide your own values.yaml which can have custom configuration.
Using Helm 3 here.
Create a chart:
$ helm create custom-nginx
$ tree custom-nginx
So my chart structure looks like this:
custom-nginx/
├── Chart.yaml
├── charts
├── templates
│ ├── NOTES.txt
│ ├── _helpers.tpl
│ ├── deployment.yaml
│ ├── hpa.yaml
│ ├── ingress.yaml
│ ├── service.yaml
│ ├── serviceaccount.yaml
│ └── tests
│ └── test-connection.yaml
└── values.yaml
There are a few extra things here. Specifically, I don't need the complete templates/ directory and its contents, so I'll just remove those:
$ rm custom-nginx/templates/*
$ rmdir custom-nginx/templates
Now, the chart structure should look like this:
custom-nginx/
├── Chart.yaml
├── charts
└── values.yaml
Since, we've to include the original nginx-ingress chart as a dependency, my Chart.yaml looks like this:
$ cat custom-nginx/Chart.yaml
apiVersion: v2
name: custom-nginx
description: A Helm chart for Kubernetes
# A chart can be either an 'application' or a 'library' chart.
#
# Application charts are a collection of templates that can be packaged into versioned archives
# to be deployed.
#
# Library charts provide useful utilities or functions for the chart developer. They're included as
# a dependency of application charts to inject those utilities and functions into the rendering
# pipeline. Library charts do not define any templates and therefore cannot be deployed.
type: application
# This is the chart version. This version number should be incremented each time you make changes
# to the chart and its templates, including the app version.
# Versions are expected to follow Semantic Versioning (https://semver.org/)
version: 1.39.1
# This is the version number of the application being deployed. This version number should be
# incremented each time you make changes to the application. Versions are not expected to
# follow Semantic Versioning. They should reflect the version the application is using.
appVersion: 0.32.0
dependencies:
- name: nginx-ingress
version: 1.39.1
repository: https://kubernetes-charts.storage.googleapis.com/
Here, appVersion is the nginx-controller docker image version and version matches with the nginx-ingress chart version that I am using.
The only thing left is to provide your custom configuration. Here is an stripped down version of my custom configuration:
$ cat custom-nginx/values.yaml
# Default values for custom-nginx.
# This is a YAML-formatted file.
# Declare variables to be passed into your templates.
nginx-ingress:
controller:
ingressClass: internal-nginx
replicaCount: 1
service:
externalTrafficPolicy: Local
publishService:
enabled: true
autoscaling:
enabled: true
minReplicas: 1
maxReplicas: 3
targetCPUUtilizationPercentage: "80"
targetMemoryUtilizationPercentage: "80"
resources:
requests:
cpu: 1
memory: 2Gi
limits:
cpu: 1
memory : 2Gi
metrics:
enabled: true
config:
compute-full-forwarded-for: "true"
We can check the keys that are available to use as configuration (config section in values.yaml) in https://kubernetes.github.io/ingress-nginx/user-guide/nginx-configuration/configmap/
And the rest of the configuration can be found here: https://github.com/helm/charts/tree/master/stable/nginx-ingress#configuration
Once configurations are set, just download the dependency of your chart:
$ helm dependency update <path/to/chart>
It's a good practice to do basic checks on your chart before deploying it:
$ helm lint <path/to/chart>
$ helm install --debug --dry-run --namespace <namespace> <release-name> <path/to/chart>
Then deploy your chart (which will deploy your nginx-ingress-controller with your own custom configurations).
Also, since you've a chart now, you can upgrade and rollback your chart.
When installing the chart through terraform, the configuration values can be set as shown below:
resource "helm_release" "ingress_nginx" {
name = "nginx"
repository = "https://kubernetes.github.io/ingress-nginx/"
chart = "ingress-nginx"
set {
name = "version"
value = "v4.0.2"
}
set {
name = "controller.config.proxy-read-timeout"
value = "86400s"
}
set {
name = "controller.config.client-max-body-size"
value = "2g"
}
set {
name = "controller.config.use-http2"
value = "false"
}
}
Just to confirm #NeverEndingQueue answer above, the name of the config map is present in the nginx-controller pod spec itself, so if you inspect the yaml of the nginx-controller pod: kubectl get po release-name-nginx-ingress-controller-random-sequence -o yaml, under spec.containers, you will find something like:
- args:
- /nginx-ingress-controller
- --default-backend-service=default/release-name-nginx-ingress-default-backend
- --election-id=ingress-controller-leader
- --ingress-class=nginx
- --configmap=default/release-name-nginx-ingress-controller
For example here, a config map named release-name-nginx-ingress-controller in the namespace default needs to be created.
Once done, you can verify if the changes have taken place by checking the logs. Normally, you will see something like:
I1116 10:35:45.174127 6 event.go:278] Event(v1.ObjectReference{Kind:"ConfigMap", Namespace:"default", Name:"release-name-nginx-ingress-controller", UID:"76819abf-4df0-41e3-a3fe-25445e754f32", APIVersion:"v1", ResourceVersion:"62559702", FieldPath:""}): type: 'Normal' reason: 'CREATE' ConfigMap default/release-name-nginx-ingress-controller
I1116 10:35:45.184627 6 controller.go:141] Configuration changes detected, backend reload required.
I1116 10:35:45.396920 6 controller.go:157] Backend successfully reloaded.
When you apply ConfigMap configuration with needful key-value data, Ingress controller picks up this information and insert it to the nested nginx-ingress-controller Pod's original configuration file /etc/nginx/nginx.conf, therefore it's easy afterwards to verify whether ConfigMap's values have been successfully reflected or not, by checking actual nginx.conf inside the corresponded Pod.
You can also check logs from the relevant nginx-ingress-controller Pod in order to check whether ConfigMap data already reloaded to the backend nginx.conf, or if not to investigate the reason.
Using enable-underscores-in-headers=true worked for me not enable-underscores-in-headers='"true"'
helm install nginx-ingress ingress-nginx/ingress-nginx
--namespace ingress-basic
--set controller.config.enable-underscores-in-headers=true
I managed to update the "large-client-header-buffers" in the nginx via configmap. Here are the steps I have followed..
Find the configmap name in the nginx ingress controller pod describition
kubectl -n utility describe pods/test-nginx-ingress-controller-584dd58494-d8fqr |grep configmap
--configmap=test-namespace/test-nginx-ingress-controller
Note: In my case, the namespace is "test-namespace" and the configmap name is "test-nginx-ingress-controller"
Create a configmap yaml
cat << EOF > test-nginx-ingress-controller-configmap.yaml
kind: ConfigMap
apiVersion: v1
metadata:
name: test-nginx-ingress-controller
namespace: test-namespace
data:
large-client-header-buffers: "4 16k"
EOF
Note: Please replace the namespace and configmap name as per finding in the step 1
Deploy the configmap yaml
kubectl apply -f test-nginx-ingress-controller-configmap.yaml
Then you will see the change is updated to nginx controller pod after mins
i.g.
kubectl -n test-namespace exec -it test-nginx-ingress-controller-584dd58494-d8fqr -- cat /etc/nginx/nginx.conf|grep large
large_client_header_buffers 4 16k;
Based on the NeverEndingQueue's answer I want to provide an update for Kubernetes v1.23 / Helm 3
This is my installation command + --dry-run --debug part:
helm upgrade --install ingress-nginx ingress-nginx/ingress-nginx --namespace ingress-nginx --create-namespace --dry-run --debug
This is the part we need from the generated output of the command above:
apiVersion: apps/v1
kind: DaemonSet
metadata:
...
spec:
...
template:
...
spec:
dnsPolicy: ClusterFirst
containers:
- name: controller
...
args:
- /nginx-ingress-controller
- --publish-service=$(POD_NAMESPACE)/ingress-nginx-controller
- --...
- --configmap=${POD_NAMESPACE}/ingress-nginx-controller
- --...
....
We need this part: --configmap=${POD_NAMESPACE}/ingress-nginx-controller.
As you can see, name of ConfigMap must be ingress-nginx-controller and namespace must be the one you use during chart installation (ie {POD_NAMESPACE}, in my example about this is --namespace ingress-nginx).
# nginx-config.yaml
apiVersion: v1
kind: ConfigMap
metadata:
name: ingress-nginx-controller
namespace: ingress-nginx
data:
map-hash-bucket-size: "128"
Then run kubectl apply -f nginx-config.yaml to apply ConfigMap and nginx's pod(s) will be auto-reloaded with updated config.
To check, that nginx config has been updated, find name of nginx's pod (you can use any one, if you have few nodes): kubectl get pods -n ingress-nginx (or kubectl get pods -A)
and then check config: kubectl exec -it ingress-nginx-controller-{generatedByKubernetesId} -n ingress-nginx cat /etc/nginx/nginx.conf
UPDATE:
The correct name (ie name: ingress-nginx-controller) is shown in the official docs. Conclusion: no need to reinvent the wheel.
What you have is an ingress yaml and not an Ingress controller deployment yaml , Ingress Controller is the Pod that actually does the work and usually is an nginx container itself. An example of such a configuration can be found here in the documentation you shared.
UPDATE
Using that example provided , you can also use following way to load config into nginx using config map
volumeMounts:
- name: nginx-config
mountPath: /etc/nginx/nginx.conf
subPath: nginx.conf
volumes:
- name: nginx-config
configMap:
name: nginx-config
nginx-config contains your nginx configuration as part of config map
I read the above answers but could not make it work.
What worked for me was the following:
release_name=tcp-udp-ic
# add the helm repo from NginX and update the chart
helm repo add nginx-stable https://helm.nginx.com/stable
helm repo update
echo "- Installing -${release_name}- into cluster ..."
#delete the config map if already exists
kubectl delete cm tcp-udp-ic-cm
helm del --purge ${release_name}
helm upgrade --install ${release_name} \
--set controller.image.tag=1.6.0 \
--set controller.config.name=tcp-udp-ic-cm \
nginx-stable/nginx-ingress --version 0.4.0 #--dry-run --debug
# update the /etc/nginx/nginx.conf file with my attributes, via the config map
kubectl apply -f tcp-udp-ic-cm.yaml
and the tcp-udp-ic-cm.yaml is :
kind: ConfigMap
apiVersion: v1
metadata:
name: tcp-udp-ic-cm
namespace: default
data:
worker-connections : "10000"
Essentially I need to deploy with helm the release and set the name of the config-map that is going to use. Helm creates the config-map but empty. Then I apply the config-map file in order to update the config-map resource with my values. This sequence is the only one i could make work.
An easier way of doing this is just modifying the values that's deployed through helm. The values needed to be changed to enter to ConfigMap are now in controller.config.entries. Show latest values with: helm show values nginx-stable/nginx-ingress and look for the format on the version you are running.
I had tons of issues with this since all references online said controller.config, until I checked with the command above.
After you've entered the values upgrade with:
helm upgrade -f <PATH_TO_FILE>.yaml <NAME> nginx-stable/nginx-ingress
The nginx ingress controller may cause issues with forwarding. While we were able to get it working with nginx, via X-Forwarded-Proto etc., but it was a bit complicated and convoluted.
Moving to haproxy instead resolved this problem. As well, make sure you are interfacing with the ingress controller over https or that may cause issues with keycloak.
Keycloak v18 with --proxy edge
annotations:
kubernetes.io/ingress.class: haproxy
...
Is there any way to pass image version from a varibale/config when passing a manifest .yaml to kubectl command
Example :
apiVersion: v1
kind: ReplicationController
metadata:
name: nginx
spec:
replicas: 1
selector:
app: nginx
template:
metadata:
name: nginx
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx:${IMAGE_VERSION}
imagePullPolicy: Always
resources:
limits:
cpu: "1.2"
memory: 100Mi
ports:
- containerPort: 80
Use case is to launch specific image version which is set at kubernetes level, and that the variable is resolved by kubernetes itself at server side.
Thanks and Regards,
Ravi
k8s manifest files are static yaml/json.
If you would like to template the manifests (and manage multiple resources in a bundle-like fashion), I strongly recommend you to have a look at Helm
I've recently created a Workshop which focuses precisely on the "Templating" features of Helm.
Helm does a lot more than just templating, it is built as a full fledged package manager for Kubernetes applications (think Apt/Yum/Homebrew).
If you want to handle everything client side, have a look at https://github.com/errordeveloper/kubegen
Although, at some point, you will need the other features of Helm and a migration will be needed when that time comes - I recommend biting the bullet and going for Helm straight up.
After looking into this recently we decided to just go with sed. Wrap kubectl apply into a small bash script and replace the placeholders before running apply.
We did look into more sophisticated tooling but we only found Helm. However Helm is a complex piece of technology that does way more than just templating. It changes your workflow a lot as you no longer deploy using kubectl and have to have a Helm package repo around to push your packages to. Our assessment was that Helm is not useful for deploying our application and using it for just the templating is overkill.
Here is an example how to do this with sed (it is a excerpt from my typical circleci config):
replaces="s/{.Namespace}/$CIRCLE_BRANCH/;";
replaces="$replaces s/{.CiBuild}/$CIRCLE_BUILD_NUM/; ";
replaces="$replaces s/{.CiCommit}/$CIRCLE_SHA1/; ";
replaces="$replaces s/{.CiUser}/$CIRCLE_USERNAME/; ";
cat ./k8s/app.yaml | sed -e "$replaces" | ./kubectl --kubeconfig=`pwd`/.kube/config apply --namespace=$NAMESPACE -f -