G034 - Deploying services 03 ~ Gitea - Part 2 - Redis cache server.md

G034 - Deploying services 03 ~ Gitea - Part 2 - Redis cache server

Here you're going to setup a Redis server as a memory cache for Gitea, in a very similar way as you did for Nextcloud.

Kustomize project folders for Gitea and Redis

First, you have to create a folder for your Gitea's main Kustomize project and, within it, a directory tree for the Redis subproject. You can do this with just one mkdir command.

$ mkdir -p $HOME/k8sprjs/gitea/components/cache-redis/{configs,resources,secrets}

Redis configuration file

Prepare the redis.conf file that will specify some configuration values for your Redis server.

1. In the configs subfolder of the Redis project, create a redis.conf file.

   $ touch $HOME/k8sprjs/gitea/components/cache-redis/configs/redis.conf

2. Copy in redis.conf the lines below.

   port 6379
   bind 0.0.0.0
   protected-mode no
   maxmemory 64mb
   maxmemory-policy allkeys-lru

   The parameters are exactly the same ones you set up in the part 2 of the Nextcloud guide, go back to it if you don't remember the meaning of the values above.

Redis password

To make your Redis instance a bit more secure, you need to set it up with a long password.

1. Create a new redis.pwd file in the secrets folder.

   $ touch $HOME/k8sprjs/gitea/components/cache-redis/secrets/redis.pwd

2. In redis.pwd just type a long alphanumeric password for your Redis instance.

   Y0ur_rE3e41Ly.lOng-S3kreT_P4s5woRd-heRE!

   BEWARE!
   Be very careful about not leaving any kind of spurious characters at the end of the password, like a line break (\n), to avoid unexpected odd issues when this password is used.
   Also notice that the password is stored as a plain text here, so be careful about who access this file.

Redis Deployment resource

Since this Redis instance will only work with data in memory, you can set it up with a Deployment resource.

1. Create a cache-redis.deployment.yaml file under the resources subfolder.

   $ touch $HOME/k8sprjs/gitea/components/cache-redis/resources/cache-redis.deployment.yaml

2. In cache-redis.deployment.yaml copy the following yaml.

   apiVersion: apps/v1
   kind: Deployment
   
   metadata:
     name: cache-redis
   spec:
     replicas: 1
     template:
       spec:
         containers:
         - name: server
           image: redis:6.2-alpine
           command:
           - redis-server
           - "/etc/redis/redis.conf"
           - "--requirepass $(REDIS_PASSWORD)"
           env:
           - name: REDIS_PASSWORD
             valueFrom:
               secretKeyRef:
                 name: cache-redis
                 key: redis-password
           ports:
           - containerPort: 6379
           resources:
             limits:
               memory: 64Mi
           volumeMounts:
           - name: redis-config
             subPath: redis.conf
             mountPath: /etc/redis/redis.conf
         - name: metrics
           image: oliver006/redis_exporter:v1.32.0-alpine
           env:
           - name: REDIS_PASSWORD
             valueFrom:
               secretKeyRef:
                 name: cache-redis
                 key: redis-password
           resources:
             limits:
               memory: 32Mi
           ports:
           - containerPort: 9121
         volumes:
         - name: redis-config
           configMap:
             name: cache-redis
             defaultMode: 0444
             items:
             - key: redis.conf
               path: redis.conf
         affinity:
           podAffinity:
             requiredDuringSchedulingIgnoredDuringExecution:
               - labelSelector:
                   matchExpressions:
                   - key: app
                     operator: In
                     values:
                     - server-gitea
                 topologyKey: "kubernetes.io/hostname"

   This Deployment resource is almost identical to the one described in the part 2 of the Nextcloud guide. The only difference is in the labelSelector block set in the affinity.podAffinity section: the key is the same, app, but the value has been changed to server-gitea.

Redis Service resource

To expose Redis you need a Service resource.

1. Generate a new file named cache-redis.service.yaml, also under the resources subfolder.

   $ touch $HOME/k8sprjs/gitea/components/cache-redis/resources/cache-redis.service.yaml

2. Fill cache-redis.service.yaml with the content below.

   apiVersion: v1
   kind: Service
   
   metadata:
     name: cache-redis
     annotations:
       prometheus.io/scrape: "true"
       prometheus.io/port: "9121"
   spec:
     type: ClusterIP
     ports:
     - port: 6379
       protocol: TCP
       name: server
     - port: 9121
       protocol: TCP
       name: metrics

   This Service resource is the same as the one declared in the Nextcloud guide, except that it doesn't have a clusterIP explicitly set to a particular internal IP. And, since that cluster IP can change everytime the Service is restarted, you'll have to invoke it by its FQDN.

Redis Service's FQDN or DNS record

To know beforehand what DNS record will be assigned to this Service, be aware of the following.

• The string format for any Service resource's FQDN is <metadata.name>.<namespace>.svc.<internal.cluster.domain>.
• The namespace for all resources of the Gitea platform will be gitea.
• The internal cluster domain that was set back in the G025 guide is deimos.cluster.io.
• All the components of the Gitea platform will also have a gitea- prefix added to their metadata.name string.

Taking all of the above into account, the correct FQDN this Service will get assigned when deployed will be like next.

gitea-cache-redis.gitea.svc.deimos.cluster.io

Redis Kustomize project

The last piece is the kustomization.yaml file that describes this Gitea's Redis service.

1. Under the cache-redis folder, produce a kustomization.yaml file.

   $ touch $HOME/k8sprjs/gitea/components/cache-redis/kustomization.yaml

2. Fill the kustomization.yaml file with the following yaml.

   # Redis setup
   apiVersion: kustomize.config.k8s.io/v1beta1
   kind: Kustomization
   
   commonLabels:
     app: cache-redis
   
   resources:
   - resources/cache-redis.deployment.yaml
   - resources/cache-redis.service.yaml
   
   replicas:
   - name: cache-redis
     count: 1
   
   images:
   - name: redis
     newTag: 6.2-alpine
   - name: oliver006/redis_exporter
     newTag: v1.32.0-alpine
   
   configMapGenerator:
   - name: cache-redis
     files:
     - configs/redis.conf
   
   secretGenerator:
   - name: cache-redis
     files:
     - redis-password=secrets/redis.pwd

   This kustomization.yaml is exactly the same as the one you declared for the Nextcloud's Redis service. No value needs to be changed here.

Checking the Kustomize yaml output

Now you can check out how the Kustomize output looks like for this Redis subproject.

1. Execute the kubectl kustomize command on the Redis Kustomize project's root folder, piped to less to get the output paginated.

   $ kubectl kustomize $HOME/k8sprjs/gitea/components/cache-redis | less

   Remember that you could also dump the yaml output on a file, called cache-redis.k.output.yaml for instance.

   $ kubectl kustomize $HOME/k8sprjs/gitea/components/cache-redis > cache-redis.k.output.yaml

2. The yaml output should be like the one next.

   apiVersion: v1
   data:
     redis.conf: |
       port 6379
       bind 0.0.0.0
       protected-mode no
       maxmemory 64mb
       maxmemory-policy allkeys-lru
   kind: ConfigMap
   metadata:
     labels:
       app: cache-redis
     name: cache-redis-6967fc5hc5
   ---
   apiVersion: v1
   data:
     redis-password: |
       Tm9wZV90aGlzX2lzX05PVF9vbmVfb2ZfbXlfcGFzc3dvcmRzX0FuZC15b3Vfc2hvdWxkbnRfdXNl
       X3RoaXNfb25lX2VpdGhlciEK
   kind: Secret
   metadata:
     labels:
       app: cache-redis
     name: cache-redis-4dg79kf68c
   type: Opaque
   ---
   apiVersion: v1
   kind: Service
   metadata:
     annotations:
       prometheus.io/port: "9121"
       prometheus.io/scrape: "true"
     labels:
       app: cache-redis
     name: cache-redis
   spec:
     ports:
     - name: server
       port: 6379
       protocol: TCP
     - name: metrics
       port: 9121
       protocol: TCP
     selector:
       app: cache-redis
     type: ClusterIP
   ---
   apiVersion: apps/v1
   kind: Deployment
   metadata:
     labels:
       app: cache-redis
     name: cache-redis
   spec:
     replicas: 1
     selector:
       matchLabels:
         app: cache-redis
     template:
       metadata:
         labels:
           app: cache-redis
       spec:
         affinity:
           podAffinity:
             requiredDuringSchedulingIgnoredDuringExecution:
             - labelSelector:
                 matchExpressions:
                 - key: app
                   operator: In
                   values:
                   - server-gitea
               topologyKey: kubernetes.io/hostname
         containers:
         - command:
           - redis-server
           - /etc/redis/redis.conf
           - --requirepass $(REDIS_PASSWORD)
           env:
           - name: REDIS_PASSWORD
             valueFrom:
               secretKeyRef:
                 key: redis-password
                 name: cache-redis-4dg79kf68c
           image: redis:6.2-alpine
           name: server
           ports:
           - containerPort: 6379
           resources:
             limits:
               memory: 64Mi
           volumeMounts:
           - mountPath: /etc/redis/redis.conf
             name: redis-config
             subPath: redis.conf
         - env:
           - name: REDIS_PASSWORD
             valueFrom:
               secretKeyRef:
                 key: redis-password
                 name: cache-redis-4dg79kf68c
           image: oliver006/redis_exporter:v1.32.0-alpine
           name: metrics
           ports:
           - containerPort: 9121
           resources:
             limits:
               memory: 32Mi
         volumes:
         - configMap:
             defaultMode: 292
             items:
             - key: redis.conf
               path: redis.conf
             name: cache-redis-6967fc5hc5
           name: redis-config

3. If you like, you can also validate the output with kubeval, if you have dumped the yaml on a file

Don't deploy this Redis project on its own

As it happened in the Nextcloud platform guide, remember that you don't want to deploy a subproject like this one on its own. You'll deploy it as component of the master Kustomize project for Gitea.

Relevant system paths

Folders in kubectl client system

• $HOME/k8sprjs/gitea
• $HOME/k8sprjs/gitea/components
• $HOME/k8sprjs/gitea/components/cache-redis
• $HOME/k8sprjs/gitea/components/cache-redis/configs
• $HOME/k8sprjs/gitea/components/cache-redis/resources
• $HOME/k8sprjs/gitea/components/cache-redis/secrets

Files in kubectl client system

• $HOME/k8sprjs/gitea/components/cache-redis/kustomization.yaml
• $HOME/k8sprjs/gitea/components/cache-redis/configs/redis.conf
• $HOME/k8sprjs/gitea/components/cache-redis/resources/cache-redis.deployment.yaml
• $HOME/k8sprjs/gitea/components/cache-redis/resources/cache-redis.service.yaml
• $HOME/k8sprjs/gitea/components/cache-redis/secrets/redis.pwd

References

Kubernetes

Pod scheduling

• Official Doc - Assigning Pods to Nodes
• Official Doc - Assign Pods to Nodes using Node Affinity
• Kubernetes API - Pod scheduling
• STRATEGIES FOR KUBERNETES POD PLACEMENT AND SCHEDULING
• Implement Node and Pod Affinity/Anti-Affinity in Kubernetes: A Practical Example
• Tutorial: Apply the Sidecar Pattern to Deploy Redis in Kubernetes
• Amazon EKS Workshop Official Doc - Assigning Pods to Nodes

Services

• DNS for Services
• Headless Services

ConfigMaps and secrets

• Official Doc - ConfigMaps
• Official Doc - Configure a Pod to Use a ConfigMap
• An Introduction to Kubernetes Secrets and ConfigMaps
• Kubernetes - Using ConfigMap SubPaths to Mount Files
• Kubernetes Secrets | Declare confidential data with examples
• Kubernetes ConfigMaps and Secrets
• Import data to config map from kubernetes secret

Environment variables

• Official Doc - Define Environment Variables for a Container
• Official Doc - Define Dependent Environment Variables

DNS

• DNS for Services and Pods

Redis

• Redis
• Redis FAQ
• Redis administration
• Redis on DockerHub
• Prometheus Redis Metrics Exporter on DockerHub
• redis.conf commented example
• Simple Redis Cache on Kubernetes with Prometheus Metrics
• Deploying single node redis in kubernetes environment
• Single server Redis
• Kubernetes Official Doc - Configuring Redis using a ConfigMap
• redis-server - Man Page
• Deploy and Operate a Redis Cluster in Kubernetes
• Redis Setup on Kubernetes
• Rancher Official Doc - Deploying Redis Cluster on Top of Kubernetes
• Running Redis on Multi-Node Kubernetes Cluster in 5 Minutes
• Redis sentinel vs clustering

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