Rollout Deployment

The Rollout Deployment chart deploys an advanced version of deployment that supports Blue/Green and Canary deployments. For functioning, it requires a rollout controller to run inside the cluster.

You can define application behavior by providing information in the following sections:

Advanced (YAML)

Container Ports

This defines the ports on which application services will be exposed to other services.

ContainerPort:
  - envoyPort: 8799
    envoyTimeout: 15s
    idleTimeout:
    name: app
    port: 8080
    servicePort: 80
    supportStreaming: true
    useHTTP2: true

EnvVariables

EnvVariables: []

EnvVariables provide run-time information to containers and allow to customize how the application works and the behavior of the applications on the system.

Here we can pass the list of env variables , every record is an object which contain the name of variable along with value.

To set environment variables for the containers that run in the Pod.

Example of EnvVariables

IMP Docker image should have env variables, whatever we want to set.

EnvVariables: 
  - name: HOSTNAME
    value: www.xyz.com
  - name: DB_NAME
    value: mydb
  - name: USER_NAME
    value: xyz

But ConfigMap and Secret are the preferred way to inject env variables. You can create this in App Configuration Section.

ConfigMap

It is a centralized storage, specific to k8s namespace where key-value pairs are stored in plain text.

Secret

It is a centralized storage, specific to k8s namespace where we can store the key-value pairs in plain text as well as in encrypted(Base64) form.

IMP All key-values of Secret and CofigMap will reflect to your application.

Liveness Probe

If this check fails, kubernetes restarts the pod. This should return error code in case of non-recoverable error.

LivenessProbe:
  Path: ""
  port: 8080
  initialDelaySeconds: 20
  periodSeconds: 10
  successThreshold: 1
  timeoutSeconds: 5
  failureThreshold: 3
  command:
    - python
    - /etc/app/healthcheck.py
  httpHeaders:
    - name: Custom-Header
      value: abc
  scheme: ""
  tcp: true

MaxUnavailable

  MaxUnavailable: 0

The maximum number of pods that can be unavailable during the update process. The value of "MaxUnavailable: " can be an absolute number or percentage of the replicas count. The default value of "MaxUnavailable: " is 25%.

MaxSurge

MaxSurge: 1

The maximum number of pods that can be created over the desired number of pods. For "MaxSurge: " also, the value can be an absolute number or percentage of the replicas count. The default value of "MaxSurge: " is 25%.

Min Ready Seconds

MinReadySeconds: 60

This specifies the minimum number of seconds for which a newly created Pod should be ready without any of its containers crashing, for it to be considered available. This defaults to 0 (the Pod will be considered available as soon as it is ready).

Readiness Probe

If this check fails, kubernetes stops sending traffic to the application. This should return error code in case of errors which can be recovered from if traffic is stopped.

ReadinessProbe:
  Path: ""
  port: 8080
  initialDelaySeconds: 20
  periodSeconds: 10
  successThreshold: 1
  timeoutSeconds: 5
  failureThreshold: 3
  command:
    - python
    - /etc/app/healthcheck.py
  httpHeaders:
    - name: Custom-Header
      value: abc
  scheme: ""
  tcp: true

Startup Probe

Startup Probe in Kubernetes is a type of probe used to determine when a container within a pod is ready to start accepting traffic. It is specifically designed for applications that have a longer startup time.

StartupProbe:
  Path: ""
  port: 8080
  initialDelaySeconds: 20
  periodSeconds: 10
  successThreshold: 1
  timeoutSeconds: 5
  failureThreshold: 3
  httpHeaders:
    - name: Custom-Header
      value: abc
  command:
    - python
    - /etc/app/healthcheck.py
  tcp: false

Autoscaling

This is connected to HPA and controls scaling up and down in response to request load.

autoscaling:
  enabled: false
  MinReplicas: 1
  MaxReplicas: 2
  TargetCPUUtilizationPercentage: 90
  TargetMemoryUtilizationPercentage: 80
  extraMetrics: []

Fullname Override

fullnameOverride: app-name

fullnameOverride replaces the release fullname created by default by devtron, which is used to construct Kubernetes object names. By default, devtron uses {app-name}-{environment-name} as release fullname.

Image

image:
  pullPolicy: IfNotPresent

Image is used to access images in kubernetes, pullpolicy is used to define the instances calling the image, here the image is pulled when the image is not present,it can also be set as "Always".

serviceAccount

serviceAccount:
  create: false
  name: ""
  annotations: {}

imagePullSecrets

imagePullSecrets contains the docker credentials that are used for accessing a registry.

imagePullSecrets:
  - regcred

regcred is the secret that contains the docker credentials that are used for accessing a registry. Devtron will not create this secret automatically, you'll have to create this secret using dt-secrets helm chart in the App store or create one using kubectl. You can follow this documentation Pull an Image from a Private Registry https://kubernetes.io/docs/tasks/configure-pod-container/pull-image-private-registry/ .

HostAliases

the hostAliases field is used in a Pod specification to associate additional hostnames with the Pod's IP address. This can be helpful in scenarios where you need to resolve specific hostnames to the Pod's IP within the Pod itself.

  hostAliases:
  - ip: "192.168.1.10"
    hostnames:
    - "hostname1.example.com"
    - "hostname2.example.com"
  - ip: "192.168.1.11"
    hostnames:
    - "hostname3.example.com"

Ingress

This allows public access to the url. Please ensure you are using the right nginx annotation for nginx class. The default value is nginx.

ingress:
  enabled: false
  # For K8s 1.19 and above use ingressClassName instead of annotation kubernetes.io/ingress.class:
  className: nginx
  annotations: {}
  hosts:
      - host: example1.com
        pathType: "ImplementationSpecific"
        paths:
            - /example
      - host: example2.com
        pathType: "ImplementationSpecific"
        paths:
            - /example2
            - /example2/healthz
  tls: []

Legacy deployment-template ingress format

ingress:
  enabled: false
  # For K8s 1.19 and above use ingressClassName instead of annotation kubernetes.io/ingress.class:
  ingressClassName: nginx-internal
  annotations: {}
  path: ""
  host: ""
  tls: []

Ingress Internal

This allows private access to the url, please ensure you are using right nginx annotation for nginx class, its default value is nginx

ingressInternal:
  enabled: false
  # For K8s 1.19 and above use ingressClassName instead of annotation kubernetes.io/ingress.class:
  ingressClassName: nginx-internal
  annotations: {}
  hosts:
      - host: example1.com
        pathType: "ImplementationSpecific"
        paths:
            - /example
      - host: example2.com
        pathType: "ImplementationSpecific"
        paths:
            - /example2
            - /example2/healthz
  tls: []

Init Containers

initContainers: 
  - reuseContainerImage: true
    securityContext:
      runAsUser: 1000
      runAsGroup: 3000
      fsGroup: 2000
    volumeMounts:
     - mountPath: /etc/ls-oms
       name: ls-oms-cm-vol
   command:
     - flyway
     - -configFiles=/etc/ls-oms/flyway.conf
     - migrate

  - name: nginx
    image: nginx:1.14.2
    securityContext:
      privileged: true
    ports:
    - containerPort: 80
    command: ["/usr/local/bin/nginx"]
    args: ["-g", "daemon off;"]

Specialized containers that run before app containers in a Pod. Init containers can contain utilities or setup scripts not present in an app image. One can use base image inside initContainer by setting the reuseContainerImage flag to true.

Pause For Seconds Before Switch Active

pauseForSecondsBeforeSwitchActive: 30

To wait for given period of time before switch active the container.

Resources

These define minimum and maximum RAM and CPU available to the application.

resources:
  limits:
    cpu: "1"
    memory: "200Mi"
  requests:
    cpu: "0.10"
    memory: "100Mi"

Resources are required to set CPU and memory usage.

Limits

Limits make sure a container never goes above a certain value. The container is only allowed to go up to the limit, and then it is restricted.

Requests

Requests are what the container is guaranteed to get.

Service

This defines annotations and the type of service, optionally can define name also.

  service:
    type: ClusterIP
    annotations: {}

Note - If loadBalancerSourceRanges is not set, Kubernetes allows traffic from 0.0.0.0/0 to the LoadBalancer / Node Security Group(s).

Volumes

volumes:
  - name: log-volume
    emptyDir: {}
  - name: logpv
    persistentVolumeClaim:
      claimName: logpvc

It is required when some values need to be read from or written to an external disk.

Volume Mounts

volumeMounts:
  - mountPath: /var/log/nginx/
    name: log-volume 
  - mountPath: /mnt/logs
    name: logpvc
    subPath: employee  

It is used to provide mounts to the volume.

Affinity and anti-affinity

Spec:
  Affinity:
    Key:
    Values:

Spec is used to define the desire state of the given container.

Node Affinity allows you to constrain which nodes your pod is eligible to schedule on, based on labels of the node.

Inter-pod affinity allow you to constrain which nodes your pod is eligible to be scheduled based on labels on pods.

Key

Key part of the label for node selection, this should be same as that on node. Please confirm with devops team.

Values

Value part of the label for node selection, this should be same as that on node. Please confirm with devops team.

Tolerations

tolerations:
 - key: "key"
   operator: "Equal"
   value: "value"
   effect: "NoSchedule|PreferNoSchedule|NoExecute(1.6 only)"

Taints are the opposite, they allow a node to repel a set of pods.

A given pod can access the given node and avoid the given taint only if the given pod satisfies a given taint.

Taints and tolerations are a mechanism which work together that allows you to ensure that pods are not placed on inappropriate nodes. Taints are added to nodes, while tolerations are defined in the pod specification. When you taint a node, it will repel all the pods except those that have a toleration for that taint. A node can have one or many taints associated with it.

Arguments

args:
  enabled: false
  value: []

This is used to give arguments to command.

Command

command:
  enabled: false
  value: []
  workingDir: {}

It contains the commands to run inside the container.

Containers

Containers section can be used to run side-car containers along with your main container within same pod. Containers running within same pod can share volumes and IP Address and can address each other @localhost. We can use base image inside container by setting the reuseContainerImage flag to true.

    containers:
      - name: nginx
        image: nginx:1.14.2
        ports:
        - containerPort: 80
        command: ["/usr/local/bin/nginx"]
        args: ["-g", "daemon off;"]
      - reuseContainerImage: true
        securityContext:
          runAsUser: 1000
          runAsGroup: 3000
          fsGroup: 2000
        volumeMounts:
        - mountPath: /etc/ls-oms
          name: ls-oms-cm-vol
        command:
          - flyway
          - -configFiles=/etc/ls-oms/flyway.conf
          - migrate

Prometheus

  prometheus:
    release: monitoring

It is a kubernetes monitoring tool and the name of the file to be monitored as monitoring in the given case.It describes the state of the prometheus.

rawYaml

rawYaml: 
  - apiVersion: v1
    kind: Service
    metadata:
      name: my-service
    spec:
      selector:
        app: MyApp
      ports:
        - protocol: TCP
          port: 80
          targetPort: 9376
      type: ClusterIP

Accepts an array of Kubernetes objects. You can specify any kubernetes yaml here and it will be applied when your app gets deployed.

Grace Period

GracePeriod: 30

Kubernetes waits for the specified time called the termination grace period before terminating the pods. By default, this is 30 seconds. If your pod usually takes longer than 30 seconds to shut down gracefully, make sure you increase the GracePeriod.

A Graceful termination in practice means that your application needs to handle the SIGTERM message and begin shutting down when it receives it. This means saving all data that needs to be saved, closing down network connections, finishing any work that is left, and other similar tasks.

There are many reasons why Kubernetes might terminate a perfectly healthy container. If you update your deployment with a rolling update, Kubernetes slowly terminates old pods while spinning up new ones. If you drain a node, Kubernetes terminates all pods on that node. If a node runs out of resources, Kubernetes terminates pods to free those resources. It’s important that your application handle termination gracefully so that there is minimal impact on the end user and the time-to-recovery is as fast as possible.

Server

server:
  deployment:
    image_tag: 1-95a53
    image: ""

It is used for providing server configurations.

Deployment

It gives the details for deployment.

Service Monitor

servicemonitor:
      enabled: true
      path: /abc
      scheme: 'http'
      interval: 30s
      scrapeTimeout: 20s
      metricRelabelings:
        - sourceLabels: [namespace]
          regex: '(.*)'
          replacement: myapp
          targetLabel: target_namespace

It gives the set of targets to be monitored.

Db Migration Config

dbMigrationConfig:
  enabled: false

It is used to configure database migration.

Istio

These Istio configurations collectively provide a comprehensive set of tools for controlling access, authenticating requests, enforcing security policies, and configuring traffic behavior within a microservices architecture. The specific settings you choose would depend on your security and traffic management requirements.

Istio

These Istio configurations collectively provide a comprehensive set of tools for controlling access, authenticating requests, enforcing security policies, and configuring traffic behavior within a microservices architecture. The specific settings you choose would depend on your security and traffic management requirements.

istio:
  enable: true

  gateway:
    enabled: true
    labels:
      app: my-gateway
    annotations:
      description: "Istio Gateway for external traffic"
    host: "example.com"
    tls:
      enabled: true
      secretName: my-tls-secret

  virtualService:
    enabled: true
    labels:
      app: my-service
    annotations:
      description: "Istio VirtualService for routing"
    gateways:
      - my-gateway
    hosts:
      - "example.com"
    http:
      - match:
          - uri:
              prefix: /v1
        route:
          - destination:
              host: my-service-v1
              subset: version-1
      - match:
          - uri:
              prefix: /v2
        route:
          - destination:
              host: my-service-v2
              subset: version-2

  destinationRule:
    enabled: true
    labels:
      app: my-service
    annotations:
      description: "Istio DestinationRule for traffic policies"
    subsets:
      - name: version-1
        labels:
          version: "v1"
      - name: version-2
        labels:
          version: "v2"
    trafficPolicy:
      connectionPool:
        tcp:
          maxConnections: 100
      outlierDetection:
        consecutiveErrors: 5
        interval: 30s
        baseEjectionTime: 60s

  peerAuthentication:
    enabled: true
    labels:
      app: my-service
    annotations:
      description: "Istio PeerAuthentication for mutual TLS"
    selector:
      matchLabels:
        version: "v1"
    mtls:
      mode: STRICT
    portLevelMtls:
      8080:
        mode: DISABLE

  requestAuthentication:
    enabled: true
    labels:
      app: my-service
    annotations:
      description: "Istio RequestAuthentication for JWT validation"
    selector:
      matchLabels:
        version: "v1"
    jwtRules:
      - issuer: "issuer-1"
        jwksUri: "https://issuer-1/.well-known/jwks.json"

  authorizationPolicy:
    enabled: true
    labels:
      app: my-service
    annotations:
      description: "Istio AuthorizationPolicy for access control"
    action: ALLOW
    provider:
      name: jwt
      kind: Authorization
    rules:
      - from:
          - source:
              requestPrincipals: ["*"]
        to:
          - operation:
              methods: ["GET"]

Application Metrics

Application metrics can be enabled to see your application's metrics-CPU Service Monitor usage, Memory Usage, Status, Throughput and Latency.

Deployment Metrics

It gives the realtime metrics of the deployed applications

Addon features in Deployment Template Chart version 3.9.0

Service Account

serviceAccountName: orchestrator

A service account provides an identity for the processes that run in a Pod.

When you access the cluster, you are authenticated by the API server as a particular User Account. Processes in containers inside pod can also contact the API server. When you are authenticated as a particular Service Account.

When you create a pod, if you do not create a service account, it is automatically assigned the default service account in the namespace.

Pod Disruption Budget

You can create PodDisruptionBudget for each application. A PDB limits the number of pods of a replicated application that are down simultaneously from voluntary disruptions. For example, an application would like to ensure the number of replicas running is never brought below the certain number.

podDisruptionBudget: 
     minAvailable: 1

or

podDisruptionBudget: 
     maxUnavailable: 50%

You can specify either maxUnavailable or minAvailable in a PodDisruptionBudget and it can be expressed as integers or as a percentage.

Application metrics Envoy Configurations

envoyproxy:
  image: envoyproxy/envoy:v1.14.1
  configMapName: ""
  resources:
    limits:
      cpu: "50m"
      memory: "50Mi"
    requests:
      cpu: "50m"
      memory: "50Mi"

Envoy is attached as a sidecar to the application container to collect metrics like 4XX, 5XX, Throughput and latency. You can now configure the envoy settings such as idleTimeout, resources etc.

Prometheus Rule

prometheusRule:
  enabled: true
  additionalLabels: {}
  namespace: ""
  rules:
    - alert: TooMany500s
      expr: 100 * ( sum( nginx_ingress_controller_requests{status=~"5.+"} ) / sum(nginx_ingress_controller_requests) ) > 5
      for: 1m
      labels:
        severity: critical
      annotations:
        description: Too many 5XXs
        summary: More than 5% of the all requests did return 5XX, this require your attention

Alerting rules allow you to define alert conditions based on Prometheus expressions and to send notifications about firing alerts to an external service.

In this case, Prometheus will check that the alert continues to be active during each evaluation for 1 minute before firing the alert. Elements that are active, but not firing yet, are in the pending state.

Pod Labels

Labels are key/value pairs that are attached to pods. Labels are intended to be used to specify identifying attributes of objects that are meaningful and relevant to users, but do not directly imply semantics to the core system. Labels can be used to organize and to select subsets of objects.

podLabels:
  severity: critical

Pod Annotations

Pod Annotations are widely used to attach metadata and configs in Kubernetes.

podAnnotations:
  fluentbit.io/exclude: "true"

Custom Metrics in HPA

autoscaling:
  enabled: true
  MinReplicas: 1
  MaxReplicas: 2
  TargetCPUUtilizationPercentage: 90
  TargetMemoryUtilizationPercentage: 80
  behavior:
    scaleDown:
      stabilizationWindowSeconds: 300
      policies:
      - type: Percent
        value: 100