Menene Deployments da ReplicaSets, kuma yaya rolling updates da rollbacks ke aiki?

Question

IT Interview Practice · Accepted Answer

**Deployment** shine daidaitaccen controller don gudanar da aikace-aikace masu stateless. Yana gudanar da **ReplicaSets**, kuma ReplicaSet yana kiyaye adadin da aka ƙayyade na Pod iri ɗaya na gudana. Kana gyara Deployment; shi kuma yana daidaita **rolling updates** da **rollbacks** maka.

## Matsayin tsari

```text
Deployment  → yana bayyana yanayin da ake so + dabarar sabuntawa (abin da KAI ke gudanarwa)
   └── ReplicaSet  → yana tabbatar da Pod N iri ɗaya sun wanzu (ɗaya ga kowane sigar app)
          └── Pod  → Pod → Pod ...  (ainihin kwafi masu gudana)

A kowane sabon sigar, Deployment yana ƙirƙira SABON ReplicaSet ya kuma canja Pod zuwa gare shi.
```

## Manifest na Deployment

```yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: web
spec:
  replicas: 4
  selector:
    matchLabels: { app: web }
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxUnavailable: 1      # a mafi yawa Pod 1 ya faɗi yayin sabuntawa
      maxSurge: 1            # a mafi yawa Pod 1 na ƙari sama da adadin da ake so
  template:
    metadata:
      labels: { app: web }
    spec:
      containers:
        - name: web
          image: myapp:1.0
          ports:
            - containerPort: 8080
```

## Rolling update: canjin sigar ba tare da tsayawar aiki ba

```bash
kubectl set image deployment/web web=myapp:2.0   # kunna rolling update
kubectl rollout status deployment/web            # kallon ci gaba
```

```text
maxSurge=1, maxUnavailable=1, replicas=4:
  v1: ████        (farko: Pod 4 na tsohuwa)
      █████       kunna Pod 1 sabo (v2), yanzu jimlar 5 (surge)
      ███ █       tsofaffi sun ragu zuwa 3, sabon ya zama Ready
      ...canja a hankali...
  v2: ████        (ƙarshe: Pod 4 na sabo, tsohuwar ReplicaSet ta ragu zuwa 0)
Zirga-zirga na zuwa Pod da suka wuce readiness probe kawai → babu tsayawar aiki.
```

## Rollback lokacin da fitarwa ta lalace

```bash
kubectl rollout history deployment/web       # jera revisions
kubectl rollout undo deployment/web          # koma zuwa revision na baya
kubectl rollout undo deployment/web --to-revision=3
```

Saboda ana ajiye tsohuwar ReplicaSet (an rage zuwa 0), rollback yana da sauri: Kubernetes kawai yana faɗaɗa ReplicaSet na baya ya kuma rage sabon.

## Scaling

```bash
kubectl scale deployment/web --replicas=10   # canja adadin da ake so
```

## Me ya sa yake da muhimmanci

Deployments su ne babbar hanyar gudanar da aikace-aikace masu stateless a kan Kubernetes, don haka fahimtar su da alaƙarsu da ReplicaSets ilimi ne mai mahimmanci, na yau da kullum. Yin matakai shine mahimmancin fahimta: kana gudanar da **Deployment**, wanda ke mallakar **ReplicaSets** (ɗaya ga kowane sigar), kuma kowane ReplicaSet yana tabbatar da cewa adadin da aka ƙayyade na Pod iri ɗaya na gudana — jerin reconciliation loops waɗanda tare suke isar da self-healing da adadin replica mai ƙarko. Ainihin ƙarfin yana cikin yadda Deployment ke gudanar da canji: **rolling update** yana ƙirƙira sabon ReplicaSet ya kuma canja Pod daga tsohuwa zuwa sabo a hankali, wanda `maxSurge` da `maxUnavailable` ke shiryawa, don haka ana kiyaye ƙarfin — kuma tare da readiness probes waɗanda ke shiryar da wanne Pod ke karɓar zirga-zirga — fitarwar tana faruwa da **babu tsayawar aiki**. Saboda ana riƙe tsohuwar ReplicaSet (an rage zuwa sifili maimakon a share), **rollback** yana da sauri da aminci: `kubectl rollout undo` kawai yana faɗaɗa tsohuwar sigar ya kuma rage marar kyau, wanda shine ainihin abin da za ka nema idan fitarwa ta yi rashin lafiya. Fahimtar waɗannan hanyoyin — da yadda ake scale (`kubectl scale`) da bincika ci gaba (`kubectl rollout status/history`) — na tushe ne don tura software cikin aminci a kan Kubernetes, kuma yana nuna tsarin bayyanawa, wanda controller ke tuƙawa da ke bayyana yadda dandalin ke aiki a production.

Matsayin tsari

Manifest na Deployment

Rolling update: canjin sigar ba tare da tsayawar aiki ba

Rollback lokacin da fitarwa ta lalace

Scaling

Me ya sa yake da muhimmanci

Tambayoyi masu alaƙa