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The basic concepts are the same, but the walkthrough is tailored to a Container Engine setup.\n\n### Prerequisites\n\nThis example requires a running Kubernetes cluster. First, check that kubectl is properly configured by getting the cluster state:\n\n```console\n$ kubectl cluster-info\n```\n\nIf you see a url response, you are ready to go. If not, read the [Getting Started guides](http://kubernetes.io/docs/getting-started-guides/) for how to get started, and follow the [prerequisites](http://kubernetes.io/docs/user-guide/prereqs/) to install and configure `kubectl`. As noted above, if you have a Google Container Engine cluster set up, read [this example](https://cloud.google.com/container-engine/docs/tutorials/guestbook) instead.\n\nAll the files referenced in this example can be downloaded in [current folder](./).\n\n### Quick Start\n\nThis section shows the simplest way to get the example work. If you want to know the details, you should skip this and read [the rest of the example](#step-one-start-up-the-redis-master).\n\nStart the guestbook with one command:\n\n```console\n$ kubectl create -f examples/guestbook/all-in-one/guestbook-all-in-one.yaml\nservice \"redis-master\" created\ndeployment \"redis-master\" created\nservice \"redis-slave\" created\ndeployment \"redis-slave\" created\nservice \"frontend\" created\ndeployment \"frontend\" created\n```\n\nAlternatively, you can start the guestbook by running:\n\n```console\n$ kubectl create -f examples/guestbook/\n```\n\nThen, list all your Services:\n\n```console\n$ kubectl get services\nNAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE\nfrontend 10.0.0.117 80/TCP 20s\nredis-master 10.0.0.170 6379/TCP 20s\nredis-slave 10.0.0.201 6379/TCP 20s\n```\n\nNow you can access the guestbook on each node with frontend Service's `:`, e.g. `10.0.0.117:80` in this guide. `` is a cluster-internal IP. If you want to access the guestbook from outside of the cluster, add `type: NodePort` to the frontend Service `spec` field. Then you can access the guestbook with `:NodePort` from outside of the cluster. On cloud providers which support external load balancers, adding `type: LoadBalancer` to the frontend Service `spec` field will provision a load balancer for your Service. There are several ways for you to access the guestbook. You may learn from [Accessing services running on the cluster](https://kubernetes.io/docs/concepts/cluster-administration/access-cluster/#accessing-services-running-on-the-cluster).\n\nClean up the guestbook:\n\n```console\n$ kubectl delete -f examples/guestbook/all-in-one/guestbook-all-in-one.yaml\n```\n\nor\n\n```console\n$ kubectl delete -f examples/guestbook/\n```\n\n\n### Step One: Start up the redis master\n\nBefore continuing to the gory details, we also recommend you to read Kubernetes [concepts and user guide](http://kubernetes.io/docs/user-guide/).\n**Note**: The redis master in this example is *not* highly available. Making it highly available would be an interesting, but intricate exercise — redis doesn't actually support multi-master Deployments at this point in time, so high availability would be a somewhat tricky thing to implement, and might involve periodic serialization to disk, and so on.\n\n#### Define a Deployment\n\nTo start the redis master, use the file [redis-master-deployment.yaml](redis-master-deployment.yaml), which describes a single [pod](http://kubernetes.io/docs/user-guide/pods/) running a redis key-value server in a container.\n\nAlthough we have a single instance of our redis master, we are using a [Deployment](http://kubernetes.io/docs/user-guide/deployments/) to enforce that exactly one pod keeps running. E.g., if the node were to go down, the Deployment will ensure that the redis master gets restarted on a healthy node. (In our simplified example, this could result in data loss.)\n\nThe file [redis-master-deployment.yaml](redis-master-deployment.yaml) defines the redis master Deployment:\n\n\n\n```yaml\napiVersion: extensions/v1beta1\nkind: Deployment\nmetadata:\n name: redis-master\n # these labels can be applied automatically \n # from the labels in the pod template if not set\n # labels:\n # app: redis\n # role: master\n # tier: backend\nspec:\n # this replicas value is default\n # modify it according to your case\n replicas: 1\n # selector can be applied automatically \n # from the labels in the pod template if not set\n # selector:\n # matchLabels:\n # app: guestbook\n # role: master\n # tier: backend\n template:\n metadata:\n labels:\n app: redis\n role: master\n tier: backend\n spec:\n containers:\n - name: master\n image: gcr.io/google_containers/redis:e2e\n resources:\n requests:\n cpu: 100m\n memory: 100Mi\n ports:\n - containerPort: 6379\n```\n\n[Download example](redis-master-deployment.yaml?raw=true)\n\n\n#### Define a Service\n\nA Kubernetes [Service](http://kubernetes.io/docs/user-guide/services/) is a named load balancer that proxies traffic to one or more containers. This is done using the [labels](http://kubernetes.io/docs/user-guide/labels/) metadata that we defined in the `redis-master` pod above. As mentioned, we have only one redis master, but we nevertheless want to create a Service for it. Why? Because it gives us a deterministic way to route to the single master using an elastic IP.\n\nServices find the pods to load balance based on the pods' labels.\nThe selector field of the Service description determines which pods will receive the traffic sent to the Service, and the `port` and `targetPort` information defines what port the Service proxy will run at.\n\nThe file [redis-master-service.yaml](redis-master-deployment.yaml) defines the redis master Service:\n\n\n\n```yaml\napiVersion: v1\nkind: Service\nmetadata:\n name: redis-master\n labels:\n app: redis\n role: master\n tier: backend\nspec:\n ports:\n # the port that this service should serve on\n - port: 6379\n targetPort: 6379\n selector:\n app: redis\n role: master\n tier: backend\n```\n\n[Download example](redis-master-service.yaml?raw=true)\n\n\n#### Create a Service\n\nAccording to the [config best practices](http://kubernetes.io/docs/user-guide/config-best-practices/), create a Service before corresponding Deployments so that the scheduler can spread the pods comprising the Service. So we first create the Service by running:\n\n```console\n$ kubectl create -f examples/guestbook/redis-master-service.yaml\nservice \"redis-master\" created\n```\n\nThen check the list of services, which should include the redis-master:\n\n```console\n$ kubectl get services\nNAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE\nredis-master 10.0.76.248 6379/TCP 1s\n```\n\nThis will cause all pods to see the redis master apparently running on `:`. A Service can map an incoming port to any `targetPort` in the backend pod. Once created, the Service proxy on each node is configured to set up a proxy on the specified port (in this case port `6379`).\n\n`targetPort` will default to `port` if it is omitted in the configuration. `targetPort` is the port the container accepts traffic on, and `port` is the abstracted Service port, which can be any port other pods use to access the Service. For simplicity's sake, we omit it in the following configurations.\n\nThe traffic flow from slaves to masters can be described in two steps:\n\n - A *redis slave* will connect to `port` on the *redis master Service*\n - Traffic will be forwarded from the Service `port` (on the Service node) to the `targetPort` on the pod that the Service listens to.\n\nFor more details, please see [Connecting applications](http://kubernetes.io/docs/user-guide/connecting-applications/).\n\n#### Finding a Service\n\nKubernetes supports two primary modes of finding a Service — environment variables and DNS.\n\n\n##### Environment variables\n\nThe services in a Kubernetes cluster are discoverable inside other containers via [environment variables](https://kubernetes.io/docs/concepts/services-networking/service/#environment-variables).\n\n##### DNS service\n\nAn alternative is to use the [cluster's DNS service](https://kubernetes.io/docs/concepts/services-networking/service/#dns), if it has been enabled for the cluster. This lets all pods do name resolution of services automatically, based on the Service name.\n\nThis example has been configured to use the DNS service by default.\n\nIf your cluster does not have the DNS service enabled, then you can use environment variables by setting the\n`GET_HOSTS_FROM` env value in both\n[redis-slave-deployment.yaml](redis-slave-deployment.yaml) and [frontend-deployment.yaml](frontend-deployment.yaml)\nfrom `dns` to `env` before you start up the app.\n(However, this is unlikely to be necessary. You can check for the DNS service in the list of the cluster's services by\nrunning `kubectl --namespace=kube-system get rc -l k8s-app=kube-dns`.)\nNote that switching to env causes creation-order dependencies, since Services need to be created before their clients that require env vars.\n\n#### Create a Deployment\n\nSecond, create the redis master pod in your Kubernetes cluster by running:\n\n```console\n$ kubectl create -f examples/guestbook/redis-master-deployment.yaml\ndeployment \"redis-master\" created\n```\n\nYou can see the Deployment for your cluster by running:\n\n```console\n$ kubectl get deployments\nNAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE\nredis-master 1 1 1 1 27s\n```\n\nThen, you can list the pods in the cluster, to verify that the master is running:\n\n```console\n$ kubectl get pods\n```\n\nYou'll see all pods in the cluster, including the redis master pod, and the status of each pod.\nThe name of the redis master will look similar to that in the following list:\n\n```console\nNAME READY STATUS RESTARTS AGE\nredis-master-2353460263-1ecey 1/1 Running 0 1m\n...\n```\n\n(Note that an initial `docker pull` to grab a container image may take a few minutes, depending on network conditions. A pod will be reported as `Pending` while its image is being downloaded.)\n\n`kubectl get pods` will show only the pods in the default [namespace](http://kubernetes.io/docs/user-guide/namespaces/). To see pods in all namespaces, run:\n\n```\nkubectl get pods --all-namespaces\n```\n\nFor more details, please see [Configuring containers](http://kubernetes.io/docs/user-guide/configuring-containers/) and [Deploying applications](http://kubernetes.io/docs/user-guide/deploying-applications/).\n\n#### Optional Interlude\n\nYou can get information about a pod, including the machine that it is running on, via `kubectl describe pods/`. E.g., for the redis master, you should see something like the following (your pod name will be different):\n\n```console\n$ kubectl describe pods redis-master-2353460263-1ecey\nName:\t\tredis-master-2353460263-1ecey\nNode:\t\tkubernetes-node-m0k7/10.240.0.5\n...\nLabels:\t\tapp=redis,pod-template-hash=2353460263,role=master,tier=backend\nStatus:\t\tRunning\nIP:\t\t10.244.2.3\nControllers:\tReplicaSet/redis-master-2353460263\nContainers:\n master:\n Container ID:\tdocker://76cf8115485966131587958ea3cbe363e2e1dcce129e2e624883f393ce256f6c\n Image:\t\tgcr.io/google_containers/redis:e2e\n Image ID:\t\tdocker://e5f6c5a2b5646828f51e8e0d30a2987df7e8183ab2c3ed0ca19eaa03cc5db08c\n Port:\t\t6379/TCP\n...\n```\n\nThe `Node` is the name and IP of the machine, e.g. `kubernetes-node-m0k7` in the example above. You can find more details about this node with `kubectl describe nodes kubernetes-node-m0k7`.\n\nIf you want to view the container logs for a given pod, you can run:\n\n```console\n$ kubectl logs \n```\n\nThese logs will usually give you enough information to troubleshoot.\n\nHowever, if you should want to SSH to the listed host machine, you can inspect various logs there directly as well. For example, with Google Compute Engine, using `gcloud`, you can SSH like this:\n\n```console\nme@workstation$ gcloud compute ssh \n```\n\nThen, you can look at the Docker containers on the remote machine. You should see something like this (the specifics of the IDs will be different):\n\n```console\nme@kubernetes-node-krxw:~$ sudo docker ps\nCONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES\n...\n0ffef9649265 redis:latest \"/entrypoint.sh redi\" About a minute ago Up About a minute k8s_master.869d22f3_redis-master-dz33o_default_1449a58a-5ead-11e5-a104-688f84ef8ef6_d74cb2b5\n```\n\nIf you want to see the logs for a given container, you can run:\n\n```console\n$ docker logs \n```\n\n### Step Two: Start up the redis slave\n\nNow that the redis master is running, we can start up its 'read slaves'.\n\nWe'll define these as replicated pods as well, though this time — unlike for the redis master — we'll define the number of replicas to be 2.\nIn Kubernetes, a Deployment is responsible for managing multiple instances of a replicated pod. The Deployment will automatically launch new pods if the number of replicas falls below the specified number.\n(This particular replicated pod is a great one to test this with -- you can try killing the Docker processes for your pods directly, then watch them come back online on a new node shortly thereafter.)\n\nJust like the master, we want to have a Service to proxy connections to the redis slaves. In this case, in addition to discovery, the slave Service will provide transparent load balancing to web app clients.\n\nThis time we put the Service and Deployment into one [file](http://kubernetes.io/docs/user-guide/managing-deployments/#organizing-resource-configurations). Grouping related objects together in a single file is often better than having separate files.\nThe specification for the slaves is in [all-in-one/redis-slave.yaml](all-in-one/redis-slave.yaml):\n\n\n\n```yaml\napiVersion: v1\nkind: Service\nmetadata:\n name: redis-slave\n labels:\n app: redis\n role: slave\n tier: backend\nspec:\n ports:\n # the port that this service should serve on\n - port: 6379\n selector:\n app: redis\n role: slave\n tier: backend\n---\napiVersion: extensions/v1beta1\nkind: Deployment\nmetadata:\n name: redis-slave\n # these labels can be applied automatically\n # from the labels in the pod template if not set\n # labels:\n # app: redis\n # role: slave\n # tier: backend\nspec:\n # this replicas value is default\n # modify it according to your case\n replicas: 2\n # selector can be applied automatically\n # from the labels in the pod template if not set\n # selector:\n # matchLabels:\n # app: guestbook\n # role: slave\n # tier: backend\n template:\n metadata:\n labels:\n app: redis\n role: slave\n tier: backend\n spec:\n containers:\n - name: slave\n image: gcr.io/google_samples/gb-redisslave:v1\n resources:\n requests:\n cpu: 100m\n memory: 100Mi\n env:\n - name: GET_HOSTS_FROM\n value: dns\n # If your cluster config does not include a dns service, then to\n # instead access an environment variable to find the master\n # service's host, comment out the 'value: dns' line above, and\n # uncomment the line below.\n # value: env\n ports:\n - containerPort: 6379\n```\n\n[Download example](all-in-one/redis-slave.yaml?raw=true)\n\n\nThis time the selector for the Service is `app=redis,role=slave,tier=backend`, because that identifies the pods running redis slaves. It is generally helpful to set labels on your Service itself as we've done here to make it easy to locate them with the `kubectl get services -l \"app=redis,role=slave,tier=backend\"` command. For more information on the usage of labels, see [using-labels-effectively](http://kubernetes.io/docs/user-guide/managing-deployments/#using-labels-effectively).\n\nNow that you have created the specification, create the Service in your cluster by running:\n\n```console\n$ kubectl create -f examples/guestbook/all-in-one/redis-slave.yaml\nservice \"redis-slave\" created\ndeployment \"redis-slave\" created\n\n$ kubectl get services\nNAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE\nredis-master 10.0.76.248 6379/TCP 20m\nredis-slave 10.0.112.188 6379/TCP 16s\n\n$ kubectl get deployments\nNAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE\nredis-master 1 1 1 1 22m\nredis-slave 2 2 2 2 2m\n```\n\nOnce the Deployment is up, you can list the pods in the cluster, to verify that the master and slaves are running. You should see a list that includes something like the following:\n\n```console\n$ kubectl get pods\nNAME READY STATUS RESTARTS AGE\nredis-master-2353460263-1ecey 1/1 Running 0 35m\nredis-slave-1691881626-dlf5f 1/1 Running 0 15m\nredis-slave-1691881626-sfn8t 1/1 Running 0 15m\n```\n\nYou should see a single redis master pod and two redis slave pods. As mentioned above, you can get more information about any pod with: `kubectl describe pods/`. And also can view the resources on [kube-ui](http://kubernetes.io/docs/user-guide/ui/).\n\n### Step Three: Start up the guestbook frontend\n\nA frontend pod is a simple PHP server that is configured to talk to either the slave or master services, depending on whether the client request is a read or a write. It exposes a simple AJAX interface, and serves an Angular-based UX.\nAgain we'll create a set of replicated frontend pods instantiated by a Deployment — this time, with three replicas.\n\nAs with the other pods, we now want to create a Service to group the frontend pods.\nThe Deployment and Service are described in the file [all-in-one/frontend.yaml](all-in-one/frontend.yaml):\n\n\n\n```yaml\napiVersion: v1\nkind: Service\nmetadata:\n name: frontend\n labels:\n app: guestbook\n tier: frontend\nspec:\n # if your cluster supports it, uncomment the following to automatically create\n # an external load-balanced IP for the frontend service.\n # type: LoadBalancer\n ports:\n # the port that this service should serve on\n - port: 80\n selector:\n app: guestbook\n tier: frontend\n---\napiVersion: extensions/v1beta1\nkind: Deployment\nmetadata:\n name: frontend\n # these labels can be applied automatically\n # from the labels in the pod template if not set\n # labels:\n # app: guestbook\n # tier: frontend\nspec:\n # this replicas value is default\n # modify it according to your case\n replicas: 3\n # selector can be applied automatically\n # from the labels in the pod template if not set\n # selector:\n # matchLabels:\n # app: guestbook\n # tier: frontend\n template:\n metadata:\n labels:\n app: guestbook\n tier: frontend\n spec:\n containers:\n - name: php-redis\n image: brightcomputing/guestbook-frontend:latest\n resources:\n requests:\n cpu: 100m\n memory: 100Mi\n env:\n - name: GET_HOSTS_FROM\n value: dns\n # If your cluster config does not include a dns service, then to\n # instead access environment variables to find service host\n # info, comment out the 'value: dns' line above, and uncomment the\n # line below.\n # value: env\n ports:\n - containerPort: 80\n```\n\n[Download example](all-in-one/frontend.yaml?raw=true)\n\n\n#### Using 'type: LoadBalancer' for the frontend service (cloud-provider-specific)\n\nFor supported cloud providers, such as Google Compute Engine or Google Container Engine, you can specify to use an external load balancer\nin the service `spec`, to expose the service onto an external load balancer IP.\nTo do this, uncomment the `type: LoadBalancer` line in the [all-in-one/frontend.yaml](all-in-one/frontend.yaml) file before you start the service.\n\n[See the appendix below](#appendix-accessing-the-guestbook-site-externally) on accessing the guestbook site externally for more details.\n\nCreate the service and Deployment like this:\n\n```console\n$ kubectl create -f examples/guestbook/all-in-one/frontend.yaml\nservice \"frontend\" created\ndeployment \"frontend\" created\n```\n\nThen, list all your services again:\n\n```console\n$ kubectl get services\nNAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE\nfrontend 10.0.63.63 80/TCP 1m\nredis-master 10.0.76.248 6379/TCP 39m\nredis-slave 10.0.112.188 6379/TCP 19m\n```\n\nAlso list all your Deployments:\n\n```console\n$ kubectl get deployments \nNAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE\nfrontend 3 3 3 3 2m\nredis-master 1 1 1 1 39m\nredis-slave 2 2 2 2 20m\n```\n\nOnce it's up, i.e. when desired replicas match current replicas (again, it may take up to thirty seconds to create the pods), you can list the pods with specified labels in the cluster, to verify that the master, slaves and frontends are all running. You should see a list containing pods with label 'tier' like the following:\n\n```console\n$ kubectl get pods -L tier\nNAME READY STATUS RESTARTS AGE TIER\nfrontend-1211764471-4e1j2 1/1 Running 0 4m frontend\nfrontend-1211764471-gkbkv 1/1 Running 0 4m frontend\nfrontend-1211764471-rk1cf 1/1 Running 0 4m frontend\nredis-master-2353460263-1ecey 1/1 Running 0 42m backend\nredis-slave-1691881626-dlf5f 1/1 Running 0 22m backend\nredis-slave-1691881626-sfn8t 1/1 Running 0 22m backend\n```\n\nYou should see a single redis master pod, two redis slaves, and three frontend pods.\n\nThe code for the PHP server that the frontends are running is in `examples/guestbook/php-redis/guestbook.php`. It looks like this:\n\n```php\n

brightcomputing/guestbook-frontend

Tags for brightcomputing/guestbook-frontend