This example shows how to build a simple multi-tier web application using Kubernetes and Docker.

The example combines a web frontend and an external service that provides MySQL database. We use CloudSQL on Google Cloud Platform in this example, but in principle any approach to running MySQL should work.

This example assumes that you have a basic understanding of kubernetes services and that you have forked the repository and turned up a Kubernetes cluster:

$ cd kubernetes $ cluster/kube-up.sh

Follow the official instructions to set up Cloud SQL instance.

In the remaining part of this example we will assume that your instance is named "phabricator-db", has IP 1.2.3.4, is listening on port 3306 and the password is "1234".

In order to allow phabricator to connect to your Cloud SQL instance you need to run the following command to authorize all your nodes within a cluster:

NODE_NAMES=`kubectl get nodes | cut -d"" -f1 | tail -n+2` NODE_IPS=`gcloud compute instances list $NODE_NAMES| tr -s ""| cut -d"" -f 5 | tail -n+2` gcloud sql instances patch phabricator-db --authorized-networks $NODE_IPS

Otherwise you will see the following logs:

$ kubectl logs phabricator-controller-02qp4 [...] Raw MySQL Error: Attempt to connect to root@1.2.3.4 failed with error #2013: Lost connection to MySQL server at 'reading initial communication packet', system error: 0.

To start Phabricator server use the file examples/phabricator/phabricator-controller.json which describes a replication controller with a single pod running an Apache server with Phabricator PHP source:

{ "kind": "ReplicationController", "apiVersion": "v1", "metadata": { "name": "phabricator-controller", "labels": { "name": "phabricator" } }, "spec": { "replicas": 1, "selector": { "name": "phabricator" }, "template": { "metadata": { "labels": { "name": "phabricator" } }, "spec": { "containers": [ { "name": "phabricator", "image": "fgrzadkowski/example-php-phabricator", "ports": [ { "name": "http-server", "containerPort": 80 } ], "env": [ { "name": "MYSQL_SERVICE_IP", "value": "1.2.3.4" }, { "name": "MYSQL_SERVICE_PORT", "value": "3306" }, { "name": "MYSQL_PASSWORD", "value": "1234" } ] } ] } } } }

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Create the phabricator pod in your Kubernetes cluster by running:

$ kubectl create -f examples/phabricator/phabricator-controller.json

Note: Remember to substitute environment variable values in json file before create replication controller.

Once that's up you can list the pods in the cluster, to verify that it is running:

kubectl get pods

You'll see a single phabricator pod. It will also display the machine that the pod is running on once it gets placed (may take up to thirty seconds):

NAME READY STATUS RESTARTS AGE phabricator-controller-9vy68 1/1 Running 0 1m 

If you ssh to that machine, you can run docker ps to see the actual pod:

me@workstation$ gcloud compute ssh --zone us-central1-b kubernetes-node-2 $ sudo docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 54983bc33494 fgrzadkowski/phabricator:latest "/run.sh" 2 hours ago Up 2 hours k8s_phabricator.d6b45054_phabricator-controller-02qp4.default.api_eafb1e53-b6a9-11e4-b1ae-42010af05ea6_01c2c4ca

(Note that initial docker pull may take a few minutes, depending on network conditions. During this time, the get pods command will return Pending because the container has not yet started )

A Kubernetes 'service' is a named load balancer that proxies traffic to one or more containers. The services in a Kubernetes cluster are discoverable inside other containers via environment variables. Services find the containers to load balance based on pod labels. These environment variables are typically referenced in application code, shell scripts, or other places where one node needs to talk to another in a distributed system. You should catch up on kubernetes services before proceeding.

The pod that you created in Step Three has the label name=phabricator. The selector field of the service determines which pods will receive the traffic sent to the service.

Use the file examples/phabricator/phabricator-service.json:

{ "kind": "Service", "apiVersion": "v1", "metadata": { "name": "phabricator" }, "spec": { "ports": [ { "port": 80, "targetPort": "http-server" } ], "selector": { "name": "phabricator" }, "type": "LoadBalancer" } }

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To create the service run:

$ kubectl create -f examples/phabricator/phabricator-service.json phabricator

To play with the service itself, find the external IP of the load balancer:

$ kubectl get servicesNAME LABELS SELECTOR IP(S) PORT(S)kubernetes component=apiserver,provider=kubernetes <none> 10.0.0.1 443/TCPphabricator <none> name=phabricator 10.0.31.173 80/TCP $ kubectl get services phabricator -o json | grep ingress -A 4 "ingress": [ { "ip": "104.197.13.125" } ]

and then visit port 80 of that IP address.

Note: Provisioning of the external IP address may take few minutes.

Note: You may need to open the firewall for port 80 using the [console][cloud-console] or the gcloud tool. The following command will allow traffic from any source to instances tagged kubernetes-node:

$ gcloud compute firewall-rules create phabricator-node-80 --allow=tcp:80 --target-tags kubernetes-node

To turn down a Kubernetes cluster:

$ cluster/kube-down.sh