Kubernetes: Modeling Jobs/Cron tasks for Postgres + Tomcat application - docker

Question

I work on an open source system that is comprised of a Postgres database and a tomcat server. I have docker images for each component. We currently use docker-compose to test the application.
I am attempting to model this application with kubernetes.
Here is my first attempt.
apiVersion: v1
kind: Pod
metadata:
name: dspace-pod
spec:
volumes:
- name: "pgdata-vol"
emptyDir: {}
- name: "assetstore"
emptyDir: {}
- name: my-local-config-map
configMap:
name: local-config-map
containers:
- image: dspace/dspace:dspace-6_x
name: dspace
ports:
- containerPort: 8080
name: http
protocol: TCP
volumeMounts:
- mountPath: "/dspace/assetstore"
name: "assetstore"
- mountPath: "/dspace/config/local.cfg"
name: "my-local-config-map"
subPath: local.cfg
#
- image: dspace/dspace-postgres-pgcrypto
name: dspacedb
ports:
- containerPort: 5432
name: http
protocol: TCP
volumeMounts:
- mountPath: "/pgdata"
name: "pgdata-vol"
env:
- name: PGDATA
value: /pgdata
I have a configMap that is setting the hostname to the name of the pod.
apiVersion: v1
kind: ConfigMap
metadata:
creationTimestamp: 2016-02-18T19:14:38Z
name: local-config-map
namespace: default
data:
local.cfg: |-
dspace.dir = /dspace
db.url = jdbc:postgresql://dspace-pod:5432/dspace
dspace.hostname = dspace-pod
dspace.baseUrl = http://dspace-pod:8080
solr.server=http://dspace-pod:8080/solr
This application has a number of tasks that are run from the command line.
I have created a 3rd Docker image that contains the jars that are needed on the command line.
I am interested in modeling these command line tasks as Jobs in Kubernetes. Assuming that is a appropriate way to handle these tasks, how do I specify that a job should run within a Pod that is already running?
Here is my first attempt at defining a job.
apiVersion: batch/v1
kind: Job
#https://kubernetes.io/docs/concepts/workloads/controllers/jobs-run-to-completion/
metadata:
name: dspace-create-admin
spec:
template:
spec:
volumes:
- name: "assetstore"
emptyDir: {}
- name: my-local-config-map
configMap:
name: local-config-map
containers:
- name: dspace-cli
image: dspace/dspace-cli:dspace-6_x
command: [
"/dspace/bin/dspace",
"create-administrator",
"-e", "test#test.edu",
"-f", "test",
"-l", "admin",
"-p", "admin",
"-c", "en"
]
volumeMounts:
- mountPath: "/dspace/assetstore"
name: "assetstore"
- mountPath: "/dspace/config/local.cfg"
name: "my-local-config-map"
subPath: local.cfg
restartPolicy: Never

Answer 1

The following configuration has allowed me to start my services (tomcat and postgres) as I hoped.
apiVersion: v1
kind: ConfigMap
metadata:
creationTimestamp: 2016-02-18T19:14:38Z
name: local-config-map
namespace: default
data:
# example of a simple property defined using --from-literal
#example.property.1: hello
#example.property.2: world
# example of a complex property defined using --from-file
local.cfg: |-
dspace.dir = /dspace
db.url = jdbc:postgresql://dspacedb-service:5432/dspace
dspace.hostname = dspace-service
dspace.baseUrl = http://dspace-service:8080
solr.server=http://dspace-service:8080/solr
---
apiVersion: v1
kind: Service
metadata:
name: dspacedb-service
labels:
app: dspacedb-app
spec:
type: NodePort
selector:
app: dspacedb-app
ports:
- protocol: TCP
port: 5432
# targetPort: 5432
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: dspacedb-deploy
labels:
app: dspacedb-app
spec:
selector:
matchLabels:
app: dspacedb-app
template:
metadata:
labels:
app: dspacedb-app
spec:
volumes:
- name: "pgdata-vol"
emptyDir: {}
containers:
- image: dspace/dspace-postgres-pgcrypto
name: dspacedb
ports:
- containerPort: 5432
name: http
protocol: TCP
volumeMounts:
- mountPath: "/pgdata"
name: "pgdata-vol"
env:
- name: PGDATA
value: /pgdata
---
apiVersion: v1
kind: Service
metadata:
name: dspace-service
labels:
app: dspace-app
spec:
type: NodePort
selector:
app: dspace-app
ports:
- protocol: TCP
port: 8080
targetPort: 8080
name: http
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: dspace-deploy
labels:
app: dspace-app
spec:
selector:
matchLabels:
app: dspace-app
template:
metadata:
labels:
app: dspace-app
spec:
volumes:
- name: "assetstore"
emptyDir: {}
- name: my-local-config-map
configMap:
name: local-config-map
containers:
- image: dspace/dspace:dspace-6_x-jdk8-test
name: dspace
ports:
- containerPort: 8080
name: http
protocol: TCP
volumeMounts:
- mountPath: "/dspace/assetstore"
name: "assetstore"
- mountPath: "/dspace/config/local.cfg"
name: "my-local-config-map"
subPath: local.cfg
After applying the configuration above, I have the following results.
$ kubectl get services -o wide
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
dspace-service NodePort 10.104.224.245 <none> 8080:32459/TCP 3s app=dspace-app
dspacedb-service NodePort 10.96.212.9 <none> 5432:30947/TCP 3s app=dspacedb-app
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 22h <none>
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
dspace-deploy-c59b77bb8-mr47k 1/1 Running 0 10m
dspacedb-deploy-58dd85f5b9-6v2lf 1/1 Running 0 10
I was pleased to see that the service name can be used for port forwarding.
$ kubectl port-forward service/dspace-service 8080:8080
Forwarding from 127.0.0.1:8080 -> 8080
Forwarding from [::1]:8080 -> 8080
I am also able to run the following job using the defined service names in the configMap.
apiVersion: batch/v1
kind: Job
metadata:
name: dspace-create-admin
spec:
template:
spec:
volumes:
- name: "assetstore"
emptyDir: {}
- name: my-local-config-map
configMap:
name: local-config-map
containers:
- name: dspace-cli
image: dspace/dspace-cli:dspace-6_x
command: [
"/dspace/bin/dspace",
"create-administrator",
"-e", "test#test.edu",
"-f", "test",
"-l", "admin",
"-p", "admin",
"-c", "en"
]
volumeMounts:
- mountPath: "/dspace/assetstore"
name: "assetstore"
- mountPath: "/dspace/config/local.cfg"
name: "my-local-config-map"
subPath: local.cfg
restartPolicy: Never
Results
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
dspace-create-admin-kl6wd 0/1 Completed 0 5m
dspace-deploy-c59b77bb8-mr47k 1/1 Running 0 10m
dspacedb-deploy-58dd85f5b9-6v2lf 1/1 Running 0 10m
I still have some work to do persisting the volumes.