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Add simple cron job reference walkthrough
**What** - Documents a very simple cronjob example in kubernetes - Includes a comment about modifying the example for multiple namespaces - Includes a comment about handling basic auth - A demo repo is available at https://github.com/LucasRoesler/openfaas-cron-demo **Why** Closes openfaas/faas#719 Signed-off-by: Lucas Roesler <[email protected]>
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‎docs/reference/cron.md

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# Scheduling function runs
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If you are deploying OpenFaaS to [Kubernetes][k8s], then we can easily run functions as cron jobs using the aptley named [Cron Job resource][k8scron].
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We assume that you have used the [recommended install of `faas-netes`][faasdeploy] which menas that you have OpenFaaS deployed into two namespaces:
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1. `openfaas` for the core componentes (ui, gateway, etc)
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2. `openfaas-fn` for the function deployments
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## Simple Cron Job
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For this example, we use the [sample `nodeinfo` function][nodeinfo], which can be deployed using this stack file
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```yaml
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# stack.yaml
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provider:
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name: faas
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gateway: http://gateway.openfaas.local
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functions:
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nodeinfo:
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lang: dockerfile
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handler: node main.js
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image: functions/nodeinfo:latest
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skip_build: true
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```
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and the cli
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```yaml
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$ faas deploy
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```
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We can then define a Kubernetes cron job to call this function every minute using this manifest file:
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```yaml
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# node-cron.yaml
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apiVersion: batch/v1beta1
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kind: CronJob
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metadata:
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name: nodeinfo
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namespace: openfaas
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spec:
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schedule: "*/1 * * * *"
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concurrencyPolicy: Forbid
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successfulJobsHistoryLimit: 1
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failedJobsHistoryLimit: 3
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jobTemplate:
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spec:
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template:
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spec:
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containers:
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- name: faas-cli
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image: openfaas/faas-cli:0.6.9
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args:
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- /bin/sh
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- -c
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- echo "verbose" | ./faas-cli invoke nodeinfo -g http://gateway:8080
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restartPolicy: OnFailure
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```
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The important thing to notice is that we are using a Docker container with the `faas-cli` to invoke the function. This keeps the job very generic and easy to generize to other functions.
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We schedule the job by applying our manifest
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```sh
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$ kubectl apply -f node-cron.yaml
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$ kubectl -n=openfaas get cronjob nodeinfo --watch
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NAME SCHEDULE SUSPEND ACTIVE LAST SCHEDULE AGE
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nodeinfo */1 * * * * False 0 <none> 42s
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nodeinfo */1 * * * * False 1 2s 44s
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nodeinfo */1 * * * * False 0 12s 54s
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nodeinfo */1 * * * * False 1 2s 1m
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nodeinfo */1 * * * * False 0 12s 1m
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```
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Unfortunately, there is no one-line command in `kubectl` for getting the logs from a cron job. Kuberenets creates new Job objects for each run of the CronJob, so we can look up that last run of our CronJob using
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```sh
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$ kubectl -n openfaas get job
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NAME DESIRED SUCCESSFUL AGE
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nodeinfo-1529226900 1 1 6s
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```
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We can use this to then get the output logs
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```sh
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$ kubectl -n openfaas logs -l "job-name=nodeinfo-1529226900"
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Hostname: nodeinfo-6fffdb4446-57mzn
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Platform: linux
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Arch: x64
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CPU count: 1
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Uptime: 997420
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[ { model: 'Intel(R) Xeon(R) CPU @ 2.20GHz',
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speed: 2199,
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times:
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{ user: 360061300,
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nice: 2053900,
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sys: 142472900,
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idle: 9425509300,
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irq: 0 } } ]
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{ lo:
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[ { address: '127.0.0.1',
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netmask: '255.0.0.0',
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family: 'IPv4',
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mac: '00:00:00:00:00:00',
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internal: true },
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{ address: '::1',
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netmask: 'ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff',
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family: 'IPv6',
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mac: '00:00:00:00:00:00',
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scopeid: 0,
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internal: true } ],
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eth0:
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[ { address: '10.4.2.40',
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netmask: '255.255.255.0',
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family: 'IPv4',
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mac: '0a:58:0a:04:02:28',
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internal: false },
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{ address: 'fe80::f08e:d8ff:fecc:9635',
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netmask: 'ffff:ffff:ffff:ffff::',
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family: 'IPv6',
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mac: '0a:58:0a:04:02:28',
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scopeid: 3,
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internal: false } ] }
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```
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## Other considerations
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This simple example uses the default deployment of OpenFaaS without any authentication.
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### Multiple Namespaces
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In this example, I created the CronJob in the same namespace as the `gateway`. If we deploy the CronJob in a different namespace, then we need to update the job arguments to accomidate. Fortunately, with Kubernetes DNS, this is simply changing the gateway parameter like this `./faas-cli invoke nodeinfo -g http://gateway.othernamespace:8080`
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### Authentication
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If you have enabled basic auth on the gateway, then the invoke command will also need to be updated to first login the cli client. Assuming that you have created a secret with a file for the username and a separate file for the password, like this
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```sh
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$ kubectl -n openfaas create secret generic faas-basic-auth --from-file=./username --from-file=./password
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```
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You could then update the CronJob to login, like this
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```yaml
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# nodeauth-cron.yaml
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apiVersion: batch/v1beta1
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kind: CronJob
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metadata:
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name: nodeinfo-auth
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namespace: openfaas
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spec:
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schedule: "*/1 * * * *"
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concurrencyPolicy: Forbid
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successfulJobsHistoryLimit: 1
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failedJobsHistoryLimit: 3
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jobTemplate:
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spec:
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template:
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spec:
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containers:
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- name: faas-cli
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image: openfaas/faas-cli:0.6.9
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env:
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- name: FAAS_USERNAME
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valueFrom:
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secretKeyRef:
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name: faas-basic-auth
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key: username
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- name: FAAS_PASSWORD
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valueFrom:
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secretKeyRef:
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name: faas-basic-auth
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key: password
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args:
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- /bin/sh
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- -c
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- ./faas-cli login -g http://gateway:8080 -u $FAAS_USERNAME -p $FAAS_PASSWORD
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- echo "verbose" | ./faas-cli invoke nodeinfo -g http://gateway:8080
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restartPolicy: OnFailure
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```
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[k8s]: https://kubernetes.io/ "Kubernetes"
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[k8scron]: https://kubernetes.io/docs/concepts/workloads/controllers/cron-jobs/ "Kuberenetes CRON Jobs"
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[k8sjob]: https://kubernetes.io/docs/concepts/workloads/controllers/cron-jobs/ "Kuberenetes Jobs"
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[faasdeploy]: https://github.com/openfaas/faas-netes/tree/master/chart/openfaas#deploy-openfaas
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[nodeinfo]: https://github.com/openfaas/faas/tree/master/sample-functions/NodeInfo

‎mkdocs.yml

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- Secrets: ./reference/secrets.md
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- Auth: ./reference/authentication.md
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- CORS: ./reference/cors.md
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- Cron: ./reference/cron.md
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- Design & Architecture:
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- Gateway: ./architecture/gateway.md
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- Watchdog: ./architecture/watchdog.md

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