Automate SQL server data pipelines with Kubernetes

Kubernetes provides a great way to run modern infrastructure. SQL server is a widely deployed database. When you combine these two, you get a robust way of running a data pipeline using a modern platform.

Data pipelines are large part of all data infrastructure. The need to move data between different systems, is almost universal and tools/process to achieve this is generally referred to as a data pipeline. In this post we will see how we can leverage Kubernetes jobs API to build and run data pipelines. This is a great way to integrate data pipelines into CI/CD practices too.

Following steps will create an example SQL pipeline and run it against SQL server using Kubernetes. We will be running a very simple query to list all the tables.

1. Lets define our job in the file sql-k8s-job.yaml.

   apiVersion: batch/v1
   kind: Job
   metadata:
   name: sqljob
   spec:
   template:
       spec:
       containers:
       - name: sqljobcontainer
           image: microsoft/mssql-tools
           command: ["/opt/mssql-tools/bin/sqlcmd"]
           args: [ "-S", "mysqlserver.database.windows.net", "-d", "mydatabase", "-U", "User", "-P", "PassWord", "-I", "-Q", "SELECT name FROM sys.tables" ]
       restartPolicy: Never

   Here, we are specifying that this is a job definition(kind: Job) with the name sqljob. The spec part is similar to other container specifications. We are specifying it to create a container with a name sqljobcontainer with the image microsoft/mssql-tools. This image has all MSSQL tools installed to connect to a remote MSSQL instance. We are also specifying that it should run sqlcmd command with the specified arguments, including server, database, password and query when it starts the container. Note that, I am specifying password in the job definition file here just for simplicity, you should use kubernetes secrets when doing anything serious.

2. Lets run it. You can run it locally using minikube or on cloud.

   kubectl create -f sql-k8s-job.yaml
   
   job "sqljob" created

3. You can see the details on the job.

   kubectl describe jobs/sqljob
   
   Name:           sqljob
   Namespace:      default
   Selector:       controller-uid=85530e4e-2eef-11e8-9e3f-92f68014defe
   Labels:         controller-uid=85530e4e-2eef-11e8-9e3f-92f68014defe
                   job-name=sqljob
   Annotations:    <none>
   Parallelism:    1
   Completions:    1
   Start Time:     Fri, 23 Mar 2018 16:11:30 -0700
   Pods Statuses:  1 Running / 0 Succeeded / 2 Failed
   Pod Template:
   Labels:  controller-uid=85530e4e-2eef-11e8-9e3f-92f68014defe
           job-name=sqljob
   Containers:
   sqljobcontainer:
       Image:  microsoft/mssql-tools
       Port:   <none>
       Command:
       /opt/mssql-tools/bin/sqlcmd
       Args:
       -S
       mysqlserver.database.windows.net
       -d
       mydatabase
       -U
       User
       -P
       PassWord
       -I
       -Q
       SELECT name FROM sys.tables
       Environment:  <none>
       Mounts:       <none>
   Volumes:        <none>
   Events:
   Type    Reason            Age   From            Message
   ----    ------            ----  ----            -------
   Normal  SuccessfulCreate  30s   job-controller  Created pod: sqljob-qsdtg
   Normal  SuccessfulCreate  20s   job-controller  Created pod: sqljob-pws2m
   Normal  SuccessfulCreate  10s   job-controller  Created pod: sqljob-lb2dz

   You can also see the job on the kubernetes dashboard. You can open the kubernetes dashboard using

   minikube dashboard

   You can see the job under jobs section in the dashboard.

   

4. Lets see the output from the job.

   kubectl logs jobs/sqljob

   You should see the list of all the tables in your database.

5. Finally you can delete the job using

   kubectl delete jobs/sqljob
   
   job "sqljob" deleted

   Now that you have are comfortable with this job, you can easily convert this into a recurring job. Kubernetes jobs support for cron jobs. You can include the cron syntax schedule in the container spec to convert a job into a cron job. For example, by including schedule: "0 * * * *" in the spec section of the job, your job will run every 1-hour. Crontab syntax is hard to remember and undertstand, but luckily you can just use crontab.guru.

Thats it. Go build your pipeline !