I needed to add parser settings for CoreDNS working on my Kubernetes cluster for troubleshooting but I got an error "nested repeat operator '+' and '' was replaced with '' in regular expression." I had no idea why it happened because the additional regular expression was valid. The cause of the error was my …

After getting the CKA, I decided to try to get CKAD. As I explained in my previous post , the Linux Foundation has a big sale on black friday every year. It's a very valuable offer because the "Course + Certification Bundles" are discounted 60% with free swag. So, I purchased "Kubernetes for Developers …

The Linux Foundation has a big sale on black friday every year. It's a very valuable offer because the "Course + Certification Bundles" are discounted 60% with free swag. It’s cheaper than the normal price of an exam! And "Power Bundles" are more discounted. So, I purchased "Kubernetes …

It’s very easy to get information about how to suspend CronJob on Kubernetes clusters. It just executes the "kubectl patch" command. However, if its job is working at that time, the job will not be stopped and it’s impossible to terminate by "kubectl delete pod" command when the restartPolicy was …

There are a lot of samples of Kubernetes and Docker Compose which define public images like nginx:alpine, golang php-fpm and so on. However even though it’s easy to use, it’s not good for production environments because there's a possibility that they are not up-to-date. For example, I’m trying with one of the famous …

One of the useful and powerful function is the roll back for me. Basically, all applications on our cluster are deployed automatically by CodePipeline in AWS but if some trouble happen, rolling back to the previous version is one of our options. At that time, all I have to do is the following command. 1$ kubectl …

When running Memcached on the Kubernetes cluster, the cache data will disappear whenever the pod restarts. I know that Redis has the built-in replication and it can be able to have data on persistence disks. However, I have some reasons to run the Memecached on our Kubernetes cluster. So, I was thinking about it and I …

Once build the CI/CD which runs automatically from build to deployment, developers are afraid that some problematic container image will be deployed and it will cause service unavailable. Especially web sites should be checked by some scraping tool like Selenium but it’s hard to do that for most start-up companies …

When getting started to use AWS EKS for building Kubernetes clusters, we should consider the limitations of the number of IP addresses it depends on the instance size. Actually, I didn’t know about it because I just overlooked it on the official document. I know it was my mistake but it should be a blind spot for some …

When I was setting up HAProxy running on our Kubernetes cluster, I defined the log format as JSON and I got a lot of BADREQ logs with status code 400 as follows. 1{ 2 "conn": { 3 "act": 7, 4 "fe": 7, 5 "be": 0, 6 "srv": 0 7 }, 8 "queue": { 9 "backend": 0, 10 …