How to limit number of requests

Did you ever need to limit requests coming to your endpoints? Say, your maximum design capacity is near 10k requests/second, and you don’t want to probe your service on higher rates. I choose to use RateLimiter - small class from Guava. The init process aren’t so huge, just couple of lines: RateLimiter rateLimiter = RateLimiter.create(10); // 10 requests/second Then, just place rateLimiter in place, where you need to have limited requests: boolean isAcquired = rateLimiter.tryAcquire(); if (!isAcquired) { throw new NotSoFastBuddyException(...); } Links Guava

Better application deployment. Monitoring your application with Graphite/Grafana

Intro In the previous part I explained how to use Terraform, Ansible, Docker and Spring Boot to deploy applications in the cloud. Today I’d like to introduce something, which will work as a monitoring tool, inside our infrastructure. If you follow my blog posts, you should remember a post about Spring and Dropwizard Module - there I explained how you could get a meaningful metrics from your app. But wait, why you should even do monitoring and can you skip this part? Well, when I first came to the project, when a wide variety of metrics was present in each of the microservices in the ecosystem, I had a feeling that this is something which I won’t use in the future. I was right, and I didn’t use them…until my first incident, on which I had to understand what’s going on. I start looking for some explanations, and found that our service is sending many 500 statuses. Then I found out, that one dependant service, which we use to get some part of response, is broken, and problem is not on our side. From that period I introduced a couple of custom dashboards, and during incidents/crashes, I can answer most...

watch - useful unix command I've never heard of

I use ImageMagick for resizing images in one of the projects, and I needed a command to monitor folder changes in a temporary folder. So I found watch: watch -d -n 0.3 'ls -l | grep ivanursul' This command check every 0.3 seconds for current folder, and find all files, created by user ivanursul Links Linux Watch

Better application deployment with DigitalOcean, Terraform, Ansible and Docker. Connecting Terraform with Ansible.

Just creating instances in the cloud is an intermediate result. Yes, you know don’t need to create them manually, but it’s not a target. We need to configure them somehow, deploy logic, restart, etc. That’s why this article is about describing how to work with Terraform instances - using Ansible tool. What do you need to do before starting Create terraform instance - here’s how Install ansible: brew install ansible How Ansible knows about Terraform Let’s take a close look how Ansible will recognize terraform instances. Normally, this is being done by specifying instances in inventory file - the idea is to have a file, which contains all the IP addresses, organized by the group. Let’s say, you have one load balancer and three instances of an application, then you need to have following inventory file: [lb] [app] Because we are creating instances on the fly, we don’t have a predefined set of IP addresses, which we’re going to use. That’s why we should use dynamic inventory. As we’re using Terraform, we need some tool, which knows how to read instances from terraform.tfstate file and represent them to ansible. Personally, I found it useful to use...

Better application deployment with DigitalOcean, Terraform, Ansible and Docker. DNS Records

As we are creating our instances on the fly, using Terraform declarative scripts, we can also need to create dns domains and records. Let’s say, you have two environments: dev and prod, and you you want to have your backend application stored under and Luckily, terraform allows to do such things Required steps Digitalocean account Ready and bought domain somewhere Already defined terraform instances. See article from previous part. Digital Ocean Domain Add additional declaration to your terraform file: resource "digitalocean_domain" "default" { name = "" ip_address = "${}" } DigitalOcean Record If you want your app to be accessible through, without wwwm you should add this lines: resource "digitalocean_record" "CNAME-www" { domain = "${}" type = "CNAME" name = "www" value = "@" } Final Check You should see your domain name in the list of networking domains here - On the next part we will see how to start working with cloud instances using ansible, and how to connect ansible with terraform.