Category Archives: docker

How Docker uses cgroups to set resource limits?

Today, I was interested to know how does Docker uses cgroups to set resource limits. In this short post, I will share with you what I learnt.

I will assume that you have a machine on which Docker is installed.

Docker allows you to pass resource limits using the command-line options. Let’s assume that you want to limit the IO read rate to 1mb per second for a container. You can start a new container with the device-read-bps option as shown below

$ docker run -it --device-read-bps /dev/sda:1mb centos

In the above command, we are instantiating a new centos container. We specified device-read-bps option to limit the read rate to 1mb per second for /dev/sda device.

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Using wait-for-it with Oracle database docker image

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Today, I was working with an application that uses Oracle as the database. We decided dockerize the application to make it easy for fellow developers to work with the beast. We found a working Oracle docker image by sath89. Oracle 12c Docker image is close to 5.7GB on disk so we are not talking about lightweight containers here :). Once image was dowloaded, running image was as easy as running the following command.
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Amazon ECS: The Modern Cluster Manager Part 1

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In the last few posts, we looked at various Docker utilities and how XL Deploy can make it easy for enterprises to adopt and use Docker. Docker streamlines software development and testing for teams that have started embracing it. The package once deploy anywhere (PODA) capability of Docker minimises the issue of environmental (like staging, quality assurance, and production) differences. Continue reading →

Upgrading Docker Compose to latest version

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If you use Docker for Mac or something similar, Docker Compose will be installed along with it. Docker Compose has a different release timeline for Docker for Mac so you will not be able to try latest version of Docker compose until you upgrade Docker for Mac. This is limiting. You should be able to install Docker compose independently. To achieve that, you can run following command

$ composeVersion=1.13.0
$ curl -L https://github.com/docker/compose/releases/download/$composeVersion/docker-compose-`uname -s`-`uname -m` > /usr/local/bin/docker-compose$ chmod +x /usr/local/bin/docker-compose

In the above commands, $ signify bash prompt. You don’t have to type it. Now, you can check Compose version using the command shown below.

$ docker-compose version

Talk: Container Performance Analysis

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Today, I watched DockerCon 2017 talk on Container Performance Analysis. Talk is given by Brendan Gregg, Senior Performance Architect at Netflix. In his talk, he shares various linux tools that can help you understand performance of your container platform. It is a great talk for anyone trying to do performance analysis of containers. In one of his slides, he shared 10 tools that he will use to start the investigation.

uptime to check load averages
dmesg | tail to check kernel errors
vmstat 1 to see overall stats by time
mpstat -P ALL 1 to check CPU balance
pidstat 1 to check process usage
iostat -xz 1 to disk I/O
free -m to check memory usage
sar -n DEV 1 to check network I/O
sar -n TCP, ETCP 1 to view TCP stats
top for overview

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Multi-stage Docker Image Build for Java Applications

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A few days back, I discovered a new Docker feature — multi-stage builds. The multi-stage build feature helps you create thin Docker images by giving possibility to divide image building process into multiple stages. Artifacts produced in one stage can be resused by another stage. This is very beneficial for languages like Java as multiple steps are required to build the Docker image. The main advantage of multi-stage build feature is that it can help you create smaller size images. This feature is not yet available in stable versions of Docker. It will become available in Docker 17.05. To use this feature, you have to use edge version of Docker CE.

To build a Docker image for a Java application, you first need to build the Java project. Java build process needs JDK and a build tool like Maven, Gradle, or Ant. Once Java binary artifact is produded, you can package the binary in a Docker image. For running a Java binary, you only need JRE so you don’t have to pay the cost of bundling the whole JDK.

You can read full blog at https://blog.xebialabs.com/2017/05/25/multi-stage-docker-image-build-for-java-applications/

5 Docker Utilities You Should Know

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There are a lot of cool Docker utilities that you can find on the web. Most of these are open source and available on Github. I have become an active user of Docker for last two years, using it for most of my development projects. As you start using Docker, you will find Docker is suitable for more use cases than you initially envisioned it for. You will want Docker to do a little more for you, and it will not disappoint you.

Docker community is very active, a lot of useful utilities keep popping daily. It is difficult to keep check of all the innovation happening in the community. In the following post, I have collected some interesting and useful Docker utilities which I use in my daily work. These utilities makes me more productive, otherwise would have been a manual work.

In this post, I will cover watchtower, docker-gc, docker-slim, rocker, and ctop utilities. You can read full blog at https://blog.xebialabs.com/2017/05/18/5-docker-utilities-you-should-know/.