Short question: is it ok (aren't there any contradictions with Docker ideology) to compile and start application from sources inside Docker container?
Assume that I have some hypothetical application. Let it be Java web service built with Maven, located somewhere in GitHub. Specifics doesn't matter here.
But before starting this service, I need to set-up several config files with right parameters, known at deployment time. Right now I can build fully-preconfigured application package with a single maven command, passing all the necessary configurations at build command.
Now assume that I need to make it a Docker container and don't have time to refactor it somehow right now. So I have a plan: let my docker image have Maven and Git, ENTRYSCRIPT clones my Git repository, builds and starts the application, passing all the necessary parameters via environment.
Is it suitable plan, or it's just wrong?
Related
I have an existing Symfony 5 project with a mysql database and a nginx Webserver. I wanna dockerize this project, but on the web I have found different opinions how to do that.
My plan is to write a multi-stage Docker file with at least a dev and a prod stage and let this build with docker-swarm. In my opinion it is useful to install the complete code during the build and having multiple composer.json files (one for every stage). In the web I have found opinions to not install the app new on every build but to copy the vendor and var folder to the container. Another opinion was to start the installation after the build process of the container is ready. But I think with that the service is not ready, when the app is successfully deployed.
What are you thinking is the best practice here?
Build exactly the same image for all environments
Do not build 2 different images for prod and dev. One of the main docker benefits is, that you can provide exactly the same environment for production and dev.
You should control your environment with ENV vars. for example, you can enable Xdebug for dev and disable it for prod.
Composer has option to install dev and production packages. You should use this feature.
If you decide to install some packages to dev. Try to use the same Dockerfile for both environment. Do not use Dockerfile.prod and Dockerfile.dev It will introduce some mess in the future.
Multistage build
You can do multistage build described in the official Docker documentation if your build environment requires much more dependencies than your runtime.
Example of it is compilation of the program. During compilation you need a lot of libraries, and you produce single binary. So your runtime does not need all dev libraries.
First stage can be build in second stage you just copy binary and it is.
Build all packages into the docker image
You should build your application when Docker image is building. All libraries and packages should be copied into image, you should not install them when the application is starting. Reasons:
Application starts faster when everything is installed
Some of the libraries can be changed in future or removed. You will be in troubles and probably you will spend a lot of time to do debugging.
Implement health checks
You should implement Health-Check. Applications require external dependencies, like Passwords, API KEY, some non sensitive data. Usually, We inject data with environment variables.
You should check if all required variables are passed, and have good format before your application is started. You can implement Health-Check or you can check it in the entrypoint.
Test your solution before it is released
You should implement mechanism of testing your images. For example in the CI:
Run your unit tests before image is built
Build the Docker image
Start new application image with dummy data. If you require PostgreSQL DB you can start another container,
Run integration tests.
Publish new version of the image only if all tests pass.
I've a simple REST API in the weblogic application. I've to deploy the application as the docker container. But, I'm facing a problem in defining the Dockerfile.
Dockerfile
FROM store/oracle/weblogic:12.2.1.4
COPY target/app.war /u01/oracle
Above is my current Dockerfile. With the current dockerfile, I have to manually deploy the application on the weblogic server. We would like to automate the application deployment using Dockerfile and didn't get the exact examples.
Please advise.
This is a complex task, so it is hard to explain the whole process here.
The high-level steps that you need to execute are the followings:
Start a properly configured WebLogic domain in Docker. This task involves the creation of the admin and managed servers and WL cluster, etc.
Build the application that you wanna deploy
Configure the database properly if you have any
Create the WL resources like connection pool, JMS, etc manually or via WLST script
Deploy your artifact via the WL web console or with WLST script or copy the file under the autodeploy directory
Be careful because the tasks that you executed manually will be lost if you drop your docker container.
You can find concrete examples, use cases, automated scripts that you can use and well prepared, ready for use WebLogic Docker images here: https://github.com/zappee/docker-images
If you have a concrete question, not a general one, like this, then please start a new thread.
Take a look at the GitHub project:
https://github.com/oracle/docker-images/tree/master/OracleWebLogic/dockerfiles
I'm trying to start two containers (each with different image) using Jenkins shell commands. I tried installing docker extension in Jenkins and/or setting docker in global configuration tools. I am also doing all this in a pipeline. After executing docker run... I'm getting Docker: not found error in Jenkins console output.
I am also having a hard time finding a guide on the internet that describes exactly what I wish to accomplish. If it is of any importance, I'm trying to start a Selenium Grid and a Selenium Chrome Node and then using maven (that is configured and works correctly) send a test suite on that node.
If u have any experience with something similiar to what I wish to accomplish, please share your thoughts as what the best approach is to this situation.
Cheers.
That's because docker images that you probably create within your pipeline cannot also run (become containers) within the pipeline environment, because that environment isn't designed to also host applications.
You need to find a hosting provider for your docker images (e.g. Azure or GCP). Once you set up the hosting part, you need to add a step to your pipeline to upload/push the image to that provider's docker registry or to the free public Docker Hub. Then, finally, add a step to your pipeline to send a command to your hosting, to download the image from whichever docker registry you chose, and to launch the image into a container (this last part of download and launch is covered by docker run). Only at that point you have a running app.
Good luck.
Somewhat relevant (maybe it'll help you understand how some of those things work):
Command docker build is comparable to the proces of producing an installer package such as MSI.
Docker image is comparable to an installation package (e.g. MSI).
Command docker run is comparable to running an installer package with the goal of installing an app. So, using same analogy, running an MSI installs an app.
Container is comparable to installed application. Just like an app, docker container can run or be in stopped state. This depends on the environment, which I referred to as "hosting" above.
Just like you can build an MSI package on one machine and run it on other machines, you build docker images on one machine (pipeline host, in your case), but you need to host them in environments that support that.
I started learning devops recently. Guys I have a doubt here please solve. After testing Jenkins package everything including code and dependencies into a war/jar file. Even dockerfile contains application's source code and dependencies. Now if we are using the docker container to deploy onto production server. Now where do we use the war file that is generated from JEnkins? someone please clarify.
So lets take Jenkins itself as an example. you can download jenkins.war but still you need a place to host this war file so you can use docker for that. think of it as an alternative for virtual machines.
So the jar file that you have generated through jenkins build needs java or tomcat or whatever external dependencies to be up and running docker can do that for you. Take a look at the following example:
Run a Simple .jar Application in a Docker Container
I don't like when it comes to release my projects on production server.. May be i just don't have enough experience, nobody taught me how to do this in a right way.
For now i have several repos with scala (on top of spray). I have everything to build and run this projects on my local machine (of course, i develop them). So installed jenkins on my production server in order to sync from git, build and run. It works for now but i don't like it, because i need to install jenkins on every machine i want to have run my projects. What if i want to show my project to my friend in cafe?
So i've come with idea: what if i run tests before building app, make portable build (e.q. with sbt native packager) and save it on remote server "release server". That server just keeps these ready to be launched apps.
Then i go to production server, run bash script that downloads executables from release server and runs my project on a machine
In future i want to:
download and run projects inside docker containers.
keep ready to be served static files for frontend. Run docker
container with nginx and linked volume with static files
I heard about nexus (http://www.sonatype.org/nexus/), that artist use to save their songs, images, so on. I believe there should be open source projects that expose idea like mine
Any help is appreciated!
A common anti-pattern, in my opinion, is to build the software every time you perform a deployment.You are best advised to separate the process of build from the act of deployment by introducing a binary repository manager (you've mentioned on such example, nexus).
Best Practice - Using a Repository Manager
Binary repository manager
How can I automatically deploy a war from Nexus to Tomcat?
Only successfully tests builds get pushed to the repository, so you can treat each successful build as a mini-release. A by-product of this is that your production server does not have to have all the build software pre-installed (like, Jenkins, ANT , Maven, etc).
It should be noted that modern repository managers like Nexus and Artifactory now support Docker registries too, so that you use these for deploying docker images too.
Update
A related chef question, a technology where there is no intermediate binary file (like a jar). In this case the software is still "released" by creating a tar distribution stored in the repo.
chef cookbook delivery - chef server vs. artifactory + berkshelf