Limitations of Immutable Deployments on AWS/EB - amazon-web-services

I am trying to understand the disadvantages of immutable deployments on AWS/Elastic Beanstalk. The docs say this:
You can't perform an immutable update in concert with resource configuration changes. For example, you can't change settings that require instance replacement while also updating other settings, or perform an immutable deployment with configuration files that change configuration settings or additional resources in your source code. If you attempt to change resource settings (for example, load balancer settings) and concurrently perform an immutable update, Elastic Beanstalk returns an error.
(Source: https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/environmentmgmt-updates-immutable.html)
However, I am unable to come up with a practical scenario that would fail. I use CloudFormation templates for all of the configuration. Can the above be interpreted that I cannot deploy CloudFormation changes as well as changes to the application (.jar) at the same time?
I would be very thankful for clarification.


Take this with a grain of salt because it's just a guess based on reading the docs; I think basic support is $40/month, would be a good question to ask them to know for sure.
Can the above be interpreted that I cannot deploy CloudFormation changes as well as changes to the application (.jar) at the same time
I'm assuming you deploy your application .jar using a different process than your CloudFormation template. Meaning when you deploy source code you don't use CloudFormation, you maybe use a CI/CD tool e.g. Codeship. And when you make a change to your CloudFormation template, you log in to AWS Console and update the the template there (or use the AWS CLI tool).
Changing both at the same time would, I think, fall under what they're saying here. Don't do it for obvious reasons; you wouldn't want CloudFormation trying to make changes to an ec2 instance at the same time that EB is shutting down that instance and starting a new one. But a more common example would be I think if you happen to use .ebextensions for some configuration settings.
.ebextensions are a way to configure some things in EB that CloudFormation can't really do or easily do. They are config files that get deployed with your source code in a folder named /.ebextensions at the root of your project. An example is changing some specific linux settings https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/customize-containers-ec2.html
You wouldn't want to make a change to your application code and an .ebextension at the same time. This is just my guess at reading the docs, you could test this out pretty easily.

Related

How to use eb's cli tool to update deployment policy to immutable?

I'm trying to update an existing environment to immutable updates to work around flaky deployments as described by this (not my) blog post.
After reading the docs - specifically the "The aws:autoscaling:updatepolicy:rollingupdate namespace" section, it appears I should be able to add an .ebextensions folder at the same level as my .elasticbeanstalk folder, and put the following in an arbitrarily-named config file:
option_settings:
aws:autoscaling:updatepolicy:rollingupdate:
RollingUpdateType: Immutable
and issue an eb deploy.
Having done this and receiving an "Environemnt update completed successfully" result, I went to check the aws console and this environment is still set to "Deployment policy: Rolling." An eb config shows aws:autoscaling:updatepolicy:rollingupdate:RollingUpdateType is set to "Health" (which doesn't make much sense but I guess that's a labeling issue so, whatever).
Will this just not work or am I doing something obviously stupid?
Pedantic Note - I'm aware I can do this by hand editing eb config and checking a box in the console, but I want to automate the change so we can apply it to other environments. ;)

It seems you need a little more.
option_settings:
aws:autoscaling:updatepolicy:rollingupdate:
RollingUpdateType: Immutable
aws:elasticbeanstalk:command:
DeploymentPolicy: Immutable
What you did enables immutable updates for configuration changes only. For deployments you need the last two lines from the code above.
You can see more here at Example .ebextensions/immutable-all.config.

Deploy only changed files on AWS Elastic Beanstalk website

I have successfully deployed my website on AWS Elastic Beanstalk. Now I want to change the code in one of my file.
If I do eb deploy, it will completely deploy a new version of my code which I don't want. I already have an updated DB on Elastic Beanstalk. If I deploy the whole code again, it will overwrite my DB file.
How can I deploy the changed file only successfully?

This may not be the answer you're looking for, but I would highly recommend deleting this file from your code repository. Hopefully you're using a version control system like Git; if you want to keep the original file for historical purposes, I would create an entirely different repository and put it in there.
Why? Even if you did come up with a solution to only deploy changed files...would you really want to trust it? If there's any problem with the solution you came up with, you would entirely erase/overwrite your production database. Not good.
In addition, if you want to build a really robust system to entirely create your app from scratch in AWS, take a look at Cloud Formation. It takes some learning and work, but you can build a script -- and maintain it in version control -- that will scaffold your entire cloud infrastructure.

How Docker and Ansible fit together to implement Continuous Delivery/Continuous Deployment

I'm new to the configuration management and deployment tools. I have to implement a Continuous Delivery/Continuous Deployment tool for one of the most interesting projects I've ever put my hands on.
First of all, individually, I'm comfortable with AWS, I know what Ansible is, the logic behind it and its purpose. I do not have same level of understanding of Docker but I got the idea. I went through a lot of Internet resources, but I can't get the the big picture.
What I've been struggling is how they fit together. Using Ansible, I can manage my Infrastructure as Code; building EC2 instances, installing packages... I can even deploy a full application by pulling its code, modify config files and start web server. Docker is, itself, a tool that packages an application and ensures that it can be run wherever you deploy it.
My problems are:
How does Docker (or Ansible and Docker) extend the Continuous Integration process!?
Suppose we have a source code repository, the team members finish working on a feature and they push their work. Jenkins detects this, runs all the acceptance/unit/integration test suites and if they all passed, it declares it as a stable build. How Docker fits here? I mean when the team pushes their work, does Jenkins have to pull the Docker file source coded within the app, build the image of the application, start the container and run all the tests against it or it runs the tests the classic way and if all is good then it builds the Docker image from the Docker file and saves it in a private place?
Should Jenkins tag the final image using x.y.z for example!?
Docker containers configuration :
Suppose we have an image built by Jenkins stored somewhere, how to handle deploying the same image into different environments, and even, different configurations parameters ( Vhosts config, DB hosts, Queues URLs, S3 endpoints, etc...) What is the most flexible way to deal with this issue without breaking Docker principles? Are these configurations backed in the image when it gets build or when the container based on it is started, if so how are they injected?
Ansible and Docker:
Ansible provides a Docker module to manage Docker containers. Assuming I solved the problems mentioned above, when I want to deploy a new version x.t.z of my app, I tell Ansible to pull that image from where it was stored on, start the app container, so how to inject the configuration settings!? Does Ansible have to log in the Docker image, before it's running ( this sounds insane to me ) and use its Jinja2 templates the same way with a classic host!? If not, how is this handled?!
Excuse me if it was a long question or if I misspelled something, but this is my thinking out loud. I'm blocked for the past two weeks and I can't figure out the correct workflow. I want this to be a reference for future readers.
Please, it would very helpful to read your experiences and solutions because this looks like a common workflow.

I would like to answer in parts
How does Docker (or Ansible and Docker) extend the Continuous Integration process!?
Since docker images same everywhere, you use your docker images as if they are production images. Therefore, when somebody committed a code, you build your docker image. You run tests against it. When all tests pass, you tag that image accordingly. Since docker is fast, this is a feasible workflow.
Also docker changes are incremental; therefore, your images will have minimal impact on storage. Also when your tests fail, you may also choose to save that image too. In this way, developer will pull that image and investigate easily why your tests failed. Developer may choose to run tests in their machine too since docker images in jenkins and their machine are not different.
What this brings that all developers will have same environment, same version of all software since you decide which one will be used in docker images. I have come across to bugs that are due to differences between developer machines. For example in the same operating system, unicode settings may affect your code. But in docker images all developers will test against same settings, same version software.
Docker containers configuration :
If you are using a private repository, and you should use one, then configuration changes will not affect hard disk space much. Therefore except security configurations, such as db passwords, you can apply configuration changes to docker images(Baking the Configuration into the Container). Then you can use ansible to apply not-stored configurations to deployed images before/after startup using environment variables or Docker Volumes.
https://dantehranian.wordpress.com/2015/03/25/how-should-i-get-application-configuration-into-my-docker-containers/
Does Ansible have to log in the Docker image, before it's running (
this sounds insane to me ) and use its Jinja2 templates the same way
with a classic host!? If not, how is this handled?!
No, ansible will not log in the Docker image, but ansible with Jinja2 templates can be used to change dockerfile. You can change dockerfile with templates and can inject your configuration to different files. Tag your files accordingly and you have configured images to spin up.

Regarding your question about handling multiple environment configurations using the same Docker image, I have been planning on using a Service Discovery tool like Consul as a centralized config/property management tool. So, when you start your container up, you set an ENV var that tells it what application it is (appID), and what environment config it should use (ex: MyApplication:Dev) and it will pull its config from Consul at startup. I still have to investigate the security around Consul (as if we are storing DB connection credentials in there for example, how do we restrict who can query/update those values). I don't want to just use this for containers, but all apps in general. Another cool capability is to change the config value in Consul and have a hook back into your app to apply the changes immediately (maybe like a REST endpoint on your app to push changes down to and dynamically apply it). Of course your app has to be written to support this!
You might be interested in checking out Martin Fowler's blog articles on immutable infrastructure and on Phoenix servers.

Although not a complete solution, I have suggestions for two of your issues. Although they might not be perfect, these are the practices we are using in our workflow, and prove themselves so far.
Defining different environments - supposing you've written a different Ansible role for each environment you launch, we define an environment variable setting the environment we wish the container to belong to. We then download the suitable configuration file from an S3 bucket using the env variable set before into the container (which should be possible if you supply AWS creds or give your server an IAM role) and inject these parameters into the code when building it.
Ansible doesn't need to log into the docker app, but the solution is a bit tricky. I've tried two ways of tackling this problem, and both aren't ideal. The first one is to download the configuration file as part of the docker image command line, and build the app on container startup. While this solution works - it breaches the Docker philosophy and makes the image highly prone to build errors.
Another solution is pushing several images to your docker hub repo, and then pulling the appropriate image according to the environment at hand.
In a broader stroke, I've tried launching our app completely with Ansible and it was hell, many configuration steps are tricky and get trickier when you try to implement them as a playbook. When I switched to maintaining the severs alone with Ansible, and deploying the app itself with Docker things got a lot easier.

AWS EB: Multiple env.config files for various environments?

I've got an env.config in source control but pretty much the only things I can put in it are things that relate to all my various environments (production, staging). I've got environment specific settings that I want to add to the env.config file (for instance, the DB host) that will change from environment to environment. How can I handle these differences? Right now I'm doing it from the AWS console where I can manage it in the GUI on a per-environment basis, but I'd love to be able to change a lot of this stuff from git so I don't have to be logging into the console whenever I want to change something.
Is there any way to have multiple, environment specific config files?

So this has been posted before in the AWS forums. (https://forums.aws.amazon.com/thread.jspa?messageID=529373) So far there's only workarounds! The problem is that the .config files would require some logic to figure out what environment you're attempting to target. Personally I don't think any logic is required, as you could simply namespace the config settings based on the AWS environment name you're targeting.

I think your usecase is similar to what is discussed in How to configure Elastic Beanstalk for RDS
You may want to use 'eb branch'. You can then have multiple environments with different configurations.
More documentation on eb branch here

How does ElasticBeanStalk deploy your application version to instances?

I am currently using AWS ElasticBeanStalk and I was curious as to how (as in internally) it knows that when you fire up an instance (or it automatically does with scaling), to unpack the zip I uploaded as a version? Is there some enviroment setting that looks up my zip in my S3 bucket and then unpacks automatically for every instance running in that environment?
If so, could this be used to automate a task such as run an SQL query on boot-up (instance deployment) too? Are these automated tasks changeable or viewable at all?
Thanks

I don't know how beanstalk knows which version to download and unpack, but running a task on start-up is trivial. Check out cloud-init, a tool written by Ubuntu that's now packaged in Amazon Linux. It allows you to pass arbitrary shell scripts into the UserData section of the instance configuration, and those shell scripts will run on startup.
It's a great way to bootstrap instances on startup, which avoids the soul-sucking misery of managing AMIs.
A quick (possibly non-applicable) warning: If you're running a SQL query on a database that lives on the beanstalk AMI, you're pretty much guaranteed to lose your database at some point. Those machines are designed to be entirely transient. Do not put databases on them. See this answer for more details.

Since your goal seems to be to run custom configuration tasks, the answer is yes, there is a way to do that. You can define custom actions in an .ebextensions file packaged with your app. For example, you can configure a command to run every time a new machine is deployed:
http://docs.aws.amazon.com/elasticbeanstalk/latest/dg/customize-containers-ec2.html#linux-commands