There are web applications - WebAppA and WebAppB. Each web application depend on a Postgres database. We want to ship these applications to a customer who will deploy the applications on its own k8s cluster.
We want to create three packages - "WebappA", "WebAppB" and "Datastore". The webapp itself made of multiple services, not mentioning for the sake of simplicity.
We want to provide apt-get/brew/yum kind of experience, so that customer can deploy one or both the applications like al-carte. Most importantly while deploying, it should identify if the common package "DataStore" is running and not spin off yet another Postgres instance.
Is there any to package applications as packages for Kubernetes which can make installation easy with dependency handling?
Of course! One way to start would be using Helm charts. You can read more about them here.
Helm defines dependency relationships declaratively using charts, allows you to manipulate/maintain dependencies simply by managing some YAML manifests. It also allows you to have personalised repositories where you can put your images to be fetched from. It's really nice.
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I’m currently using kubernetes and I came across of helm.
Let’s say I don’t like the idea of “infecting” my kubernetes cluster with a process that is not related to my applications but I would gladly accept it if it could be beneficial.
So I made some researches but I still can’t find anything I can’t easily do by using my yaml descriptor and kubectl so for now I can’t find an use except,maybe, for the environizing.
For example (taking it from guides I read:
you can easily install application, eg. helm install nginx —> I add an nginx image to my deployment descriptor, done
repositories -> I have docker ones (where I pull my images from)
you can easily helm rollback in case of release failure-> I just change the image version to the previous one in my kubernetes descriptor, easy
What bothers me is that, at level of commands, I do pretty much the same effort (helm update->kubectl apply).
In exchange for that I have a lot of boilerplate because of keeping the directory structure helm wants and I feel like missing the control I have with plain deployment descriptors ...what am I missing?
It is totally understandable your question. For small and simple deploys the benefits is not actually that great. But when the deploy of something is very complex Helm helps a lot.
Think that you have a couple squads that develop microservice for some company. If you can make a Chart that works for most of them, the deploy of each microservices would differ only by the image and the resources required. This way you get an standardized deployment and easier to all developers.
Another use case is deploying applications which requires a lot of moving parts. For example, if you want to deploy a Grafana server on Kubernetes you're probably going to need at least a Deployment and a Configmap, then you would need a service that matches this deployment. And if you want to expose it to the internet you need an ingress too.
One relatively simple application, would require 4 different YAMLs that you would to manually configure and make sure everything is correct instead you could do a simple helm install and reuse the configuration that someone has already made, sometimes even the company who created the Application.
There are a lot of other use cases, but these two are the ones that I would say are the most common.
Here's three suggestions of ways Helm can be useful:
Your continuous deployment system somewhat routinely produces new builds and wants to send them to the Kubernetes cluster. You can use templating to specify the image name and tag in a deployment, and so helm upgrade ... --set tag=201907211931 to request a specific tag.
You might have various service-specific controls like the log level or external database hostnames. The Helm values mechanism gives a uniform way to specify them, without having to know the details of the Kubernetes YAML files.
There is a repository of pre-packaged application charts, so if you want replicated PostgreSQL with in-cluster persistent storage, that's already built for you and you can just depend on it, rather than figuring out the right combination of StatefulSets and PersistentVolumeClaims yourself.
You can combine these in interesting (and potentially complex) ways: use an in-cluster database for developer testing but use a cloud-hosted and backed-up database for production, for example, and compute the database host name based on what combination of settings are provided.
There are, of course, alternative ways to do all of these things. Kustomize in particular can change the image value fairly straightforwardly, and is notable for having been included in the kubectl tool since Kubernetes 1.14 (see also Declarative Management of Kubernetes Objects Using Kustomize in the Kubernetes documentation). The "operator" pattern gives an alternate path to install software in your cluster, but even more so than Helm you're trusting an arbitrary program with API access.
I will be building an Android application (not a game) soon. I heard of containerized development and Docker/Kubernetes but I'm not well-versed in its functions and use cases.
Why should I build my Android application with Kubernetes?
Your question can be split up into two parts:
1. Why should I containerize my deployment?
I hope by "deployment", you are referring to the backend services that serve your Android application; not the application itself (not sure how one would do that...). Here is a good article.
Containerization is a powerful abstraction that can help you manage both your code and environment. Setting up a container with the correct dependencies, utilities etc., and securing them is a lot of work, as is the case with any server setup. However, once you have packaged everything into a container, you can deploy said container multiple times and build on-top of it. The value of the grunt work that you have done in the past is therefore carried forward in your future deployments; conversely, so are the bugs... Additionally, you can also leverage the Docker ecosystem and build on various community contributions greatly accelerating your workflows.
A possible unintended advantage is also protection against configuration drift. Whenever services fail or your application crashes, you can simply restart your container, and a fresh version of the service will be created again. However, to support these operations, you need to ensure that your containerized service behaves nicely across restarts and fails gracefully. There are many other caveats and advantages that are not listed here; you can find more discussion on Google.
2. Why should I use Kubernetes for my container orchestration?
If you have many containers (think in the order of 100s), then using a single-node solution like Docker/docker-compose to manage them becomes tedious.
If only there was a tool to manage across multiple nodes, implement service discovery between your nodes, have fault tolerance (ie. automatic restarts, backoff policies), do health-checking of your services, manage storage assets, and conveniently expose your containers to the public. That tool is Kubernetes.
Here is a more in-depth intro.
Hope this helps!
We have multiple(20+) services running inside docker containers which are being managed using Kubernetes. These services include databases, streaming pipelines and custom applications. We want to make this product available as an on-premises solution so that it can be easily installed, like a one-click installation sort of thing, hiding all the complexity of the infrastructure.
What would be the best way of doing this? Currently we have scripts managing this but as we move into production there will be frequent upgrades and it will become more and more complex to manage all the dependencies.
I am currently looking into helm and am wondering if I am exploring in the right direction. Any guidance will be really helpful to me. Thanks.
Helm seems like the way to go, but what you need to think about in my opinion is more about how will you deliver updates to your software. For example, will you provide a single 'version' of your whole stack, that translates into particular composition of infra setup and microservice versions, or will you allow your customers to upgrade single microservices as they are released. You can have one huge helm chart for everything, or you can use, like I do in most cases, an "umbrella" chart. It contains subcharts for all microservices etc.
My usual setup contains a subchart for every service, then services names are correctly namespaced, so they can be referenced within as .Release.Name-subchart[-optional]. Also, when I need to upgrade, I just upgraed whole chart with something like --reuse-values --set subchart.image.tag=v1.x.x which gives granular control over each service version. I also gate each subcharts resources with if .Values.enabled so I can individualy enabe/diable each subcharts resources.
The ugly side of this, is that if you do want to release single service upgrade, you still need to run the whole umbrella chart, leaving more surface for some kind of error, but on the other hand it gives this capability to deploy whole solution in one command (the default tags are :latest so clean install will always install latest versions published, and then get updated with tagged releases)
I want the ability for clients to create their own stateless services and be able to upload/publish it to join an existing cluster. Is this doable? I understand that I need to update the application manifests dynamically but not sure how or if this is possible programmatically without side effects of the service fabric runtime processes.
The workflow is to upload the code (zipped file maybe or whatever) via an API gateway.
The first thing to keep in mind is that you do not deploy individual services to a Service Fabric cluster. You deploy applications, which can contain one or more services.
So the key question to ask is whether you need the new code to be integrated with an existing application type or not. It sounds like what you're trying to do is just enable multiple clients to deploy independent applications on a shared Service Fabric cluster, in which case you would not be modifying existing application types, but deploying entirely new ones.
Thus, you would need your API gateway to dynamically generate application and service manifests, combine them with the client-provided code to create an application package, then copy, register, and create those applications in the cluster. As far as the Service Fabric runtime is concerned, this looks no different than if you had deployed an application type built and packaged in Visual Studio. Processes running existing applications are not impacted.
From the documentation and examples I've seen it seems that the preferred way to deploy Service Fabric services is to package them all up into an application package.
If I have 30 services and I make a change to one of them I'm not interested in having my CI server pull down the entire repository, build the solution, package it and then have Service Fabric decide that only one service changed and so only one should be updated.
Is there a way to create an application package with just one service?
You want to perform a partial upgrade (Differential Packaging). See here. Differential packaging