I got a question regarding namespaces and seeking your expertise to clear out my doubts.
What I understood about namespaces is that they are there to introduce logical boundaries among teams and projects.
Of course, I read somewhere namespaces can be used to introduce/define different environments within the same cluster.
E.g Test, UAT and PRODUCTION.
However, if an organization is developing a solution and that solution consists of X number of microservices and have dedicated teams to look after those services,
should we still need to use namespaces to separate them or are they gonna deploy in one single namespace reflecting the solution?
E.g if we are developing an e-commerce application:
Inventory, ShoppingCart, Payment, Orders etc. would be the microservices that I can think of. Should we deploy them under the namespace of sky-commerce for an instance? or should they need dedicated namespaces.?
My other question is. if we deploy services in different namespaces, is it possible for us to access them through APIGateway/ Ingress controller?
For an instance, I have the front-end SPA application and it has its BFF (Backend For Frontend). can the BFF access the other services through the APIGateway/Ingress controller?
Please help me to clear these doubts.
Thanks in advance for your prompt reply in this regard.
RSF
Namespaces are cheap, use lots of them. Only ever put two things in the same namespace if they are 100% a single unit (two daemons that are always updated at the same time and are functionally a single deployment) or if you must because a related object is used (such as a Service being in the same ns as Pods it references).
When creating a new Kubernetes namespace, a request is sent using the namespace API using the defined syscalls, and since Kubernetes has admin privileges, a new namespace will be created. The new namespace will contain specifications for the capabilities of a new process assigned under its domain.
In regards to your question above, yes you can keep services in different namespaces as long as they are able to talk together and render the services to the outside world as one piece.
Since all organizations are different, it is up to you to figure out how best to implement and manage Kubernetes Namespaces. In general, aim to:
Create an effective Kubernetes Namespace structure
Keep namespaces simple and application-specific
Label everything
Use cluster separation when necessary
Related
Given that Kubernetes doesn’t offer full visibility into how services interact with each other I want to derive and map services automatically. For eg as shown in the below diagram, how can we derive that the payment service interacts with the cart service and cart service interacts with catalogue and redis.
So far what I had tried is,
kubectl get services command - This command only gives the list of services but does not hint on any communication happening between the services.
Tried Kubeview -> This plots only the deployment architecture and gives a graphical representation but mapping between various services is not derived.
So what is the easiest way to derive information about services interacting with each other and what could be the data source for this information in Kubernetes?
We faced this as well when we were building Otterize -- we needed something to map "who is talking to who" in order to bootstrap our solution, but every tool seemed to be ill suited for the task of simply creating a "network map" without all sorts of stuff we didn't want. We ended up rolling our own, and open sourced it: https://github.com/otterize/network-mapper .
It's based on combining information from DNS queries (actually just query responses) as well as detecting open connections, which gives you an IP-level network map, and then adding a simple resolution heuristic to derive a logical name-level map. You can read more details in this blog post, by one of the guys who built the tool: https://otterize.com/blog/kubernetes-traffic-discovery .
Hope this helps!
You can consider linkerd or other similar tools which offer service Observability
A service mesh like Linkerd is a tool for adding observability, security, and reliability features to “cloud native” applications by transparently inserting this functionality at the platform layer rather than the application layer.
service-mesh
For example, in below screenshot you can see how gate-way service interact with another service
It will also show how the request is going, amount of request with inbound and outbound
So in your case,if payment app is part of mesh you will able to see the inbound and outbound for the service along with requests info.
linkerd-install-helm
Service meshes have three main goals around interservice communication:
Connectivity
Security
Observability
I want to deploy a traditional monolithic application in Kubernetes.
Thousands of customers use this application and each customer has its own instance of application. if we have 5 customers we should run 5 separate instances of this application.
The application also calls Kubernetes API for running some jobs.
I want to make sure that everything is isolated, Is it a good idea to create a separate namespace for each customer? Does it cause some performance issues? Is there any better solution for it?
I think you should create multi-tenant cluster.
Such clusters shared by multiple users and/or workloads which are referred to as "tenants". The operators of multi-tenant clusters must isolate tenants from each other to avoid the damage that a compromised. You should know that cluster resources must be fairly allocated among tenants.
When you plan a multi-tenant architecture you should consider the layers of resource isolation in Kubernetes: cluster, namespace, node, pod, and container. You should also consider the security aspects of sharing different types of resources among specific tenants.
Although Kubernetes cannot guarantee perfectly secure isolation between tenants, it does offer features that may be sufficient for specific solutions. For example you can separate each tenant and their Kubernetes resources into their own separate namespaces. Then use policies to enforce tenant isolation. Policies are usually scoped by namespace and can be used to restrict API access, to constrain resource usage, and to restrict what containers are allowed to do.
Read more: multi-tenant-cluster.
However while implementing multi-tenancy with Kubernetes, you need to decide if you need soft multi-tenancy (is focused on minimising accidents and managing the fallout) or hard multi-tenancy(assumes tenants to be malicious and therefore advocates zero trust between them). In any case, you have to answer questions: how to limit their resource usage, how to manage the users/tenants and how to isolate them from each other. There are many tools, for example: loft which can help you to get multi-tenancy with Kubernetes.
See: multi-tenant-loft.
Take a look: best-practices-multitenant.
I have an API, and a consumer web app, both written in Node and Express. The API is defined by a OpenAPI Specification. Implemented by swagger-ui-express.
The above web apps are Dockerised and managed in Kubernetes.
The API has a handful of endpoints for managing the lifecycle of a user's registration/application to the service.
Currently, when I need to cleardown completed/abandoned applications, or resubmit failed applications, I employ a periodically run cronjob to carry out a database query for the actions mentioned. The cronjob is defined by a Kubernetes config YAML file. This is quickly becoming unmanageable, and hard to maintain.
I am looking in to having a dedicated endpoint for each of the above tasks. Then a dedicated cronjob could periodically send a request to the API endpoint to carry out the complex task. This moves the business logic back in to the API, and avoids duplication within a cronjob hosted elsewhere. I am ultimately asking if this is a good approach or is there a better workflow documented somewhere I could implement?
My thinking is that I could add these new endpoints to the already-existing consumer API, but have the new (housekeeping/management) endpoints separated from the others.
To separate each (current) endpoint in to their respective resource, I am defining tags within the specification. Tags don't seem to be sufficient for the separation of these new "housekeeping" endpoints.
Looking through the SwaggerUI documentation I can see that I can define multiple definitions (via the urls property) to switch between. These definitions being powered by individual Specification documents. This looks like a very clean way of separating the consumer API from the admin API, is this best practice?
Any input would be appreciated on this as I am struggling to find much documentation on this kind of issue.
If I want to develop a SaaS system and want to use k8's namespace to do isolation, i.e., I will create a namespace for every user, it's a multi-tenancy system, then, how many namespaces can I have? Will k8s be slowdown when namespace increases?
To answer your question, namespace is a logical entity that is used to isolate the application environment from another application environment. It doesn't consume cluster resources like cpu and memory. Ideally you can create any number of namespaces. Am not sure if there is a limit on number of namespaces that is allowed in a custer
On the other hand it is not a good approach to have one namespace each for user. Applications multi tenancy should be better handled in the application code itself. Namespace is recommended to isolate the environment like one for Development, one for TEST, one for QA and Another one for production
This is a pretty good write-up on some best-practices around namespaces and how to organize things with them:
https://cloud.google.com/blog/products/containers-kubernetes/kubernetes-best-practices-organizing-with-namespaces
There are likely use-cases where you can have too many namespaces, but it is very unlikely that you will see this unless you have a custom application or controller that is doing something unwise and needs some of its logic reworked.
What is the difference between an SOA service and other kinds of services like an application or domain service ?
Have a look here. http://www.bennadel.com/blog/2385-application-services-vs-infrastructure-services-vs-domain-services.htm
Short answer
DDD Domain Services operate on Domain Entities. Usually where the work that needs to be done spans multiple Aggregate roots.
DDD Application Services drives workflow. For example if you want to do some work on a domain entity, the Application Service would be responsible to fetch the entity from the data store, call the domain service to do the work, do some work via an integration service if needed, and then lastly persist the change.
This is an interesting question since SOA is such as broad and overloaded term.
If we take SOA to mean any implementation that results in a mechanism to reach 'services' then even application and domain services will form part of SOA services. Application and domain services will even fall within the realm of micro-services although application services are usually surfaced through some integration mechanism.
I like to think of these things in terms of 'reachability'. WikiPedia:
In graph theory, reachability refers to the ability to get from one vertex to another within a graph
So, it depends on how reachable your code is. A bunch of domain services could, theoretically, form a service-oriented architecture.
The only differences is in how you surface your services.