I have a SaaS based multi-tenant monolith application (built with Django), that I want to divide into microservices based architecture. But I am not sure how to divide the application into correct partitions. And on what aspects should I take care of?
In case of monolith application, it's easy to understand that I have a tenant model that decides the schemas but how this will be done in microservices if I want each service to be multi-tenant? Or should I even make the services multi-tenant?
If you're already using OAuth and/or generating JWTs for user authentication/authorization, I'd recommend any new services that need tenant scoping to require a user access token be provided in requests just like your Django app. This lets you standardize how credentials and tenant scoping is expected to be passed, and verifying JWTs is a pretty easy process to implement.
That being said, it's also important to point out that you shouldn't require that services use access tokens or have any kind of tenant scoping at all. Not only is it possible that specific services don't require tenant scoping, but it's also possible that they might want to define a tenant differently from the main Django app (e.g. a simple tenant_id). For example, a payments service that only accepts a dollar amount and a credit card doesn't care what the tenant is and would be perfectly safe to call from the main Django application (of course you should prevent public access to the service too).
The best way to think about how new services should be designed is in a vacuum - without care for how other services are designed or how they store their data. Your service was built to perform a task and it defines for itself what parameters it needs to perform that task, how it executes that task, and how it stores the data it needs for future tasks. This independence from the design of other microservices in the stack is part of the power of designing service-oriented systems. It allows creators to pick the right tools for the job, and allows them to create meaningful features without needing to collaborate with dozens of team members that they often don't know.
Hope this helps, and good luck.
Related
i just arrived on this architecture, am doing a lot of research and i understood how it work in general but it's all theorical.
I decided to separate each step for the development of this architecture to start implementing so i can understand better these steps.
The first that i wanted to learn was the tenant provisioning, i wanted to apply it on AWS to mirror a production software example.
So, starting on that the common AWS service that i see most people using is AWS Cognito, but it's not clear in my mind the steps of the implementation, like how should i get the tenant data to onboard him in my app? Assuming it's tier based.
Should i have one database to store all tenants data separate from the application database?
I want to use microservices on this one because i think is better to onboard the tenant with different tiers and much more benefits.
Which AWS services should i use to make this process work? I'm not really asking about the implementation itself but a path to understand which services to use and how it connects with each other.
I hope i was clear about my doubts, english is not my mother tongue, sorry about that!
You are thinking in the right direction. However, there are decisions you need to make before diving into any saas service stack. I would start with
Planning my infrastructure - how many tenants/group.
the kind of tenant onboarding system you want
How will tenants onboard their users and manage authorization/authentication
Multitenant architecture, which needs to account for several things at the least like - DB model, shared vs isolated, data privacy, design keeping in mind industry data security standards
what will be your tenant deployment model. Remember one of the disadvantages of multitenancy is also slow time to market.
Your API stack needs to account for which apis needs to be multitenant and which are generic product offerings.
operational tool to monitor app health, client analytics.
how will you meter and bill the client and other non-functional decisions.
AWS offers good documentation to get started here : https://aws.amazon.com/blogs/apn/building-a-multi-tenant-saas-solution-using-aws-serverless-services/
I'm creating a web-application and decided to use micro-services approach. Would you please tell me what is the best approach or at least common to organize access to the database from all web-services (login, comments and etc. web-services). Is it well to create DAO web-service and use only it to to read/write values in the database of the application. Or each web-service should have its own dao layer.
Each microservice should be a full-fledged application with all necessary layers (which doesn't mean there cannot be shared code between microservices, but they have to run in separate processes).
Besides, it is often recommended that each microservice have its own database. See http://microservices.io/patterns/data/database-per-service.html https://www.nginx.com/blog/microservices-at-netflix-architectural-best-practices/ Therefore, I don't really see the point of a web service that would only act as a data access facade.
Microservices are great, but it is not good to start with too many microservices right away. If you have doubt about how to define the boundaries between microservices in your application, start by a monolith (all the time keeping the code clean and a good object-oriented with well designed layers and interfaces). When you get to a more mature state of the application, you will more easily see the right places to split to independently deployable services.
The key is to keep together things that should really be coupled. When we try to decouple everything from everything, we end up creating too many layers of interfaces, and this slows us down.
I think it's not a good approach.
DB operation is critical in any process, so it must be in the DAO layer inside de microservice. Why you don't what to implement inside.
Using a service, you loose control, and if you have to change the process logic you have to change DAO service (Affecting to all the services).
In my opinion it is not good idea.
I think that using Services to expose data from a database is ideal due to the flexibility it provides. Development of a REST service to expose some or all of your data as a service provides flexibility to consume the data directly to the UI via AJAX or by other services which can process the data and generate new information. These consumers do not need to implement a DAO and can be in any language. While a REST Service of your entire database is probably not a Micro-Service, a case could be made for breaking this down as Read only for Students, Professors and Classes for exposing on the School Web site(s), with different services for Create, Update and Delete (CUD) available only to the Registrars office desktop applications.
For example building a Service to exposes a statistical value on data will protect the data from examination by a user/program who only needs a statistical value without the requirement of having the service implement an entire DAO for the components of that statistic. Full function databases like SQL Server or Oracle provide a lot of functionality that application developers can use, including complex queries(using indexes), statistics the application of set operations on data.
Having a database service is a completely valid pattern. In fact, this is one of the key examples of where to start to export aspects of a monolith to a micro service in the Building Microservices book.
How to organize your code around such idea is a different issue. Yes, from the db client programmer's stand point, having the same DAO layer on each DB client makes a lot of sense.
The DAO pattern may be suitable to bind your DB to one programming language that you use. But then you need to ask yourself why you are exposing your database as a web service if all access to it will be mediated by the same DAO infrastructure. Or are you going to create one DAO pattern for each client programming language binding?
If all database clients are going to be written on the same programming language, then are you sure you really need to wrap your DB as a microservice? After all, the DB is usually already a remote service with a well-defined network protocol optimized to transfer data fast and reliably. Why adding HTTP on top of it? What are you expecting to gain from adding such complexity?
Another problem with using the DAO pattern is that the DAO structure does not necessarily follow the evolution of the web service. The web service may evolve in a way that does not make old clients incompatible. You may have different clients using different features of the micro service. In this case you are not sharing the same DAO layer structure on each client.
Make sure you are not using RPC-style programming over web services, which does not make much sense. You will be basically throwing away one of the key advantages of micro services, which is the decoupling between service and client.
Kinvey is Backend as a Service | Mobile Cloud Backend as a Service
Is Kinvey ( http://www.kinvey.com/ ) good, or using custom Java server with database a good idea ?
I am a member of the Kinvey engineering team, and can talk a bit about BaaS in general. While creating your own backend gives you a lot of flexibility and control, it is also a lot of work.
Back-end as a service providers like Kinvey offer a platform to speed up app development and have already done a lot of the work for you. Tasks like managing a database server and a web service front-end, managing the storage and streaming of files, providing a cross-platform push notification, providing a centralized user and authentication store, integration with social networks, buisiness logic and more are easily implemented with SDKs for each platform.
If I were to list the three main advantages of BaaS, they are:
Ease of implementation
Ready-made back-end platform for cross-platform apps
Automatic scalability if your app becomes successful
As far as disadvantages, your backend feature set becomes dependent on the vendor, and you certainly get more flexibility with a custom solution, but that can often be overcome with business logic. In my own (admittedly biased) opinion, the flexibility and cost savings make it worth at least giving BaaS a try seeing if the feature sets meet your specific needs.
What exactly is web service composition?
Composition refers to the way something is build, the new term at the moment is mash-up which basically means utilising a variety of different services in a composite application. So that functionality of disparate application can be used in one application.
I think your referring to service granularity - which means how much functionality a service exposes. a coarse grained service will expose a whole process as a consumable unit whereas a fine grained service will expose a specific unit of logic from a larger process. Obviously, it is up to the service architects to determine what granularity of service works best in the given environment.
This also, in a way has to do with the style of SOAP message you are using whether it is RPC style or document and that a service should be atomic and not hold external state. Meaning it does not need to know any more information other than that in the SOAP message to perform its function.
Hope this gives you a good starting point. The trouble with service-orientation is that it differs depending on who you read, but the main points stay the same!
Jon
Some web services which are provided for clients are abstract and composition of some smaller web services and it's called web service composition.
Sometimes there are more than one web service in order to use as the mentioned small web services, so we choose them based on QoS (Quality of Service) and many researches have been done on this subject.
Web service composition involves integration of two or more web service to achieve more added value of business functionality. A work flow composer is responsible of aggregating different web services to act as a single service according to functional requirements as well as QoS constrains. BPEL is one of the popular composers uses XML language to perform service composition. Fine-grained services perform single business task and provides higher flexibility and reusability. However, coarse-grained service involves performing complex business functionality leading to lower flexibility
Currently inside my organization we are trying to come up w/ some conventions for a pilot SOA project. At first glance we thought it would be best to force users of the service to use the business service w/out direct access to any data endpoints .. but are there specific scenarios where this is not true or it might be "valid" for developers to have access to specific data endpoints outside of a service?
I always fear that if we open this up, it will actually hurt reuse because everyone will just "re-invent" similar business services using the same back-end data as it's available and would be "in theory .. easier" to just write a new business service rather than ask "what does this other service do that uses my database?"
Because even if the service is almost a direct pass through to the database we would have the ability to apply rules that would save developers time and ultimately the business money.
Thoughts?
Wouldn't your webservice just be a thin wrapper for your business layer anyway? Your service layer probably shouldn't have anything more than your business layer besides some dumbed-down DTOs perhaps. Then noone is asking "what does this other service do that uses my database?" because it isn't using your db, it is using your BL.
You're waving a red flag when you describe "forcing" users to do anything. Maybe you can think about your question and rephrase it in terms something like "enable" users, because this should be the starting point for your decision, and SOA offers advantages and disadvantages for different UI strategies.