hat is the standard pattern of orchestrating microservices?
If a microservice only knows about its own domain, but there is a flow of data that requires that multiple services interact in some manner, what's the way to go about it?
Let's say we have something like this:
Invoicing
Shipment
And for the sake of the argument, let's say that once an an order has been shipped, the invoice should be created.
Somewhere, someone presses a button in a GUI, "I'm done, let's do this!" In a classic monolith service architecture, I'd say that there is either an ESB handling this, or the Shipment service has knowledge of the invoice service and just calls that.
But what is the way people deal with this in this brave new world of micro-services?
I do get that this could be considered highly opinion-based. but there is a concrete side to it, as micro-services are not supposed to do the above. So there has to be a "what should it by definition do instead", which is not opinion-based.
Shoot.
well there are various ways of best database practices when dealing in micro services , it may differ with respect to domain of the entities which are being used , and also the scope of your application use.
There are few best practices for database design in micor services , to start with listing few of them
1 - Private-tables-per-service – each service owns a set of tables that must only be accessed by that service
2 - Schema-per-service – each service has a database schema that’s private to that service
3 - Database-server-per-service – each service has it’s own database server.
You can mix and match these are per your data size and data count.
I would like you to refer and go through this page for a perfect example.
Microservices Database Best practices
Related
It seems that in the traditional microservice architecture, each service gets its own database with a different understanding of the data (described here). Sometimes it is considered permissible for databases to duplicate data. For instance, the "Users" service might know essentially everything about a user, whereas the "Posts" service might just store primary keys and usernames (so that the author of a post can have their name displayed, for instance). This page talks about eventual consistency, sources of truth, and other related concepts when data is duplicated. I understand that microservice architectures sometimes include a shared database, but most places I look suggest that this is a rare strategy.
As for why each service typically gets its own database, all I've seen so far is "so that each service owns its own resources," but I'm not convinced that a) the service layer in any way "owns" the persisted resources accessed through the database to begin with, or that b) services even need to own the resources they require rather than accessing necessary subsets of the master resources through a shared database.
So what are some of the justifications that each service in a microservice architecture should get its own database?
There are a few reasons why it does make sense to use a separate database per micro-service. Some of them are:
Scaling
Splitting your domain in micro-services is fine. You can scale your particular micro-service on the deployed web-server on demand or scale out as needed. That it obviously one of the benefits when using micro-services. More importantly you can have micro-service-1 running for example on 10 servers as it demands this traffic but micro-service-2 only requires 1 web-server so you deploy it on 1 server. The good thing is that you control this and you can manage your computing resources like in order to save money as Cloud providers are not cheap.
Considering this what about the database?
If you have one database for multiple services you could not do this. You could not scale the databases individually as they would be on one server.
Data partitioning to reduce size
Automatically as you split your domain in micro-services with each containing 1 database you split the amount of data that is stored in each database. Ideally if you do this you can have smaller database servers with less computing power and/or RAM.
In general paying for multiple small servers is cheaper then one large one.
So in this case you could make use of this fact and save some resources as well.
If it happens that the already spited by domain database have large amount of data techniques like data sharding or data partitioning could be applied additional, but this is another topic.
Which db technology fits the business requirement
This is very important pro fact for having multiple databases. It would allow you to pick the database technology which fits your Business requirement best in order to get the best performance or usage of it. For example some specific micro-service might have some Read-heavy operations with very complex filter options and a full text search requirement. Using Elastic Search in this case would be a good choice. Some other micro-service might use SQL Server as it requires SQL specific features like transnational behavior or similar. If for some reason you have one database for all services you would be stuck with the particular database technology which might not be so performant for those requirement. It is a compromise for sure.
Developer discipline
If for some reason you would have a couple micro-services which would share their database you would need to deal with the human factor. The developers would need to be disciplined to not cross domains and access/modify the other micro-services database(tables, collections and etc) which would be hard to achieve and control. In large organisations with a lot of developers this could be a serious problem. With a hard/physical split this is not an issue.
Summary
There are some arguments for having database per micro-service but also some against it. In general the guidelines and suggestions when using micro-services are to have the micro-service together with its data autonomous in order to work independent in Ideal case(this is not the case always). It is defiantly a compromise as well as using micro-services in general. As always the rule is the rule but there are exceptions to it. Micro-services architecture is flexible and very dependent of your Domain needs and requirements. If you and your team identify that it makes sense to merge multiple micro-service databases to 1 and that it solves a lot of your problems then go for it.
Microservices
Microservices advocate design constraints where each service is developed, deployed and scaled independently. This philosophy is only possible if you have database per service. How can i continue my business if i have DB failure and what steps i can take to mitigate this?DB is essential part of any enterprise application. I agree there are different number of challenges when services has its own databases.
Why Independent database?
Unlike other approaches this approach not only keeps your code-base clean and extendable but you truly omit the single point of failure in your business. To achieve this services sometimes can have duplicated data as well, as long as my service is autonomous and services can only be autonomous if i have database per service.
From business point of view, Lets take eCommerce application. you have microserivces like Booking, Order, Payment, Recommendation , search and so on. Database is shared. What happens if the DB is down ? All your services are down ! and there is no point using Microservies architecture other than you have clean code base.
If you have each service having it's own database , i don't mind if my recommendation service is not working but i can still search and book the order and i haven't lost the customer. that's the whole point.
It comes at cost and challenges, but in longer run it pays off.
SQL / NoSQL
Each service has it's own needs. To get the best performance I can use SQL for payment service (transaction) and I can use (I should) NoSQL for recommendation service. Shared database wouldn't help me in this case. In modern cloud Architectures like CQRS, Event Sourcing, Materialized views, we sometimes use 2 different databases for same service to get the performance out of it.
Again Database per service is not only about resources or how much data should it own. But we really have to see the bigger picture. Yes we have certain practices how much data and duplication is good or bad but that's another debate.
Hope that helps !
Yet another question on how to or how not to split up a microservice :-D
The scenario:
What do we need?
Sending emails at different points of time within the work flow of an ecommerce order process. These mails will be containing order information.
What do we have?
1 x persistence service which retrieves order information
Several services which subscribe to order events and processes the relevant use case (e.g. Confirmation, delivery, invoice)
1 x service which can be triggered to send a mail
What's the next step?
Designing the architectural component which transforms the order information so they will fit the data structure of the email rendering service.
The current options are
1 having each processing service transform already existing order information for the mail template and send them to the mail rendering service.
2 have each processing service call a new service which would aggregate and transform the order information and call the mail rendering service.
Currently we're not sure yet if the data structures for the mail templates will be mostly common or if there will be differences.
So what do you think of these options in terms of cohesion, coupling and separation of concerns?
Do you need any more information? Any constructive thoughts are welcome!
Your software architecture should reflect your organizational structure, see Conway's law
Do you have multiple teams, and you want to minimize dependencies between the teams.
Are "services" large and complex enough to justify them being separated into modules?
Does the size of the product justify having advanced devops in place to orchestrate the microservices?
Do you need the flexibility in terms of deployment and replaceability of individual "services"?
If you can answer yes to most of these questions, it would make sense to go for microservices. Otherwise, you are just making your life complicated.
Frankly, microservices require a lot of coordination overhead which makes sense only if the product is large enough. Most (small) projects are just fine with monolithic and MVC architecture.
This is how I propose to proceed man, it's how one of my project's architecture does all SMTP related stuff.
API receives an HTTP request
It persists data needed to the database.
It offloads the long-running and memory intensive processes to mail builder.
Optional, mail builder builds attachment files (XLSX, PDF, etc)
Mail builder uploads to File Server
Mail builder offloads generic SMTP sending to SMTP service.
I suggested this format because it allows you to scale the instance of each piece (Mail builder will have tons of instances) depending on bottlenecks in your processing pipeline.
Given that you have asked this question in microservices, I am assuming you are asking the question in reference to cloud native patterns.
I suggest you start with looking at microservices pattern. An excellent site for the patterns is https://microservices.io/patterns/microservices.html.
Your question does not have the necessary details to provide an educated advice on what patterns are suitable and what are not. So, I suggest you look at these few patterns...
https://microservices.io/patterns/data/shared-database.html
https://microservices.io/patterns/data/database-per-service.html
Also take a look at event sourcing pattern
https://microservices.io/patterns/data/event-sourcing.html
Hope this helps.
I am now trying to design database for my micro service-oriented application in a distributed way. My application is related with management of universities. I have different universities say A, B, C. Each university have separate users for using their business data. Now I am planning to design separate databases for separate universities for storing their user data. So each university has their own database for their users and additional one database for managing their application tables. If I have 2 universities, Then I have 2 user details DB and other 2 DB for application tables.
Here my confusion is that, when I am searching for database design, I only see the approach of keeping one common database for storing all users (Here for one DB for all users of all universities). So every user is mixed within one database.
If I am following separate database for each university, Is possible to support distributed DB architecture pattern and micro service oriented standard? Or Do I need to keep one DB for all users?
How can I find out which method is appropriate for microservice / Distributed database design pattern?
Actually there could be multiple solutions and not one solution is best, the best solution is the one which is appropriate for your product's requirements.
I think it would be a better idea to go with separate databases for each of your client (university) to keep the data always isolated even if somethings wrong happens. Also with time, the database could go so huge that it could cause problems to configure/manage separate backups, cleanups for individual clients etc.
Now with separate databases there comes a challenge for managing distributed transactions across databases as you don't know which part is going to fail among many. To manage that, you may have to implement message/event driven mechanism across all your micro-services and ensure consistency.
Regarding message/event mechanism, here is a simple use case scenario, suppose there are two services "A" (user-registration) and "B" (email-service)
"A" registers a user temporarily and publishes an event of sending confirmation email.
The message goes to message broker
The message is received by "B".
The confirmation email is sent to the user.
The user confirms the email to "B"
The "B" publishes event of user confirmation to the broker
"A" receives the event of confirmation and the process is completed.
The above is the best case scenario, problems still can happen in between even with broker itself.
You have to go deep into it if you think you need this.
Some links that may help.
http://how-to-implement-a-microservice-event-driven-architecture-with-spring-cloud-stre
A Guide to Transactions Across Microservices
I don't think that this is a valid design, using a database per client which is a Multi-tenant architecture practice, and database per microservice is a microservice architecture practice. you are mixing things up.
if you will use microservice architecture you better design it as Bounded contexts and each Context has its own database to achieve microservices main rule Autonomy
I'm a beginner in microservice architecture and I have read in a lot of blog that in a microservice architecture, it is mandatory that each micro service has its own database. In my case it may cost very expensive.
My question is, is it possible to make the persistence layer as micro service in itself ? Which would have the function of allowing other microservices to have read/write access to the database.
Thanks
To answer your question first of all lets understand :
it is mandatory that each micro service has its own database. In my
case it may cost very expensive.
Yes it is said that every microservice should have its own database.
What they mean is tables/collection of each microservice should be separate (you could use a single scalable database instance) and one microservice should only access the data of other microservices only through API calls
Benefits of having a separate model are:
Model will be clean. Eg: In E-Commerce Customer have diff. meaning for Shipping Microservice, Order Microservice, Customer Management Microservice and so on. If we put all data required by multiple microserives Customer Object will become very big
Microservices could evolve independently. In this case if we have a single Customer object and one microservice lets say Order one want to add something to the schema, all microservices needs to change
If we have a single Database Schema we will be getting into a big mess.
In my case it may cost very expensive.
If expensive means read model actually require data from multiple microservices. then its better to listen to events from multiple microservices and create a single read model , little duplication of data is ok.
If anything else, ask more specific question.
Having all Microservices accessing the same database will result in Loose Cohesion and Strong Coupling
Try to see if you can define separate Schema for each of the Microservices, so that you can ensure Microservices doesn't refer to the tables of other MicroServices.
This way in future, you can seamlessly move to separate Database for each service when your infrastructure cost concern goes off.
Micro services follows database per service model
How can I share database connection aong in spring cloud module microservices. If there are many microservices how can i use same db connection or should i use db connection per microservices?
In my opinion, the thing that you've asked for is impossible only because each microservice is a dedicated process and it runs inside its own JVM (probably in more than one server). When you create a connection to the database (assuming you use connection pool) its always at the level of a single JVM.
I understand that the chances are that you meant something different but I had to put it on because it directly answers your question
Now, you can share the same database between microservices (the same schema, tables, etc) so that each JVM will have a set of connections opened (in accordance with connection pool definitions).
However, this is a really bad practice - you don't want to share the databases between microservice. The reason is the cost of change: if you (as a maintainer of microservice A) decide to, say, alter one of the tables, now all microservices will have to support this, and this is not a trivial thing to do.
So, a better approach is to have a service that has a "sole responsibility" for your data in some domain. Now, all the services could contact this service and ask for the required data through well-established APIs that should never be broken. In this approach, the cost of change is much "cheaper" since only this "data service" should be changed in a way that it doesn't break existing APIs.
Now regarding the database connection thing: you usually will have more than one JVM that runs the same microservice (like data microservice) so, it's not that you share connections between them, but rather you share the same way of working with database (because after all its the same code).
When dealing with a mircoservice architecture it is usually the case that you have a distributed system.
Most microservices that communicate with each other are not on the same machine, instance or container. Communication between them is most commonly done via http, though there are many other ways.
I would suggest designing mircoservices around a single concern of your application. For example, in your case, you could have a "persistence microservice" that would be responsible for dealing with data persistence operations on a single or multiple types data-stores. It could possibly deal with relational DBs, noSQL, file storage etc. Then, via REST endpoints, you can expose any persistence functionality to the mircoservices that deal with business logic.
A very easy way to build a REST service like this would be with the help of Spring Data REST project.
To answer your actual question, I'm not aware of any way to share actual connections between processes. Beyond that, having many microservices running on the same instance is not a good practice most of the time.
Mircoservices are very popular these days and everybody is trying to transition to them. My advice would be to make sure you don't "over-engineer" your project.
Hope I didn't misunderstand your question, but to be fair it is a little vague. If you could provide a longer more detailed description of your architecture and use case I can suggest more tools/frameworks you can use to achieve your cloudy goals.
First and most important - your microservice should be responsible for handling all data in a given business domain/bounded context. So the question is - 'Why do you need to share database connection between microservices and isn't this a sign you went too far with slicing your system?' Microservice is a tool and word 'micro' may be misleading a bit :)
For more reading I would suggest e.g. https://learn.microsoft.com/en-us/dotnet/standard/microservices-architecture/architect-microservice-container-applications/identify-microservice-domain-model-boundaries (don' t worry, it's general enough to be applicable also to Spring).