I am new in microservices. I am coming from monolithic background in current environment i have different kinds services for different purposes like search, file, email, notification. I have taken so many courses but in that the instructor separate each entity and make it's own database also create API for that(like separate shopping cart entity, product entity) it makes no sense, I am not getting what is real world use of microservices or how to make separate component to build it's own microservice.
Can anyone give Real Project example?
Thanks in advance
Read this and this. Also look here and here. I don't think that anyone will give a link to the real working project, so you can try this.
I am not getting what is real world use of microservices
mostly as you heard in all of those tutorials the microservices architecture leverage advantages of:
the smaller services are easy to maintain and develop
easily can scale specific services rather than the whole project(monolith). for example you scale service-1 to 4 instances that request traffic split into these 4 instance and service-2 to 2 instances and go on (load balance). and these services may distributed in to different servers and locations.
if one service failed to work it does not terminate the whole system since they are independent.
services can be reusable for other scenarios or features.
small team can works for each services and its easy to manage both project and development flow.
and also it suffer from disadvantages of
services are simple and small but all as a whole system is complex so designing part are very critical.
poor performance and it requires do some extras to improve the performance (different types of caching on different levels).
transactions are complex and its developments are time costly. imagine simple update should be projected to other services if its required and you have to consider failure and rollback strategy ( SAGA ).
how to make separate component to build it's own microservice
this is the most challenging part of microservices. you need deep study on Domain driven design DDD.
Decompose by subdomain
Decompose by Business Capabilities
Can anyone give Real Project example?
there are many projects the develop microservices with different patterns. I think you have to start your own and make your hands dirty.
Related
I'm new to DDD and CQRS and I'm planning to build a simple application to improve my skills a bit.
What I'm planning to do is a simple Taxi Corp application.
Requirements:
Client orders a taxi.
Client can have only one order at a time.
Driver picks an order.
Driver can have only one order at a time.
Driver goes to client.
Client enters cab.
Course starts.
Course finishes.
Client is purchased and driver is paid
And so on.
I can see there can be three aggregates: Client, Order and Driver. I want to split them into separate microservices. Do you think it's a good idea or I should start with one microservice?
I'm currently focused on the ordering a taxi. First of all I need to check if client doesn't already have a course assigned, later on I can create an order. After the order is created, I need to assign it to client. As during one request only one aggregate can be updated/created I wonder how to do it correctly. I've read something about Process Managers and I think it will be very useful in this case. I even draw a schema of communication. Can anyone tell me if my approach is correct and give me some tips on how to going further?
Process of creating an order
Do you think it's a good idea or I should start with one microservice?
I refer you to the wisdom of John Gall
A complex system that works is invariably found to have evolved from a simple system that worked. A complex system designed from scratch never works and cannot be patched up to make it work. You have to start over, beginning with a working simple system.
Instead of worrying about microservices, give your attention to messages.
Someone said: "If you have more microservices than customers, you are doing it wrong".
And if you really follow CQRS/ES approach, resulting system is much easier to split apart than traditional ORM monolyths.
So focus on the domain first and start with monolyth.
start with the microservices design even in a wrong way, you get a better insight into desired architecture. because problems in microservices architecture design show themselves very soon.
client and driver are both users of systems and have some commonalities so you can consider them as one domain and one micro-service for them.
consider an order manager micro-service to assign client and driver to a trip by their ids. the order database may include trips table with two id keys for driver-Id and client-Id and some columns for the different states. after finishing each trip you can remove it from the trip table and insert that in an archive table. also, you can leave it there and partition your table daily to keep your database performance high.
consider an accounting micro-service for keeping payments and transactions. It's ok if you opt to use NoSql databases for other microservices, but do use SQL database for your transactions.
you may need another microservice for reporting and dashboards. mirror other dbs in a new one for reporting.
you also need an API gateway to route requests to micro-services or do authentication
your process is a set of events. definitely, you will expand the system later on and perhaps will have some long-running tasks, better to have a message broker and implement your flow as an event/task flow using patterns like event sourcing.
I can see there can be three aggregates: Client, Order and Driver. I
want to split them into separate microservices. Do you think it's a
good idea or I should start with one microservice?
They all belong to the same bounded context. Bounded context translates nicely to microservices (see Eric Evans video: https://www.infoq.com/news/2015/06/dddx-microservices-boundaries). But don't start by designing a micro service, you are doing it in the wrong order. Design first your bounded context then if it makes sense create a micro service around the hexagonal architecture.
After the order is created, I need to assign it to client. As during
one request only one aggregate can be updated/created I wonder how to
do it correctly.
This is the perfect example of why you need to do it all in the same process.
But in the case you want to go multiple micro services, think of eventual consistency (https://en.wikipedia.org/wiki/Eventual_consistency) and create a message driven architecture between your services. Might be too much work in my opinion but for learning purpose can be a good idea.
I am working on a monolith system. All of it's code is in one repository (Web API and background workers). System is written in Nodejs and MongoDB (Mongoose) is used as a data store. My goal is to set a new path how project should evolve. At first I was wondering if I could move towards microservices based architecture.
Monolith architecture creates some problems:
If my background workers needs to scale. I have to deploy all the project to the server despite only using a small fraction of it.
All system must be redeployed when code changes. What if payment processor calls webhook while system is being redeployed?
Using microsevices advantages are quite obvious:
Smaller code base for individual microservice. Easier to reason about it.
Ability to select programming tools best for particular use case.
Easier to scale.
Looking at the current code I noticed that Mongoose ODM (Object Document Mapper) models are used across all the project to create, query and update models in database. As a principle of a good programming all such interactions with database should be abstracted. Business logic should not leak into other system layers. I could do that by introducing REPOSITORY pattern (Domain Driven Design). While code is still being shared across web api and it's background workers it is not a hard task to do.
If i decide to extract repositories into standalone microservices than all bunch of problems arise:
Some sort of query language must be introduced to accommodate complex search queries.
Interface must provide a way to iterate over search results (cursor based navigation) without returning all database documents over network.
Since project is in it's early stage and I am the only developer, going to microservices based architecture seems like an overkill. Maybe there are other approaches I should consider?
Extracting business logic and interaction with database into separate repository and sharing among services to avoid complex communication protocols between services?
Based on my experience with working in Microservices for last few years, it seems like an overkill in current scenario but pays off in long-term.
Based on the information stated above, my thoughts are:
Code Structure - Microservices Architecture (MSA) applying in above context means not separating DAO, Business Logic etc. rather is more on the designing system as per business functions. For example, if it is an eCommerce application, then you can shipping, cart, search as separate services, which can further be divided into smaller services. Read it more about domain-driven design here.
Deployment Unit - Keeping microservices apps as an independent deployment unit is a key principle. Hence, keep a vertical slice of the application and package them as Docker Image with Application Code, App Server (if any), Database and OS (Linux etc.)
Communication - With MSA, communication between services become a key and hence general practice is to remain with the message-oriented approach for communication (read about the reactive system and reactive programming for more insight).
PaaS Solution - There are multiple PaaS solutions available, which you can apply so that you don't need to worry about all the other aspects like container management, container orchestration, auto-scaling, configuration management, log management and monitoring etc. See following PaaS solutions:
https://www.nanoscale.io/ by TIBCO
https://fabric8.io/ - by RedHat
https://openshift.io - by RedHat
Cloud Vendor Platforms - AWS, Azure & Google Cloud all of them have specific support for Microservices App from the deployment perspective, which we can use as an alternative solution if you don't want to deploy PaaS solution in your organization.
Hope these pointers will have in understanding the overall landscape so that you can structure your architecture for future need.
I am working on a monolith system... My goal is to set a new path how project should evolve. At first I was wondering if I could move towards microservices based architecture.
In what ways do you need to evolve the project? Will it be mostly bugfixes, adding features, improving performance and/or scalability? Do you anticipate other developers collaborating in the future? Are you currently having maintenance issues? The answers to these questions (and many more) should be considered in guiding your choices.
You seem to be doing your homework around the pros and cons of a microservice architecture, so if you haven't asked yourself why you're even doing this in the first place, now would be good time to do so.
Maybe there are other approaches I should consider?
There's always the good old don't-break-what's-going ;)
Currently I am working toward splitting monolith REST api into microservices. I would like to introduce Domain Driven Design (currently learning). My biggest concern at this moment is implementing Repository.
Domain UBIQUITOUS LANGUAGE defines Profile entity (Social media profile e.g Twitter profile). I am thinking to extract Profile in to separate microservice. To query profiles i would introduce ProfileRepository.
Other microservices including API gateway have their own Profile search patterns. How should I design Repository to meet all those search patterns. Should I create find method for every query? Should I introduce some sort of dynamic query language?
In a monolith architecture I could create multiple repositories. One for each use case. In microservices architecture I would need to change microservice responsible for Profile every time other microservices needs new query.
Adding a dynamic query language will introduce another level of complexity my personal opinion is that you should avoid this unless you really, really need it - i.e. when other people are going to integrate your system a lot. I strongly agree with #plalx 's comment to your post - adding complexity always has its price and that goes both ways.
On the ubiquitous language & terminology mix - you should really avoid duplicate terms in your domain. The "Profile" concerning a social media account could be named "SocialProfile". So when a "Profile" means two different things in two different contexts: try to find a better term for one of those. Sure you can know that a 'Profile' in the context of 'API gateway' is something and at the same time it is something else in that other context however this will not do you good in the long term - try adding new people to the project and explaining how many different things you call 'a Profile'.
On your last question:
In a monolith architecture I could create multiple repositories. One for each use case. In microservices architecture I would need to change microservice responsible for Profile every time other microservices needs new query.
It really depends on your architecture - do your micro-services use the same code-base & Repository classes? Are they even in the same name-space? You could have one Repository for each micro-service to use and that is the logical approach since your different micro-services will do different things.
If you take my advice and find concrete terms for each Entity in your Domain you will not have to wonder around this. :)
And a side-note on REST APIs from my practice:
If your API is truly REST you can just use Repositories behind each endpoint. However if you find your API endpoints are not just reading & returning data (or entities) but also 'doing something' then there are 2 things to note:
- your API is most-probably not REST but plain RPC
- the objects you use behind endpoints are most-likely Services and not Repositories
In "Implementing Domain-Driven Design", Vernon give detailed examples for integrating bounded context with a messaging or REST based solution, it also mention database integration, but I understand it is not a very clean solution to share database or at least db tables between BC.
But what if the 2 BCs I want to integrate are hosted locally on the same server, is it really a good idea to use a messaging/rest/rpc solution ? (which seems more suitable for a remotely hosted BC to me)
Otherwise, except with DB integration, what are the other alternatives ? Hosting both BC in the same process and calling it directly (still using adapters and translators for clean seperation) ?
Thanks
You could look into using something like 0MQ for inter-process communication on the same server. I've also in the past just hosted things in the same process as you suggest and just used interfaces / in-memory messaging to separate out contexts.
Everything is about trade-offs in the end, so you just need to decide what level of isolation you are willing to accept. The simplest solution would be to separate inside a solution via folders and interfaces, the other end of the spectrum being completely separate servers.
I don't think that location should come into play w.r.t. integration between BCs.
There really are other factors to consider such as guaranteed delivery to the recipient in order to ensure that the processing takes place. This should be required whether or not the two BCs are hosted on the same server.
Another reason to ignore location is that when you need to scale, your architecture should be able to handle it from the get-go.
As tomliversidge mentioned it is possible to use some deployment mechanisms such as non-durable messaging to speed up things but there will definitely be a trade-off and that has to be a conscious decision.
I curently have an application writen in php using the symfony framework. Rather than have seperate installs for customer on a hosted server, I would like to move to as SaaS model with one install for all customers posible running of google code or another cloud based service. I am not tied to PHP though i would like to have the benifits of a good framework.
So the chalenge: If all customers are using the same application we then have fin a way isolating each customers data. Customers do for eample have admin access and can manager their own users and privlages. At a simplistic leve you could just have a organisation identifier in each table take and add that to all database operations. However most application framewors use and ORM of some kind, and I have not been able to find one that will easly / seemlesly facinatate this at a leve the has minimum impact on the application code.
Has anyone looked at this, are there any good aproaches to this problem?
As Itay says, a multi-tenant system is a common requirement. A while back I was doing some research on this problem and came across a pretty good presentation on the different ways to handle this issue, and the pros and cons of each: http://aac2009.confreaks.com/06-feb-2009-14-30-writing-multi-tenant-applications-in-rails-guy-naor.html
This particular presentation is targeted to a Rails audience, but the principles are the same as with any language.
The approach you described is common, and PHP (One of the strengths) will allow you to comparatively easily go into the ORM code and modify it to your needs.
Second approach is to create a separate DB for each organization and a joint DB for shared resources.
A bit of a design challenge (but just a bit).
if you are really big, then you will even need to consider a separate DB server for each organization (I would say this is a serious overkill in 99.99999% of the cases).
This MSDN article gives you a very good overview of Data Architecture in Multi-tenancy: http://msdn.microsoft.com/en-us/library/aa479086.aspx