Really a useful article for all the TechGeeks and technology experts to know the Pros & Cons of having Microservice based applications and development

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Microservice is application architecturalstyle to build applicationwhich best
suits for large complex system. Microservice based application contains
loosely coupled small independent deployable projects.
Components of Microservice
1) Service Fabric
 Azure Service Fabric is a Microsoft’s microservice platform and
includes container orchestration as well as developer programming
models to build highlyscalable microservice applications.
 We can deployservice fabric platform to Azure, AWS or on premise
(on Windows orLinux machine)
Microservices with ASP.NET Core:
A Next Gen. Technology

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 As of now we can deploystateless containerized application to service
fabric.
 Service fabricplatform provides features like Naming Service (Service
Discovery and Service Registry), Monitoring,Logging, fault tolerance
capabilityetc.
 We can add host/virtual machines from different geographicand
network location to service fabric cluster by ‘Powershell’cli or through
service fabric manifest file.
 Service fabricthen automaticallybalance the nodes,if any node goes
down it will up other node and host required application instance on
the newly added node.
2) Service programming model
Stateless Services
 When we need to persist data to external storage, we will build
stateless service.
 Most of the time we need to store data in external storage (MS SQL,
NoSQL storage) so stateless services use most of the time.
 We can containerize this type of services, as of nowwe can host this
type of service to ‘Docker’ in service fabric.
Stateful Service
 When we need to persist data to service itself, in that case we can
build Stateful service.
 We can reduce latency between business logicand data.
 Stateful services stores through reliable collections to node itself(In
main memory, hard disk)

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 Data will be stored across different partitions to scale and replicate to
several nodes to make sure data availability24X7
 As of now we cannot host service to container but in future, this
feature might be included
3) Communication between services
 Client application will communicate with service through Rest APIs
(HTTP Request/Response) protocol. This type of communication is
synchronous in nature, caller will wait till response get back.
 We can follow different technique to communicate between services
(communication between services within cluster)
 We can communicate between services asynchronously (Using Event
Bus – (Service can Publish – Subscribe to specific event by other
service)) wherever possible in case somehow we will not able to
communicate asynchronously then we will synchronously
communicate between services over Rest APIs.
 So that way we can reduce the tight couplingbetween the system and
in case if we need to implement other behaviorfor specific event then
in that case service just need to subscribe that specific event, so that’s
the way we can choreograph the system and we can make the system
more loosely coupled
 We can use Azure service bus to perform asynchronous message based
communication between services there are other tools also available
i.e. RabbitMQ, ActiveMQ etc.
4) Event bus
 Event bus allowed the publish-subscribe style of communication
between services.

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 Usingevent bus we can establish asynchronousstyle ofcommunication
between services.
 Each service can subscribe particular event and whenever any event
occurred specified method will be invoked in service.
 For instance, if‘Service A’publish event named ‘OrderCreated’andthis
event is subscribed by ‘Service B’ then whenever ‘OrderCreated’event
published by‘Service A’ this event will be pushed to queue and later it
will be processed by ‘Service B’.
 We can further extend ‘Event Bus’ to implement ‘Event Sourcing’ and
‘CQRS (Command Query Responsibility segregation)’ pattern.
 Event bus is enabled us to implement asynchronous messagingpattern
thus system can be choreographed properly and we can reduce
coupling between service.
 Azure Service Bus can be used to implement this
5) Circuit Breaker

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Many times due to the fault of downstream service the caller system might
get collapsed due to all resource exhausted, due to this we might end up
whole system down because of cascade fall down, to prevent this we use
Circuit Breaker pattern which works like a switch between caller service and
downstream service. if downstream service get time out or return any
exception occurred (i.e. HTTP 5XX errors) then switch will be set off
To apply Circuit breaker pattern we use POLLY (http://thepollyproject.org)
library.
Polly provides features like Circuit Breaker, Bulkhead isolation.
6) Load Balancer
 Load balancer will route traffic to different nodes to distribute traffics
over available nodes.
 Load balancer first query to Service Registry (Naming Service) to get
details ofavailable online nodes. So that it can route traffic to nodes.
 We can use Azure Load Balancer service to implement this.
7) Service Discovery and Service Registry (Naming Service)
 This both techniques are responsible to find the physical location of
particular service in cluster.
 Whenever any service up in cluster it will register its IP address with
service registry. after particular timespan heartbeat signal will be sent
to know whether service is still alive or not.
 Wheneveranyservice request come to networkit will first send request
to service registry to find out location of service, this mechanism

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implemented on top of load balancer. once load balancer get physical
location of that node it will redirect request to that specific node.
 If we use Service Fabric as our microservice platform, then Service
Discovery and Service Registry mechanism will be built in implemented
(Naming Service in Service Fabric)
8) API Gateway
 API Gateway consist of several small projects which act like an
aggregator or a proxy to inner service layer.
 API Gateway acts like entry point to the application.
 There are several benefits of API Gateways like, we can implement
Authorization, HTTPS termination, we can aggregate response from
various service and send backit to caller so that theydo not need to call
multiple service, this will very helpful for mobile clients.
 We can use APIgatewayas back end forfront end.We do haveseparate
gateway for different type of consumer i.e. Web client, Mobile client
etc.
9) Authentication and Authorization
 We can use ‘IdentityServer4’or ‘auth0’or ‘octa’ for authentication
and authorizationpurpose.
 IdentityServer4is communitydriven project which offers features like
Single Sign on, Refresh token, token based security, one can revoke
generated token,Support External Identityprovider (Google,
Facebook),Admin UI (in beta version)for user management etc.
 Built on top of .NET Core so we can deployit on both Windows or
Linux machine.

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Advantage of having Microservice based application
 Each service is relativelysmall,so it is easier to maintain code and
reduced build time
 We can add more feature in less time compare to monolith application
 Each service can be deployed independently,we can do releases more
aggressively
 Easy to scale (Horizontal scaling)
 Different technologystack can be used in different services
Disadvantages
 Limited toolingsupport available to deal with complexityin
microservice based application
 Difficult to create testing environment
 Memory/bandwidthconsumptionwill be increased
 There is no support fortransaction
 One should havedomain knowledge to break functionalityinto
individual service
 Must havedeal with problems of distributedsystem
 Performance might be reduced
 Not suitable forsmall application
Source:
http://www.evincedev.com/blog/microservices-asp-net-core-
next-gen-technology/

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