Service Discovery in Microservices

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Service Discovery in Microservices
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• Microservice architectures are now driving the
  evolution of service discovery. The lifespan of
  service in a microservice architecture is
  measured in seconds and minutes. Addresses are
  constantly added and changed in microservices as
  ports are changed, new hosts, or service
  termination.
• When dealing with microservices, a mechanism that
  allows one service to use another without knowing
  its exact location becomes necessary. Lets look
  at the concept of Service Discovery in this PPT.

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What is Service Discovery?

• Service Discovery is the process by which
  applications and microservices find each other on
  a network. It includes a central server that
  maintains a global view of addresses as well as
  clients that connect to the central server to
  update and retrieve addresses through the
  Implementations.

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• The Service Discovery mechanism assists us in
  determining the location of each instance. Its
  component functions as a registry, tracking the
  addresses of all instances. The network paths for
  the instances are assigned dynamically. As a
  result, if a client wants to request a service,
  it must do so through a Service Discovery
  mechanism.
• Your code must be aware of the network location,
  IP address, and port of a service instance in
  order to make a request. The network locations of
  service instances in a traditional application
  running on physical hardware are relatively
  static.

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What is Service Registry?

• A service registry is a database that tracks the
  availability of each microservice in an
  application. The service registry must be updated
  whenever a new service is added to the system and
  whenever a service is taken offline or becomes
  unavailable. This can be accomplished through
  self-registration or through third-party
  registration.

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Why should you use Service Discovery?

• The service registry is an important component of
  service discovery. A management API and a query
  API are provided by the service registry. The
  management API is used to register and deregister
  service instances with the service registry.
  System components use the query API to discover
  available service instances.

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• Client-side discovery and service-side discovery
  are the two main service-discovery patterns.
  Clients query the service registry, select an
  available instance, and make a request in systems
  that use client-side service discovery. Clients
  make requests through a router in server-side
  discovery systems, which queries the service
  registry and forwards the request to an available
  instance.

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• Service instances are registered with and
  deregistered from the service registry in two
  ways. The self-registration pattern allows
  service instances to register themselves with the
  service registry. The third-party registration
  pattern requires another system component to
  handle registration and deregistration on behalf
  of the service.

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How does Service Discovery Function?

• Service Discovery is divided into two parts. For
  starters, it provides a way for an instance to
  register and declare, Second, it makes it
  possible to locate the service once it has been
  registered.
• Lets use an example to clarify the concept a
  Service Consumer and a Service Provider (a
  service exposing REST API). The Service Provider
  is required by the Service Consumer to read and
  write data.

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The Service Discovery function is depicted in the
diagram below
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The process steps depicted in the above diagram

• The Service Providers location is transmitted to
  the Service Registry (a database containing the
  locations of all available service instances).
• The Service Consumer requests the location of the
  Service Provider from the Service Discovery
  Server.
• The Service Registry searches its internal
  database for the Service Providers location and
  returns it to the Service Consumer.
• The Service Consumer now has the ability to make
  direct requests to the Service Provider.

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Implementation of Service Discovery

• The Service Consumer is responsible for
  determining the network locations of available
  service instances and balancing requests between
  them when using Client-Side Discovery.
• The client requests information from the Service
  Register then employs a load-balancing algorithm
  to select one of the available service instances
  and issue a request.

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The diagram below depicts how client-side service
discovery works
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Advantages and Disadvantages of Client-side
Service Discovery Implementation

• Advantage Eliminating an extra hop requires a
  dedicated load balancer.
• Disadvantage The load balancing logic must be
  implemented by the Service Consumer.
• The Service Consumer and the Service Registry are
  inextricably linked in the client-side service
  discovery implementation. This means that logic
  for Client-Side Discovery must be implemented for
  each programming language and framework used by
  Service Consumers.

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Server-Side Service Discovery Implementation

• The Server-Side Discovery model uses an
  intermediary that acts as a Load Balancer. Here,
  the client sends a request to a service through a
  load balancer, which serves as an orchestrator,
  and the load balancer searches the Service
  Registry for available service instances and
  routes each request to one of them.

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The diagram below depicts how communication
occurs in service-side service discovery
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Advantages and Disadvantages of using
Service-Side Service Discovery

• Advantages The main advantage of this method is
  the approach of using a Load balancer, which
  creates such a level of abstraction lightens the
  Service Consumer by removing the need to deal
  with the lookup procedure. Here, we dont need to
  implement the discovery logic for each language
  and framework that the Service Consumer employs.
• Disadvantages The main disadvantage is that we
  must configure and manage the Load Balancer
  unless it is already included in the deployment
  environment.

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Thank You

• Thanks for reading our PPT. Consult us to know
  more about Service Discovery in Microservices. or
  any other Digital Transformation services.