![]() $ ballerina grpc -mode service -input proto/checkout.proto -output gen_code gRPC Client Streaming You can use the ballerina grpc command to generate boilerplate code for checkout.proto. Listing 4: Service contract for Checkout microservice ( checkout.proto) Resource function UpdateOrder(grpc:Caller caller, Item value) This generates the OrderService server boilerplate code. $ ballerina grpc -mode service -input proto/order.proto -output gen_code Here I use the Ballerina gRPC tool to generate a gRPC service boilerplate code and the stub/client respectively. The Order microservice will get shopping items and the quantity and return the subtotal. Listing 1: Service contract for Order microservice ( order.proto) Let’s define service contracts for each service. Since gRPC is supported by many major programming languages, when we define the service contracts, implementation can be carried out with a well-suited programming language. Figure 1 illustrates a segment of an online retail shop microservice architecture, where four microservices are implemented in Ballerina (referred to as Ballerina in the rest of the article) and Golang working together to provide some functionality of the retail online shop. One of the main benefits of microservice architecture is to build different services by using the most appropriate programming language rather than building everything in one language. A Pragmatic Microservices Use Case with gRPCįigure 1: A segment of an online retail shop microservices architecture Using major programming language provided tools, a server-side skeleton and client-side code (stub) can be generated using the same Protocol Buffers file which defines the service contract. You can define the gRPC service contract by using Protocol Buffers where each service definition specifies the number of methods with the expected input and output messages with the data structure of the parameters and return types. gRPC uses HTTP/2, the latest network transport protocol, as the default transport protocol and this makes gRPC fast and robust compared to REST over HTTP/1.1. Same as other binary protocols like Thrift and Avro, gRPC uses an interface description language (IDL) to define a service contract. Like all other RPCs, it allows directly invoking methods on a server application on a different machine as if it were a local object. GRPC is a relatively new Remote Procedure Call (RPC) API paradigm for inter-service communications. In this article, we will take a closer look at how we can leverage a binary protocol such as gRPC which can be an optimized communication protocol for inter-service communication What is gRPC?īring together legacy systems, RPA bots, microservices, and more with Camunda. In many cases, we can see the use of REST APIs over HTTP as a synchronous mode but that would not be the best technology to use. Internal microservices use either synchronous or asynchronous communication. ![]() These microservices interact with each other to complete a given set of tasks. The other group of microservices are internal and don’t communicate with external systems or external developers. GraphQL can be an alternative for the HTTP-based REST APIs but it is out of scope for this article. API management systems work well with these APIs and provide security, rate limiting, caching, and monetizing along with business requirements. OpenAPIprovides well-defined specifications for describing, producing, consuming, and visualizing these REST APIs. REST’s ubiquity and rich ecosystem play a vital role in the success of these external-facing microservices. They are mainly HTTP-based APIs that use conventional text-based messaging payloads (JSON, XML, etc.) that are optimized for external developers, and use Representational State Transfer (REST) as the de facto communication technology. The first group of microservices acts as external-facing microservices, which are directly exposed to consumers. In modern microservice architecture, we can categorize microservices into two main groups based on their interaction and communication.
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