This is the MSF4J sample that demonstrates how to use Open Feign client to call microservices deployed in MSF4J and trace the request response flow with WSO2 DAS. Feign is a java to http client binder that allows you to write Java HTTP REST clients easily. You can create a Java interface and declare your service contracts using annotations. In this example we create 3 microservices; CustomerService, InvoiceService, ReportService. This sample contains Java HTTP/REST bindings and Feign clients created for CustomerService and InvoiceService microservices. The service message flow is as follows;
The ReportService uses Feign clients to call InvoiceService and CustomerService to generate the report. It uses a TracingClient (which extends feign.Client.Default class) to trace request/response flow by injecting traceable headers to the request. TracingClient publishes trace events which are created in request/response exchanges to WSO2 Data Analytics Server.
Add the msf4j tracing and Open Feign dependencies to the pom of you MSF4J service.
<dependencies>
<dependency>
<groupId>org.wso2.msf4j</groupId>
<artifactId>msf4j-analytics</artifactId>
</dependency>
<!-- Feign -->
<dependency>
<groupId>io.github.openfeign</groupId>
<artifactId>feign-core</artifactId>
</dependency>
<dependency>
<groupId>io.github.openfeign</groupId>
<artifactId>feign-slf4j</artifactId>
</dependency>
<dependency>
<groupId>io.github.openfeign</groupId>
<artifactId>feign-gson</artifactId>
</dependency>
</dependencies>Register the tracing interceptor when starting the microservice.
new MicroservicesRunner()
.addExceptionMapper(new EntityNotFoundMapper(), new CustomerNotFoundMapper())
.addInterceptor(new MSF4JTracingInterceptor("Service-Chaining"))
.deploy(new InvoiceService())
.deploy(new CustomerService())
.deploy(new ReportService())
.start();CustomerServiceAPI is defined as a Java interface which binds to HTTP/REST API via annotations.
public interface CustomerServiceAPI {
@RequestLine("GET /customer/{id}")
Customer getCustomer(@Param("id") String id) throws ClientException;
}Register the FeignTracingClient (which extends feign.Client.Default) when building the Feign client instance. You only need FeignTracingClient to trace request/response flow with WSO2 Data Analytics Server. This client will publish client request/response trace events to WSO2 DAS. You can use MSF4J Message Tracing Dashboard to visualize the trace events. See below for installation instructions.
Feign.Builder b = Feign.builder()
.client(new FeignTracingClient("Customer-Service-Client", analyticsEndpoint))
.encoder(new GsonEncoder(ModelUtils.GSON))
.logger(new Slf4jLogger())
.decoder(new GsonDecoder(ModelUtils.GSON))
.errorDecoder(new ClientErrorDecoder());
CustomerServiceAPI client = b.target(CustomerServiceAPI.class, serviceEndpoint);From this directory, run
mvn clean install
Download WSO2 DAS Version 3.0.1 and start it with default configurations.
Build wso2das-tracing-capp module and get the wso2das-msf4j-tracing-*.car file. Then, deploy wso2das-msf4j-tracing-*.car file in the WSO2 DAS instance you just started. Now you can check the MSF4J Message Tracing Dashboard at https://localhost:9443/portal/dashboards/msf4j-message-tracing.
After that, from the target directory of this sample, run the following command to start the sample microservice.
java -jar das-tracing-feign-client-*.jar
We will use the cURL command line tool for testing. You can use your preferred HTTP or REST client too.
curl http://localhost:8080/report/invoice/I001
You should get a response similar to the following:
{"id":"I001","customer":{"id":"C001","firstName":"Akila","lastName":"Perera","address":"DreamWorld!"},"amount":250.15,"date":"Aug 22, 2016 4:50:23 PM"}
The above response was generated by 'ReportService' which in turn calls 'InvoiceService' and 'CustomerService' microservices to aggregate the result. So after receiving the above response, you can go to the WSO2 DAS dashboard and find the traces.
