a13z / expense-report

A demo with Spring Boot and .NET Microservices that use Consul's service mesh and key-value capabilities.

Expense Report

A set of .NET Core and Java Spring Boot services that records expenses and returns a report for a given trip identifier.

What it does

Expense Report uses Consul for service mesh, application configuration, and feature toggling capabilities.

For multiple frameworks, Consul Connect provides service mesh capabilities that enable a consistent method of configuring:

• Service Discovery
• Network Policy (via Consul intentions)
• Load balancing
• Additional Tracing Metadata
• Circuit Breaking (AKA Outlier Detection)

In addition to using Consul Connect, the expense microservice demonstrates the use of Spring Cloud Consul Config for retrieving application properties from Consul KV.

Finally, the report microservice uses consul-template to feature toggle the addition of a "Number of Items" field for the report.

APIs

Below are the most useful endpoints for the expense service:

• curl -X GET 'http://localhost:${port}/api/expense'
• curl -X POST 'http://localhost:${port}/api/expense' -H 'Content-Type:application/json' -d @example/expense.json

${port} will depend on the framework. Java defaults to :8080 and .NET Core defaults to :5001.

Below are the most useful endpoints for the report service:

• curl -X GET 'http://localhost:5002/api/report/trip/${trip_id}'

${trip_id} denotes the trip identifer passed in the body of the expense item created in the POST method to expense. Since the report application is currently only available in .NET Core, it runs by default on port :5002.

Prerequisites

• Docker
• docker-compose

Startup

1. To start, bring up the Consul server, MySQL database, Microsoft SQL Server database, consul-template, Jaeger for tracing, and the expense services in .NET Core and Java.

   > make all

   This will not only bring up the stack but add the application configuration for the expense service.

   

2. Open Jaeger on http://localhost:16686 and Consul on http://localhost:8500.

Service Networking with Consul Connect

To try out:

• Service discovery
• Network policy
• Load balancing
• Additional tracing metadata

You can create the report service by running make report-app.

Circuit Breaking

To try circuit breaking (outlier detection in Envoy), note that it the configuration requires an unsupported Consul escape hatch override. It cannot have any service resolver or splitter configuration. To run it, issue make circuit-break. Note that by running this command, it will delete existing Consul L7 configuration and redeploy the report service.

You can run a test with make circuit-break-test. This will stop the Microsoft SQL Server database and fail calls to the .NET Core expense service. As a result, circuit breaker will trip in the report service and route all traffic to the Java expense service.

Feature Toggling with Consul KV & consul-template

To try feature toggling, you can trigger a toggle that enables the number of expense items to print out in the report service. Issue make toggle-on to enable and you will see a number of items listed.

> curl -s http://localhost:5002/api/report/trip/d7fd4bf6-aeb9-45a0-b671-85dfc4d095aa | jq                                                                                                        
{
  "tripId": "d7fd4bf6-aeb9-45a0-b671-85dfc4d095aa",
  "expenses": [],
  "total": 0,
  "numberOfExpenses": 0
}

Run make toggle-off to disable and remove the number of expense items.

 curl -s http://localhost:5002/api/report/trip/d7fd4bf6-aeb9-45a0-b671-85dfc4d095aa | jq                                                                                                        
{
  "tripId": "d7fd4bf6-aeb9-45a0-b671-85dfc4d095aa",
  "expenses": [],
  "total": 0,
}

Application Configuration with Consul KV

To try application configuration storage, you can go to the Consul UI and examine the configuration path under "Key/Value". This uses a file format to add the application.properties required for a Spring Boot application.