A container is an isolated process environment that packages an application or dependency with its required runtime components. In a microservice system, each service runs in its own container and can be deployed, configured, and scaled independently. section 1.4.2
Use containers to support independent service operations:
- Define resource requests, runtime settings, and scaling factors separately for each service. section 1.4.2
- Deploy services through Kubernetes specifications in a CI/CD pipeline and discover gRPC endpoints through Kubernetes service names. section 1.4.2
- Run the same cloud-native service on Kubernetes, AWS Fargate, AWS ECS, or Docker for local development. section 1.4.2
Containers also provide repeatable infrastructure for integration tests. Testcontainers can start a MySQL image, expose its port, wait for a liveness or SQL readiness probe, and pass the resulting endpoint to the test suite. Docker Compose can instead provision a database with initialization SQL and a health check before connections are accepted. section 7.3.2 section 7.4.4
MySQL container for order tests
Configure a MySQL 8.0.30 container with an orders database, expose port 3306, wait for SQL readiness, obtain its connection URL, and run save-and-get integration tests with `go test ./...`. Use a nonroot database user outside the simplified test setup. section 7.3.2
func (o *OrderDatabaseTestSuite) SetupSuite() { #1
ctx := context.Background()
port := "3306/tcp"
dbURL := func(port nat.Port) string {
return fmt.Sprintf("root:s3cr3t@tcp(localhost:%s)/
orders?charset=utf8mb4&parseTime=True&loc=Local",
port.Port()) #2
}
req := testcontainers.ContainerRequest{
Image: "docker.io/mysql:8.0.30",
ExposedPorts: []string{port},
Env: map[string]string{
"MYSQL_ROOT_PASSWORD": "s3cr3t",
"MYSQL_DATABASE": "orders",
},
WaitingFor: wait.ForSQL(nat.Port(port), "mysql",
dbURL).Timeout(time.Second * 30), #3
}
mysqlContainer, err := testcontainers.GenericContainer(ctx,
testcontainers.GenericContainerRequest{
ContainerRequest: req,
Started: true,
})
if err != nil {
log.Fatal("Failed to start Mysql.", err)
}
endpoint, _ := mysqlContainer.Endpoint(ctx, "")
o.DataSourceUrl =
fmt.Sprintf("root:s3cr3t@tcp(%s)/
orders?charset=utf8mb4&parseTime=True&loc=Local", endpoint) #4
}
Shows the Testcontainers request, environment variables, exposed port, and SQL readiness configuration used to start MySQL for tests. section 7.3.2
