Setting up a skeleton “Hello, World!” server
This section of the tutorial enhances the application to (trivially) respond to HTTP requests.
Let’s create simple HTTP server process that responds with a 200 OK/Hello World response for each request.
Each process is initialized by calling its Init function with a configuration container (more on this in the next section). On initialization success, the Start method is invoked in a dedicated go-routine. This method is expected to block for long-running processes such as servers. On application shutdown, the Stop method is invoked which should unblock any active work being done in the Start method.
Here, the Init method creates a server and configures its handler. The Start creates a TCP listener and starts serving HTTP traffic. The Stop method signals for the server to stop accepting new connections and shutdown.
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| import (
"context"
"fmt"
"net"
"net/http"
// ...
)
type server struct {
server *http.Server
port int
}
func (s *server) Init(ctx context.Context) error {
s.server = &http.Server{}
s.server.Handler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
w.WriteHeader(http.StatusOK)
w.Write([]byte("Hello, World!\n"))
})
return nil
}
func (s *server) Run(ctx context.Context) error {
addr, err := net.ResolveTCPAddr("tcp", fmt.Sprintf(":%d", s.port))
if err != nil {
return err
}
listener, err := net.ListenTCP("tcp", addr)
if err != nil {
return err
}
defer listener.Close()
defer s.server.Close()
// Run server, block until shutdown (do not return ErrServerClosed)
if err := s.server.Serve(listener); err != http.ErrServerClosed {
return err
}
return nil
}
func (s *server) Stop(ctx context.Context) error {
s.server.Shutdown(context.Background())
return nil
}
|
Now, we modify the setup function to register this server process.
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| func setup(ctx context.Context, processes *nacelle.ProcessContainerBuilder, services *nacelle.ServiceContainer) error {
processes.RegisterProcess(&server{port: 5000}, nacelle.WithMetaName("hw-server"))
return nil
}
|
If you were to run this application, you would see Nacelle initialize and start the hw-server process. Curl-ing any path at http://localhost:5000 will return the same 200-level response.
