Add healthcheck listener (#244)

* Add healthcheck listener

* Update improper comments

---------

Co-authored-by: Derek Duncan <derekduncan@gmail.com>
Co-authored-by: JB <28275108+mochi-co@users.noreply.github.com>

listeners/http_healthcheck.go

@@ -0,0 +1,100 @@
+package listeners
+
+import (
+	"context"
+	"net/http"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/rs/zerolog"
+)
+
+// HTTPHealthCheck is a listener for providing an HTTP healthcheck endpoint.
+type HTTPHealthCheck struct {
+	sync.RWMutex
+	id      string          // the internal id of the listener
+	address string          // the network address to bind to
+	config  *Config         // configuration values for the listener
+	listen  *http.Server    // the http server
+	log     *zerolog.Logger // server logger
+	end     uint32          // ensure the close methods are only called once
+}
+
+// NewHTTPHealthCheck initialises and returns a new HTTP listener, listening on an address.
+func NewHTTPHealthCheck(id, address string, config *Config) *HTTPHealthCheck {
+	if config == nil {
+		config = new(Config)
+	}
+	return &HTTPHealthCheck{
+		id:      id,
+		address: address,
+		config:  config,
+	}
+}
+
+// ID returns the id of the listener.
+func (l *HTTPHealthCheck) ID() string {
+	return l.id
+}
+
+// Address returns the address of the listener.
+func (l *HTTPHealthCheck) Address() string {
+	return l.address
+}
+
+// Protocol returns the address of the listener.
+func (l *HTTPHealthCheck) Protocol() string {
+	if l.listen != nil && l.listen.TLSConfig != nil {
+		return "https"
+	}
+
+	return "http"
+}
+
+// Init initializes the listener.
+func (l *HTTPHealthCheck) Init(log *zerolog.Logger) error {
+	l.log = log
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("/healthcheck", func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodGet {
+			w.WriteHeader(http.StatusMethodNotAllowed)
+		}
+	})
+	l.listen = &http.Server{
+		ReadTimeout:  5 * time.Second,
+		WriteTimeout: 5 * time.Second,
+		Addr:         l.address,
+		Handler:      mux,
+	}
+
+	if l.config.TLSConfig != nil {
+		l.listen.TLSConfig = l.config.TLSConfig
+	}
+
+	return nil
+}
+
+// Serve starts listening for new connections and serving responses.
+func (l *HTTPHealthCheck) Serve(establish EstablishFn) {
+	if l.listen.TLSConfig != nil {
+		l.listen.ListenAndServeTLS("", "")
+	} else {
+		l.listen.ListenAndServe()
+	}
+}
+
+// Close closes the listener and any client connections.
+func (l *HTTPHealthCheck) Close(closeClients CloseFn) {
+	l.Lock()
+	defer l.Unlock()
+
+	if atomic.CompareAndSwapUint32(&l.end, 0, 1) {
+		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
+		l.listen.Shutdown(ctx)
+	}
+
+	closeClients(l.id)
+}

listeners/http_healthcheck_test.go

@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: MIT
+// SPDX-FileCopyrightText: 2022 mochi-co
+// SPDX-FileContributor: mochi-co
+
+package listeners
+
+import (
+	"io"
+	"net/http"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestNewHTTPHealthCheck(t *testing.T) {
+	l := NewHTTPHealthCheck("healthcheck", testAddr, nil)
+	require.Equal(t, "healthcheck", l.id)
+	require.Equal(t, testAddr, l.address)
+}
+
+func TestHTTPHealthCheckID(t *testing.T) {
+	l := NewHTTPHealthCheck("healthcheck", testAddr, nil)
+	require.Equal(t, "healthcheck", l.ID())
+}
+
+func TestHTTPHealthCheckAddress(t *testing.T) {
+	l := NewHTTPHealthCheck("healthcheck", testAddr, nil)
+	require.Equal(t, testAddr, l.Address())
+}
+
+func TestHTTPHealthCheckProtocol(t *testing.T) {
+	l := NewHTTPHealthCheck("healthcheck", testAddr, nil)
+	require.Equal(t, "http", l.Protocol())
+}
+
+func TestHTTPHealthCheckTLSProtocol(t *testing.T) {
+	l := NewHTTPHealthCheck("healthcheck", testAddr, &Config{
+		TLSConfig: tlsConfigBasic,
+	})
+
+	l.Init(nil)
+	require.Equal(t, "https", l.Protocol())
+}
+
+func TestHTTPHealthCheckInit(t *testing.T) {
+	l := NewHTTPHealthCheck("healthcheck", testAddr, nil)
+	err := l.Init(nil)
+	require.NoError(t, err)
+
+	require.NotNil(t, l.listen)
+	require.Equal(t, testAddr, l.listen.Addr)
+}
+
+func TestHTTPHealthCheckServeAndClose(t *testing.T) {
+	// setup http stats listener
+	l := NewHTTPHealthCheck("healthcheck", testAddr, nil)
+	err := l.Init(nil)
+	require.NoError(t, err)
+
+	o := make(chan bool)
+	go func(o chan bool) {
+		l.Serve(MockEstablisher)
+		o <- true
+	}(o)
+
+	time.Sleep(time.Millisecond)
+
+	// call healthcheck
+	resp, err := http.Get("http://localhost" + testAddr + "/healthcheck")
+	require.NoError(t, err)
+	require.NotNil(t, resp)
+
+	defer resp.Body.Close()
+	_, err = io.ReadAll(resp.Body)
+	require.NoError(t, err)
+
+	// ensure listening is closed
+	var closed bool
+	l.Close(func(id string) {
+		closed = true
+	})
+
+	require.Equal(t, true, closed)
+
+	_, err = http.Get("http://localhost/healthcheck" + testAddr + "/healthcheck")
+	require.Error(t, err)
+	<-o
+}
+
+func TestHTTPHealthCheckServeAndCloseMethodNotAllowed(t *testing.T) {
+	// setup http stats listener
+	l := NewHTTPHealthCheck("healthcheck", testAddr, nil)
+	err := l.Init(nil)
+	require.NoError(t, err)
+
+	o := make(chan bool)
+	go func(o chan bool) {
+		l.Serve(MockEstablisher)
+		o <- true
+	}(o)
+
+	time.Sleep(time.Millisecond)
+
+	// make disallowed method type http request
+	resp, err := http.Post("http://localhost"+testAddr+"/healthcheck", "application/json", http.NoBody)
+	require.NoError(t, err)
+	require.NotNil(t, resp)
+
+	defer resp.Body.Close()
+	_, err = io.ReadAll(resp.Body)
+	require.NoError(t, err)
+
+	// ensure listening is closed
+	var closed bool
+	l.Close(func(id string) {
+		closed = true
+	})
+
+	require.Equal(t, true, closed)
+
+	_, err = http.Post("http://localhost/healthcheck"+testAddr+"/healthcheck", "application/json", http.NoBody)
+	require.Error(t, err)
+	<-o
+}
+
+func TestHTTPHealthCheckServeTLSAndClose(t *testing.T) {
+	l := NewHTTPHealthCheck("healthcheck", testAddr, &Config{
+		TLSConfig: tlsConfigBasic,
+	})
+
+	err := l.Init(nil)
+	require.NoError(t, err)
+
+	o := make(chan bool)
+	go func(o chan bool) {
+		l.Serve(MockEstablisher)
+		o <- true
+	}(o)
+
+	time.Sleep(time.Millisecond)
+	l.Close(MockCloser)
+}