Added health check client

CHANGELOG.md

@@ -1,9 +1,13 @@
 # Changelog
 
-## 1.0.1
+## 1.1.0: Added health check client
+
+This release adds a dedicated client library for health checks. It also adds an "Enable" field to the configuration.
+
+## 1.0.1: JSON and YAML tags
 
 Add JSON and YAML tag as well as a sane default for the HTTP configuration.
 
-## 1.0.0
+## 1.0.0: Initial version
 
-Initial version of a health check service using an external configuration.
+Initial version of a health check service using an external configuration.

CODES.md

@@ -0,0 +1,7 @@
+# Message / error codes
+
+| Code | Explanation |
+|------|-------------|
+| `HEALTH_AVAILABLE` | The health check service is now online and ready for service. |
+| `HEALTH_REQUEST_FAILED` | A request to the health check endpoint failed. |
+

README.md

@@ -18,6 +18,7 @@ You can instantiate this service as described in the [service library](https://g
 ```go
 svc, err := health.New(
     health.Config{
+        Enable: true
         ServerConfiguration: http.ServerConfiguration{
             Listen: "0.0.0.0:23074",
         },
@@ -33,4 +34,25 @@ You can change the `ok`/`not ok` status by calling `srv.ChangeStatus(bool)`, lik
 
 ```go
 srv.ChangeStatus(true)
-```
+```
+
+## Health check client
+
+This library also provides a built-in client for running health checks. This can be used as follows:
+
+```go
+client, err := health.NewClient(
+    health.Config{
+        Enable: true
+        Client: http.ClientConfiguration{
+            URL: "http://0.0.0.0:23074",
+        },
+    },
+    logger)
+)
+if client.Run() {
+    // Success
+} else {
+    // Failed
+}
+```

codes.go

@@ -0,0 +1,7 @@
+package health
+
+// The health check service is now online and ready for service.
+const MServiceAvailable = "HEALTH_AVAILABLE"
+
+// A request to the health check endpoint failed.
+const ERequestFailed = "HEALTH_REQUEST_FAILED"

codes_doc.go

@@ -0,0 +1,3 @@
+package health
+
+//go:generate containerssh-generate-codes

go.mod

@@ -3,7 +3,7 @@ module github.com/containerssh/health
 go 1.16
 
 require (
-	github.com/containerssh/http v1.1.0
+	github.com/containerssh/http v1.2.0
 	github.com/containerssh/log v1.1.6
 	github.com/containerssh/service v1.0.0
 )

go.sum

@@ -1,6 +1,9 @@
 github.com/containerssh/http v1.1.0 h1:N3nYCra07//pYyVCW/ryZTDh/G4CHFzd5ht27pUtKu0=
 github.com/containerssh/http v1.1.0/go.mod h1:0czFGNEJTPpEjkSp/YcPseNzJSOvwc8H5rMRpQQ+Kj4=
+github.com/containerssh/http v1.2.0 h1:PH6LxDErDZyryLfGJduI4F15puVlOyUP6MApwS8yV4k=
+github.com/containerssh/http v1.2.0/go.mod h1:aUBi5CsAZsvYBn6NYeT3oUwnvzZRkneL/k2o2pOMdU0=
 github.com/containerssh/log v1.0.0/go.mod h1:7Gy+sx0H1UDtjYBySvK0CnXRRHPHZPXMsa9MYmLBI0I=
+github.com/containerssh/log v1.1.3/go.mod h1:JER/AjoAHhb8arGN6bsAPF1r1S8p6sUAnvBOL4s32ZU=
 github.com/containerssh/log v1.1.6 h1:5fBBZA2MZss5NMUP2FgJ/iERNwN4y+68uwRE8XjbEKA=
 github.com/containerssh/log v1.1.6/go.mod h1:JER/AjoAHhb8arGN6bsAPF1r1S8p6sUAnvBOL4s32ZU=
 github.com/containerssh/service v1.0.0 h1:+AcBsmeaR0iMDnemXJ6OgeTEYB3C0YJF3h03MNIo1Ak=

health.go

@@ -1,46 +1,92 @@
 package health
 
 import (
+	"fmt"
+
 	"github.com/containerssh/http"
 	"github.com/containerssh/log"
 	"github.com/containerssh/service"
 )
 
-// Config is the configuration for the HealthCheckService.
+// Config is the configuration for the Service.
 type Config struct {
-	http.ServerConfiguration `json:",inline" yaml:",inline" default:"{\"listen\":\"0.0.0.0:23074\"}"`
+	Enable                   bool `json:"enable" yaml:"enable"`
+	http.ServerConfiguration `json:",inline" yaml:",inline" default:"{\"listen\":\"0.0.0.0:7000\"}"`
+	Client                   http.ClientConfiguration `json:"client" yaml:"client" default:"{\"url\":\"http://127.0.0.1:7000/\"}"`
 }
 
-// New creates a new HTTP health service on port 23074
-func New(config Config, logger log.Logger) (HealthCheckService, error) {
+func (c Config) Validate() error {
+	if !c.Enable {
+		return nil
+	}
+	if err := c.ServerConfiguration.Validate(); err != nil {
+		return err
+	}
+	if err := c.Client.Validate(); err != nil {
+		return fmt.Errorf("invalid client configuration (%w)", err)
+	}
+	return nil
+}
 
-	rh := &requestHandler{}
+// New creates a new HTTP health service on port 23074
+func New(config Config, logger log.Logger) (Service, error) {
+	if err := config.Validate(); err != nil {
+		return nil, err
+	}
 
-	handler := http.NewServerHandler(rh, logger)
+	handler := &requestHandler{}
 	svc, err := http.NewServer(
-		"health",
+		"Health check endpoint",
 		config.ServerConfiguration,
-		handler,
+		http.NewServerHandlerNegotiate(handler, logger),
 		logger,
-		func(url string) {},
+		func(url string) {
+			logger.Info(log.NewMessage(MServiceAvailable, "Health check endpoint available at %s", url))
+		},
 	)
-
 	if err != nil {
 		return nil, err
 	}
 
 	return &healthCheckService{
 		Service:        svc,
-		requestHandler: rh,
+		requestHandler: handler,
+	}, nil
+}
+
+// NewClient creates a new health check client based on the supplied configuration. If the health check is not enabled
+// no client is returned.
+func NewClient(config Config, logger log.Logger) (Client, error) {
+	if !config.Enable {
+		return nil, nil
+	}
+	if err := config.Validate(); err != nil {
+		return nil, fmt.Errorf("invalid health check configuration (%w)", err)
+	}
+
+	httpClient, err := http.NewClient(config.Client, logger)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create health check client (%w)", err)
+	}
+
+	return &healthCheckClient{
+		httpClient: httpClient,
+		logger:     logger,
 	}, nil
 }
 
-// HealthCheckService is an HTTP service that lets you change the status via ChangeStatus().
-type HealthCheckService interface {
+// Service is an HTTP service that lets you change the status via ChangeStatus().
+type Service interface {
 	service.Service
 	ChangeStatus(ok bool)
 }
 
+// Client is the client to run health checks.
+type Client interface {
+	// Run runs a HTTP query against the health check service.
+	Run() bool
+}
+
 type healthCheckService struct {
 	service.Service
 	requestHandler *requestHandler
@@ -54,7 +100,7 @@ type requestHandler struct {
 	ok bool
 }
 
-func (r requestHandler) OnRequest(request http.ServerRequest, response http.ServerResponse) error {
+func (r requestHandler) OnRequest(_ http.ServerRequest, response http.ServerResponse) error {
 	if r.ok {
 		response.SetBody("ok")
 	} else {
@@ -63,3 +109,17 @@ func (r requestHandler) OnRequest(request http.ServerRequest, response http.Serv
 	}
 	return nil
 }
+
+type healthCheckClient struct {
+	httpClient http.Client
+	logger     log.Logger
+}
+
+func (h *healthCheckClient) Run() bool {
+	responseBody := ""
+	statusCode, err := h.httpClient.Get("", &responseBody)
+	if err != nil {
+		h.logger.Warning(log.Wrap(err, ERequestFailed, "Request to health check endpoint failed"))
+	}
+	return statusCode == 200
+}

health_test.go

@@ -11,22 +11,26 @@ import (
 
 func TestOk(t *testing.T) {
 	logger := log.NewTestLogger(t)
-	srv, err := health.New(
-		health.Config{
-			ServerConfiguration: http.ServerConfiguration{
-				Listen: "127.0.0.1:23074",
-			},
+	config := health.Config{
+		Enable: true,
+		ServerConfiguration: http.ServerConfiguration{
+			Listen: "127.0.0.1:23074",
 		},
-		logger)
+		Client: http.ClientConfiguration{
+			URL:            "http://127.0.0.1:23074",
+			AllowRedirects: false,
+			Timeout:        5 * time.Second,
+		},
+	}
 
+	srv, err := health.New(config, logger)
 	if err != nil {
 		t.Fatal(err)
 	}
 
 	l := service.NewLifecycle(srv)
 
 	running := make(chan struct{})
-
 	l.OnRunning(func(s service.Service, l service.Lifecycle) {
 		running <- struct{}{}
 	})
@@ -37,39 +41,22 @@ func TestOk(t *testing.T) {
 
 	<-running
 
-	client, err := http.NewClient(http.ClientConfiguration{
-		URL:            "http://127.0.0.1:23074",
-		AllowRedirects: false,
-		Timeout:        5 * time.Second,
-	},
-		logger,
-	)
-
+	client, err := health.NewClient(config, logger)
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	srv.ChangeStatus(true)
-	checkStatusResponse(t, client, 200, "ok")
-
-	srv.ChangeStatus(false)
-
-	checkStatusResponse(t, client, 503, "not ok")
-}
-
-func checkStatusResponse(t *testing.T, client http.Client, expectedStatusCode int, expectedResponse string) {
-	response := ""
-	status, err := client.Get("", &response)
-
-	if err != nil {
-		t.Fatal(err)
+	if client.Run() {
+		t.Fatal("Health check did not fail, even though status is false.")
 	}
 
-	if status != expectedStatusCode {
-		t.Fatalf("Unexpected status code: %d", status)
+	srv.ChangeStatus(true)
+	if !client.Run() {
+		t.Fatal("Health check failed, even though status is true.")
 	}
 
-	if response != expectedResponse {
-		t.Fatalf("Unexpected response: %s", response)
+	srv.ChangeStatus(false)
+	if client.Run() {
+		t.Fatal("Health check did not fail, even though status is false.")
 	}
 }