Adding upstream version 1.6.0.

Signed-off-by: Daniel Baumann <daniel@debian.org>

health.go

@@ -0,0 +1,142 @@
+package health
+
+import (
+	"encoding/json"
+	"net/http"
+	"sync"
+)
+
+var (
+	handler = &healthHandler{
+		useJSON: false,
+		status:  Up,
+	}
+)
+
+// responseBody is the body of the response returned by the health handler.
+type responseBody struct {
+	Status string `json:"status"`
+	Reason string `json:"reason,omitempty"`
+}
+
+// healthHandler is the HTTP handler for serving the health endpoint
+type healthHandler struct {
+	useJSON bool
+
+	status Status
+	reason string
+
+	mutex sync.RWMutex
+}
+
+// WithJSON configures whether the handler should output a response in JSON or in raw text
+//
+// Defaults to false
+func (h *healthHandler) WithJSON(v bool) *healthHandler {
+	h.useJSON = v
+	return h
+}
+
+// ServeHTTP serves the HTTP request for the health handler
+func (h *healthHandler) ServeHTTP(writer http.ResponseWriter, _ *http.Request) {
+	statusCode, body, useJSON := h.getResponseStatusCodeAndBodyAndWhetherBodyUsesJSON()
+	if useJSON {
+		writer.Header().Set("Content-Type", "application/json")
+	}
+	writer.WriteHeader(statusCode)
+	_, _ = writer.Write(body)
+}
+
+func (h *healthHandler) GetResponseStatusCodeAndBody() (statusCode int, body []byte) {
+	statusCode, body, _ = h.getResponseStatusCodeAndBodyAndWhetherBodyUsesJSON()
+	return statusCode, body
+}
+
+func (h *healthHandler) getResponseStatusCodeAndBodyAndWhetherBodyUsesJSON() (statusCode int, body []byte, useJSON bool) {
+	var status Status
+	var reason string
+	h.mutex.RLock()
+	status, reason, useJSON = h.status, h.reason, h.useJSON
+	h.mutex.RUnlock()
+	if status == Up {
+		statusCode = http.StatusOK
+	} else {
+		statusCode = http.StatusInternalServerError
+	}
+	if useJSON {
+		// We can safely ignore the error here because we know that both values are strings, therefore are supported encoders.
+		body, _ = json.Marshal(responseBody{Status: string(status), Reason: reason})
+	} else {
+		if len(reason) == 0 {
+			body = []byte(status)
+		} else {
+			body = []byte(string(status) + ": " + reason)
+		}
+	}
+	return
+}
+
+// Handler retrieves the health handler
+func Handler() *healthHandler {
+	return handler
+}
+
+// GetStatus retrieves the current status returned by the health handler
+func GetStatus() Status {
+	handler.mutex.RLock()
+	defer handler.mutex.RUnlock()
+	return handler.status
+}
+
+// SetStatus sets the status to be returned by the health handler
+func SetStatus(status Status) {
+	handler.mutex.Lock()
+	handler.status = status
+	handler.mutex.Unlock()
+}
+
+// GetReason retrieves the current status returned by the health handler
+func GetReason() string {
+	handler.mutex.RLock()
+	defer handler.mutex.RUnlock()
+	return handler.reason
+}
+
+// SetReason sets a reason for the current status to be returned by the health handler
+func SetReason(reason string) {
+	handler.mutex.Lock()
+	handler.reason = reason
+	handler.mutex.Unlock()
+}
+
+// SetStatusAndReason sets the status and reason to be returned by the health handler
+func SetStatusAndReason(status Status, reason string) {
+	handler.mutex.Lock()
+	handler.status = status
+	handler.reason = reason
+	handler.mutex.Unlock()
+}
+
+// SetStatusAndResetReason sets the status and resets the reason to a blank string
+func SetStatusAndResetReason(status Status) {
+	handler.mutex.Lock()
+	handler.status = status
+	handler.reason = ""
+	handler.mutex.Unlock()
+}
+
+// SetHealthy sets the status to Up and the reason to a blank string
+func SetHealthy() {
+	SetStatusAndResetReason(Up)
+}
+
+// SetUnhealthy sets the status to Down and the reason to the string passed as parameter
+//
+// Unlike SetHealthy, this function enforces setting a reason, because it's good practice to give at least a bit
+// of information as to why an application is unhealthy, and this library attempts to promote good practices.
+func SetUnhealthy(reason string) {
+	handler.mutex.Lock()
+	handler.status = Down
+	handler.reason = reason
+	handler.mutex.Unlock()
+}