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|
package health
import (
"expvar"
"fmt"
"log"
"net/http"
"github.com/coreos/pkg/httputil"
)
// Checkables should return nil when the thing they are checking is healthy, and an error otherwise.
type Checkable interface {
Healthy() error
}
// Checker provides a way to make an endpoint which can be probed for system health.
type Checker struct {
// Checks are the Checkables to be checked when probing.
Checks []Checkable
// Unhealthyhandler is called when one or more of the checks are unhealthy.
// If not provided DefaultUnhealthyHandler is called.
UnhealthyHandler UnhealthyHandler
// HealthyHandler is called when all checks are healthy.
// If not provided, DefaultHealthyHandler is called.
HealthyHandler http.HandlerFunc
}
func (c Checker) ServeHTTP(w http.ResponseWriter, r *http.Request) {
unhealthyHandler := c.UnhealthyHandler
if unhealthyHandler == nil {
unhealthyHandler = DefaultUnhealthyHandler
}
successHandler := c.HealthyHandler
if successHandler == nil {
successHandler = DefaultHealthyHandler
}
if r.Method != "GET" {
w.Header().Set("Allow", "GET")
w.WriteHeader(http.StatusMethodNotAllowed)
return
}
if err := Check(c.Checks); err != nil {
unhealthyHandler(w, r, err)
return
}
successHandler(w, r)
}
type UnhealthyHandler func(w http.ResponseWriter, r *http.Request, err error)
type StatusResponse struct {
Status string `json:"status"`
Details *StatusResponseDetails `json:"details,omitempty"`
}
type StatusResponseDetails struct {
Code int `json:"code,omitempty"`
Message string `json:"message,omitempty"`
}
func Check(checks []Checkable) (err error) {
errs := []error{}
for _, c := range checks {
if e := c.Healthy(); e != nil {
errs = append(errs, e)
}
}
switch len(errs) {
case 0:
err = nil
case 1:
err = errs[0]
default:
err = fmt.Errorf("multiple health check failure: %v", errs)
}
return
}
func DefaultHealthyHandler(w http.ResponseWriter, r *http.Request) {
err := httputil.WriteJSONResponse(w, http.StatusOK, StatusResponse{
Status: "ok",
})
if err != nil {
// TODO(bobbyrullo): replace with logging from new logging pkg,
// once it lands.
log.Printf("Failed to write JSON response: %v", err)
}
}
func DefaultUnhealthyHandler(w http.ResponseWriter, r *http.Request, err error) {
writeErr := httputil.WriteJSONResponse(w, http.StatusInternalServerError, StatusResponse{
Status: "error",
Details: &StatusResponseDetails{
Code: http.StatusInternalServerError,
Message: err.Error(),
},
})
if writeErr != nil {
// TODO(bobbyrullo): replace with logging from new logging pkg,
// once it lands.
log.Printf("Failed to write JSON response: %v", err)
}
}
// ExpvarHandler is copied from https://golang.org/src/expvar/expvar.go, where it's sadly unexported.
func ExpvarHandler(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json; charset=utf-8")
fmt.Fprintf(w, "{\n")
first := true
expvar.Do(func(kv expvar.KeyValue) {
if !first {
fmt.Fprintf(w, ",\n")
}
first = false
fmt.Fprintf(w, "%q: %s", kv.Key, kv.Value)
})
fmt.Fprintf(w, "\n}\n")
}
|
