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