[PATCH] CORE-6348 add ability to depool vtgates via liveness check en…

…dpoint (vitessio#3)

`/debug/liveness` endpoint now returns a 503 when `/etc/etsy/depool` is present on the filesystem

note: included "unit" test currently relies on `/etc/etsy` existing and being writable. run with `go test go/vt/servenv/*.go`

Signed-off-by: Mackenzie Starr <mstarr@etsy.com>

go/vt/servenv/liveness.go

@@ -18,6 +18,7 @@ package servenv
 
 import (
  "net/http"
+ "os"
 )
 
 // This file registers a handler that immediately responds with HTTP 200 OK.
@@ -30,6 +31,9 @@ import (
 
 func init() {
  http.HandleFunc("/debug/liveness", func(rw http.ResponseWriter, r *http.Request) {
- // Do nothing. Return success immediately.
+ if _, err := os.Stat("/etc/etsy/depool"); !os.IsNotExist(err) {
+ rw.WriteHeader(http.StatusServiceUnavailable)
+ return
+ }
  })
 }

go/vt/servenv/liveness_test.go

@@ -20,13 +20,15 @@ import (
  "io"
  "net/http"
  "net/http/httptest"
+ "os"
  "testing"
+
+ "github.com/stretchr/testify/assert"
 )
 
 func TestLivenessHandler(t *testing.T) {
  server := httptest.NewServer(nil)
  defer server.Close()
-
  resp, err := http.Get(server.URL + "/debug/liveness")
  if err != nil {
  t.Fatalf("http.Get: %v", err)
@@ -40,3 +42,42 @@ func TestLivenessHandler(t *testing.T) {
  }
  t.Logf("body: %q", body)
 }
+
+func TestLivenessHandlerDepool(t *testing.T) {
+ assert := assert.New(t)
+ server := httptest.NewServer(nil)
+ defer server.Close()
+
+ var resp, err = http.Get(server.URL + "/debug/liveness")
+ if err != nil {
+ t.Fatalf("http.Get: %v", err)
+ }
+ assert.Equal(
+ http.StatusOK,
+ resp.StatusCode,
+ "should return 200 response code when depool file is not present",
+ )
+
+ // requires
+ // ```
+ // sudo mkdir -p /etc/etsy
+ // sudo chmod 777 /etc/etsy
+ // ```
+ var path = "/etc/etsy/depool"
+ _, err = os.Create(path)
+ if err != nil {
+ t.Error(err)
+ }
+ defer os.Remove(path)
+
+ resp, err = http.Get(server.URL + "/debug/liveness")
+ if err != nil {
+ t.Fatalf("http.Get: %v", err)
+ }
+ assert.Equal(
+ http.StatusServiceUnavailable,
+ resp.StatusCode,
+ "should return 503 response code when depool file is present",
+ )
+ defer resp.Body.Close()
+}