Add tracker healthcheck client

tracker/announceclient/client.go

@@ -4,7 +4,7 @@
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
-//     http://www.apache.org/licenses/LICENSE-2.0
+//	http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ -23,6 +23,7 @@ import (
 	"time"
 
 	"github.com/uber/kraken/core"
+	"github.com/uber/kraken/lib/backend"
 	"github.com/uber/kraken/lib/hashring"
 	"github.com/uber/kraken/utils/httputil"
 )
@@ -58,6 +59,8 @@ type Response struct {
 
 // Client defines a client for announcing and getting peers.
 type Client interface {
+	// CheckHealth calls a tracker's health endpoint.
+	CheckHealth() error
 	Announce(
 		d core.Digest,
 		h core.InfoHash,
@@ -89,6 +92,18 @@ func getEndpoint(version int, addr string, h core.InfoHash) (method, url string)
 	return "POST", fmt.Sprintf("http://%s/announce/%s", addr, h.String())
 }
 
+func (c *client) CheckHealth() error {
+	addr := c.ring.Locations(backend.ReadinessCheckDigest)[0]
+	_, err := httputil.Get(
+		fmt.Sprintf("http://%s/health", addr),
+		httputil.SendTimeout(2*time.Second),
+		httputil.SendTLS(c.tls))
+	if err != nil {
+		return fmt.Errorf("tracker not ready: %v", err)
+	}
+	return nil
+}
+
 // Announce announces the torrent identified by (d, h) with the number of
 // downloaded bytes. Returns a list of all other peers announcing for said torrent,
 // sorted by priority, and the interval for the next announce.
@@ -142,6 +157,10 @@ func Disabled() Client {
 	return DisabledClient{}
 }
 
+func (c DisabledClient) CheckHealth() error {
+	return nil
+}
+
 // Announce always returns error.
 func (c DisabledClient) Announce(
 	d core.Digest, h core.InfoHash, complete bool, version int) ([]*core.PeerInfo, time.Duration, error) {

tracker/trackerserver/announce_test.go

@@ -4,7 +4,7 @@
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
-//     http://www.apache.org/licenses/LICENSE-2.0
+//	http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ -16,6 +16,7 @@ package trackerserver
 import (
 	"errors"
 	"fmt"
+	"regexp"
 	"testing"
 	"time"
 
@@ -33,6 +34,50 @@ func newAnnounceClient(pctx core.PeerContext, addr string) announceclient.Client
 	return announceclient.New(pctx, hashring.NoopPassiveRing(hostlist.Fixture(addr)), nil)
 }
 
+func TestCheckHealth(t *testing.T) {
+	for _, tc := range []struct {
+		name                string
+		serverIsUp          bool
+		expectedErrMsgRegex string
+	}{
+		{
+			name:                "success",
+			serverIsUp:          true,
+			expectedErrMsgRegex: "",
+		},
+		{
+			name:                "failure",
+			serverIsUp:          false,
+			expectedErrMsgRegex: `tracker not ready: network error: Get "http://127\.0\.0\.1:\d+/health": dial tcp 127\.0\.0\.1:\d+: connect: connection refused`,
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			require := require.New(t)
+
+			mocks, cleanup := newServerMocks(t, Config{})
+			defer cleanup()
+
+			addr, stop := testutil.StartServer(mocks.handler())
+			if tc.serverIsUp {
+				defer stop()
+			} else {
+				stop()
+			}
+
+			pctx := core.PeerContextFixture()
+			client := newAnnounceClient(pctx, addr)
+
+			err := client.CheckHealth()
+			if tc.expectedErrMsgRegex == "" {
+				require.NoError(err)
+			} else {
+				r, _ := regexp.Compile(tc.expectedErrMsgRegex)
+				require.True(r.MatchString(err.Error()))
+			}
+		})
+	}
+}
+
 func TestAnnounceSinglePeerResponse(t *testing.T) {
 	for _, version := range []int{announceclient.V1, announceclient.V2} {
 		t.Run(fmt.Sprintf("V%d", version), func(t *testing.T) {