Support load-balanced runner groups for multitenant compute isolation (#814)

* Initial stab at the protocol * initial protocol sketch for node pool manager * Added http header frame as a message * Force the use of WithAgent variants when creating a server * adds grpc models for node pool manager plus go deps * Naming things is really hard * Merge (and optionally purge) details received by the NPM * WIP: starting to add the runner-side functionality of the new data plane * WIP: Basic startup of grpc server for pure runner. Needs proper certs. * Go fmt * Initial agent for LB nodes. * Agent implementation for LB nodes. * Pass keys and certs to LB node agent. * Remove accidentally left reference to env var. * Add env variables for certificate files * stub out the capacity and group membership server channels * implement server-side runner manager service * removes unused variable * fixes build error * splits up GetCall and GetLBGroupId * Change LB node agent to use TLS connection. * Encode call model as JSON to send to runner node. * Use hybrid client in LB node agent. This should provide access to get app and route information for the call from an API node. * More error handling on the pure runner side * Tentative fix for GetCall problem: set deadlines correctly when reserving slot * Connect loop for LB agent to runner nodes. * Extract runner connection function in LB agent. * drops committed capacity counts * Bugfix - end state tracker only in submit * Do logs properly * adds first pass of tracking capacity metrics in agent * maked memory capacity metric uint64 * maked memory capacity metric uint64 * removes use of old capacity field * adds remove capacity call * merges overwritten reconnect logic * First pass of a NPM Provide a service that talks to a (simulated) CP. - Receive incoming capacity assertions from LBs for LBGs - expire LB requests after a short period - ask the CP to add runners to a LBG - note runner set changes and readvertise - scale down by marking runners as "draining" - shut off draining runners after some cool-down period * add capacity update on schedule * Send periodic capcacity metrics Sending capcacity metrics to node pool manager * splits grpc and api interfaces for capacity manager * failure to advertise capacity shouldn't panic * Add some instructions for starting DP/CP parts. * Create the poolmanager server with TLS * Use logrus * Get npm compiling with cert fixups. * Fix: pure runner should not start async processing * brings runner, nulb and npm together * Add field to acknowledgment to record slot allocation latency; fix a bug too * iterating on pool manager locking issue * raises timeout of placement retry loop * Fix up NPM Improve logging Ensure that channels etc. are actually initialised in the structure creation! * Update the docs - runners GRPC port is 9120 * Bugfix: return runner pool accurately. * Double locking * Note purges as LBs stop talking to us * Get the purging of old LBs working. * Tweak: on restart, load runner set before making scaling decisions. * more agent synchronization improvements * Deal with teh CP pulling out active hosts from under us. * lock at lbgroup level * Send request and receive response from runner. * Add capacity check right before slot reservation * Pass the full Call into the receive loop. * Wait for the data from the runner before finishing * force runner list refresh every time * Don't init db and mq for pure runners * adds shutdown of npm * fixes broken log line * Extract an interface for the Predictor used by the NPM * purge drained connections from npm * Refactor of the LB agent into the agent package * removes capacitytest wip * Fix undefined err issue * updating README for poolmanager set up * ues retrying dial for lb to npm connections * Rename lb_calls to lb_agent now that all functionality is there * Use the right deadline and errors in LBAgent * Make stream error flag per-call rather than global otherwise the whole runner is damaged by one call dropping * abstracting gRPCNodePool * Make stream error flag per-call rather than global otherwise the whole runner is damaged by one call dropping * Add some init checks for LB and pure runner nodes * adding some useful debug * Fix default db and mq for lb node * removes unreachable code, fixes typo * Use datastore as logstore in API nodes. This fixes a bug caused by trying to insert logs into a nil logstore. It was nil because it wasn't being set for API nodes. * creates placement abstraction and moves capacity APIs to NodePool * removed TODO, added logging * Dial reconnections for LB <-> runners LB grpc connections to runners are established using a backoff stategy in event of reconnections, this allows to let the LB up even in case one of the runners go away and reconnect to it as soon as it is back. * Add a status call to the Runner protocol Stub at the moment. To be used for things like draindown, health checks. * Remove comment. * makes assign/release capacity lockless * Fix hanging issue in lb agent when connections drop * Add the CH hash from fnlb Select this with FN_PLACER=ch when launching the LB. * small improvement for locking on reloadLBGmembership * Stabilise the list of Runenrs returned by NodePool The NodePoolManager makes some attempt to keep the list of runner nodes advertised as stable as possible. Let's preserve this effort in the client side. The main point of this is to attempt to keep the same runner at the same inxed in the []Runner returned by NodePool.Runners(lbgid); the ch algorithm likes it when this is the case. * Factor out a generator function for the Runners so that mocks can be injected * temporarily allow lbgroup to be specified in HTTP header, while we sort out changes to the model * fixes bug with nil runners * Initial work for mocking things in tests * fix for anonymouse go routine error * fixing lb_test to compile * Refactor: internal objects for gRPCNodePool are now injectable, with defaults for the real world case * Make GRPC port configurable, fix weird handling of web port too * unit test reload Members * check on runner creation failure * adding nullRunner in case of failure during runner creation * Refactored capacity advertisements/aggregations. Made grpc advertisement post asynchronous and non-blocking. * make capacityEntry private * Change the runner gRPC bind address. This uses the existing `whoAmI` function, so that the gRPC server works when the runner is running on a different host. * Add support for multiple fixed runners to pool mgr * Added harness for dataplane system tests, minor refactors * Add Dockerfiles for components, along with docs. * Doc fix: second runner needs a different name. * Let us have three runners in system tests, why not * The first system test running a function in API/LB/PureRunner mode * Add unit test for Advertiser logic * Fix issue with Pure Runner not sending the last data frame * use config in models.Call as a temporary mechanism to override lb group ID * make gofmt happy * Updates documentation for how to configure lb groups for an app/route * small refactor unit test * Factor NodePool into its own package * Lots of fixes to Pure Runner - concurrency woes with errors and cancellations * New dataplane with static runnerpool (#813) Added static node pool as default implementation * moved nullRunner to grpc package * remove duplication in README * fix go vet issues * Fix server initialisation in api tests * Tiny logging changes in pool manager. Using `WithError` instead of `Errorf` when appropriate. * Change some log levels in the pure runner * fixing readme * moves multitenant compute documentation * adds introduction to multitenant readme * Proper triggering of system tests in makefile * Fix insructions about starting up the components * Change db file for system tests to avoid contention in parallel tests * fixes revisions from merge * Fix merge issue with handling of reserved slot * renaming nulb to lb in the doc and images folder * better TryExec sleep logic clean shutdown In this change we implement a better way to deal with the sleep inside the for loop during the attempt for placing a call. Plus we added a clean way to shutdown the connections with external component when we shut down the server. * System_test mysql port set mysql port for system test to a different value to the one set for the api tests to avoid conflicts as they can run in parallel. * change the container name for system-test * removes flaky test TestRouteRunnerExecution pending resolution by issue #796 * amend remove_containers to remove new added containers * Rework capacity reservation logic at a higher level for now * LB agent implements Submit rather than delegating. * Fix go vet linting errors * Changed a couple of error levels * Fix formatting * removes commmented out test * adds snappy to vendor directory * updates Gopkg and vendor directories, removing snappy and addhing siphash * wait for db containers to come up before starting the tests * make system tests start API node on 8085 to avoid port conflict with api_tests * avoid port conflicts with api_test.sh which are run in parallel * fixes postgres port conflict and issue with removal of old containers * Remove spurious println
2022-10-28 21:29:17 +03:00 · 2018-03-08 22:45:19 +00:00
parent d5da6fd8c5
commit 8af57da7b2
510 changed files with 263280 additions and 92 deletions
--- a/vendor/google.golang.org/grpc/resolver/dns/dns_resolver.go
+++ b/vendor/google.golang.org/grpc/resolver/dns/dns_resolver.go
@@ -0,0 +1,377 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * 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
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package dns implements a dns resolver to be installed as the default resolver
+// in grpc.
+package dns
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"math/rand"
+	"net"
+	"os"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/resolver"
+)
+
+func init() {
+	resolver.Register(NewBuilder())
+}
+
+const (
+	defaultPort = "443"
+	defaultFreq = time.Minute * 30
+	golang      = "GO"
+	// In DNS, service config is encoded in a TXT record via the mechanism
+	// described in RFC-1464 using the attribute name grpc_config.
+	txtAttribute = "grpc_config="
+)
+
+var errMissingAddr = errors.New("missing address")
+
+// NewBuilder creates a dnsBuilder which is used to factory DNS resolvers.
+func NewBuilder() resolver.Builder {
+	return &dnsBuilder{freq: defaultFreq}
+}
+
+type dnsBuilder struct {
+	// frequency of polling the DNS server.
+	freq time.Duration
+}
+
+// Build creates and starts a DNS resolver that watches the name resolution of the target.
+func (b *dnsBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOption) (resolver.Resolver, error) {
+	host, port, err := parseTarget(target.Endpoint)
+	if err != nil {
+		return nil, err
+	}
+
+	// IP address.
+	if net.ParseIP(host) != nil {
+		host, _ = formatIP(host)
+		addr := []resolver.Address{{Addr: host + ":" + port}}
+		i := &ipResolver{
+			cc: cc,
+			ip: addr,
+			rn: make(chan struct{}, 1),
+			q:  make(chan struct{}),
+		}
+		cc.NewAddress(addr)
+		go i.watcher()
+		return i, nil
+	}
+
+	// DNS address (non-IP).
+	ctx, cancel := context.WithCancel(context.Background())
+	d := &dnsResolver{
+		freq:   b.freq,
+		host:   host,
+		port:   port,
+		ctx:    ctx,
+		cancel: cancel,
+		cc:     cc,
+		t:      time.NewTimer(0),
+		rn:     make(chan struct{}, 1),
+	}
+
+	d.wg.Add(1)
+	go d.watcher()
+	return d, nil
+}
+
+// Scheme returns the naming scheme of this resolver builder, which is "dns".
+func (b *dnsBuilder) Scheme() string {
+	return "dns"
+}
+
+// ipResolver watches for the name resolution update for an IP address.
+type ipResolver struct {
+	cc resolver.ClientConn
+	ip []resolver.Address
+	// rn channel is used by ResolveNow() to force an immediate resolution of the target.
+	rn chan struct{}
+	q  chan struct{}
+}
+
+// ResolveNow resend the address it stores, no resolution is needed.
+func (i *ipResolver) ResolveNow(opt resolver.ResolveNowOption) {
+	select {
+	case i.rn <- struct{}{}:
+	default:
+	}
+}
+
+// Close closes the ipResolver.
+func (i *ipResolver) Close() {
+	close(i.q)
+}
+
+func (i *ipResolver) watcher() {
+	for {
+		select {
+		case <-i.rn:
+			i.cc.NewAddress(i.ip)
+		case <-i.q:
+			return
+		}
+	}
+}
+
+// dnsResolver watches for the name resolution update for a non-IP target.
+type dnsResolver struct {
+	freq   time.Duration
+	host   string
+	port   string
+	ctx    context.Context
+	cancel context.CancelFunc
+	cc     resolver.ClientConn
+	// rn channel is used by ResolveNow() to force an immediate resolution of the target.
+	rn chan struct{}
+	t  *time.Timer
+	// wg is used to enforce Close() to return after the watcher() goroutine has finished.
+	// Otherwise, data race will be possible. [Race Example] in dns_resolver_test we
+	// replace the real lookup functions with mocked ones to facilitate testing.
+	// If Close() doesn't wait for watcher() goroutine finishes, race detector sometimes
+	// will warns lookup (READ the lookup function pointers) inside watcher() goroutine
+	// has data race with replaceNetFunc (WRITE the lookup function pointers).
+	wg sync.WaitGroup
+}
+
+// ResolveNow invoke an immediate resolution of the target that this dnsResolver watches.
+func (d *dnsResolver) ResolveNow(opt resolver.ResolveNowOption) {
+	select {
+	case d.rn <- struct{}{}:
+	default:
+	}
+}
+
+// Close closes the dnsResolver.
+func (d *dnsResolver) Close() {
+	d.cancel()
+	d.wg.Wait()
+	d.t.Stop()
+}
+
+func (d *dnsResolver) watcher() {
+	defer d.wg.Done()
+	for {
+		select {
+		case <-d.ctx.Done():
+			return
+		case <-d.t.C:
+		case <-d.rn:
+		}
+		result, sc := d.lookup()
+		// Next lookup should happen after an interval defined by d.freq.
+		d.t.Reset(d.freq)
+		d.cc.NewServiceConfig(string(sc))
+		d.cc.NewAddress(result)
+	}
+}
+
+func (d *dnsResolver) lookupSRV() []resolver.Address {
+	var newAddrs []resolver.Address
+	_, srvs, err := lookupSRV(d.ctx, "grpclb", "tcp", d.host)
+	if err != nil {
+		grpclog.Infof("grpc: failed dns SRV record lookup due to %v.\n", err)
+		return nil
+	}
+	for _, s := range srvs {
+		lbAddrs, err := lookupHost(d.ctx, s.Target)
+		if err != nil {
+			grpclog.Warningf("grpc: failed load banlacer address dns lookup due to %v.\n", err)
+			continue
+		}
+		for _, a := range lbAddrs {
+			a, ok := formatIP(a)
+			if !ok {
+				grpclog.Errorf("grpc: failed IP parsing due to %v.\n", err)
+				continue
+			}
+			addr := a + ":" + strconv.Itoa(int(s.Port))
+			newAddrs = append(newAddrs, resolver.Address{Addr: addr, Type: resolver.GRPCLB, ServerName: s.Target})
+		}
+	}
+	return newAddrs
+}
+
+func (d *dnsResolver) lookupTXT() string {
+	ss, err := lookupTXT(d.ctx, d.host)
+	if err != nil {
+		grpclog.Warningf("grpc: failed dns TXT record lookup due to %v.\n", err)
+		return ""
+	}
+	var res string
+	for _, s := range ss {
+		res += s
+	}
+
+	// TXT record must have "grpc_config=" attribute in order to be used as service config.
+	if !strings.HasPrefix(res, txtAttribute) {
+		grpclog.Warningf("grpc: TXT record %v missing %v attribute", res, txtAttribute)
+		return ""
+	}
+	return strings.TrimPrefix(res, txtAttribute)
+}
+
+func (d *dnsResolver) lookupHost() []resolver.Address {
+	var newAddrs []resolver.Address
+	addrs, err := lookupHost(d.ctx, d.host)
+	if err != nil {
+		grpclog.Warningf("grpc: failed dns A record lookup due to %v.\n", err)
+		return nil
+	}
+	for _, a := range addrs {
+		a, ok := formatIP(a)
+		if !ok {
+			grpclog.Errorf("grpc: failed IP parsing due to %v.\n", err)
+			continue
+		}
+		addr := a + ":" + d.port
+		newAddrs = append(newAddrs, resolver.Address{Addr: addr})
+	}
+	return newAddrs
+}
+
+func (d *dnsResolver) lookup() ([]resolver.Address, string) {
+	var newAddrs []resolver.Address
+	newAddrs = d.lookupSRV()
+	// Support fallback to non-balancer address.
+	newAddrs = append(newAddrs, d.lookupHost()...)
+	sc := d.lookupTXT()
+	return newAddrs, canaryingSC(sc)
+}
+
+// formatIP returns ok = false if addr is not a valid textual representation of an IP address.
+// If addr is an IPv4 address, return the addr and ok = true.
+// If addr is an IPv6 address, return the addr enclosed in square brackets and ok = true.
+func formatIP(addr string) (addrIP string, ok bool) {
+	ip := net.ParseIP(addr)
+	if ip == nil {
+		return "", false
+	}
+	if ip.To4() != nil {
+		return addr, true
+	}
+	return "[" + addr + "]", true
+}
+
+// parseTarget takes the user input target string, returns formatted host and port info.
+// If target doesn't specify a port, set the port to be the defaultPort.
+// If target is in IPv6 format and host-name is enclosed in sqarue brackets, brackets
+// are strippd when setting the host.
+// examples:
+// target: "www.google.com" returns host: "www.google.com", port: "443"
+// target: "ipv4-host:80" returns host: "ipv4-host", port: "80"
+// target: "[ipv6-host]" returns host: "ipv6-host", port: "443"
+// target: ":80" returns host: "localhost", port: "80"
+// target: ":" returns host: "localhost", port: "443"
+func parseTarget(target string) (host, port string, err error) {
+	if target == "" {
+		return "", "", errMissingAddr
+	}
+	if ip := net.ParseIP(target); ip != nil {
+		// target is an IPv4 or IPv6(without brackets) address
+		return target, defaultPort, nil
+	}
+	if host, port, err = net.SplitHostPort(target); err == nil {
+		// target has port, i.e ipv4-host:port, [ipv6-host]:port, host-name:port
+		if host == "" {
+			// Keep consistent with net.Dial(): If the host is empty, as in ":80", the local system is assumed.
+			host = "localhost"
+		}
+		if port == "" {
+			// If the port field is empty(target ends with colon), e.g. "[::1]:", defaultPort is used.
+			port = defaultPort
+		}
+		return host, port, nil
+	}
+	if host, port, err = net.SplitHostPort(target + ":" + defaultPort); err == nil {
+		// target doesn't have port
+		return host, port, nil
+	}
+	return "", "", fmt.Errorf("invalid target address %v, error info: %v", target, err)
+}
+
+type rawChoice struct {
+	ClientLanguage *[]string        `json:"clientLanguage,omitempty"`
+	Percentage     *int             `json:"percentage,omitempty"`
+	ClientHostName *[]string        `json:"clientHostName,omitempty"`
+	ServiceConfig  *json.RawMessage `json:"serviceConfig,omitempty"`
+}
+
+func containsString(a *[]string, b string) bool {
+	if a == nil {
+		return true
+	}
+	for _, c := range *a {
+		if c == b {
+			return true
+		}
+	}
+	return false
+}
+
+func chosenByPercentage(a *int) bool {
+	if a == nil {
+		return true
+	}
+	s := rand.NewSource(time.Now().UnixNano())
+	r := rand.New(s)
+	if r.Intn(100)+1 > *a {
+		return false
+	}
+	return true
+}
+
+func canaryingSC(js string) string {
+	if js == "" {
+		return ""
+	}
+	var rcs []rawChoice
+	err := json.Unmarshal([]byte(js), &rcs)
+	if err != nil {
+		grpclog.Warningf("grpc: failed to parse service config json string due to %v.\n", err)
+		return ""
+	}
+	cliHostname, err := os.Hostname()
+	if err != nil {
+		grpclog.Warningf("grpc: failed to get client hostname due to %v.\n", err)
+		return ""
+	}
+	var sc string
+	for _, c := range rcs {
+		if !containsString(c.ClientLanguage, golang) ||
+			!chosenByPercentage(c.Percentage) ||
+			!containsString(c.ClientHostName, cliHostname) ||
+			c.ServiceConfig == nil {
+			continue
+		}
+		sc = string(*c.ServiceConfig)
+		break
+	}
+	return sc
+}
--- a/vendor/google.golang.org/grpc/resolver/dns/dns_resolver_test.go
+++ b/vendor/google.golang.org/grpc/resolver/dns/dns_resolver_test.go
@@ -0,0 +1,894 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * 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
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package dns
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"reflect"
+	"sync"
+	"testing"
+	"time"
+
+	"google.golang.org/grpc/resolver"
+	"google.golang.org/grpc/test/leakcheck"
+)
+
+func TestMain(m *testing.M) {
+	cleanup := replaceNetFunc()
+	code := m.Run()
+	cleanup()
+	os.Exit(code)
+}
+
+const (
+	txtBytesLimit = 255
+)
+
+type testClientConn struct {
+	target string
+	m1     sync.Mutex
+	addrs  []resolver.Address
+	a      int
+	m2     sync.Mutex
+	sc     string
+	s      int
+}
+
+func (t *testClientConn) NewAddress(addresses []resolver.Address) {
+	t.m1.Lock()
+	defer t.m1.Unlock()
+	t.addrs = addresses
+	t.a++
+}
+
+func (t *testClientConn) getAddress() ([]resolver.Address, int) {
+	t.m1.Lock()
+	defer t.m1.Unlock()
+	return t.addrs, t.a
+}
+
+func (t *testClientConn) NewServiceConfig(serviceConfig string) {
+	t.m2.Lock()
+	defer t.m2.Unlock()
+	t.sc = serviceConfig
+	t.s++
+}
+
+func (t *testClientConn) getSc() (string, int) {
+	t.m2.Lock()
+	defer t.m2.Unlock()
+	return t.sc, t.s
+}
+
+var hostLookupTbl = struct {
+	sync.Mutex
+	tbl map[string][]string
+}{
+	tbl: map[string][]string{
+		"foo.bar.com":          {"1.2.3.4", "5.6.7.8"},
+		"ipv4.single.fake":     {"1.2.3.4"},
+		"srv.ipv4.single.fake": {"2.4.6.8"},
+		"ipv4.multi.fake":      {"1.2.3.4", "5.6.7.8", "9.10.11.12"},
+		"ipv6.single.fake":     {"2607:f8b0:400a:801::1001"},
+		"ipv6.multi.fake":      {"2607:f8b0:400a:801::1001", "2607:f8b0:400a:801::1002", "2607:f8b0:400a:801::1003"},
+	},
+}
+
+func hostLookup(host string) ([]string, error) {
+	hostLookupTbl.Lock()
+	defer hostLookupTbl.Unlock()
+	if addrs, cnt := hostLookupTbl.tbl[host]; cnt {
+		return addrs, nil
+	}
+	return nil, fmt.Errorf("failed to lookup host:%s resolution in hostLookupTbl", host)
+}
+
+var srvLookupTbl = struct {
+	sync.Mutex
+	tbl map[string][]*net.SRV
+}{
+	tbl: map[string][]*net.SRV{
+		"_grpclb._tcp.srv.ipv4.single.fake": {&net.SRV{Target: "ipv4.single.fake", Port: 1234}},
+		"_grpclb._tcp.srv.ipv4.multi.fake":  {&net.SRV{Target: "ipv4.multi.fake", Port: 1234}},
+		"_grpclb._tcp.srv.ipv6.single.fake": {&net.SRV{Target: "ipv6.single.fake", Port: 1234}},
+		"_grpclb._tcp.srv.ipv6.multi.fake":  {&net.SRV{Target: "ipv6.multi.fake", Port: 1234}},
+	},
+}
+
+func srvLookup(service, proto, name string) (string, []*net.SRV, error) {
+	cname := "_" + service + "._" + proto + "." + name
+	srvLookupTbl.Lock()
+	defer srvLookupTbl.Unlock()
+	if srvs, cnt := srvLookupTbl.tbl[cname]; cnt {
+		return cname, srvs, nil
+	}
+	return "", nil, fmt.Errorf("failed to lookup srv record for %s in srvLookupTbl", cname)
+}
+
+// div divides a byte slice into a slice of strings, each of which is of maximum
+// 255 bytes length, which is the length limit per TXT record in DNS.
+func div(b []byte) []string {
+	var r []string
+	for i := 0; i < len(b); i += txtBytesLimit {
+		if i+txtBytesLimit > len(b) {
+			r = append(r, string(b[i:]))
+		} else {
+			r = append(r, string(b[i:i+txtBytesLimit]))
+		}
+	}
+	return r
+}
+
+// scfs contains an array of service config file string in JSON format.
+// Notes about the scfs contents and usage:
+// scfs contains 4 service config file JSON strings for testing. Inside each
+// service config file, there are multiple choices. scfs[0:3] each contains 5
+// choices, and first 3 choices are nonmatching choices based on canarying rule,
+// while the last two are matched choices. scfs[3] only contains 3 choices, and
+// all of them are nonmatching based on canarying rule. For each of scfs[0:3],
+// the eventually returned service config, which is from the first of the two
+// matched choices, is stored in the corresponding scs element (e.g.
+// scfs[0]->scs[0]). scfs and scs elements are used in pair to test the dns
+// resolver functionality, with scfs as the input and scs used for validation of
+// the output. For scfs[3], it corresponds to empty service config, since there
+// isn't a matched choice.
+var scfs = []string{
+	`[
+	{
+		"clientLanguage": [
+			"CPP",
+			"JAVA"
+		],
+		"serviceConfig": {
+			"loadBalancingPolicy": "grpclb",
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"service": "all"
+						}
+					],
+					"timeout": "1s"
+				}
+			]
+		}
+	},
+	{
+		"percentage": 0,
+		"serviceConfig": {
+			"loadBalancingPolicy": "grpclb",
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"service": "all"
+						}
+					],
+					"timeout": "1s"
+				}
+			]
+		}
+	},
+	{
+		"clientHostName": [
+			"localhost"
+		],
+		"serviceConfig": {
+			"loadBalancingPolicy": "grpclb",
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"service": "all"
+						}
+					],
+					"timeout": "1s"
+				}
+			]
+		}
+	},
+	{
+		"clientLanguage": [
+			"GO"
+		],
+		"percentage": 100,
+		"serviceConfig": {
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"method": "bar"
+						}
+					],
+					"maxRequestMessageBytes": 1024,
+					"maxResponseMessageBytes": 1024
+				}
+			]
+		}
+	},
+	{
+		"serviceConfig": {
+			"loadBalancingPolicy": "round_robin",
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"service": "foo",
+							"method": "bar"
+						}
+					],
+					"waitForReady": true
+				}
+			]
+		}
+	}
+]`,
+	`[
+	{
+		"clientLanguage": [
+			"CPP",
+			"JAVA"
+		],
+		"serviceConfig": {
+			"loadBalancingPolicy": "grpclb",
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"service": "all"
+						}
+					],
+					"timeout": "1s"
+				}
+			]
+		}
+	},
+	{
+		"percentage": 0,
+		"serviceConfig": {
+			"loadBalancingPolicy": "grpclb",
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"service": "all"
+						}
+					],
+					"timeout": "1s"
+				}
+			]
+		}
+	},
+	{
+		"clientHostName": [
+			"localhost"
+		],
+		"serviceConfig": {
+			"loadBalancingPolicy": "grpclb",
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"service": "all"
+						}
+					],
+					"timeout": "1s"
+				}
+			]
+		}
+	},
+	{
+		"clientLanguage": [
+			"GO"
+		],
+		"percentage": 100,
+		"serviceConfig": {
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"service": "foo",
+							"method": "bar"
+						}
+					],
+					"waitForReady": true,
+					"timeout": "1s",
+					"maxRequestMessageBytes": 1024,
+					"maxResponseMessageBytes": 1024
+				}
+			]
+		}
+	},
+	{
+		"serviceConfig": {
+			"loadBalancingPolicy": "round_robin",
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"service": "foo",
+							"method": "bar"
+						}
+					],
+					"waitForReady": true
+				}
+			]
+		}
+	}
+]`,
+	`[
+	{
+		"clientLanguage": [
+			"CPP",
+			"JAVA"
+		],
+		"serviceConfig": {
+			"loadBalancingPolicy": "grpclb",
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"service": "all"
+						}
+					],
+					"timeout": "1s"
+				}
+			]
+		}
+	},
+	{
+		"percentage": 0,
+		"serviceConfig": {
+			"loadBalancingPolicy": "grpclb",
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"service": "all"
+						}
+					],
+					"timeout": "1s"
+				}
+			]
+		}
+	},
+	{
+		"clientHostName": [
+			"localhost"
+		],
+		"serviceConfig": {
+			"loadBalancingPolicy": "grpclb",
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"service": "all"
+						}
+					],
+					"timeout": "1s"
+				}
+			]
+		}
+	},
+	{
+		"clientLanguage": [
+			"GO"
+		],
+		"percentage": 100,
+		"serviceConfig": {
+			"loadBalancingPolicy": "round_robin",
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"service": "foo"
+						}
+					],
+					"waitForReady": true,
+					"timeout": "1s"
+				},
+				{
+					"name": [
+						{
+							"service": "bar"
+						}
+					],
+					"waitForReady": false
+				}
+			]
+		}
+	},
+	{
+		"serviceConfig": {
+			"loadBalancingPolicy": "round_robin",
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"service": "foo",
+							"method": "bar"
+						}
+					],
+					"waitForReady": true
+				}
+			]
+		}
+	}
+]`,
+	`[
+	{
+		"clientLanguage": [
+			"CPP",
+			"JAVA"
+		],
+		"serviceConfig": {
+			"loadBalancingPolicy": "grpclb",
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"service": "all"
+						}
+					],
+					"timeout": "1s"
+				}
+			]
+		}
+	},
+	{
+		"percentage": 0,
+		"serviceConfig": {
+			"loadBalancingPolicy": "grpclb",
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"service": "all"
+						}
+					],
+					"timeout": "1s"
+				}
+			]
+		}
+	},
+	{
+		"clientHostName": [
+			"localhost"
+		],
+		"serviceConfig": {
+			"loadBalancingPolicy": "grpclb",
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"service": "all"
+						}
+					],
+					"timeout": "1s"
+				}
+			]
+		}
+	}
+]`,
+}
+
+// scs contains an array of service config string in JSON format.
+var scs = []string{
+	`{
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"method": "bar"
+						}
+					],
+					"maxRequestMessageBytes": 1024,
+					"maxResponseMessageBytes": 1024
+				}
+			]
+		}`,
+	`{
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"service": "foo",
+							"method": "bar"
+						}
+					],
+					"waitForReady": true,
+					"timeout": "1s",
+					"maxRequestMessageBytes": 1024,
+					"maxResponseMessageBytes": 1024
+				}
+			]
+		}`,
+	`{
+			"loadBalancingPolicy": "round_robin",
+			"methodConfig": [
+				{
+					"name": [
+						{
+							"service": "foo"
+						}
+					],
+					"waitForReady": true,
+					"timeout": "1s"
+				},
+				{
+					"name": [
+						{
+							"service": "bar"
+						}
+					],
+					"waitForReady": false
+				}
+			]
+		}`,
+}
+
+// scLookupTbl is a set, which contains targets that have service config. Target
+// not in this set should not have service config.
+var scLookupTbl = map[string]bool{
+	"foo.bar.com":          true,
+	"srv.ipv4.single.fake": true,
+	"srv.ipv4.multi.fake":  true,
+	"no.attribute":         true,
+}
+
+// generateSCF generates a slice of strings (aggregately representing a single
+// service config file) for the input name, which mocks the result from a real
+// DNS TXT record lookup.
+func generateSCF(name string) []string {
+	var b []byte
+	switch name {
+	case "foo.bar.com":
+		b = []byte(scfs[0])
+	case "srv.ipv4.single.fake":
+		b = []byte(scfs[1])
+	case "srv.ipv4.multi.fake":
+		b = []byte(scfs[2])
+	default:
+		b = []byte(scfs[3])
+	}
+	if name == "no.attribute" {
+		return div(b)
+	}
+	return div(append([]byte(txtAttribute), b...))
+}
+
+// generateSC returns a service config string in JSON format for the input name.
+func generateSC(name string) string {
+	_, cnt := scLookupTbl[name]
+	if !cnt || name == "no.attribute" {
+		return ""
+	}
+	switch name {
+	case "foo.bar.com":
+		return scs[0]
+	case "srv.ipv4.single.fake":
+		return scs[1]
+	case "srv.ipv4.multi.fake":
+		return scs[2]
+	default:
+		return ""
+	}
+}
+
+var txtLookupTbl = struct {
+	sync.Mutex
+	tbl map[string][]string
+}{
+	tbl: map[string][]string{
+		"foo.bar.com":          generateSCF("foo.bar.com"),
+		"srv.ipv4.single.fake": generateSCF("srv.ipv4.single.fake"),
+		"srv.ipv4.multi.fake":  generateSCF("srv.ipv4.multi.fake"),
+		"srv.ipv6.single.fake": generateSCF("srv.ipv6.single.fake"),
+		"srv.ipv6.multi.fake":  generateSCF("srv.ipv6.multi.fake"),
+		"no.attribute":         generateSCF("no.attribute"),
+	},
+}
+
+func txtLookup(host string) ([]string, error) {
+	txtLookupTbl.Lock()
+	defer txtLookupTbl.Unlock()
+	if scs, cnt := txtLookupTbl.tbl[host]; cnt {
+		return scs, nil
+	}
+	return nil, fmt.Errorf("failed to lookup TXT:%s resolution in txtLookupTbl", host)
+}
+
+func TestResolve(t *testing.T) {
+	testDNSResolver(t)
+	testDNSResolveNow(t)
+	testIPResolver(t)
+}
+
+func testDNSResolver(t *testing.T) {
+	defer leakcheck.Check(t)
+	tests := []struct {
+		target   string
+		addrWant []resolver.Address
+		scWant   string
+	}{
+		{
+			"foo.bar.com",
+			[]resolver.Address{{Addr: "1.2.3.4" + colonDefaultPort}, {Addr: "5.6.7.8" + colonDefaultPort}},
+			generateSC("foo.bar.com"),
+		},
+		{
+			"foo.bar.com:1234",
+			[]resolver.Address{{Addr: "1.2.3.4:1234"}, {Addr: "5.6.7.8:1234"}},
+			generateSC("foo.bar.com"),
+		},
+		{
+			"srv.ipv4.single.fake",
+			[]resolver.Address{{Addr: "1.2.3.4:1234", Type: resolver.GRPCLB, ServerName: "ipv4.single.fake"}, {Addr: "2.4.6.8" + colonDefaultPort}},
+			generateSC("srv.ipv4.single.fake"),
+		},
+		{
+			"srv.ipv4.multi.fake",
+			[]resolver.Address{
+				{Addr: "1.2.3.4:1234", Type: resolver.GRPCLB, ServerName: "ipv4.multi.fake"},
+				{Addr: "5.6.7.8:1234", Type: resolver.GRPCLB, ServerName: "ipv4.multi.fake"},
+				{Addr: "9.10.11.12:1234", Type: resolver.GRPCLB, ServerName: "ipv4.multi.fake"},
+			},
+			generateSC("srv.ipv4.multi.fake"),
+		},
+		{
+			"srv.ipv6.single.fake",
+			[]resolver.Address{{Addr: "[2607:f8b0:400a:801::1001]:1234", Type: resolver.GRPCLB, ServerName: "ipv6.single.fake"}},
+			generateSC("srv.ipv6.single.fake"),
+		},
+		{
+			"srv.ipv6.multi.fake",
+			[]resolver.Address{
+				{Addr: "[2607:f8b0:400a:801::1001]:1234", Type: resolver.GRPCLB, ServerName: "ipv6.multi.fake"},
+				{Addr: "[2607:f8b0:400a:801::1002]:1234", Type: resolver.GRPCLB, ServerName: "ipv6.multi.fake"},
+				{Addr: "[2607:f8b0:400a:801::1003]:1234", Type: resolver.GRPCLB, ServerName: "ipv6.multi.fake"},
+			},
+			generateSC("srv.ipv6.multi.fake"),
+		},
+		{
+			"no.attribute",
+			nil,
+			generateSC("no.attribute"),
+		},
+	}
+
+	for _, a := range tests {
+		b := NewBuilder()
+		cc := &testClientConn{target: a.target}
+		r, err := b.Build(resolver.Target{Endpoint: a.target}, cc, resolver.BuildOption{})
+		if err != nil {
+			t.Fatalf("%v\n", err)
+		}
+		var addrs []resolver.Address
+		var cnt int
+		for {
+			addrs, cnt = cc.getAddress()
+			if cnt > 0 {
+				break
+			}
+			time.Sleep(time.Millisecond)
+		}
+		var sc string
+		for {
+			sc, cnt = cc.getSc()
+			if cnt > 0 {
+				break
+			}
+			time.Sleep(time.Millisecond)
+		}
+		if !reflect.DeepEqual(a.addrWant, addrs) {
+			t.Errorf("Resolved addresses of target: %q = %+v, want %+v\n", a.target, addrs, a.addrWant)
+		}
+		if !reflect.DeepEqual(a.scWant, sc) {
+			t.Errorf("Resolved service config of target: %q = %+v, want %+v\n", a.target, sc, a.scWant)
+		}
+		r.Close()
+	}
+}
+
+func mutateTbl(target string) func() {
+	hostLookupTbl.Lock()
+	oldHostTblEntry := hostLookupTbl.tbl[target]
+	hostLookupTbl.tbl[target] = hostLookupTbl.tbl[target][:len(oldHostTblEntry)-1]
+	hostLookupTbl.Unlock()
+	txtLookupTbl.Lock()
+	oldTxtTblEntry := txtLookupTbl.tbl[target]
+	txtLookupTbl.tbl[target] = []string{""}
+	txtLookupTbl.Unlock()
+
+	return func() {
+		hostLookupTbl.Lock()
+		hostLookupTbl.tbl[target] = oldHostTblEntry
+		hostLookupTbl.Unlock()
+		txtLookupTbl.Lock()
+		txtLookupTbl.tbl[target] = oldTxtTblEntry
+		txtLookupTbl.Unlock()
+	}
+}
+
+func testDNSResolveNow(t *testing.T) {
+	defer leakcheck.Check(t)
+	tests := []struct {
+		target   string
+		addrWant []resolver.Address
+		addrNext []resolver.Address
+		scWant   string
+		scNext   string
+	}{
+		{
+			"foo.bar.com",
+			[]resolver.Address{{Addr: "1.2.3.4" + colonDefaultPort}, {Addr: "5.6.7.8" + colonDefaultPort}},
+			[]resolver.Address{{Addr: "1.2.3.4" + colonDefaultPort}},
+			generateSC("foo.bar.com"),
+			"",
+		},
+	}
+
+	for _, a := range tests {
+		b := NewBuilder()
+		cc := &testClientConn{target: a.target}
+		r, err := b.Build(resolver.Target{Endpoint: a.target}, cc, resolver.BuildOption{})
+		if err != nil {
+			t.Fatalf("%v\n", err)
+		}
+		var addrs []resolver.Address
+		var cnt int
+		for {
+			addrs, cnt = cc.getAddress()
+			if cnt > 0 {
+				break
+			}
+			time.Sleep(time.Millisecond)
+		}
+		var sc string
+		for {
+			sc, cnt = cc.getSc()
+			if cnt > 0 {
+				break
+			}
+			time.Sleep(time.Millisecond)
+		}
+		if !reflect.DeepEqual(a.addrWant, addrs) {
+			t.Errorf("Resolved addresses of target: %q = %+v, want %+v\n", a.target, addrs, a.addrWant)
+		}
+		if !reflect.DeepEqual(a.scWant, sc) {
+			t.Errorf("Resolved service config of target: %q = %+v, want %+v\n", a.target, sc, a.scWant)
+		}
+		revertTbl := mutateTbl(a.target)
+		r.ResolveNow(resolver.ResolveNowOption{})
+		for {
+			addrs, cnt = cc.getAddress()
+			if cnt == 2 {
+				break
+			}
+			time.Sleep(time.Millisecond)
+		}
+		for {
+			sc, cnt = cc.getSc()
+			if cnt == 2 {
+				break
+			}
+			time.Sleep(time.Millisecond)
+		}
+		if !reflect.DeepEqual(a.addrNext, addrs) {
+			t.Errorf("Resolved addresses of target: %q = %+v, want %+v\n", a.target, addrs, a.addrNext)
+		}
+		if !reflect.DeepEqual(a.scNext, sc) {
+			t.Errorf("Resolved service config of target: %q = %+v, want %+v\n", a.target, sc, a.scNext)
+		}
+		revertTbl()
+		r.Close()
+	}
+}
+
+const colonDefaultPort = ":" + defaultPort
+
+func testIPResolver(t *testing.T) {
+	defer leakcheck.Check(t)
+	tests := []struct {
+		target string
+		want   []resolver.Address
+	}{
+		{"127.0.0.1", []resolver.Address{{Addr: "127.0.0.1" + colonDefaultPort}}},
+		{"127.0.0.1:12345", []resolver.Address{{Addr: "127.0.0.1:12345"}}},
+		{"::1", []resolver.Address{{Addr: "[::1]" + colonDefaultPort}}},
+		{"[::1]:12345", []resolver.Address{{Addr: "[::1]:12345"}}},
+		{"[::1]:", []resolver.Address{{Addr: "[::1]:443"}}},
+		{"2001:db8:85a3::8a2e:370:7334", []resolver.Address{{Addr: "[2001:db8:85a3::8a2e:370:7334]" + colonDefaultPort}}},
+		{"[2001:db8:85a3::8a2e:370:7334]", []resolver.Address{{Addr: "[2001:db8:85a3::8a2e:370:7334]" + colonDefaultPort}}},
+		{"[2001:db8:85a3::8a2e:370:7334]:12345", []resolver.Address{{Addr: "[2001:db8:85a3::8a2e:370:7334]:12345"}}},
+		{"[2001:db8::1]:http", []resolver.Address{{Addr: "[2001:db8::1]:http"}}},
+		// TODO(yuxuanli): zone support?
+	}
+
+	for _, v := range tests {
+		b := NewBuilder()
+		cc := &testClientConn{target: v.target}
+		r, err := b.Build(resolver.Target{Endpoint: v.target}, cc, resolver.BuildOption{})
+		if err != nil {
+			t.Fatalf("%v\n", err)
+		}
+		var addrs []resolver.Address
+		var cnt int
+		for {
+			addrs, cnt = cc.getAddress()
+			if cnt > 0 {
+				break
+			}
+			time.Sleep(time.Millisecond)
+		}
+		if !reflect.DeepEqual(v.want, addrs) {
+			t.Errorf("Resolved addresses of target: %q = %+v, want %+v\n", v.target, addrs, v.want)
+		}
+		r.ResolveNow(resolver.ResolveNowOption{})
+		for {
+			addrs, cnt = cc.getAddress()
+			if cnt == 2 {
+				break
+			}
+			time.Sleep(time.Millisecond)
+		}
+		if !reflect.DeepEqual(v.want, addrs) {
+			t.Errorf("Resolved addresses of target: %q = %+v, want %+v\n", v.target, addrs, v.want)
+		}
+		r.Close()
+	}
+}
+
+func TestResolveFunc(t *testing.T) {
+	defer leakcheck.Check(t)
+	tests := []struct {
+		addr string
+		want error
+	}{
+		// TODO(yuxuanli): More false cases?
+		{"www.google.com", nil},
+		{"foo.bar:12345", nil},
+		{"127.0.0.1", nil},
+		{"127.0.0.1:12345", nil},
+		{"[::1]:80", nil},
+		{"[2001:db8:a0b:12f0::1]:21", nil},
+		{":80", nil},
+		{"127.0.0...1:12345", nil},
+		{"[fe80::1%lo0]:80", nil},
+		{"golang.org:http", nil},
+		{"[2001:db8::1]:http", nil},
+		{":", nil},
+		{"", errMissingAddr},
+		{"[2001:db8:a0b:12f0::1", errForInvalidTarget},
+	}
+
+	b := NewBuilder()
+	for _, v := range tests {
+		cc := &testClientConn{target: v.addr}
+		r, err := b.Build(resolver.Target{Endpoint: v.addr}, cc, resolver.BuildOption{})
+		if err == nil {
+			r.Close()
+		}
+		if !reflect.DeepEqual(err, v.want) {
+			t.Errorf("Build(%q, cc, resolver.BuildOption{}) = %v, want %v", v.addr, err, v.want)
+		}
+	}
+}
--- a/vendor/google.golang.org/grpc/resolver/dns/go17.go
+++ b/vendor/google.golang.org/grpc/resolver/dns/go17.go
@@ -0,0 +1,35 @@
+// +build go1.6, !go1.8
+
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * 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
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package dns
+
+import (
+	"net"
+
+	"golang.org/x/net/context"
+)
+
+var (
+	lookupHost = func(ctx context.Context, host string) ([]string, error) { return net.LookupHost(host) }
+	lookupSRV  = func(ctx context.Context, service, proto, name string) (string, []*net.SRV, error) {
+		return net.LookupSRV(service, proto, name)
+	}
+	lookupTXT = func(ctx context.Context, name string) ([]string, error) { return net.LookupTXT(name) }
+)
--- a/vendor/google.golang.org/grpc/resolver/dns/go17_test.go
+++ b/vendor/google.golang.org/grpc/resolver/dns/go17_test.go
@@ -0,0 +1,50 @@
+// +build go1.6, !go1.8
+
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * 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
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package dns
+
+import (
+	"fmt"
+	"net"
+
+	"golang.org/x/net/context"
+)
+
+var errForInvalidTarget = fmt.Errorf("invalid target address [2001:db8:a0b:12f0::1, error info: missing ']' in address [2001:db8:a0b:12f0::1:443")
+
+func replaceNetFunc() func() {
+	oldLookupHost := lookupHost
+	oldLookupSRV := lookupSRV
+	oldLookupTXT := lookupTXT
+	lookupHost = func(ctx context.Context, host string) ([]string, error) {
+		return hostLookup(host)
+	}
+	lookupSRV = func(ctx context.Context, service, proto, name string) (string, []*net.SRV, error) {
+		return srvLookup(service, proto, name)
+	}
+	lookupTXT = func(ctx context.Context, host string) ([]string, error) {
+		return txtLookup(host)
+	}
+	return func() {
+		lookupHost = oldLookupHost
+		lookupSRV = oldLookupSRV
+		lookupTXT = oldLookupTXT
+	}
+}
--- a/vendor/google.golang.org/grpc/resolver/dns/go18.go
+++ b/vendor/google.golang.org/grpc/resolver/dns/go18.go
@@ -0,0 +1,29 @@
+// +build go1.8
+
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * 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
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package dns
+
+import "net"
+
+var (
+	lookupHost = net.DefaultResolver.LookupHost
+	lookupSRV  = net.DefaultResolver.LookupSRV
+	lookupTXT  = net.DefaultResolver.LookupTXT
+)
--- a/vendor/google.golang.org/grpc/resolver/dns/go18_test.go
+++ b/vendor/google.golang.org/grpc/resolver/dns/go18_test.go
@@ -0,0 +1,49 @@
+// +build go1.8
+
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * 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
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package dns
+
+import (
+	"context"
+	"fmt"
+	"net"
+)
+
+var errForInvalidTarget = fmt.Errorf("invalid target address [2001:db8:a0b:12f0::1, error info: address [2001:db8:a0b:12f0::1:443: missing ']' in address")
+
+func replaceNetFunc() func() {
+	oldLookupHost := lookupHost
+	oldLookupSRV := lookupSRV
+	oldLookupTXT := lookupTXT
+	lookupHost = func(ctx context.Context, host string) ([]string, error) {
+		return hostLookup(host)
+	}
+	lookupSRV = func(ctx context.Context, service, proto, name string) (string, []*net.SRV, error) {
+		return srvLookup(service, proto, name)
+	}
+	lookupTXT = func(ctx context.Context, host string) ([]string, error) {
+		return txtLookup(host)
+	}
+	return func() {
+		lookupHost = oldLookupHost
+		lookupSRV = oldLookupSRV
+		lookupTXT = oldLookupTXT
+	}
+}
--- a/vendor/google.golang.org/grpc/resolver/manual/manual.go
+++ b/vendor/google.golang.org/grpc/resolver/manual/manual.go
@@ -0,0 +1,91 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * 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
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package manual defines a resolver that can be used to manually send resolved
+// addresses to ClientConn.
+package manual
+
+import (
+	"strconv"
+	"time"
+
+	"google.golang.org/grpc/resolver"
+)
+
+// NewBuilderWithScheme creates a new test resolver builder with the given scheme.
+func NewBuilderWithScheme(scheme string) *Resolver {
+	return &Resolver{
+		scheme: scheme,
+	}
+}
+
+// Resolver is also a resolver builder.
+// It's build() function always returns itself.
+type Resolver struct {
+	scheme string
+
+	// Fields actually belong to the resolver.
+	cc             resolver.ClientConn
+	bootstrapAddrs []resolver.Address
+}
+
+// InitialAddrs adds resolved addresses to the resolver so that
+// NewAddress doesn't need to be explicitly called after Dial.
+func (r *Resolver) InitialAddrs(addrs []resolver.Address) {
+	r.bootstrapAddrs = addrs
+}
+
+// Build returns itself for Resolver, because it's both a builder and a resolver.
+func (r *Resolver) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOption) (resolver.Resolver, error) {
+	r.cc = cc
+	if r.bootstrapAddrs != nil {
+		r.NewAddress(r.bootstrapAddrs)
+	}
+	return r, nil
+}
+
+// Scheme returns the test scheme.
+func (r *Resolver) Scheme() string {
+	return r.scheme
+}
+
+// ResolveNow is a noop for Resolver.
+func (*Resolver) ResolveNow(o resolver.ResolveNowOption) {}
+
+// Close is a noop for Resolver.
+func (*Resolver) Close() {}
+
+// NewAddress calls cc.NewAddress.
+func (r *Resolver) NewAddress(addrs []resolver.Address) {
+	r.cc.NewAddress(addrs)
+}
+
+// NewServiceConfig calls cc.NewServiceConfig.
+func (r *Resolver) NewServiceConfig(sc string) {
+	r.cc.NewServiceConfig(sc)
+}
+
+// GenerateAndRegisterManualResolver generates a random scheme and a Resolver
+// with it. It also regieter this Resolver.
+// It returns the Resolver and a cleanup function to unregister it.
+func GenerateAndRegisterManualResolver() (*Resolver, func()) {
+	scheme := strconv.FormatInt(time.Now().UnixNano(), 36)
+	r := NewBuilderWithScheme(scheme)
+	resolver.Register(r)
+	return r, func() { resolver.UnregisterForTesting(scheme) }
+}
--- a/vendor/google.golang.org/grpc/resolver/passthrough/passthrough.go
+++ b/vendor/google.golang.org/grpc/resolver/passthrough/passthrough.go
@@ -0,0 +1,57 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * 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
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package passthrough implements a pass-through resolver. It sends the target
+// name without scheme back to gRPC as resolved address.
+package passthrough
+
+import "google.golang.org/grpc/resolver"
+
+const scheme = "passthrough"
+
+type passthroughBuilder struct{}
+
+func (*passthroughBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOption) (resolver.Resolver, error) {
+	r := &passthroughResolver{
+		target: target,
+		cc:     cc,
+	}
+	r.start()
+	return r, nil
+}
+
+func (*passthroughBuilder) Scheme() string {
+	return scheme
+}
+
+type passthroughResolver struct {
+	target resolver.Target
+	cc     resolver.ClientConn
+}
+
+func (r *passthroughResolver) start() {
+	r.cc.NewAddress([]resolver.Address{{Addr: r.target.Endpoint}})
+}
+
+func (*passthroughResolver) ResolveNow(o resolver.ResolveNowOption) {}
+
+func (*passthroughResolver) Close() {}
+
+func init() {
+	resolver.Register(&passthroughBuilder{})
+}
--- a/vendor/google.golang.org/grpc/resolver/resolver.go
+++ b/vendor/google.golang.org/grpc/resolver/resolver.go
@@ -0,0 +1,152 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * 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
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package resolver defines APIs for name resolution in gRPC.
+// All APIs in this package are experimental.
+package resolver
+
+var (
+	// m is a map from scheme to resolver builder.
+	m = make(map[string]Builder)
+	// defaultScheme is the default scheme to use.
+	defaultScheme = "passthrough"
+)
+
+// TODO(bar) install dns resolver in init(){}.
+
+// Register registers the resolver builder to the resolver map.
+// b.Scheme will be used as the scheme registered with this builder.
+func Register(b Builder) {
+	m[b.Scheme()] = b
+}
+
+// Get returns the resolver builder registered with the given scheme.
+// If no builder is register with the scheme, the default scheme will
+// be used.
+// If the default scheme is not modified, "passthrough" will be the default
+// scheme, and the preinstalled dns resolver will be used.
+// If the default scheme is modified, and a resolver is registered with
+// the scheme, that resolver will be returned.
+// If the default scheme is modified, and no resolver is registered with
+// the scheme, nil will be returned.
+func Get(scheme string) Builder {
+	if b, ok := m[scheme]; ok {
+		return b
+	}
+	if b, ok := m[defaultScheme]; ok {
+		return b
+	}
+	return nil
+}
+
+// SetDefaultScheme sets the default scheme that will be used.
+// The default default scheme is "passthrough".
+func SetDefaultScheme(scheme string) {
+	defaultScheme = scheme
+}
+
+// AddressType indicates the address type returned by name resolution.
+type AddressType uint8
+
+const (
+	// Backend indicates the address is for a backend server.
+	Backend AddressType = iota
+	// GRPCLB indicates the address is for a grpclb load balancer.
+	GRPCLB
+)
+
+// Address represents a server the client connects to.
+// This is the EXPERIMENTAL API and may be changed or extended in the future.
+type Address struct {
+	// Addr is the server address on which a connection will be established.
+	Addr string
+	// Type is the type of this address.
+	Type AddressType
+	// ServerName is the name of this address.
+	//
+	// e.g. if Type is GRPCLB, ServerName should be the name of the remote load
+	// balancer, not the name of the backend.
+	ServerName string
+	// Metadata is the information associated with Addr, which may be used
+	// to make load balancing decision.
+	Metadata interface{}
+}
+
+// BuildOption includes additional information for the builder to create
+// the resolver.
+type BuildOption struct {
+}
+
+// ClientConn contains the callbacks for resolver to notify any updates
+// to the gRPC ClientConn.
+//
+// This interface is to be implemented by gRPC. Users should not need a
+// brand new implementation of this interface. For the situations like
+// testing, the new implementation should embed this interface. This allows
+// gRPC to add new methods to this interface.
+type ClientConn interface {
+	// NewAddress is called by resolver to notify ClientConn a new list
+	// of resolved addresses.
+	// The address list should be the complete list of resolved addresses.
+	NewAddress(addresses []Address)
+	// NewServiceConfig is called by resolver to notify ClientConn a new
+	// service config. The service config should be provided as a json string.
+	NewServiceConfig(serviceConfig string)
+}
+
+// Target represents a target for gRPC, as specified in:
+// https://github.com/grpc/grpc/blob/master/doc/naming.md.
+type Target struct {
+	Scheme    string
+	Authority string
+	Endpoint  string
+}
+
+// Builder creates a resolver that will be used to watch name resolution updates.
+type Builder interface {
+	// Build creates a new resolver for the given target.
+	//
+	// gRPC dial calls Build synchronously, and fails if the returned error is
+	// not nil.
+	Build(target Target, cc ClientConn, opts BuildOption) (Resolver, error)
+	// Scheme returns the scheme supported by this resolver.
+	// Scheme is defined at https://github.com/grpc/grpc/blob/master/doc/naming.md.
+	Scheme() string
+}
+
+// ResolveNowOption includes additional information for ResolveNow.
+type ResolveNowOption struct{}
+
+// Resolver watches for the updates on the specified target.
+// Updates include address updates and service config updates.
+type Resolver interface {
+	// ResolveNow will be called by gRPC to try to resolve the target name
+	// again. It's just a hint, resolver can ignore this if it's not necessary.
+	//
+	// It could be called multiple times concurrently.
+	ResolveNow(ResolveNowOption)
+	// Close closes the resolver.
+	Close()
+}
+
+// UnregisterForTesting removes the resolver builder with the given scheme from the
+// resolver map.
+// This function is for testing only.
+func UnregisterForTesting(scheme string) {
+	delete(m, scheme)
+}