action_agent.go

// Copyright 2012, Google Inc. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

/*
Package tabletmanager exports the ActionAgent object. It keeps the local tablet
state, starts / stops all associated services (query service,
update stream, binlog players, ...), and handles tabletmanager RPCs
to update the state.

The agent is responsible for maintaining the tablet record in the
topology server. Only 'vtctl DeleteTablet'
should be run by other processes, everything else should ask
the tablet server to make the change.

Most RPC calls lock the actionMutex, except the easy read-only ones.
RPC calls that change the tablet record will also call updateState.

See rpc_server.go for all cases, and which actions take the actionMutex,
and which run changeCallback.
*/
package tabletmanager

import (
	"encoding/hex"
	"flag"
	"fmt"
	"math/rand"
	"net"
	"os"
	"path"
	"regexp"
	"sync"
	"time"

	log "github.com/golang/glog"
	"golang.org/x/net/context"

	"github.com/golang/protobuf/proto"
	"github.com/youtube/vitess/go/history"
	"github.com/youtube/vitess/go/netutil"
	"github.com/youtube/vitess/go/stats"
	"github.com/youtube/vitess/go/vt/binlog"
	"github.com/youtube/vitess/go/vt/binlog/binlogplayer"
	"github.com/youtube/vitess/go/vt/dbconfigs"
	"github.com/youtube/vitess/go/vt/health"
	"github.com/youtube/vitess/go/vt/key"
	"github.com/youtube/vitess/go/vt/logutil"
	"github.com/youtube/vitess/go/vt/mysqlctl"
	"github.com/youtube/vitess/go/vt/servenv"
	"github.com/youtube/vitess/go/vt/topo"
	"github.com/youtube/vitess/go/vt/topo/topoproto"
	"github.com/youtube/vitess/go/vt/vttablet/tabletserver"
	"github.com/youtube/vitess/go/vt/vttablet/tabletservermock"

	querypb "github.com/youtube/vitess/go/vt/proto/query"
	topodatapb "github.com/youtube/vitess/go/vt/proto/topodata"
)

const (
	// slaveStoppedFile is the file name for the file whose existence informs
	// vttablet to NOT try to repair replication.
	slaveStoppedFile = "do_not_replicate"
)

var (
	tabletHostname = flag.String("tablet_hostname", "", "if not empty, this hostname will be assumed instead of trying to resolve it")
)

// ActionAgent is the main class for the agent.
type ActionAgent struct {
	// The following fields are set during creation
	QueryServiceControl tabletserver.Controller
	UpdateStream        binlog.UpdateStreamControl
	HealthReporter      health.Reporter
	TopoServer          topo.Server
	TabletAlias         *topodatapb.TabletAlias
	MysqlDaemon         mysqlctl.MysqlDaemon
	DBConfigs           dbconfigs.DBConfigs
	BinlogPlayerMap     *BinlogPlayerMap

	// exportStats is set only for production tablet.
	exportStats bool

	// statsTabletType is set to expose the current tablet type,
	// only used if exportStats is true.
	statsTabletType *stats.String

	// skipMysqlPortCheck is set when we don't want healthcheck to
	// alter the mysql port of the Tablet record. This is used by
	// vtcombo, because we dont configure the 'dba' pool, used to
	// get the mysql port.
	skipMysqlPortCheck bool

	// batchCtx is given to the agent by its creator, and should be used for
	// any background tasks spawned by the agent.
	batchCtx context.Context

	// finalizeReparentCtx represents the background finalize step of a
	// TabletExternallyReparented call.
	finalizeReparentCtx context.Context

	// History of the health checks, public so status
	// pages can display it
	History *history.History

	// actionMutex is there to run only one action at a time. If
	// both agent.actionMutex and agent.mutex needs to be taken,
	// take actionMutex first.
	actionMutex sync.Mutex

	// initReplication remembers whether an action has initialized
	// replication.  It is protected by actionMutex.
	initReplication bool

	// initialTablet remembers the state of the tablet record at startup.
	// It can be used to notice, for example, if another tablet has taken
	// over the record.
	initialTablet *topodatapb.Tablet

	// orc is an optional client for Orchestrator HTTP API calls.
	// If this is nil, those calls will be skipped.
	// It's only set once in NewActionAgent() and never modified after that.
	orc *orcClient

	// mutex protects all the following fields (that start with '_'),
	// only hold the mutex to update the fields, nothing else.
	mutex sync.Mutex

	// _tablet has the Tablet record we last read from the topology server.
	_tablet *topodatapb.Tablet

	// _disallowQueryService is set to the reason we should be
	// disallowing queries from being served. It is set from changeCallback,
	// and used by healthcheck. If empty, we should allow queries.
	// It is set if the current type is not serving, if a TabletControl
	// tells us not to serve, or if filtered replication is running.
	_disallowQueryService string

	// _enableUpdateStream is true if we should be running the
	// UpdateStream service. Note if we can't start the query
	// service, or if the server health check fails, we will
	// disable UpdateStream.
	_enableUpdateStream bool

	// _blacklistedTables has the list of tables we are currently
	// blacklisting.
	_blacklistedTables []string

	// set to true if mysql is not up when we start. That way, we
	// only log once that we'r waiting for mysql.
	_waitingForMysql bool

	// if the agent is healthy, this is nil. Otherwise it contains
	// the reason we're not healthy.
	_healthy error

	// this is the last time health check ran
	_healthyTime time.Time

	// replication delay the last time we got it
	_replicationDelay time.Duration

	// last time we ran TabletExternallyReparented
	_tabletExternallyReparentedTime time.Time

	// _ignoreHealthErrorExpr can be set by RPC to selectively disable certain
	// healthcheck errors. It should only be accessed while holding actionMutex.
	_ignoreHealthErrorExpr *regexp.Regexp

	// _slaveStopped remembers if we've been told to stop replicating.
	// If it's nil, we'll try to check for the slaveStoppedFile.
	_slaveStopped *bool
}

// NewActionAgent creates a new ActionAgent and registers all the
// associated services.
//
// batchCtx is the context that the agent will use for any background tasks
// it spawns.
func NewActionAgent(
	batchCtx context.Context,
	ts topo.Server,
	mysqld mysqlctl.MysqlDaemon,
	queryServiceControl tabletserver.Controller,
	tabletAlias *topodatapb.TabletAlias,
	dbcfgs dbconfigs.DBConfigs,
	mycnf *mysqlctl.Mycnf,
	port, gRPCPort int32,
) (agent *ActionAgent, err error) {
	orc, err := newOrcClient()
	if err != nil {
		return nil, err
	}

	agent = &ActionAgent{
		QueryServiceControl: queryServiceControl,
		HealthReporter:      health.DefaultAggregator,
		batchCtx:            batchCtx,
		TopoServer:          ts,
		TabletAlias:         tabletAlias,
		MysqlDaemon:         mysqld,
		DBConfigs:           dbcfgs,
		History:             history.New(historyLength),
		_healthy:            fmt.Errorf("healthcheck not run yet"),
		orc:                 orc,
	}
	agent.registerQueryRuleSources()

	// try to initialize the tablet if we have to
	if err := agent.InitTablet(port, gRPCPort); err != nil {
		return nil, fmt.Errorf("agent.InitTablet failed: %v", err)
	}

	// Create the TabletType stats
	agent.exportStats = true
	agent.statsTabletType = stats.NewString("TabletType")

	// Start the binlog player services, not playing at start.
	agent.BinlogPlayerMap = NewBinlogPlayerMap(ts, mysqld, func() binlogplayer.VtClient {
		return binlogplayer.NewDbClient(&agent.DBConfigs.Filtered)
	})
	// Stop all binlog players upon entering lameduck.
	servenv.OnTerm(agent.BinlogPlayerMap.StopAllPlayersAndReset)
	RegisterBinlogPlayerMap(agent.BinlogPlayerMap)

	// try to figure out the mysql port
	mysqlPort := mycnf.MysqlPort
	if mysqlPort == 0 {
		// we don't know the port, try to get it from mysqld
		var err error
		mysqlPort, err = mysqld.GetMysqlPort()
		if err != nil {
			log.Warningf("Cannot get current mysql port, will use 0 for now: %v", err)
		}
	}

	// Start will get the tablet info, and update our state from it
	if err := agent.Start(batchCtx, int32(mysqlPort), port, gRPCPort, true); err != nil {
		return nil, err
	}

	// register the RPC services from the agent
	servenv.OnRun(func() {
		agent.registerQueryService()
	})

	// two cases then:
	// - restoreFromBackup is set: we restore, then initHealthCheck, all
	//   in the background
	// - restoreFromBackup is not set: we initHealthCheck right away
	if *restoreFromBackup {
		go func() {
			// restoreFromBackup wil just be a regular action
			// (same as if it was triggered remotely)
			if err := agent.RestoreData(batchCtx, logutil.NewConsoleLogger(), false /* deleteBeforeRestore */); err != nil {
				println(fmt.Sprintf("RestoreFromBackup failed: %v", err))
				log.Fatalf("RestoreFromBackup failed: %v", err)
			}

			// after the restore is done, start health check
			agent.initHealthCheck()
		}()
	} else {
		// update our state
		if err := agent.refreshTablet(batchCtx, "Start"); err != nil {
			return nil, err
		}

		// synchronously start health check if needed
		agent.initHealthCheck()
	}

	// Start periodic Orchestrator self-registration, if configured.
	if agent.orc != nil {
		go agent.orc.DiscoverLoop(agent)
	}

	return agent, nil
}

// NewTestActionAgent creates an agent for test purposes. Only a
// subset of features are supported now, but we'll add more over time.
func NewTestActionAgent(batchCtx context.Context, ts topo.Server, tabletAlias *topodatapb.TabletAlias, vtPort, grpcPort int32, mysqlDaemon mysqlctl.MysqlDaemon, preStart func(*ActionAgent)) *ActionAgent {
	agent := &ActionAgent{
		QueryServiceControl: tabletservermock.NewController(),
		UpdateStream:        binlog.NewUpdateStreamControlMock(),
		HealthReporter:      health.DefaultAggregator,
		batchCtx:            batchCtx,
		TopoServer:          ts,
		TabletAlias:         tabletAlias,
		MysqlDaemon:         mysqlDaemon,
		DBConfigs:           dbconfigs.DBConfigs{},
		BinlogPlayerMap:     nil,
		History:             history.New(historyLength),
		_healthy:            fmt.Errorf("healthcheck not run yet"),
	}
	if preStart != nil {
		preStart(agent)
	}

	// Start will update the topology and setup services.
	if err := agent.Start(batchCtx, 0, vtPort, grpcPort, false); err != nil {
		panic(fmt.Errorf("agent.Start(%v) failed: %v", tabletAlias, err))
	}

	// Update our running state.
	if err := agent.refreshTablet(batchCtx, "Start"); err != nil {
		panic(fmt.Errorf("agent.refreshTablet(%v) failed: %v", tabletAlias, err))
	}

	return agent
}

// NewComboActionAgent creates an agent tailored specifically to run
// within the vtcombo binary. It cannot be called concurrently,
// as it changes the flags.
func NewComboActionAgent(batchCtx context.Context, ts topo.Server, tabletAlias *topodatapb.TabletAlias, vtPort, grpcPort int32, queryServiceControl tabletserver.Controller, dbcfgs dbconfigs.DBConfigs, mysqlDaemon mysqlctl.MysqlDaemon, keyspace, shard, dbname, tabletType string) *ActionAgent {
	agent := &ActionAgent{
		QueryServiceControl: queryServiceControl,
		UpdateStream:        binlog.NewUpdateStreamControlMock(),
		HealthReporter:      health.DefaultAggregator,
		batchCtx:            batchCtx,
		TopoServer:          ts,
		TabletAlias:         tabletAlias,
		MysqlDaemon:         mysqlDaemon,
		DBConfigs:           dbcfgs,
		BinlogPlayerMap:     nil,
		skipMysqlPortCheck:  true,
		History:             history.New(historyLength),
		_healthy:            fmt.Errorf("healthcheck not run yet"),
	}
	agent.registerQueryRuleSources()

	// Initialize the tablet.
	*initDbNameOverride = dbname
	*initKeyspace = keyspace
	*initShard = shard
	*initTabletType = tabletType
	if err := agent.InitTablet(vtPort, grpcPort); err != nil {
		panic(fmt.Errorf("agent.InitTablet failed: %v", err))
	}

	// Start the agent.
	if err := agent.Start(batchCtx, 0, vtPort, grpcPort, false); err != nil {
		panic(fmt.Errorf("agent.Start(%v) failed: %v", tabletAlias, err))
	}

	// And update our running state.
	if err := agent.refreshTablet(batchCtx, "Start"); err != nil {
		panic(fmt.Errorf("agent.refreshTablet(%v) failed: %v", tabletAlias, err))
	}

	return agent
}

// registerQueryRuleSources registers query rule sources under control of agent
func (agent *ActionAgent) registerQueryRuleSources() {
	agent.QueryServiceControl.RegisterQueryRuleSource(blacklistQueryRules)
}

func (agent *ActionAgent) setTablet(tablet *topodatapb.Tablet) {
	agent.mutex.Lock()
	agent._tablet = proto.Clone(tablet).(*topodatapb.Tablet)
	agent.mutex.Unlock()
}

// Tablet reads the stored Tablet from the agent, protected by mutex.
func (agent *ActionAgent) Tablet() *topodatapb.Tablet {
	agent.mutex.Lock()
	tablet := proto.Clone(agent._tablet).(*topodatapb.Tablet)
	agent.mutex.Unlock()
	return tablet
}

// Healthy reads the result of the latest healthcheck, protected by mutex.
// If that status is too old, it means healthcheck hasn't run for a while,
// and is probably stuck, this is not good, we're not healthy.
func (agent *ActionAgent) Healthy() (time.Duration, error) {
	agent.mutex.Lock()
	defer agent.mutex.Unlock()

	healthy := agent._healthy
	if healthy == nil {
		timeSinceLastCheck := time.Since(agent._healthyTime)
		if timeSinceLastCheck > *healthCheckInterval*3 {
			healthy = fmt.Errorf("last health check is too old: %s > %s", timeSinceLastCheck, *healthCheckInterval*3)
		}
	}

	return agent._replicationDelay, healthy
}

// BlacklistedTables returns the list of currently blacklisted tables.
func (agent *ActionAgent) BlacklistedTables() []string {
	agent.mutex.Lock()
	defer agent.mutex.Unlock()
	return agent._blacklistedTables
}

// DisallowQueryService returns the reason the query service should be
// disabled, if any.
func (agent *ActionAgent) DisallowQueryService() string {
	agent.mutex.Lock()
	defer agent.mutex.Unlock()
	return agent._disallowQueryService
}

// EnableUpdateStream returns if we should enable update stream or not
func (agent *ActionAgent) EnableUpdateStream() bool {
	agent.mutex.Lock()
	defer agent.mutex.Unlock()
	return agent._enableUpdateStream
}

func (agent *ActionAgent) slaveStopped() bool {
	agent.mutex.Lock()
	defer agent.mutex.Unlock()

	// If we already know the value, don't bother checking the file.
	if agent._slaveStopped != nil {
		return *agent._slaveStopped
	}

	// If the marker file exists, we're stopped.
	// Treat any read error as if the file doesn't exist.
	_, err := os.Stat(path.Join(agent.MysqlDaemon.TabletDir(), slaveStoppedFile))
	slaveStopped := err == nil
	agent._slaveStopped = &slaveStopped
	return slaveStopped
}

func (agent *ActionAgent) setSlaveStopped(slaveStopped bool) {
	agent.mutex.Lock()
	defer agent.mutex.Unlock()

	agent._slaveStopped = &slaveStopped

	// Make a best-effort attempt to persist the value across tablet restarts.
	// We store a marker in the filesystem so it works regardless of whether
	// mysqld is running, and so it's tied to this particular instance of the
	// tablet data dir (the one that's paused at a known replication position).
	tabletDir := agent.MysqlDaemon.TabletDir()
	if tabletDir == "" {
		return
	}
	markerFile := path.Join(tabletDir, slaveStoppedFile)
	if slaveStopped {
		file, err := os.Create(markerFile)
		if err == nil {
			file.Close()
		}
	} else {
		os.Remove(markerFile)
	}
}

func (agent *ActionAgent) setServicesDesiredState(disallowQueryService string, enableUpdateStream bool) {
	agent.mutex.Lock()
	agent._disallowQueryService = disallowQueryService
	agent._enableUpdateStream = enableUpdateStream
	agent.mutex.Unlock()
}

func (agent *ActionAgent) setBlacklistedTables(value []string) {
	agent.mutex.Lock()
	agent._blacklistedTables = value
	agent.mutex.Unlock()
}

func (agent *ActionAgent) verifyTopology(ctx context.Context) {
	if err := topo.Validate(ctx, agent.TopoServer, agent.TabletAlias); err != nil {
		// Don't stop, it's not serious enough, this is likely transient.
		log.Warningf("tablet validate failed: %v %v", agent.TabletAlias, err)
	}
}

// Start validates and updates the topology records for the tablet, and performs
// the initial state change callback to start tablet services.
// If initUpdateStream is set, update stream service will also be registered.
func (agent *ActionAgent) Start(ctx context.Context, mysqlPort, vtPort, gRPCPort int32, initUpdateStream bool) error {
	// find our hostname as fully qualified, and IP
	hostname := *tabletHostname
	if hostname == "" {
		var err error
		hostname, err = netutil.FullyQualifiedHostname()
		if err != nil {
			return err
		}
	}
	ipAddrs, err := net.LookupHost(hostname)
	if err != nil {
		return err
	}
	ipAddr := ipAddrs[0]

	// Update bind addr for mysql and query service in the tablet node.
	f := func(tablet *topodatapb.Tablet) error {
		tablet.Hostname = hostname
		tablet.Ip = ipAddr
		if tablet.PortMap == nil {
			tablet.PortMap = make(map[string]int32)
		}
		if mysqlPort != 0 {
			// only overwrite mysql port if we know it, otherwise
			// leave it as is.
			tablet.PortMap["mysql"] = mysqlPort
		}
		if vtPort != 0 {
			tablet.PortMap["vt"] = vtPort
		} else {
			delete(tablet.PortMap, "vt")
		}
		delete(tablet.PortMap, "vts")
		if gRPCPort != 0 {
			tablet.PortMap["grpc"] = gRPCPort
		} else {
			delete(tablet.PortMap, "grpc")
		}

		// Save the original tablet for ownership tests later.
		agent.initialTablet = tablet
		return nil
	}
	if _, err := agent.TopoServer.UpdateTabletFields(ctx, agent.TabletAlias, f); err != nil {
		return err
	}

	// Verify the topology is correct.
	agent.verifyTopology(ctx)

	// Get and fix the dbname if necessary, only for real instances.
	if !agent.DBConfigs.IsZero() {
		dbname := topoproto.TabletDbName(agent.initialTablet)

		// Update our DB config to match the info we have in the tablet
		if agent.DBConfigs.App.DbName == "" {
			agent.DBConfigs.App.DbName = dbname
		}
		if agent.DBConfigs.Filtered.DbName == "" {
			agent.DBConfigs.Filtered.DbName = dbname
		}
	}

	// create and register the RPC services from UpdateStream
	// (it needs the dbname, so it has to be delayed up to here,
	// but it has to be before updateState below that may use it)
	if initUpdateStream {
		us := binlog.NewUpdateStream(agent.TopoServer, agent.initialTablet.Keyspace, agent.TabletAlias.Cell, agent.MysqlDaemon, agent.QueryServiceControl.SchemaEngine(), agent.DBConfigs.App.DbName)
		agent.UpdateStream = us
		servenv.OnRun(func() {
			us.RegisterService()
		})
	}
	servenv.OnTerm(func() {
		// Disable UpdateStream (if any) upon entering lameduck.
		// We do this regardless of initUpdateStream, since agent.UpdateStream
		// may have been set from elsewhere.
		if agent.UpdateStream != nil {
			agent.UpdateStream.Disable()
		}
	})

	// initialize tablet server
	if err := agent.QueryServiceControl.InitDBConfig(querypb.Target{
		Keyspace:   agent.initialTablet.Keyspace,
		Shard:      agent.initialTablet.Shard,
		TabletType: agent.initialTablet.Type,
	}, agent.DBConfigs, agent.MysqlDaemon); err != nil {
		return fmt.Errorf("failed to InitDBConfig: %v", err)
	}

	// export a few static variables
	if agent.exportStats {
		statsKeyspace := stats.NewString("TabletKeyspace")
		statsShard := stats.NewString("TabletShard")
		statsKeyRangeStart := stats.NewString("TabletKeyRangeStart")
		statsKeyRangeEnd := stats.NewString("TabletKeyRangeEnd")

		statsKeyspace.Set(agent.initialTablet.Keyspace)
		statsShard.Set(agent.initialTablet.Shard)
		if key.KeyRangeIsPartial(agent.initialTablet.KeyRange) {
			statsKeyRangeStart.Set(hex.EncodeToString(agent.initialTablet.KeyRange.Start))
			statsKeyRangeEnd.Set(hex.EncodeToString(agent.initialTablet.KeyRange.End))
		}
	}

	// Initialize the current tablet to match our current running
	// state: Has most field filled in, but type is UNKNOWN.
	// Subsequents calls to updateState or refreshTablet
	// will then work as expected.
	startingTablet := proto.Clone(agent.initialTablet).(*topodatapb.Tablet)
	startingTablet.Type = topodatapb.TabletType_UNKNOWN
	agent.setTablet(startingTablet)

	// run a background task to rebuild the SrvKeyspace in our cell/keyspace
	// if it doesn't exist yet
	go agent.maybeRebuildKeyspace(agent.initialTablet.Alias.Cell, agent.initialTablet.Keyspace)

	return nil
}

// Stop shuts down the agent. Normally this is not necessary, since we use
// servenv OnTerm and OnClose hooks to coordinate shutdown automatically,
// while taking lameduck into account. However, this may be useful for tests,
// when you want to clean up an agent immediately.
func (agent *ActionAgent) Stop() {
	if agent.UpdateStream != nil {
		agent.UpdateStream.Disable()
	}
	if agent.BinlogPlayerMap != nil {
		agent.BinlogPlayerMap.StopAllPlayersAndReset()
	}
	if agent.MysqlDaemon != nil {
		agent.MysqlDaemon.Close()
	}
}

// hookExtraEnv returns the map to pass to local hooks
func (agent *ActionAgent) hookExtraEnv() map[string]string {
	return map[string]string{"TABLET_ALIAS": topoproto.TabletAliasString(agent.TabletAlias)}
}

// checkTabletMysqlPort will check the mysql port for the tablet is good,
// and if not will try to update it. It returns the modified Tablet record,
// if it was changed.
func (agent *ActionAgent) checkTabletMysqlPort(ctx context.Context, tablet *topodatapb.Tablet) *topodatapb.Tablet {
	mport, err := agent.MysqlDaemon.GetMysqlPort()
	if err != nil {
		log.Warningf("Cannot get current mysql port, not checking it: %v", err)
		return nil
	}

	if mport == tablet.PortMap["mysql"] {
		return nil
	}

	log.Warningf("MySQL port has changed from %v to %v, updating it in tablet record", tablet.PortMap["mysql"], mport)
	newTablet, err := agent.TopoServer.UpdateTabletFields(ctx, tablet.Alias, func(t *topodatapb.Tablet) error {
		t.PortMap["mysql"] = mport
		return nil
	})
	if err != nil {
		log.Warningf("Failed to update tablet record, may use old mysql port")
		return nil
	}

	// update worked, return the new record
	return newTablet
}

// withRetry will exponentially back off and retry a function upon
// failure, until the context is Done(), or the function returned with
// no error. We use this at startup with a context timeout set to the
// value of the init_timeout flag, so we can try to modify the
// topology over a longer period instead of dying right away.
func (agent *ActionAgent) withRetry(ctx context.Context, description string, work func() error) error {
	backoff := 1 * time.Second
	for {
		err := work()
		if err == nil || err == context.Canceled || err == context.DeadlineExceeded {
			return err
		}

		log.Warningf("%v failed (%v), backing off %v before retrying", description, err, backoff)
		select {
		case <-ctx.Done():
			return ctx.Err()
		case <-time.After(backoff):
			// Exponential backoff with 1.3 as a factor,
			// and randomized down by at most 20
			// percent. The generated time series looks
			// good.  Also note rand.Seed is called at
			// init() time in binlog_players.go.
			f := float64(backoff) * 1.3
			f -= f * 0.2 * rand.Float64()
			backoff = time.Duration(f)
		}
	}
}