vertical_split_diff.go

// Copyright 2013, 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 worker

import (
	"fmt"
	"html/template"
	"sync"

	"golang.org/x/net/context"

	"github.com/youtube/vitess/go/sync2"
	"github.com/youtube/vitess/go/vt/concurrency"
	"github.com/youtube/vitess/go/vt/mysqlctl/tmutils"
	"github.com/youtube/vitess/go/vt/topo"
	"github.com/youtube/vitess/go/vt/topo/topoproto"
	"github.com/youtube/vitess/go/vt/wrangler"

	tabletmanagerdatapb "github.com/youtube/vitess/go/vt/proto/tabletmanagerdata"
	topodatapb "github.com/youtube/vitess/go/vt/proto/topodata"
)

// VerticalSplitDiffWorker executes a diff between a destination shard and its
// source shards in a shard split case.
type VerticalSplitDiffWorker struct {
	StatusWorker

	wr                      *wrangler.Wrangler
	cell                    string
	keyspace                string
	shard                   string
	minHealthyRdonlyTablets int
	cleaner                 *wrangler.Cleaner

	// populated during WorkerStateInit, read-only after that
	keyspaceInfo *topo.KeyspaceInfo
	shardInfo    *topo.ShardInfo

	// populated during WorkerStateFindTargets, read-only after that
	sourceAlias      *topodatapb.TabletAlias
	destinationAlias *topodatapb.TabletAlias

	// populated during WorkerStateDiff
	sourceSchemaDefinition      *tabletmanagerdatapb.SchemaDefinition
	destinationSchemaDefinition *tabletmanagerdatapb.SchemaDefinition
}

// NewVerticalSplitDiffWorker returns a new VerticalSplitDiffWorker object.
func NewVerticalSplitDiffWorker(wr *wrangler.Wrangler, cell, keyspace, shard string, minHealthyRdonlyTablets int) Worker {
	return &VerticalSplitDiffWorker{
		StatusWorker: NewStatusWorker(),
		wr:           wr,
		cell:         cell,
		keyspace:     keyspace,
		shard:        shard,
		minHealthyRdonlyTablets: minHealthyRdonlyTablets,
		cleaner:                 &wrangler.Cleaner{},
	}
}

// StatusAsHTML is part of the Worker interface.
func (vsdw *VerticalSplitDiffWorker) StatusAsHTML() template.HTML {
	state := vsdw.State()

	result := "<b>Working on:</b> " + vsdw.keyspace + "/" + vsdw.shard + "</br>\n"
	result += "<b>State:</b> " + state.String() + "</br>\n"
	switch state {
	case WorkerStateDiff:
		result += "<b>Running</b>:</br>\n"
	case WorkerStateDone:
		result += "<b>Success</b>:</br>\n"
	}

	return template.HTML(result)
}

// StatusAsText is part of the Worker interface.
func (vsdw *VerticalSplitDiffWorker) StatusAsText() string {
	state := vsdw.State()

	result := "Working on: " + vsdw.keyspace + "/" + vsdw.shard + "\n"
	result += "State: " + state.String() + "\n"
	switch state {
	case WorkerStateDiff:
		result += "Running...\n"
	case WorkerStateDone:
		result += "Success.\n"
	}
	return result
}

// Run is mostly a wrapper to run the cleanup at the end.
func (vsdw *VerticalSplitDiffWorker) Run(ctx context.Context) error {
	resetVars()
	err := vsdw.run(ctx)

	vsdw.SetState(WorkerStateCleanUp)
	cerr := vsdw.cleaner.CleanUp(vsdw.wr)
	if cerr != nil {
		if err != nil {
			vsdw.wr.Logger().Errorf("CleanUp failed in addition to job error: %v", cerr)
		} else {
			err = cerr
		}
	}
	if err != nil {
		vsdw.SetState(WorkerStateError)
		return err
	}
	vsdw.SetState(WorkerStateDone)
	return nil
}

func (vsdw *VerticalSplitDiffWorker) run(ctx context.Context) error {
	// first state: read what we need to do
	if err := vsdw.init(ctx); err != nil {
		return fmt.Errorf("init() failed: %v", err)
	}
	if err := checkDone(ctx); err != nil {
		return err
	}

	// second state: find targets
	if err := vsdw.findTargets(ctx); err != nil {
		return fmt.Errorf("findTargets() failed: %v", err)
	}
	if err := checkDone(ctx); err != nil {
		return err
	}

	// third phase: synchronize replication
	if err := vsdw.synchronizeReplication(ctx); err != nil {
		return fmt.Errorf("synchronizeReplication() failed: %v", err)
	}
	if err := checkDone(ctx); err != nil {
		return err
	}

	// fourth phase: diff
	if err := vsdw.diff(ctx); err != nil {
		return fmt.Errorf("diff() failed: %v", err)
	}
	if err := checkDone(ctx); err != nil {
		return err
	}

	return nil
}

// init phase:
// - read the shard info, make sure it has sources
func (vsdw *VerticalSplitDiffWorker) init(ctx context.Context) error {
	vsdw.SetState(WorkerStateInit)

	var err error

	// read the keyspace and validate it
	vsdw.keyspaceInfo, err = vsdw.wr.TopoServer().GetKeyspace(ctx, vsdw.keyspace)
	if err != nil {
		return fmt.Errorf("cannot read keyspace %v: %v", vsdw.keyspace, err)
	}
	if len(vsdw.keyspaceInfo.ServedFroms) == 0 {
		return fmt.Errorf("keyspace %v has no KeyspaceServedFrom", vsdw.keyspace)
	}

	// read the shardinfo and validate it
	vsdw.shardInfo, err = vsdw.wr.TopoServer().GetShard(ctx, vsdw.keyspace, vsdw.shard)
	if err != nil {
		return fmt.Errorf("cannot read shard %v/%v: %v", vsdw.keyspace, vsdw.shard, err)
	}
	if len(vsdw.shardInfo.SourceShards) != 1 {
		return fmt.Errorf("shard %v/%v has bad number of source shards", vsdw.keyspace, vsdw.shard)
	}
	if len(vsdw.shardInfo.SourceShards[0].Tables) == 0 {
		return fmt.Errorf("shard %v/%v has no tables in source shard[0]", vsdw.keyspace, vsdw.shard)
	}
	if !vsdw.shardInfo.HasMaster() {
		return fmt.Errorf("shard %v/%v has no master", vsdw.keyspace, vsdw.shard)
	}

	return nil
}

// findTargets phase:
// - find one rdonly per source shard
// - find one rdonly in destination shard
// - mark them all as 'worker' pointing back to us
func (vsdw *VerticalSplitDiffWorker) findTargets(ctx context.Context) error {
	vsdw.SetState(WorkerStateFindTargets)

	// find an appropriate tablet in destination shard
	var err error
	vsdw.destinationAlias, err = FindWorkerTablet(ctx, vsdw.wr, vsdw.cleaner, nil /* tsc */, vsdw.cell, vsdw.keyspace, vsdw.shard, vsdw.minHealthyRdonlyTablets)
	if err != nil {
		return fmt.Errorf("FindWorkerTablet() failed for %v/%v/%v: %v", vsdw.cell, vsdw.keyspace, vsdw.shard, err)
	}

	// find an appropriate tablet in the source shard
	vsdw.sourceAlias, err = FindWorkerTablet(ctx, vsdw.wr, vsdw.cleaner, nil /* tsc */, vsdw.cell, vsdw.shardInfo.SourceShards[0].Keyspace, vsdw.shardInfo.SourceShards[0].Shard, vsdw.minHealthyRdonlyTablets)
	if err != nil {
		return fmt.Errorf("FindWorkerTablet() failed for %v/%v/%v: %v", vsdw.cell, vsdw.shardInfo.SourceShards[0].Keyspace, vsdw.shardInfo.SourceShards[0].Shard, err)
	}

	return nil
}

// synchronizeReplication phase:
// 1 - ask the master of the destination shard to pause filtered replication,
//   and return the source binlog positions
//   (add a cleanup task to restart filtered replication on master)
// 2 - stop the source tablet at a binlog position higher than the
//   destination master. Get that new position.
//   (add a cleanup task to restart binlog replication on it, and change
//    the existing ChangeSlaveType cleanup action to 'spare' type)
// 3 - ask the master of the destination shard to resume filtered replication
//   up to the new list of positions, and return its binlog position.
// 4 - wait until the destination tablet is equal or passed that master
//   binlog position, and stop its replication.
//   (add a cleanup task to restart binlog replication on it, and change
//    the existing ChangeSlaveType cleanup action to 'spare' type)
// 5 - restart filtered replication on destination master.
//   (remove the cleanup task that does the same)
// At this point, all source and destination tablets are stopped at the same point.

func (vsdw *VerticalSplitDiffWorker) synchronizeReplication(ctx context.Context) error {
	vsdw.SetState(WorkerStateSyncReplication)

	shortCtx, cancel := context.WithTimeout(ctx, *remoteActionsTimeout)
	masterInfo, err := vsdw.wr.TopoServer().GetTablet(shortCtx, vsdw.shardInfo.MasterAlias)
	cancel()
	if err != nil {
		return fmt.Errorf("synchronizeReplication: cannot get Tablet record for master %v: %v", topoproto.TabletAliasString(vsdw.shardInfo.MasterAlias), err)
	}

	// 1 - stop the master binlog replication, get its current position
	vsdw.wr.Logger().Infof("Stopping master binlog replication on %v", topoproto.TabletAliasString(vsdw.shardInfo.MasterAlias))
	shortCtx, cancel = context.WithTimeout(ctx, *remoteActionsTimeout)
	blpPositionList, err := vsdw.wr.TabletManagerClient().StopBlp(shortCtx, masterInfo.Tablet)
	cancel()
	if err != nil {
		return fmt.Errorf("StopBlp on master %v failed: %v", topoproto.TabletAliasString(vsdw.shardInfo.MasterAlias), err)
	}
	wrangler.RecordStartBlpAction(vsdw.cleaner, masterInfo.Tablet)

	// 2 - stop the source tablet at a binlog position
	//     higher than the destination master
	stopPositionList := make([]*tabletmanagerdatapb.BlpPosition, 1)
	ss := vsdw.shardInfo.SourceShards[0]
	// find where we should be stopping
	blpPos := tmutils.FindBlpPositionByID(blpPositionList, ss.Uid)
	if blpPos == nil {
		return fmt.Errorf("no binlog position on the master for Uid %v", ss.Uid)
	}

	// stop replication
	vsdw.wr.Logger().Infof("Stopping slave %v at a minimum of %v", topoproto.TabletAliasString(vsdw.sourceAlias), blpPos.Position)
	shortCtx, cancel = context.WithTimeout(ctx, *remoteActionsTimeout)
	sourceTablet, err := vsdw.wr.TopoServer().GetTablet(shortCtx, vsdw.sourceAlias)
	cancel()
	if err != nil {
		return err
	}
	shortCtx, cancel = context.WithTimeout(ctx, *remoteActionsTimeout)
	stoppedAt, err := vsdw.wr.TabletManagerClient().StopSlaveMinimum(shortCtx, sourceTablet.Tablet, blpPos.Position, *remoteActionsTimeout)
	cancel()
	if err != nil {
		return fmt.Errorf("cannot stop slave %v at right binlog position %v: %v", topoproto.TabletAliasString(vsdw.sourceAlias), blpPos.Position, err)
	}
	stopPositionList[0] = &tabletmanagerdatapb.BlpPosition{
		Uid:      ss.Uid,
		Position: stoppedAt,
	}

	// change the cleaner actions from ChangeSlaveType(rdonly)
	// to StartSlave() + ChangeSlaveType(spare)
	wrangler.RecordStartSlaveAction(vsdw.cleaner, sourceTablet.Tablet)

	// 3 - ask the master of the destination shard to resume filtered
	//     replication up to the new list of positions
	vsdw.wr.Logger().Infof("Restarting master %v until it catches up to %v", topoproto.TabletAliasString(vsdw.shardInfo.MasterAlias), stopPositionList)
	shortCtx, cancel = context.WithTimeout(ctx, *remoteActionsTimeout)
	masterPos, err := vsdw.wr.TabletManagerClient().RunBlpUntil(shortCtx, masterInfo.Tablet, stopPositionList, *remoteActionsTimeout)
	cancel()
	if err != nil {
		return fmt.Errorf("RunBlpUntil on %v until %v failed: %v", topoproto.TabletAliasString(vsdw.shardInfo.MasterAlias), stopPositionList, err)
	}

	// 4 - wait until the destination tablet is equal or passed
	//     that master binlog position, and stop its replication.
	vsdw.wr.Logger().Infof("Waiting for destination tablet %v to catch up to %v", topoproto.TabletAliasString(vsdw.destinationAlias), masterPos)
	shortCtx, cancel = context.WithTimeout(ctx, *remoteActionsTimeout)
	destinationTablet, err := vsdw.wr.TopoServer().GetTablet(shortCtx, vsdw.destinationAlias)
	cancel()
	if err != nil {
		return err
	}
	shortCtx, cancel = context.WithTimeout(ctx, *remoteActionsTimeout)
	_, err = vsdw.wr.TabletManagerClient().StopSlaveMinimum(shortCtx, destinationTablet.Tablet, masterPos, *remoteActionsTimeout)
	cancel()
	if err != nil {
		return fmt.Errorf("StopSlaveMinimum on %v at %v failed: %v", topoproto.TabletAliasString(vsdw.destinationAlias), masterPos, err)
	}
	wrangler.RecordStartSlaveAction(vsdw.cleaner, destinationTablet.Tablet)

	// 5 - restart filtered replication on destination master
	vsdw.wr.Logger().Infof("Restarting filtered replication on master %v", topoproto.TabletAliasString(vsdw.shardInfo.MasterAlias))
	shortCtx, cancel = context.WithTimeout(ctx, *remoteActionsTimeout)
	err = vsdw.wr.TabletManagerClient().StartBlp(shortCtx, masterInfo.Tablet)
	if err := vsdw.cleaner.RemoveActionByName(wrangler.StartBlpActionName, topoproto.TabletAliasString(vsdw.shardInfo.MasterAlias)); err != nil {
		vsdw.wr.Logger().Warningf("Cannot find cleaning action %v/%v: %v", wrangler.StartBlpActionName, topoproto.TabletAliasString(vsdw.shardInfo.MasterAlias), err)
	}
	cancel()
	if err != nil {
		return fmt.Errorf("StartBlp on %v failed: %v", topoproto.TabletAliasString(vsdw.shardInfo.MasterAlias), err)
	}

	return nil
}

// diff phase: will create a list of messages regarding the diff.
// - get the schema on all tablets
// - if some table schema mismatches, record them (use existing schema diff tools).
// - for each table in destination, run a diff pipeline.

func (vsdw *VerticalSplitDiffWorker) diff(ctx context.Context) error {
	vsdw.SetState(WorkerStateDiff)

	vsdw.wr.Logger().Infof("Gathering schema information...")
	wg := sync.WaitGroup{}
	rec := &concurrency.AllErrorRecorder{}
	wg.Add(1)
	go func() {
		var err error
		shortCtx, cancel := context.WithTimeout(ctx, *remoteActionsTimeout)
		vsdw.destinationSchemaDefinition, err = vsdw.wr.GetSchema(
			shortCtx, vsdw.destinationAlias, vsdw.shardInfo.SourceShards[0].Tables, nil /* excludeTables */, false /* includeViews */)
		cancel()
		rec.RecordError(err)
		vsdw.wr.Logger().Infof("Got schema from destination %v", topoproto.TabletAliasString(vsdw.destinationAlias))
		wg.Done()
	}()
	wg.Add(1)
	go func() {
		var err error
		shortCtx, cancel := context.WithTimeout(ctx, *remoteActionsTimeout)
		vsdw.sourceSchemaDefinition, err = vsdw.wr.GetSchema(
			shortCtx, vsdw.sourceAlias, vsdw.shardInfo.SourceShards[0].Tables, nil /* excludeTables */, false /* includeViews */)
		cancel()
		rec.RecordError(err)
		vsdw.wr.Logger().Infof("Got schema from source %v", topoproto.TabletAliasString(vsdw.sourceAlias))
		wg.Done()
	}()
	wg.Wait()
	if rec.HasErrors() {
		return rec.Error()
	}

	// Check the schema
	vsdw.wr.Logger().Infof("Diffing the schema...")
	rec = &concurrency.AllErrorRecorder{}
	tmutils.DiffSchema("destination", vsdw.destinationSchemaDefinition, "source", vsdw.sourceSchemaDefinition, rec)
	if rec.HasErrors() {
		vsdw.wr.Logger().Warningf("Different schemas: %v", rec.Error())
	} else {
		vsdw.wr.Logger().Infof("Schema match, good.")
	}

	// run the diffs, 8 at a time
	vsdw.wr.Logger().Infof("Running the diffs...")
	sem := sync2.NewSemaphore(8, 0)
	for _, tableDefinition := range vsdw.destinationSchemaDefinition.TableDefinitions {
		wg.Add(1)
		go func(tableDefinition *tabletmanagerdatapb.TableDefinition) {
			defer wg.Done()
			sem.Acquire()
			defer sem.Release()

			vsdw.wr.Logger().Infof("Starting the diff on table %v", tableDefinition.Name)
			sourceQueryResultReader, err := TableScan(ctx, vsdw.wr.Logger(), vsdw.wr.TopoServer(), vsdw.sourceAlias, tableDefinition)
			if err != nil {
				newErr := fmt.Errorf("TableScan(source) failed: %v", err)
				rec.RecordError(newErr)
				vsdw.wr.Logger().Errorf("%v", newErr)
				return
			}
			defer sourceQueryResultReader.Close(ctx)

			destinationQueryResultReader, err := TableScan(ctx, vsdw.wr.Logger(), vsdw.wr.TopoServer(), vsdw.destinationAlias, tableDefinition)
			if err != nil {
				newErr := fmt.Errorf("TableScan(destination) failed: %v", err)
				rec.RecordError(newErr)
				vsdw.wr.Logger().Errorf("%v", newErr)
				return
			}
			defer destinationQueryResultReader.Close(ctx)

			differ, err := NewRowDiffer(sourceQueryResultReader, destinationQueryResultReader, tableDefinition)
			if err != nil {
				newErr := fmt.Errorf("NewRowDiffer() failed: %v", err)
				rec.RecordError(newErr)
				vsdw.wr.Logger().Errorf("%v", newErr)
				return
			}

			report, err := differ.Go(vsdw.wr.Logger())
			if err != nil {
				vsdw.wr.Logger().Errorf("Differ.Go failed: %v", err)
			} else {
				if report.HasDifferences() {
					err := fmt.Errorf("Table %v has differences: %v", tableDefinition.Name, report.String())
					rec.RecordError(err)
					vsdw.wr.Logger().Errorf("%v", err)
				} else {
					vsdw.wr.Logger().Infof("Table %v checks out (%v rows processed, %v qps)", tableDefinition.Name, report.processedRows, report.processingQPS)
				}
			}
		}(tableDefinition)
	}
	wg.Wait()

	return rec.Error()
}