Merge pull request #73 from github/throttle-critical

Throttling & critical load

build.sh

@@ -1,7 +1,7 @@
 #!/bin/bash
 #
 #
-RELEASE_VERSION="0.9.4"
+RELEASE_VERSION="0.9.5"
 
 buildpath=/tmp/gh-ost
 target=gh-ost

go/base/context.go

@@ -7,7 +7,6 @@ package base
 
 import (
 	"fmt"
-	"strconv"
 	"strings"
 	"sync"
 	"sync/atomic"
@@ -65,9 +64,10 @@ type MigrationContext struct {
 	ThrottleControlReplicaKeys          *mysql.InstanceKeyMap
 	ThrottleFlagFile                    string
 	ThrottleAdditionalFlagFile          string
+	ThrottleQuery                       string
 	ThrottleCommandedByUser             int64
-	maxLoad                             map[string]int64
+	maxLoad                             LoadMap
-	maxLoadMutex                        *sync.Mutex
+	criticalLoad                        LoadMap
 	PostponeCutOverFlagFile             string
 	SwapTablesTimeoutSeconds            int64
 	PanicFlagFile                       string
@@ -148,8 +148,8 @@ func newMigrationContext() *MigrationContext {
 		ApplierConnectionConfig:             mysql.NewConnectionConfig(),
 		MaxLagMillisecondsThrottleThreshold: 1000,
 		SwapTablesTimeoutSeconds:            3,
-		maxLoad:                             make(map[string]int64),
+		maxLoad:                             NewLoadMap(),
-		maxLoadMutex:                        &sync.Mutex{},
+		criticalLoad:                        NewLoadMap(),
 		throttleMutex:                       &sync.Mutex{},
 		ThrottleControlReplicaKeys:          mysql.NewInstanceKeyMap(),
 		configMutex:                         &sync.Mutex{},
@@ -278,46 +278,64 @@ func (this *MigrationContext) IsThrottled() (bool, string) {
 	return this.isThrottled, this.throttleReason
 }
 
-func (this *MigrationContext) GetMaxLoad() map[string]int64 {
+func (this *MigrationContext) GetThrottleQuery() string {
-	this.maxLoadMutex.Lock()
+	var query string
-	defer this.maxLoadMutex.Unlock()
 
-	tmpMaxLoadMap := make(map[string]int64)
+	this.throttleMutex.Lock()
-	for k, v := range this.maxLoad {
+	defer this.throttleMutex.Unlock()
-		tmpMaxLoadMap[k] = v
+
+	query = this.ThrottleQuery
+	return query
 }
-	return tmpMaxLoadMap
+
+func (this *MigrationContext) SetThrottleQuery(newQuery string) {
+	this.throttleMutex.Lock()
+	defer this.throttleMutex.Unlock()
+
+	this.ThrottleQuery = newQuery
+}
+
+func (this *MigrationContext) GetMaxLoad() LoadMap {
+	this.throttleMutex.Lock()
+	defer this.throttleMutex.Unlock()
+
+	return this.maxLoad.Duplicate()
+}
+
+func (this *MigrationContext) GetCriticalLoad() LoadMap {
+	this.throttleMutex.Lock()
+	defer this.throttleMutex.Unlock()
+
+	return this.criticalLoad.Duplicate()
 }
 
 // ReadMaxLoad parses the `--max-load` flag, which is in multiple key-value format,
 // such as: 'Threads_running=100,Threads_connected=500'
 // It only applies changes in case there's no parsing error.
 func (this *MigrationContext) ReadMaxLoad(maxLoadList string) error {
-	if maxLoadList == "" {
+	loadMap, err := ParseLoadMap(maxLoadList)
+	if err != nil {
+		return err
+	}
+	this.throttleMutex.Lock()
+	defer this.throttleMutex.Unlock()
+
+	this.maxLoad = loadMap
 	return nil
 }
-	this.maxLoadMutex.Lock()
-	defer this.maxLoadMutex.Unlock()
 
-	tmpMaxLoadMap := make(map[string]int64)
+// ReadMaxLoad parses the `--max-load` flag, which is in multiple key-value format,
+// such as: 'Threads_running=100,Threads_connected=500'
+// It only applies changes in case there's no parsing error.
+func (this *MigrationContext) ReadCriticalLoad(criticalLoadList string) error {
+	loadMap, err := ParseLoadMap(criticalLoadList)
+	if err != nil {
+		return err
+	}
+	this.throttleMutex.Lock()
+	defer this.throttleMutex.Unlock()
 
-	maxLoadConditions := strings.Split(maxLoadList, ",")
+	this.criticalLoad = loadMap
-	for _, maxLoadCondition := range maxLoadConditions {
-		maxLoadTokens := strings.Split(maxLoadCondition, "=")
-		if len(maxLoadTokens) != 2 {
-			return fmt.Errorf("Error parsing max-load condition: %s", maxLoadCondition)
-		}
-		if maxLoadTokens[0] == "" {
-			return fmt.Errorf("Error parsing status variable in max-load condition: %s", maxLoadCondition)
-		}
-		if n, err := strconv.ParseInt(maxLoadTokens[1], 10, 0); err != nil {
-			return fmt.Errorf("Error parsing numeric value in max-load condition: %s", maxLoadCondition)
-		} else {
-			tmpMaxLoadMap[maxLoadTokens[0]] = n
-		}
-	}
-
-	this.maxLoad = tmpMaxLoadMap
 	return nil
 }
 

go/base/load_map.go

@@ -0,0 +1,70 @@
+/*
+   Copyright 2016 GitHub Inc.
+	 See https://github.com/github/gh-ost/blob/master/LICENSE
+*/
+
+package base
+
+import (
+	"fmt"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+// LoadMap is a mapping of status variable & threshold
+// e.g. [Threads_connected: 100, Threads_running: 50]
+type LoadMap map[string]int64
+
+func NewLoadMap() LoadMap {
+	result := make(map[string]int64)
+	return result
+}
+
+// NewLoadMap parses a `--*-load` flag (e.g. `--max-load`), which is in multiple
+// key-value format, such as:
+//   'Threads_running=100,Threads_connected=500'
+func ParseLoadMap(loadList string) (LoadMap, error) {
+	result := NewLoadMap()
+	if loadList == "" {
+		return result, nil
+	}
+
+	loadConditions := strings.Split(loadList, ",")
+	for _, loadCondition := range loadConditions {
+		loadTokens := strings.Split(loadCondition, "=")
+		if len(loadTokens) != 2 {
+			return result, fmt.Errorf("Error parsing load condition: %s", loadCondition)
+		}
+		if loadTokens[0] == "" {
+			return result, fmt.Errorf("Error parsing status variable in load condition: %s", loadCondition)
+		}
+		if n, err := strconv.ParseInt(loadTokens[1], 10, 0); err != nil {
+			return result, fmt.Errorf("Error parsing numeric value in load condition: %s", loadCondition)
+		} else {
+			result[loadTokens[0]] = n
+		}
+	}
+
+	return result, nil
+}
+
+// Duplicate creates a clone of this map
+func (this *LoadMap) Duplicate() LoadMap {
+	dup := make(map[string]int64)
+	for k, v := range *this {
+		dup[k] = v
+	}
+	return dup
+}
+
+// String() returns a string representation of this map
+func (this *LoadMap) String() string {
+	tokens := []string{}
+	for key, val := range *this {
+		token := fmt.Sprintf("%s=%d", key, val)
+		tokens = append(tokens, token)
+	}
+	sort.Strings(tokens)
+	return strings.Join(tokens, ",")
+}

go/base/load_map_test.go

@@ -0,0 +1,58 @@
+/*
+   Copyright 2016 GitHub Inc.
+	 See https://github.com/github/gh-ost/blob/master/LICENSE
+*/
+
+package base
+
+import (
+	"testing"
+
+	"github.com/outbrain/golib/log"
+	test "github.com/outbrain/golib/tests"
+)
+
+func init() {
+	log.SetLevel(log.ERROR)
+}
+
+func TestParseLoadMap(t *testing.T) {
+	{
+		loadList := ""
+		m, err := ParseLoadMap(loadList)
+		test.S(t).ExpectNil(err)
+		test.S(t).ExpectEquals(len(m), 0)
+	}
+	{
+		loadList := "threads_running=20,threads_connected=10"
+		m, err := ParseLoadMap(loadList)
+		test.S(t).ExpectNil(err)
+		test.S(t).ExpectEquals(len(m), 2)
+		test.S(t).ExpectEquals(m["threads_running"], int64(20))
+		test.S(t).ExpectEquals(m["threads_connected"], int64(10))
+	}
+	{
+		loadList := "threads_running=20=30,threads_connected=10"
+		_, err := ParseLoadMap(loadList)
+		test.S(t).ExpectNotNil(err)
+	}
+	{
+		loadList := "threads_running=20,threads_connected"
+		_, err := ParseLoadMap(loadList)
+		test.S(t).ExpectNotNil(err)
+	}
+}
+
+func TestString(t *testing.T) {
+	{
+		m, _ := ParseLoadMap("")
+		s := m.String()
+		test.S(t).ExpectEquals(s, "")
+	}
+	{
+		loadList := "threads_running=20,threads_connected=10"
+		m, _ := ParseLoadMap(loadList)
+		s := m.String()
+		test.S(t).ExpectEquals(s, "threads_connected=10,threads_running=20")
+	}
+}

go/base/utils.go

@@ -33,10 +33,12 @@ func FileExists(fileName string) bool {
 	return false
 }
 
+// StringContainsAll returns true if `s` contains all non empty given `substrings`
+// The function returns `false` if no non-empty arguments are given.
 func StringContainsAll(s string, substrings ...string) bool {
 	nonEmptyStringsFound := false
 	for _, substring := range substrings {
-		if s == "" {
+		if substring == "" {
 			continue
 		}
 		if strings.Contains(s, substring) {

go/base/utils_test.go

@@ -0,0 +1,29 @@
+/*
+   Copyright 2016 GitHub Inc.
+	 See https://github.com/github/gh-ost/blob/master/LICENSE
+*/
+
+package base
+
+import (
+	"testing"
+
+	"github.com/outbrain/golib/log"
+	test "github.com/outbrain/golib/tests"
+)
+
+func init() {
+	log.SetLevel(log.ERROR)
+}
+
+func TestStringContainsAll(t *testing.T) {
+	s := `insert,delete,update`
+
+	test.S(t).ExpectFalse(StringContainsAll(s))
+	test.S(t).ExpectFalse(StringContainsAll(s, ""))
+	test.S(t).ExpectFalse(StringContainsAll(s, "drop"))
+	test.S(t).ExpectTrue(StringContainsAll(s, "insert"))
+	test.S(t).ExpectFalse(StringContainsAll(s, "insert", "drop"))
+	test.S(t).ExpectTrue(StringContainsAll(s, "insert", ""))
+	test.S(t).ExpectTrue(StringContainsAll(s, "insert", "update", "delete"))
+}

go/binlog/mysqlbinlog_reader.go

@@ -1,226 +0,0 @@
-/*
-   Copyright 2016 GitHub Inc.
-	 See https://github.com/github/gh-ost/blob/master/LICENSE
-*/
-
-package binlog
-
-import (
-	"bufio"
-	"bytes"
-	"fmt"
-	"path"
-	"regexp"
-	"strconv"
-	//	"strings"
-
-	"github.com/github/gh-ost/go/os"
-	"github.com/outbrain/golib/log"
-)
-
-var (
-	binlogChunkSizeBytes         uint64 = 32 * 1024 * 1024
-	startEntryRegexp                    = regexp.MustCompile("^# at ([0-9]+)$")
-	startEntryUnknownTableRegexp        = regexp.MustCompile("^### Row event for unknown table .*? at ([0-9]+)$")
-	endLogPosRegexp                     = regexp.MustCompile("^#[0-9]{6} .*? end_log_pos ([0-9]+)")
-	statementRegxp                      = regexp.MustCompile("### (INSERT INTO|UPDATE|DELETE FROM) `(.*?)`[.]`(.*?)`")
-	tokenRegxp                          = regexp.MustCompile("### (WHERE|SET)$")
-	positionalColumnRegexp              = regexp.MustCompile("###   @([0-9]+)=(.+)$")
-)
-
-// BinlogEntryState is a state in the binlog parser automaton / state machine
-type BinlogEntryState string
-
-// States of the state machine
-const (
-	InvalidState                      BinlogEntryState = "InvalidState"
-	SearchForStartPosOrStatementState                  = "SearchForStartPosOrStatementState"
-	ExpectEndLogPosState                               = "ExpectEndLogPosState"
-	ExpectTokenState                                   = "ExpectTokenState"
-	PositionalColumnAssignmentState                    = "PositionalColumnAssignmentState"
-)
-
-// MySQLBinlogReader reads binary log entries by executing the `mysqlbinlog`
-// process and textually parsing its output
-type MySQLBinlogReader struct {
-	Basedir           string
-	Datadir           string
-	MySQLBinlogBinary string
-}
-
-// NewMySQLBinlogReader creates a new reader that directly parses binlog files from the filesystem
-func NewMySQLBinlogReader(basedir string, datadir string) (mySQLBinlogReader *MySQLBinlogReader) {
-	mySQLBinlogReader = &MySQLBinlogReader{
-		Basedir: basedir,
-		Datadir: datadir,
-	}
-	mySQLBinlogReader.MySQLBinlogBinary = path.Join(mySQLBinlogReader.Basedir, "bin/mysqlbinlog")
-	return mySQLBinlogReader
-}
-
-// ReadEntries will read binlog entries from parsed text output of `mysqlbinlog` utility
-func (this *MySQLBinlogReader) ReadEntries(logFile string, startPos uint64, stopPos uint64) (entries [](*BinlogEntry), err error) {
-	if startPos == 0 {
-		startPos = 4
-	}
-	done := false
-	chunkStartPos := startPos
-	for !done {
-		chunkStopPos := chunkStartPos + binlogChunkSizeBytes
-		if chunkStopPos > stopPos && stopPos != 0 {
-			chunkStopPos = stopPos
-		}
-		log.Debugf("Next chunk range %d - %d", chunkStartPos, chunkStopPos)
-		binlogFilePath := path.Join(this.Datadir, logFile)
-		command := fmt.Sprintf(`%s --verbose --base64-output=DECODE-ROWS --start-position=%d --stop-position=%d %s`, this.MySQLBinlogBinary, chunkStartPos, chunkStopPos, binlogFilePath)
-		entriesBytes, err := os.RunCommandWithOutput(command)
-		if err != nil {
-			return entries, log.Errore(err)
-		}
-
-		chunkEntries, err := parseEntries(bufio.NewScanner(bytes.NewReader(entriesBytes)), logFile)
-		if err != nil {
-			return entries, log.Errore(err)
-		}
-
-		if len(chunkEntries) == 0 {
-			done = true
-		} else {
-			entries = append(entries, chunkEntries...)
-			lastChunkEntry := chunkEntries[len(chunkEntries)-1]
-			chunkStartPos = lastChunkEntry.EndLogPos
-		}
-	}
-	return entries, err
-}
-
-// automaton step: accept wither beginning of new entry, or beginning of new statement
-func searchForStartPosOrStatement(scanner *bufio.Scanner, binlogEntry *BinlogEntry, previousEndLogPos uint64) (nextState BinlogEntryState, nextBinlogEntry *BinlogEntry, err error) {
-	onStartEntry := func(submatch []string) (BinlogEntryState, *BinlogEntry, error) {
-		startLogPos, _ := strconv.ParseUint(submatch[1], 10, 64)
-
-		if previousEndLogPos != 0 && startLogPos != previousEndLogPos {
-			return InvalidState, binlogEntry, fmt.Errorf("Expected startLogPos %+v to equal previous endLogPos %+v", startLogPos, previousEndLogPos)
-		}
-		nextBinlogEntry = binlogEntry
-		if binlogEntry.Coordinates.LogPos != 0 && binlogEntry.DmlEvent != nil {
-			// Current entry is already a true entry, with startpos and with statement
-			nextBinlogEntry = NewBinlogEntry(binlogEntry.Coordinates.LogFile, startLogPos)
-		}
-		return ExpectEndLogPosState, nextBinlogEntry, nil
-	}
-
-	onStatementEntry := func(submatch []string) (BinlogEntryState, *BinlogEntry, error) {
-		nextBinlogEntry = binlogEntry
-		if binlogEntry.Coordinates.LogPos != 0 && binlogEntry.DmlEvent != nil {
-			// Current entry is already a true entry, with startpos and with statement
-			nextBinlogEntry = binlogEntry.Duplicate()
-		}
-		nextBinlogEntry.DmlEvent = NewBinlogDMLEvent(submatch[2], submatch[3], ToEventDML(submatch[1]))
-
-		return ExpectTokenState, nextBinlogEntry, nil
-	}
-
-	// Defuncting the following:
-
-	// onPositionalColumn := func(submatch []string) (BinlogEntryState, *BinlogEntry, error) {
-	// 	columnIndex, _ := strconv.ParseUint(submatch[1], 10, 64)
-	// 	if _, found := binlogEntry.PositionalColumns[columnIndex]; found {
-	// 		return InvalidState, binlogEntry, fmt.Errorf("Positional column %+v found more than once in %+v, statement=%+v", columnIndex, binlogEntry.LogPos, binlogEntry.DmlEvent.DML)
-	// 	}
-	// 	columnValue := submatch[2]
-	// 	columnValue = strings.TrimPrefix(columnValue, "'")
-	// 	columnValue = strings.TrimSuffix(columnValue, "'")
-	// 	binlogEntry.PositionalColumns[columnIndex] = columnValue
-	//
-	// 	return SearchForStartPosOrStatementState, binlogEntry, nil
-	// }
-
-	line := scanner.Text()
-	if submatch := startEntryRegexp.FindStringSubmatch(line); len(submatch) > 1 {
-		return onStartEntry(submatch)
-	}
-	if submatch := startEntryUnknownTableRegexp.FindStringSubmatch(line); len(submatch) > 1 {
-		return onStartEntry(submatch)
-	}
-	if submatch := statementRegxp.FindStringSubmatch(line); len(submatch) > 1 {
-		return onStatementEntry(submatch)
-	}
-	if submatch := positionalColumnRegexp.FindStringSubmatch(line); len(submatch) > 1 {
-		// Defuncting		return onPositionalColumn(submatch)
-	}
-	// Haven't found a match
-	return SearchForStartPosOrStatementState, binlogEntry, nil
-}
-
-// automaton step: expect an end_log_pos line`
-func expectEndLogPos(scanner *bufio.Scanner, binlogEntry *BinlogEntry) (nextState BinlogEntryState, err error) {
-	line := scanner.Text()
-
-	submatch := endLogPosRegexp.FindStringSubmatch(line)
-	if len(submatch) > 1 {
-		binlogEntry.EndLogPos, _ = strconv.ParseUint(submatch[1], 10, 64)
-		return SearchForStartPosOrStatementState, nil
-	}
-	return InvalidState, fmt.Errorf("Expected to find end_log_pos following pos %+v", binlogEntry.Coordinates.LogPos)
-}
-
-// automaton step: a not-strictly-required but good-to-have-around validation that
-// we see an expected token following a statement
-func expectToken(scanner *bufio.Scanner, binlogEntry *BinlogEntry) (nextState BinlogEntryState, err error) {
-	line := scanner.Text()
-	if submatch := tokenRegxp.FindStringSubmatch(line); len(submatch) > 1 {
-		return SearchForStartPosOrStatementState, nil
-	}
-	return InvalidState, fmt.Errorf("Expected to find token following pos %+v", binlogEntry.Coordinates.LogPos)
-}
-
-// parseEntries will parse output of `mysqlbinlog --verbose --base64-output=DECODE-ROWS`
-// It issues an automaton / state machine to do its thang.
-func parseEntries(scanner *bufio.Scanner, logFile string) (entries [](*BinlogEntry), err error) {
-	binlogEntry := NewBinlogEntry(logFile, 0)
-	var state BinlogEntryState = SearchForStartPosOrStatementState
-	var endLogPos uint64
-
-	appendBinlogEntry := func() {
-		if binlogEntry.Coordinates.LogPos == 0 {
-			return
-		}
-		if binlogEntry.DmlEvent == nil {
-			return
-		}
-		entries = append(entries, binlogEntry)
-		log.Debugf("entry: %+v", *binlogEntry)
-		fmt.Println(fmt.Sprintf("%s `%s`.`%s`", binlogEntry.DmlEvent.DML, binlogEntry.DmlEvent.DatabaseName, binlogEntry.DmlEvent.TableName))
-	}
-	for scanner.Scan() {
-		switch state {
-		case SearchForStartPosOrStatementState:
-			{
-				var nextBinlogEntry *BinlogEntry
-				state, nextBinlogEntry, err = searchForStartPosOrStatement(scanner, binlogEntry, endLogPos)
-				if nextBinlogEntry != binlogEntry {
-					appendBinlogEntry()
-					binlogEntry = nextBinlogEntry
-				}
-			}
-		case ExpectEndLogPosState:
-			{
-				state, err = expectEndLogPos(scanner, binlogEntry)
-			}
-		case ExpectTokenState:
-			{
-				state, err = expectToken(scanner, binlogEntry)
-			}
-		default:
-			{
-				err = fmt.Errorf("Unexpected state %+v", state)
-			}
-		}
-		if err != nil {
-			return entries, log.Errore(err)
-		}
-	}
-	appendBinlogEntry()
-	return entries, err
-}

go/binlog/mysqlbinlog_reader_test.go

@@ -1,50 +0,0 @@
-/*
-   Copyright 2016 GitHub Inc.
-	 See https://github.com/github/gh-ost/blob/master/LICENSE
-*/
-
-package binlog
-
-import (
-	"bufio"
-	"os"
-	"testing"
-
-	"github.com/outbrain/golib/log"
-	test "github.com/outbrain/golib/tests"
-)
-
-func init() {
-	log.SetLevel(log.ERROR)
-}
-
-func __TestRBRSample0(t *testing.T) {
-	testFile, err := os.Open("testdata/rbr-sample-0.txt")
-	test.S(t).ExpectNil(err)
-	defer testFile.Close()
-
-	scanner := bufio.NewScanner(testFile)
-	entries, err := parseEntries(scanner)
-	test.S(t).ExpectNil(err)
-
-	test.S(t).ExpectEquals(len(entries), 17)
-	test.S(t).ExpectEquals(entries[0].DatabaseName, "test")
-	test.S(t).ExpectEquals(entries[0].TableName, "samplet")
-	test.S(t).ExpectEquals(entries[0].StatementType, "INSERT")
-	test.S(t).ExpectEquals(entries[1].StatementType, "INSERT")
-	test.S(t).ExpectEquals(entries[2].StatementType, "INSERT")
-	test.S(t).ExpectEquals(entries[3].StatementType, "INSERT")
-	test.S(t).ExpectEquals(entries[4].StatementType, "INSERT")
-	test.S(t).ExpectEquals(entries[5].StatementType, "INSERT")
-	test.S(t).ExpectEquals(entries[6].StatementType, "UPDATE")
-	test.S(t).ExpectEquals(entries[7].StatementType, "DELETE")
-	test.S(t).ExpectEquals(entries[8].StatementType, "UPDATE")
-	test.S(t).ExpectEquals(entries[9].StatementType, "INSERT")
-	test.S(t).ExpectEquals(entries[10].StatementType, "INSERT")
-	test.S(t).ExpectEquals(entries[11].StatementType, "DELETE")
-	test.S(t).ExpectEquals(entries[12].StatementType, "DELETE")
-	test.S(t).ExpectEquals(entries[13].StatementType, "INSERT")
-	test.S(t).ExpectEquals(entries[14].StatementType, "UPDATE")
-	test.S(t).ExpectEquals(entries[15].StatementType, "DELETE")
-	test.S(t).ExpectEquals(entries[16].StatementType, "INSERT")
-}

go/cmd/gh-ost/main.go

@@ -73,6 +73,7 @@ func main() {
 	flag.Int64Var(&migrationContext.MaxLagMillisecondsThrottleThreshold, "max-lag-millis", 1500, "replication lag at which to throttle operation")
 	flag.StringVar(&migrationContext.ReplictionLagQuery, "replication-lag-query", "", "Query that detects replication lag in seconds. Result can be a floating point (by default gh-ost issues SHOW SLAVE STATUS and reads Seconds_behind_master). If you're using pt-heartbeat, query would be something like: SELECT ROUND(UNIX_TIMESTAMP() - MAX(UNIX_TIMESTAMP(ts))) AS delay FROM my_schema.heartbeat")
 	throttleControlReplicas := flag.String("throttle-control-replicas", "", "List of replicas on which to check for lag; comma delimited. Example: myhost1.com:3306,myhost2.com,myhost3.com:3307")
+	flag.StringVar(&migrationContext.ThrottleQuery, "throttle-query", "", "when given, issued (every second) to check if operation should throttle. Expecting to return zero for no-throttle, >0 for throttle. Query is issued on the migrated server. Make sure this query is lightweight")
 	flag.StringVar(&migrationContext.ThrottleFlagFile, "throttle-flag-file", "", "operation pauses when this file exists; hint: use a file that is specific to the table being altered")
 	flag.StringVar(&migrationContext.ThrottleAdditionalFlagFile, "throttle-additional-flag-file", "/tmp/gh-ost.throttle", "operation pauses when this file exists; hint: keep default, use for throttling multiple gh-ost operations")
 	flag.StringVar(&migrationContext.PostponeCutOverFlagFile, "postpone-cut-over-flag-file", "", "while this file exists, migration will postpone the final stage of swapping tables, and will keep on syncing the ghost table. Cut-over/swapping would be ready to perform the moment the file is deleted.")
@@ -81,7 +82,8 @@ func main() {
 	flag.StringVar(&migrationContext.ServeSocketFile, "serve-socket-file", "", "Unix socket file to serve on. Default: auto-determined and advertised upon startup")
 	flag.Int64Var(&migrationContext.ServeTCPPort, "serve-tcp-port", 0, "TCP port to serve on. Default: disabled")
 
-	maxLoad := flag.String("max-load", "", "Comma delimited status-name=threshold. e.g: 'Threads_running=100,Threads_connected=500'")
+	maxLoad := flag.String("max-load", "", "Comma delimited status-name=threshold. e.g: 'Threads_running=100,Threads_connected=500'. When status exceeds threshold, app throttles writes")
+	criticalLoad := flag.String("critical-load", "", "Comma delimited status-name=threshold, same format as `--max-load`. When status exceeds threshold, app panics and quits")
 	quiet := flag.Bool("quiet", false, "quiet")
 	verbose := flag.Bool("verbose", false, "verbose")
 	debug := flag.Bool("debug", false, "debug mode (very verbose)")
@@ -156,6 +158,9 @@ func main() {
 	if err := migrationContext.ReadMaxLoad(*maxLoad); err != nil {
 		log.Fatale(err)
 	}
+	if err := migrationContext.ReadCriticalLoad(*criticalLoad); err != nil {
+		log.Fatale(err)
+	}
 	if migrationContext.ServeSocketFile == "" {
 		migrationContext.ServeSocketFile = fmt.Sprintf("/tmp/gh-ost.%s.%s.sock", migrationContext.DatabaseName, migrationContext.OriginalTableName)
 	}

go/logic/applier.go

@@ -263,6 +263,19 @@ func (this *Applier) InitiateHeartbeat(heartbeatIntervalMilliseconds int64) {
 	}
 }
 
+func (this *Applier) ExecuteThrottleQuery() (int64, error) {
+	throttleQuery := this.migrationContext.GetThrottleQuery()
+
+	if throttleQuery == "" {
+		return 0, nil
+	}
+	var result int64
+	if err := this.db.QueryRow(throttleQuery).Scan(&result); err != nil {
+		return 0, log.Errore(err)
+	}
+	return result, nil
+}
+
 // ReadMigrationMinValues
 func (this *Applier) ReadMigrationMinValues(uniqueKey *sql.UniqueKey) error {
 	log.Debugf("Reading migration range according to key: %s", uniqueKey.Name)

go/logic/migrator.go

@@ -40,6 +40,14 @@ const (
 	heartbeatIntervalMilliseconds = 1000
 )
 
+type PrintStatusRule int
+
+const (
+	HeuristicPrintStatusRule PrintStatusRule = iota
+	ForcePrintStatusRule                     = iota
+	ForcePrintStatusAndHint                  = iota
+)
+
 // Migrator is the main schema migration flow manager.
 type Migrator struct {
 	parser           *sql.Parser
@@ -106,6 +114,17 @@ func (this *Migrator) shouldThrottle() (result bool, reason string) {
 			this.panicAbort <- fmt.Errorf("Found panic-file %s. Aborting without cleanup", this.migrationContext.PanicFlagFile)
 		}
 	}
+	criticalLoad := this.migrationContext.GetCriticalLoad()
+	for variableName, threshold := range criticalLoad {
+		value, err := this.applier.ShowStatusVariable(variableName)
+		if err != nil {
+			return true, fmt.Sprintf("%s %s", variableName, err)
+		}
+		if value >= threshold {
+			this.panicAbort <- fmt.Errorf("critical-load met: %s=%d, >=%d", variableName, value, threshold)
+		}
+	}
+
 	// Back to throttle considerations
 
 	// User-based throttle
@@ -145,8 +164,13 @@ func (this *Migrator) shouldThrottle() (result bool, reason string) {
 		if err != nil {
 			return true, fmt.Sprintf("%s %s", variableName, err)
 		}
-		if value > threshold {
+		if value >= threshold {
-			return true, fmt.Sprintf("%s=%d", variableName, value)
+			return true, fmt.Sprintf("max-load %s=%d >= %d", variableName, value, threshold)
+		}
+	}
+	if this.migrationContext.GetThrottleQuery() != "" {
+		if res, _ := this.applier.ExecuteThrottleQuery(); res > 0 {
+			return true, "throttle-query"
 		}
 	}
 
@@ -311,6 +335,7 @@ func (this *Migrator) validateStatement() (err error) {
 		if !this.migrationContext.ApproveRenamedColumns {
 			return fmt.Errorf("Alter statement has column(s) renamed. gh-ost suspects the following renames: %v; but to proceed you must approve via `--approve-renamed-columns` (or you can skip renamed columns via `--skip-renamed-columns`)", this.parser.GetNonTrivialRenames())
 		}
+		log.Infof("Alter statement has column(s) renamed. gh-ost finds the following renames: %v; --approve-renamed-columns is given and so migration proceeds.", this.parser.GetNonTrivialRenames())
 	}
 	return nil
 }
@@ -375,7 +400,7 @@ func (this *Migrator) Migrate() (err error) {
 	log.Debugf("Operating until row copy is complete")
 	this.consumeRowCopyComplete()
 	log.Infof("Row copy complete")
-	this.printStatus()
+	this.printStatus(ForcePrintStatusRule)
 
 	if err := this.cutOver(); err != nil {
 		return err
@@ -459,8 +484,7 @@ func (this *Migrator) waitForEventsUpToLock() (err error) {
 	waitForEventsUpToLockDuration := time.Now().Sub(waitForEventsUpToLockStartTime)
 
 	log.Infof("Done waiting for events up to lock; duration=%+v", waitForEventsUpToLockDuration)
-	this.printMigrationStatusHint()
+	this.printStatus(ForcePrintStatusAndHint)
-	this.printStatus()
 
 	return nil
 }
@@ -623,15 +647,16 @@ func (this *Migrator) onServerCommand(command string, writer *bufio.Writer) (err
 			fmt.Fprintln(writer, `available commands:
 status                 # Print a status message
 chunk-size=<newsize>   # Set a new chunk-size
-  max-load=<maxload>   # Set a new set of max-load thresholds
+critical-load=<load>   # Set a new set of max-load thresholds
+max-load=<load>        # Set a new set of max-load thresholds
+throttle-query=<query> # Set a new throttle-query
 throttle               # Force throttling
 no-throttle            # End forced throttling (other throttling may still apply)
 help                   # This message
 `)
 		}
 	case "info", "status":
-		this.printMigrationStatusHint(writer)
+		this.printStatus(ForcePrintStatusAndHint, writer)
-		this.printStatus(writer)
 	case "chunk-size":
 		{
 			if chunkSize, err := strconv.Atoi(arg); err != nil {
@@ -639,7 +664,7 @@ func (this *Migrator) onServerCommand(command string, writer *bufio.Writer) (err
 				return log.Errore(err)
 			} else {
 				this.migrationContext.SetChunkSize(int64(chunkSize))
-				this.printMigrationStatusHint(writer)
+				this.printStatus(ForcePrintStatusAndHint, writer)
 			}
 		}
 	case "max-load":
@@ -648,7 +673,20 @@ func (this *Migrator) onServerCommand(command string, writer *bufio.Writer) (err
 				fmt.Fprintf(writer, "%s\n", err.Error())
 				return log.Errore(err)
 			}
-			this.printMigrationStatusHint(writer)
+			this.printStatus(ForcePrintStatusAndHint, writer)
+		}
+	case "critical-load":
+		{
+			if err := this.migrationContext.ReadCriticalLoad(arg); err != nil {
+				fmt.Fprintf(writer, "%s\n", err.Error())
+				return log.Errore(err)
+			}
+			this.printStatus(ForcePrintStatusAndHint, writer)
+		}
+	case "throttle-query":
+		{
+			this.migrationContext.SetThrottleQuery(arg)
+			this.printStatus(ForcePrintStatusAndHint, writer)
 		}
 	case "throttle", "pause", "suspend":
 		{
@@ -715,17 +753,16 @@ func (this *Migrator) initiateInspector() (err error) {
 }
 
 func (this *Migrator) initiateStatus() error {
-	this.printStatus()
+	this.printStatus(ForcePrintStatusAndHint)
 	statusTick := time.Tick(1 * time.Second)
 	for range statusTick {
-		go this.printStatus()
+		go this.printStatus(HeuristicPrintStatusRule)
 	}
 
 	return nil
 }
 
 func (this *Migrator) printMigrationStatusHint(writers ...io.Writer) {
-	writers = append(writers, os.Stdout)
 	w := io.MultiWriter(writers...)
 	fmt.Fprintln(w, fmt.Sprintf("# Migrating %s.%s; Ghost table is %s.%s",
 		sql.EscapeName(this.migrationContext.DatabaseName),
@@ -737,10 +774,12 @@ func (this *Migrator) printMigrationStatusHint(writers ...io.Writer) {
 		this.migrationContext.StartTime.Format(time.RubyDate),
 	))
 	maxLoad := this.migrationContext.GetMaxLoad()
-	fmt.Fprintln(w, fmt.Sprintf("# chunk-size: %+v; max lag: %+vms; max-load: %+v",
+	criticalLoad := this.migrationContext.GetCriticalLoad()
+	fmt.Fprintln(w, fmt.Sprintf("# chunk-size: %+v; max lag: %+vms; max-load: %s; critical-load: %s",
 		atomic.LoadInt64(&this.migrationContext.ChunkSize),
 		atomic.LoadInt64(&this.migrationContext.MaxLagMillisecondsThrottleThreshold),
-		maxLoad,
+		maxLoad.String(),
+		criticalLoad.String(),
 	))
 	if this.migrationContext.ThrottleFlagFile != "" {
 		fmt.Fprintln(w, fmt.Sprintf("# Throttle flag file: %+v",
@@ -752,6 +791,11 @@ func (this *Migrator) printMigrationStatusHint(writers ...io.Writer) {
 			this.migrationContext.ThrottleAdditionalFlagFile,
 		))
 	}
+	if throttleQuery := this.migrationContext.GetThrottleQuery(); throttleQuery != "" {
+		fmt.Fprintln(w, fmt.Sprintf("# Throttle query: %+v",
+			throttleQuery,
+		))
+	}
 	if this.migrationContext.PostponeCutOverFlagFile != "" {
 		fmt.Fprintln(w, fmt.Sprintf("# Postpone cut-over flag file: %+v",
 			this.migrationContext.PostponeCutOverFlagFile,
@@ -770,7 +814,9 @@ func (this *Migrator) printMigrationStatusHint(writers ...io.Writer) {
 	}
 }
 
-func (this *Migrator) printStatus(writers ...io.Writer) {
+func (this *Migrator) printStatus(rule PrintStatusRule, writers ...io.Writer) {
+	writers = append(writers, os.Stdout)
+
 	elapsedTime := this.migrationContext.ElapsedTime()
 	elapsedSeconds := int64(elapsedTime.Seconds())
 	totalRowsCopied := this.migrationContext.GetTotalRowsCopied()
@@ -782,8 +828,11 @@ func (this *Migrator) printStatus(writers ...io.Writer) {
 
 	// Before status, let's see if we should print a nice reminder for what exactly we're doing here.
 	shouldPrintMigrationStatusHint := (elapsedSeconds%600 == 0)
+	if rule == ForcePrintStatusAndHint {
+		shouldPrintMigrationStatusHint = true
+	}
 	if shouldPrintMigrationStatusHint {
-		this.printMigrationStatusHint()
+		this.printMigrationStatusHint(writers...)
 	}
 
 	var etaSeconds float64 = math.MaxFloat64
@@ -820,6 +869,9 @@ func (this *Migrator) printStatus(writers ...io.Writer) {
 	} else {
 		shouldPrintStatus = (elapsedSeconds%30 == 0)
 	}
+	if rule == ForcePrintStatusRule || rule == ForcePrintStatusAndHint {
+		shouldPrintStatus = true
+	}
 	if !shouldPrintStatus {
 		return
 	}
@@ -838,7 +890,6 @@ func (this *Migrator) printStatus(writers ...io.Writer) {
 		fmt.Sprintf("copy iteration %d at %d", this.migrationContext.GetIteration(), time.Now().Unix()),
 		status,
 	)
-	writers = append(writers, os.Stdout)
 	w := io.MultiWriter(writers...)
 	fmt.Fprintln(w, status)
 }

go/mysql/binlog_test.go

@@ -3,7 +3,7 @@
 	 See https://github.com/github/gh-ost/blob/master/LICENSE
 */
 
-package binlog
+package mysql
 
 import (
 	"testing"

go/sql/parser.go

@@ -11,7 +11,7 @@ import (
 )
 
 var (
-	renameColumnRegexp = regexp.MustCompile(`(?i)CHANGE\s+(column\s+|)([\S]+)\s+([\S]+)\s+`)
+	renameColumnRegexp = regexp.MustCompile(`(?i)change\s+(column\s+|)([\S]+)\s+([\S]+)\s+`)
 )
 
 type Parser struct {
@@ -27,8 +27,12 @@ func NewParser() *Parser {
 func (this *Parser) ParseAlterStatement(alterStatement string) (err error) {
 	allStringSubmatch := renameColumnRegexp.FindAllStringSubmatch(alterStatement, -1)
 	for _, submatch := range allStringSubmatch {
-		submatch[2], _ = strconv.Unquote(submatch[2])
+		if unquoted, err := strconv.Unquote(submatch[2]); err == nil {
-		submatch[3], _ = strconv.Unquote(submatch[3])
+			submatch[2] = unquoted
+		}
+		if unquoted, err := strconv.Unquote(submatch[3]); err == nil {
+			submatch[3] = unquoted
+		}
 
 		this.columnRenameMap[submatch[2]] = submatch[3]
 	}

go/sql/parser_test.go

@@ -0,0 +1,68 @@
+/*
+   Copyright 2016 GitHub Inc.
+	 See https://github.com/github/gh-ost/blob/master/LICENSE
+*/
+
+package sql
+
+import (
+	"testing"
+
+	"github.com/outbrain/golib/log"
+	test "github.com/outbrain/golib/tests"
+)
+
+func init() {
+	log.SetLevel(log.ERROR)
+}
+
+func TestParseAlterStatement(t *testing.T) {
+	statement := "add column t int, engine=innodb"
+	parser := NewParser()
+	err := parser.ParseAlterStatement(statement)
+	test.S(t).ExpectNil(err)
+	test.S(t).ExpectFalse(parser.HasNonTrivialRenames())
+}
+
+func TestParseAlterStatementTrivialRename(t *testing.T) {
+	statement := "add column t int, change ts ts timestamp, engine=innodb"
+	parser := NewParser()
+	err := parser.ParseAlterStatement(statement)
+	test.S(t).ExpectNil(err)
+	test.S(t).ExpectFalse(parser.HasNonTrivialRenames())
+	test.S(t).ExpectEquals(len(parser.columnRenameMap), 1)
+	test.S(t).ExpectEquals(parser.columnRenameMap["ts"], "ts")
+}
+
+func TestParseAlterStatementTrivialRenames(t *testing.T) {
+	statement := "add column t int, change ts ts timestamp, CHANGE f `f` float, engine=innodb"
+	parser := NewParser()
+	err := parser.ParseAlterStatement(statement)
+	test.S(t).ExpectNil(err)
+	test.S(t).ExpectFalse(parser.HasNonTrivialRenames())
+	test.S(t).ExpectEquals(len(parser.columnRenameMap), 2)
+	test.S(t).ExpectEquals(parser.columnRenameMap["ts"], "ts")
+	test.S(t).ExpectEquals(parser.columnRenameMap["f"], "f")
+}
+
+func TestParseAlterStatementNonTrivial(t *testing.T) {
+	statements := []string{
+		`add column b bigint, change f fl float, change i count int, engine=innodb`,
+		"add column b bigint, change column `f` fl float, change `i` `count` int, engine=innodb",
+		"add column b bigint, change column `f` fl float, change `i` `count` int, change ts ts timestamp, engine=innodb",
+		`change
+		  f fl float,
+			CHANGE COLUMN i
+			  count int, engine=innodb`,
+	}
+
+	for _, statement := range statements {
+		parser := NewParser()
+		err := parser.ParseAlterStatement(statement)
+		test.S(t).ExpectNil(err)
+		renames := parser.GetNonTrivialRenames()
+		test.S(t).ExpectEquals(len(renames), 2)
+		test.S(t).ExpectEquals(renames["i"], "count")
+		test.S(t).ExpectEquals(renames["f"], "fl")
+	}
+}