From cdf393a30e4f019fa69766eaa075ad32ce7050fc Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Fri, 19 Aug 2016 14:52:49 +0200
Subject: [PATCH 01/20] initial support for hooks

---
 go/logic/hooks.go    | 87 ++++++++++++++++++++++++++++++++++++++++++++
 go/logic/migrator.go | 45 ++++++++++++++++++++++-
 2 files changed, 130 insertions(+), 2 deletions(-)
 create mode 100644 go/logic/hooks.go

diff --git a/go/logic/hooks.go b/go/logic/hooks.go
new file mode 100644
index 0000000..2d71dc7
--- /dev/null
+++ b/go/logic/hooks.go
@@ -0,0 +1,87 @@
+/*
+   Copyright 2016 GitHub Inc.
+	 See https://github.com/github/gh-ost/blob/master/LICENSE
+*/
+
+package logic
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+
+	"github.com/github/gh-ost/go/base"
+	"github.com/openark/golib/log"
+)
+
+type HooksExecutor struct {
+	migrationContext *base.MigrationContext
+}
+
+func NewHooksExecutor() *HooksExecutor {
+	return &HooksExecutor{
+		migrationContext: base.GetMigrationContext(),
+	}
+}
+
+func (this *HooksExecutor) detectHooks() error {
+	return nil
+}
+
+func (this *HooksExecutor) applyEnvironmentVairables() []string {
+	env := os.Environ()
+	env = append(env, fmt.Sprintf("GH_OST_DATABASE_NAME=%s", this.migrationContext.DatabaseName))
+	env = append(env, fmt.Sprintf("GH_OST_TABLE_NAME=%s", this.migrationContext.OriginalTableName))
+	env = append(env, fmt.Sprintf("GH_OST_GHOST_TABLE_NAME=%s", this.migrationContext.GetGhostTableName()))
+	env = append(env, fmt.Sprintf("GH_OST_OLD_TABLE_NAME=%s", this.migrationContext.GetOldTableName()))
+	env = append(env, fmt.Sprintf("GH_OST_DDL=%s", this.migrationContext.AlterStatement))
+	env = append(env, fmt.Sprintf("GH_OST_ELAPSED_SECONDS=%f", this.migrationContext.ElapsedTime().Seconds()))
+	return env
+}
+
+// commandRun executes a command with arguments, and set relevant environment variables
+func (this *HooksExecutor) commandRun(commandText string, arguments ...string) error {
+	cmd := exec.Command(commandText, arguments...)
+	cmd.Env = this.applyEnvironmentVairables()
+
+	if err := cmd.Run(); err != nil {
+		return log.Errore(err)
+	}
+	return nil
+}
+
+func (this *HooksExecutor) onStartup() error {
+	return nil
+}
+
+func (this *HooksExecutor) onValidated() error {
+	return nil
+}
+
+func (this *HooksExecutor) onAboutToRowCopy() error {
+	return nil
+}
+
+func (this *HooksExecutor) onRowCopyComplete() error {
+	return nil
+}
+
+func (this *HooksExecutor) onBeginPostponed() error {
+	return nil
+}
+
+func (this *HooksExecutor) onAboutToCutOver() error {
+	return nil
+}
+
+func (this *HooksExecutor) onInteractiveCommand(command string) error {
+	return nil
+}
+
+func (this *HooksExecutor) onSuccess() error {
+	return nil
+}
+
+func (this *HooksExecutor) onFailure() error {
+	return nil
+}
diff --git a/go/logic/migrator.go b/go/logic/migrator.go
index 600381e..2850e91 100644
--- a/go/logic/migrator.go
+++ b/go/logic/migrator.go
@@ -56,6 +56,7 @@ type Migrator struct {
 	applier          *Applier
 	eventsStreamer   *EventsStreamer
 	server           *Server
+	hooksExecutor    *HooksExecutor
 	migrationContext *base.MigrationContext
 	hostname         string
 
@@ -110,6 +111,15 @@ func (this *Migrator) acceptSignals() {
 	}()
 }
 
+// initiateHooksExecutor
+func (this *Migrator) initiateHooksExecutor() (err error) {
+	this.hooksExecutor = NewHooksExecutor()
+	if err := this.hooksExecutor.detectHooks(); err != nil {
+		return err
+	}
+	return nil
+}
+
 // shouldThrottle performs checks to see whether we should currently be throttling.
 // It also checks for critical-load and panic aborts.
 func (this *Migrator) shouldThrottle() (result bool, reason string) {
@@ -277,7 +287,7 @@ func (this *Migrator) executeAndThrottleOnError(operation func() error) (err err
 }
 
 // consumeRowCopyComplete blocks on the rowCopyComplete channel once, and then
-// consumers and drops any further incoming events that may be left hanging.
+// consumes and drops any further incoming events that may be left hanging.
 func (this *Migrator) consumeRowCopyComplete() {
 	<-this.rowCopyComplete
 	atomic.StoreInt64(&this.rowCopyCompleteFlag, 1)
@@ -371,6 +381,12 @@ func (this *Migrator) Migrate() (err error) {
 
 	go this.listenOnPanicAbort()
 
+	if err := this.initiateHooksExecutor(); err != nil {
+		return err
+	}
+	if err := this.hooksExecutor.onStartup(); err != nil {
+		return err
+	}
 	if err := this.parser.ParseAlterStatement(this.migrationContext.AlterStatement); err != nil {
 		return err
 	}
@@ -397,6 +413,11 @@ func (this *Migrator) Migrate() (err error) {
 	if err := this.inspector.InspectOriginalAndGhostTables(); err != nil {
 		return err
 	}
+	// Validation complete! We're good to execute this migration
+	if err := this.hooksExecutor.onValidated(); err != nil {
+		return err
+	}
+
 	if err := this.initiateServer(); err != nil {
 		return err
 	}
@@ -419,6 +440,9 @@ func (this *Migrator) Migrate() (err error) {
 		return err
 	}
 	go this.initiateThrottler()
+	if err := this.hooksExecutor.onAboutToRowCopy(); err != nil {
+		return err
+	}
 	go this.executeWriteFuncs()
 	go this.iterateChunks()
 	this.migrationContext.MarkRowCopyStartTime()
@@ -427,8 +451,14 @@ func (this *Migrator) Migrate() (err error) {
 	log.Debugf("Operating until row copy is complete")
 	this.consumeRowCopyComplete()
 	log.Infof("Row copy complete")
+	if err := this.hooksExecutor.onRowCopyComplete(); err != nil {
+		return err
+	}
 	this.printStatus(ForcePrintStatusRule)
 
+	if err := this.hooksExecutor.onAboutToCutOver(); err != nil {
+		return err
+	}
 	if err := this.cutOver(); err != nil {
 		return err
 	}
@@ -436,6 +466,9 @@ func (this *Migrator) Migrate() (err error) {
 	if err := this.finalCleanup(); err != nil {
 		return nil
 	}
+	if err := this.hooksExecutor.onSuccess(); err != nil {
+		return err
+	}
 	log.Infof("Done migrating %s.%s", sql.EscapeName(this.migrationContext.DatabaseName), sql.EscapeName(this.migrationContext.OriginalTableName))
 	return nil
 }
@@ -463,8 +496,12 @@ func (this *Migrator) cutOver() (err error) {
 			}
 			if base.FileExists(this.migrationContext.PostponeCutOverFlagFile) {
 				// Throttle file defined and exists!
+				if atomic.LoadInt64(&this.migrationContext.IsPostponingCutOver) == 0 {
+					if err := this.hooksExecutor.onBeginPostponed(); err != nil {
+						return true, err
+					}
+				}
 				atomic.StoreInt64(&this.migrationContext.IsPostponingCutOver, 1)
-				//log.Debugf("Postponing final table swap as flag file exists: %+v", this.migrationContext.PostponeCutOverFlagFile)
 				return true, nil
 			}
 			return false, nil
@@ -659,6 +696,10 @@ func (this *Migrator) onServerCommand(command string, writer *bufio.Writer) (err
 
 	throttleHint := "# Note: you may only throttle for as long as your binary logs are not purged\n"
 
+	if err := this.hooksExecutor.onInteractiveCommand(command); err != nil {
+		return err
+	}
+
 	switch command {
 	case "help":
 		{

From 6acbe7e3ae34b8510299b4e55da5705d4fbf95e2 Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Sat, 20 Aug 2016 08:24:20 +0200
Subject: [PATCH 02/20] detecting and executing hooks

---
 go/base/context.go   |  1 +
 go/logic/hooks.go    | 31 +++++++++++++++++++++++++++----
 go/logic/migrator.go |  2 +-
 3 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/go/base/context.go b/go/base/context.go
index ea5ab68..78a7a41 100644
--- a/go/base/context.go
+++ b/go/base/context.go
@@ -78,6 +78,7 @@ type MigrationContext struct {
 	PostponeCutOverFlagFile             string
 	CutOverLockTimeoutSeconds           int64
 	PanicFlagFile                       string
+	HooksPath                           string
 
 	DropServeSocket bool
 	ServeSocketFile string
diff --git a/go/logic/hooks.go b/go/logic/hooks.go
index 2d71dc7..c6c5981 100644
--- a/go/logic/hooks.go
+++ b/go/logic/hooks.go
@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"os"
 	"os/exec"
+	"path/filepath"
 
 	"github.com/github/gh-ost/go/base"
 	"github.com/openark/golib/log"
@@ -24,7 +25,7 @@ func NewHooksExecutor() *HooksExecutor {
 	}
 }
 
-func (this *HooksExecutor) detectHooks() error {
+func (this *HooksExecutor) initHooks() error {
 	return nil
 }
 
@@ -39,9 +40,9 @@ func (this *HooksExecutor) applyEnvironmentVairables() []string {
 	return env
 }
 
-// commandRun executes a command with arguments, and set relevant environment variables
-func (this *HooksExecutor) commandRun(commandText string, arguments ...string) error {
-	cmd := exec.Command(commandText, arguments...)
+// executeHook executes a command with arguments, and set relevant environment variables
+func (this *HooksExecutor) executeHook(hook string, arguments ...string) error {
+	cmd := exec.Command(hook, arguments...)
 	cmd.Env = this.applyEnvironmentVairables()
 
 	if err := cmd.Run(); err != nil {
@@ -50,6 +51,28 @@ func (this *HooksExecutor) commandRun(commandText string, arguments ...string) e
 	return nil
 }
 
+func (this *HooksExecutor) detectHooks(baseName string) (hooks []string, err error) {
+	if this.migrationContext.HooksPath == "" {
+		return hooks, err
+	}
+	pattern := fmt.Sprintf("%s/%s*", this.migrationContext.HooksPath, baseName)
+	hooks, err = filepath.Glob(pattern)
+	return hooks, err
+}
+
+func (this *HooksExecutor) executeHooks(baseName string) error {
+	hooks, err := this.detectHooks(baseName)
+	if err != nil {
+		return err
+	}
+	for _, hook := range hooks {
+		if err := this.executeHook(hook); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 func (this *HooksExecutor) onStartup() error {
 	return nil
 }
diff --git a/go/logic/migrator.go b/go/logic/migrator.go
index 2850e91..efad40a 100644
--- a/go/logic/migrator.go
+++ b/go/logic/migrator.go
@@ -114,7 +114,7 @@ func (this *Migrator) acceptSignals() {
 // initiateHooksExecutor
 func (this *Migrator) initiateHooksExecutor() (err error) {
 	this.hooksExecutor = NewHooksExecutor()
-	if err := this.hooksExecutor.detectHooks(); err != nil {
+	if err := this.hooksExecutor.initHooks(); err != nil {
 		return err
 	}
 	return nil

From 972728cf40f468f9dbb646cbf0a3ba21fc4a720c Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Mon, 22 Aug 2016 16:24:41 +0200
Subject: [PATCH 03/20] added onStatus hook

---
 go/logic/hooks.go    | 4 ++++
 go/logic/migrator.go | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/go/logic/hooks.go b/go/logic/hooks.go
index c6c5981..58c1403 100644
--- a/go/logic/hooks.go
+++ b/go/logic/hooks.go
@@ -108,3 +108,7 @@ func (this *HooksExecutor) onSuccess() error {
 func (this *HooksExecutor) onFailure() error {
 	return nil
 }
+
+func (this *HooksExecutor) onStatus(statusMessage string) error {
+	return nil
+}
diff --git a/go/logic/migrator.go b/go/logic/migrator.go
index efad40a..9d1ba6a 100644
--- a/go/logic/migrator.go
+++ b/go/logic/migrator.go
@@ -1065,6 +1065,10 @@ func (this *Migrator) printStatus(rule PrintStatusRule, writers ...io.Writer) {
 	)
 	w := io.MultiWriter(writers...)
 	fmt.Fprintln(w, status)
+
+	if elapsedSeconds%60 == 0 {
+		this.hooksExecutor.onStatus(status)
+	}
 }
 
 // initiateHeartbeatListener listens for heartbeat events. gh-ost implements its own

From 1c2a77ef95f2b2874afb474ed14b03230bccb050 Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Tue, 23 Aug 2016 11:35:48 +0200
Subject: [PATCH 04/20] hook names; added on-stop-replication hook

---
 go/base/context.go    |  1 +
 go/cmd/gh-ost/main.go |  1 +
 go/logic/hooks.go     | 61 +++++++++++++++++++++++++++++++------------
 go/logic/migrator.go  | 12 ++++++---
 4 files changed, 55 insertions(+), 20 deletions(-)

diff --git a/go/base/context.go b/go/base/context.go
index 78a7a41..438490b 100644
--- a/go/base/context.go
+++ b/go/base/context.go
@@ -92,6 +92,7 @@ type MigrationContext struct {
 	InitiallyDropGhostTable bool
 	CutOverType             CutOver
 
+	Hostname                  string
 	TableEngine               string
 	RowsEstimate              int64
 	UsedRowsEstimateMethod    RowsEstimateMethod
diff --git a/go/cmd/gh-ost/main.go b/go/cmd/gh-ost/main.go
index b614831..501d04b 100644
--- a/go/cmd/gh-ost/main.go
+++ b/go/cmd/gh-ost/main.go
@@ -189,6 +189,7 @@ func main() {
 	migrator := logic.NewMigrator()
 	err := migrator.Migrate()
 	if err != nil {
+		migrator.ExecOnFailureHook()
 		log.Fatale(err)
 	}
 	log.Info("Done")
diff --git a/go/logic/hooks.go b/go/logic/hooks.go
index 58c1403..1c562ef 100644
--- a/go/logic/hooks.go
+++ b/go/logic/hooks.go
@@ -15,6 +15,20 @@ import (
 	"github.com/openark/golib/log"
 )
 
+const (
+	onStartup            = "gh-ost-on-startup"
+	onValidated          = "gh-ost-on-validated"
+	onAboutToRowCopy     = "gh-ost-on-about-row-copy"
+	onRowCopyComplete    = "gh-ost-on-row-copy-complete"
+	onBeginPostponed     = "gh-ost-on-begin-postponed"
+	onAboutToCutOver     = "gh-ost-on-about-cut-over"
+	onInteractiveCommand = "gh-ost-on-interactive-command"
+	onSuccess            = "gh-ost-on-success"
+	onFailure            = "gh-ost-on-failure"
+	onStatus             = "gh-ost-on-status"
+	onStopReplication    = "gh-ost-on-stop-replication"
+)
+
 type HooksExecutor struct {
 	migrationContext *base.MigrationContext
 }
@@ -29,7 +43,7 @@ func (this *HooksExecutor) initHooks() error {
 	return nil
 }
 
-func (this *HooksExecutor) applyEnvironmentVairables() []string {
+func (this *HooksExecutor) applyEnvironmentVairables(extraVariables ...string) []string {
 	env := os.Environ()
 	env = append(env, fmt.Sprintf("GH_OST_DATABASE_NAME=%s", this.migrationContext.DatabaseName))
 	env = append(env, fmt.Sprintf("GH_OST_TABLE_NAME=%s", this.migrationContext.OriginalTableName))
@@ -37,13 +51,20 @@ func (this *HooksExecutor) applyEnvironmentVairables() []string {
 	env = append(env, fmt.Sprintf("GH_OST_OLD_TABLE_NAME=%s", this.migrationContext.GetOldTableName()))
 	env = append(env, fmt.Sprintf("GH_OST_DDL=%s", this.migrationContext.AlterStatement))
 	env = append(env, fmt.Sprintf("GH_OST_ELAPSED_SECONDS=%f", this.migrationContext.ElapsedTime().Seconds()))
+	env = append(env, fmt.Sprintf("GH_OST_MIGRATED_HOST=%s", this.migrationContext.ApplierConnectionConfig.ImpliedKey.Hostname))
+	env = append(env, fmt.Sprintf("GH_OST_INSPECTED_HOST=%s", this.migrationContext.InspectorConnectionConfig.ImpliedKey.Hostname))
+	env = append(env, fmt.Sprintf("GH_OST_EXECUTING_HOST=%s", this.migrationContext.Hostname))
+
+	for _, variable := range extraVariables {
+		env = append(env, variable)
+	}
 	return env
 }
 
-// executeHook executes a command with arguments, and set relevant environment variables
-func (this *HooksExecutor) executeHook(hook string, arguments ...string) error {
-	cmd := exec.Command(hook, arguments...)
-	cmd.Env = this.applyEnvironmentVairables()
+// executeHook executes a command, and sets relevant environment variables
+func (this *HooksExecutor) executeHook(hook string, extraVariables ...string) error {
+	cmd := exec.Command(hook)
+	cmd.Env = this.applyEnvironmentVairables(extraVariables...)
 
 	if err := cmd.Run(); err != nil {
 		return log.Errore(err)
@@ -60,13 +81,13 @@ func (this *HooksExecutor) detectHooks(baseName string) (hooks []string, err err
 	return hooks, err
 }
 
-func (this *HooksExecutor) executeHooks(baseName string) error {
+func (this *HooksExecutor) executeHooks(baseName string, extraVariables ...string) error {
 	hooks, err := this.detectHooks(baseName)
 	if err != nil {
 		return err
 	}
 	for _, hook := range hooks {
-		if err := this.executeHook(hook); err != nil {
+		if err := this.executeHook(hook, extraVariables...); err != nil {
 			return err
 		}
 	}
@@ -74,41 +95,47 @@ func (this *HooksExecutor) executeHooks(baseName string) error {
 }
 
 func (this *HooksExecutor) onStartup() error {
-	return nil
+	return this.executeHooks(onStartup)
 }
 
 func (this *HooksExecutor) onValidated() error {
-	return nil
+	return this.executeHooks(onValidated)
 }
 
 func (this *HooksExecutor) onAboutToRowCopy() error {
-	return nil
+	return this.executeHooks(onAboutToRowCopy)
 }
 
 func (this *HooksExecutor) onRowCopyComplete() error {
-	return nil
+	return this.executeHooks(onRowCopyComplete)
 }
 
 func (this *HooksExecutor) onBeginPostponed() error {
-	return nil
+	return this.executeHooks(onBeginPostponed)
 }
 
 func (this *HooksExecutor) onAboutToCutOver() error {
-	return nil
+	return this.executeHooks(onAboutToCutOver)
 }
 
 func (this *HooksExecutor) onInteractiveCommand(command string) error {
-	return nil
+	v := fmt.Sprintf("GH_OST_COMMAND='%s'", command)
+	return this.executeHooks(onInteractiveCommand, v)
 }
 
 func (this *HooksExecutor) onSuccess() error {
-	return nil
+	return this.executeHooks(onSuccess)
 }
 
 func (this *HooksExecutor) onFailure() error {
-	return nil
+	return this.executeHooks(onFailure)
 }
 
 func (this *HooksExecutor) onStatus(statusMessage string) error {
-	return nil
+	v := fmt.Sprintf("GH_OST_STATUS='%s'", statusMessage)
+	return this.executeHooks(onStatus, v)
+}
+
+func (this *HooksExecutor) onStopReplication() error {
+	return this.executeHooks(onStopReplication)
 }
diff --git a/go/logic/migrator.go b/go/logic/migrator.go
index 9d1ba6a..17c37c7 100644
--- a/go/logic/migrator.go
+++ b/go/logic/migrator.go
@@ -58,7 +58,6 @@ type Migrator struct {
 	server           *Server
 	hooksExecutor    *HooksExecutor
 	migrationContext *base.MigrationContext
-	hostname         string
 
 	tablesInPlace              chan bool
 	rowCopyComplete            chan bool
@@ -375,7 +374,7 @@ func (this *Migrator) validateStatement() (err error) {
 func (this *Migrator) Migrate() (err error) {
 	log.Infof("Migrating %s.%s", sql.EscapeName(this.migrationContext.DatabaseName), sql.EscapeName(this.migrationContext.OriginalTableName))
 	this.migrationContext.StartTime = time.Now()
-	if this.hostname, err = os.Hostname(); err != nil {
+	if this.migrationContext.Hostname, err = os.Hostname(); err != nil {
 		return err
 	}
 
@@ -473,6 +472,12 @@ func (this *Migrator) Migrate() (err error) {
 	return nil
 }
 
+// ExecOnFailureHook executes the onFailure hook, and this method is provided as the only external
+// hook access point
+func (this *Migrator) ExecOnFailureHook() (err error) {
+	return this.hooksExecutor.onFailure()
+}
+
 // cutOver performs the final step of migration, based on migration
 // type (on replica? bumpy? safe?)
 func (this *Migrator) cutOver() (err error) {
@@ -516,6 +521,7 @@ func (this *Migrator) cutOver() (err error) {
 		// and swap the tables.
 		// The difference is that we will later swap the tables back.
 		log.Debugf("testing on replica. Stopping replication IO thread")
+		this.hooksExecutor.onStopReplication()
 		if err := this.retryOperation(this.applier.StopReplication); err != nil {
 			return err
 		}
@@ -909,7 +915,7 @@ func (this *Migrator) printMigrationStatusHint(writers ...io.Writer) {
 	fmt.Fprintln(w, fmt.Sprintf("# Migrating %+v; inspecting %+v; executing on %+v",
 		*this.applier.connectionConfig.ImpliedKey,
 		*this.inspector.connectionConfig.ImpliedKey,
-		this.hostname,
+		this.migrationContext.Hostname,
 	))
 	fmt.Fprintln(w, fmt.Sprintf("# Migration started at %+v",
 		this.migrationContext.StartTime.Format(time.RubyDate),

From a1e191078ac65c2423298ff966e87c7f96952403 Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Tue, 23 Aug 2016 11:40:32 +0200
Subject: [PATCH 05/20] rename 'about'->'before'

---
 go/logic/hooks.go    | 12 ++++++------
 go/logic/migrator.go |  4 ++--
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/go/logic/hooks.go b/go/logic/hooks.go
index 1c562ef..dd74973 100644
--- a/go/logic/hooks.go
+++ b/go/logic/hooks.go
@@ -18,10 +18,10 @@ import (
 const (
 	onStartup            = "gh-ost-on-startup"
 	onValidated          = "gh-ost-on-validated"
-	onAboutToRowCopy     = "gh-ost-on-about-row-copy"
+	onBeforeRowCopy      = "gh-ost-on-before-row-copy"
 	onRowCopyComplete    = "gh-ost-on-row-copy-complete"
 	onBeginPostponed     = "gh-ost-on-begin-postponed"
-	onAboutToCutOver     = "gh-ost-on-about-cut-over"
+	onBeforeCutOver      = "gh-ost-on-before-cut-over"
 	onInteractiveCommand = "gh-ost-on-interactive-command"
 	onSuccess            = "gh-ost-on-success"
 	onFailure            = "gh-ost-on-failure"
@@ -102,8 +102,8 @@ func (this *HooksExecutor) onValidated() error {
 	return this.executeHooks(onValidated)
 }
 
-func (this *HooksExecutor) onAboutToRowCopy() error {
-	return this.executeHooks(onAboutToRowCopy)
+func (this *HooksExecutor) onBeforeRowCopy() error {
+	return this.executeHooks(onBeforeRowCopy)
 }
 
 func (this *HooksExecutor) onRowCopyComplete() error {
@@ -114,8 +114,8 @@ func (this *HooksExecutor) onBeginPostponed() error {
 	return this.executeHooks(onBeginPostponed)
 }
 
-func (this *HooksExecutor) onAboutToCutOver() error {
-	return this.executeHooks(onAboutToCutOver)
+func (this *HooksExecutor) onBeforeCutOver() error {
+	return this.executeHooks(onBeforeCutOver)
 }
 
 func (this *HooksExecutor) onInteractiveCommand(command string) error {
diff --git a/go/logic/migrator.go b/go/logic/migrator.go
index 17c37c7..5956c95 100644
--- a/go/logic/migrator.go
+++ b/go/logic/migrator.go
@@ -439,7 +439,7 @@ func (this *Migrator) Migrate() (err error) {
 		return err
 	}
 	go this.initiateThrottler()
-	if err := this.hooksExecutor.onAboutToRowCopy(); err != nil {
+	if err := this.hooksExecutor.onBeforeRowCopy(); err != nil {
 		return err
 	}
 	go this.executeWriteFuncs()
@@ -455,7 +455,7 @@ func (this *Migrator) Migrate() (err error) {
 	}
 	this.printStatus(ForcePrintStatusRule)
 
-	if err := this.hooksExecutor.onAboutToCutOver(); err != nil {
+	if err := this.hooksExecutor.onBeforeCutOver(); err != nil {
 		return err
 	}
 	if err := this.cutOver(); err != nil {

From b064174ab4aae5f4caa27ee5e14e44b16aeca839 Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Thu, 25 Aug 2016 13:54:21 +0200
Subject: [PATCH 06/20] added elapsedSeconds to status hook

---
 go/logic/migrator.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/go/logic/migrator.go b/go/logic/migrator.go
index 5aaf9f1..83dffdd 100644
--- a/go/logic/migrator.go
+++ b/go/logic/migrator.go
@@ -1077,7 +1077,7 @@ func (this *Migrator) printStatus(rule PrintStatusRule, writers ...io.Writer) {
 	fmt.Fprintln(w, status)
 
 	if elapsedSeconds%60 == 0 {
-		this.hooksExecutor.onStatus(status)
+		this.hooksExecutor.onStatus(status, elapsedSeconds)
 	}
 }
 

From fad6743150ff33ed44e7a64f1cdf632b78ad0781 Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Thu, 25 Aug 2016 13:54:42 +0200
Subject: [PATCH 07/20] added hooks hint message

---
 go/base/context.go | 1 +
 1 file changed, 1 insertion(+)

diff --git a/go/base/context.go b/go/base/context.go
index f1c3111..7a7a0a2 100644
--- a/go/base/context.go
+++ b/go/base/context.go
@@ -79,6 +79,7 @@ type MigrationContext struct {
 	CutOverLockTimeoutSeconds           int64
 	PanicFlagFile                       string
 	HooksPath                           string
+	HooksHintMessage                    string
 
 	DropServeSocket bool
 	ServeSocketFile string

From ecd33969bf40db6ef67e162b5428dde07702d4eb Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Thu, 25 Aug 2016 13:55:22 +0200
Subject: [PATCH 08/20] added onRowCountComplete(); supporting elapsedSeconds
 in on-status

---
 go/logic/hooks.go | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/go/logic/hooks.go b/go/logic/hooks.go
index dd74973..7b831d8 100644
--- a/go/logic/hooks.go
+++ b/go/logic/hooks.go
@@ -18,6 +18,7 @@ import (
 const (
 	onStartup            = "gh-ost-on-startup"
 	onValidated          = "gh-ost-on-validated"
+	onRowCountComplete   = "gh-ost-on-rowcount-complete"
 	onBeforeRowCopy      = "gh-ost-on-before-row-copy"
 	onRowCopyComplete    = "gh-ost-on-row-copy-complete"
 	onBeginPostponed     = "gh-ost-on-begin-postponed"
@@ -54,6 +55,7 @@ func (this *HooksExecutor) applyEnvironmentVairables(extraVariables ...string) [
 	env = append(env, fmt.Sprintf("GH_OST_MIGRATED_HOST=%s", this.migrationContext.ApplierConnectionConfig.ImpliedKey.Hostname))
 	env = append(env, fmt.Sprintf("GH_OST_INSPECTED_HOST=%s", this.migrationContext.InspectorConnectionConfig.ImpliedKey.Hostname))
 	env = append(env, fmt.Sprintf("GH_OST_EXECUTING_HOST=%s", this.migrationContext.Hostname))
+	env = append(env, fmt.Sprintf("GH_OST_HOOKS_HINT=%s", this.migrationContext.HooksHintMessage))
 
 	for _, variable := range extraVariables {
 		env = append(env, variable)
@@ -102,6 +104,9 @@ func (this *HooksExecutor) onValidated() error {
 	return this.executeHooks(onValidated)
 }
 
+func (this *HooksExecutor) onRowCountComplete() error {
+	return this.executeHooks(onRowCountComplete)
+}
 func (this *HooksExecutor) onBeforeRowCopy() error {
 	return this.executeHooks(onBeforeRowCopy)
 }
@@ -131,9 +136,10 @@ func (this *HooksExecutor) onFailure() error {
 	return this.executeHooks(onFailure)
 }
 
-func (this *HooksExecutor) onStatus(statusMessage string) error {
-	v := fmt.Sprintf("GH_OST_STATUS='%s'", statusMessage)
-	return this.executeHooks(onStatus, v)
+func (this *HooksExecutor) onStatus(statusMessage string, elapsedSeconds int64) error {
+	v0 := fmt.Sprintf("GH_OST_STATUS='%s'", statusMessage)
+	v1 := fmt.Sprintf("GH_OST_ELAPSED_SECONDS='%d'", elapsedSeconds)
+	return this.executeHooks(onStatus, v0, v1)
 }
 
 func (this *HooksExecutor) onStopReplication() error {

From b60875f32ffdaf1151bcae46634406f5b6255ef3 Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Thu, 25 Aug 2016 13:55:34 +0200
Subject: [PATCH 09/20] added and improved sample hooks

---
 resources/hooks-sample/gh-ost-on-before-cut-over-hook     | 5 +++++
 resources/hooks-sample/gh-ost-on-before-row-copy-hook     | 5 +++++
 resources/hooks-sample/gh-ost-on-begin-postponed-hook     | 5 +++++
 resources/hooks-sample/gh-ost-on-failure-hook             | 5 +++++
 resources/hooks-sample/gh-ost-on-interactive-command-hook | 5 +++++
 resources/hooks-sample/gh-ost-on-row-copy-complete-hook   | 5 +++++
 resources/hooks-sample/gh-ost-on-rowcount-complete-hook   | 5 +++++
 resources/hooks-sample/gh-ost-on-startup-hook             | 5 +++++
 resources/hooks-sample/gh-ost-on-status-hook              | 5 +++++
 resources/hooks-sample/gh-ost-on-stop-replication-hook    | 5 +++++
 resources/hooks-sample/gh-ost-on-success-hook             | 5 +++++
 resources/hooks-sample/gh-ost-on-success-hook-2           | 5 +++++
 resources/hooks-sample/gh-ost-on-validated-hook           | 5 +++++
 13 files changed, 65 insertions(+)
 create mode 100755 resources/hooks-sample/gh-ost-on-before-cut-over-hook
 create mode 100755 resources/hooks-sample/gh-ost-on-before-row-copy-hook
 create mode 100755 resources/hooks-sample/gh-ost-on-begin-postponed-hook
 create mode 100755 resources/hooks-sample/gh-ost-on-failure-hook
 create mode 100755 resources/hooks-sample/gh-ost-on-interactive-command-hook
 create mode 100755 resources/hooks-sample/gh-ost-on-row-copy-complete-hook
 create mode 100755 resources/hooks-sample/gh-ost-on-rowcount-complete-hook
 create mode 100755 resources/hooks-sample/gh-ost-on-startup-hook
 create mode 100755 resources/hooks-sample/gh-ost-on-status-hook
 create mode 100755 resources/hooks-sample/gh-ost-on-stop-replication-hook
 create mode 100755 resources/hooks-sample/gh-ost-on-success-hook
 create mode 100755 resources/hooks-sample/gh-ost-on-success-hook-2
 create mode 100755 resources/hooks-sample/gh-ost-on-validated-hook

diff --git a/resources/hooks-sample/gh-ost-on-before-cut-over-hook b/resources/hooks-sample/gh-ost-on-before-cut-over-hook
new file mode 100755
index 0000000..41bf2d0
--- /dev/null
+++ b/resources/hooks-sample/gh-ost-on-before-cut-over-hook
@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# Sample hook file for gh-ost-on-before-cut-over
+
+echo "$(date) gh-ost-on-before-cut-over $GH_OST_DATABASE_NAME.$GH_OST_TABLE_NAME" >> /tmp/gh-ost.log
diff --git a/resources/hooks-sample/gh-ost-on-before-row-copy-hook b/resources/hooks-sample/gh-ost-on-before-row-copy-hook
new file mode 100755
index 0000000..4282bcd
--- /dev/null
+++ b/resources/hooks-sample/gh-ost-on-before-row-copy-hook
@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# Sample hook file for gh-ost-on-before-row-copy
+
+echo "$(date) gh-ost-on-before-row-copy $GH_OST_DATABASE_NAME.$GH_OST_TABLE_NAME" >> /tmp/gh-ost.log
diff --git a/resources/hooks-sample/gh-ost-on-begin-postponed-hook b/resources/hooks-sample/gh-ost-on-begin-postponed-hook
new file mode 100755
index 0000000..85cc7a1
--- /dev/null
+++ b/resources/hooks-sample/gh-ost-on-begin-postponed-hook
@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# Sample hook file for gh-ost-on-begin-postponed
+
+echo "$(date) gh-ost-on-begin-postponed $GH_OST_DATABASE_NAME.$GH_OST_TABLE_NAME" >> /tmp/gh-ost.log
diff --git a/resources/hooks-sample/gh-ost-on-failure-hook b/resources/hooks-sample/gh-ost-on-failure-hook
new file mode 100755
index 0000000..42ccaea
--- /dev/null
+++ b/resources/hooks-sample/gh-ost-on-failure-hook
@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# Sample hook file for gh-ost-on-failure
+
+echo "$(date) gh-ost-on-failure $GH_OST_DATABASE_NAME.$GH_OST_TABLE_NAME; ghost: $GH_OST_OLD_TABLE_NAME" >> /tmp/gh-ost.log
diff --git a/resources/hooks-sample/gh-ost-on-interactive-command-hook b/resources/hooks-sample/gh-ost-on-interactive-command-hook
new file mode 100755
index 0000000..09b35ea
--- /dev/null
+++ b/resources/hooks-sample/gh-ost-on-interactive-command-hook
@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# Sample hook file for gh-ost-on-interactive-command
+
+echo "$(date) gh-ost-on-interactive-command $GH_OST_COMMAND" >> /tmp/gh-ost.log
diff --git a/resources/hooks-sample/gh-ost-on-row-copy-complete-hook b/resources/hooks-sample/gh-ost-on-row-copy-complete-hook
new file mode 100755
index 0000000..1718ee4
--- /dev/null
+++ b/resources/hooks-sample/gh-ost-on-row-copy-complete-hook
@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# Sample hook file for gh-ost-on-row-copy-complete
+
+echo "$(date) gh-ost-on-row-copy-complete $GH_OST_DATABASE_NAME.$GH_OST_TABLE_NAME" >> /tmp/gh-ost.log
diff --git a/resources/hooks-sample/gh-ost-on-rowcount-complete-hook b/resources/hooks-sample/gh-ost-on-rowcount-complete-hook
new file mode 100755
index 0000000..970e127
--- /dev/null
+++ b/resources/hooks-sample/gh-ost-on-rowcount-complete-hook
@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# Sample hook file for gh-ost-on-rowcount-complete
+
+echo "$(date) gh-ost-on-rowcount-complete $GH_OST_DATABASE_NAME.$GH_OST_TABLE_NAME" >> /tmp/gh-ost.log
diff --git a/resources/hooks-sample/gh-ost-on-startup-hook b/resources/hooks-sample/gh-ost-on-startup-hook
new file mode 100755
index 0000000..f439af5
--- /dev/null
+++ b/resources/hooks-sample/gh-ost-on-startup-hook
@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# Sample hook file for gh-ost-on-startup
+
+echo "$(date) gh-ost-on-startup $GH_OST_DATABASE_NAME.$GH_OST_TABLE_NAME" >> /tmp/gh-ost.log
diff --git a/resources/hooks-sample/gh-ost-on-status-hook b/resources/hooks-sample/gh-ost-on-status-hook
new file mode 100755
index 0000000..50bd934
--- /dev/null
+++ b/resources/hooks-sample/gh-ost-on-status-hook
@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# Sample hook file for gh-ost-on-status
+
+echo "$(date) gh-ost-on-status; elapsed: ${GH_OST_ELAPSED_SECONDS}; msg: ${GH_OST_STATUS}" >> /tmp/gh-ost.log
diff --git a/resources/hooks-sample/gh-ost-on-stop-replication-hook b/resources/hooks-sample/gh-ost-on-stop-replication-hook
new file mode 100755
index 0000000..232ad95
--- /dev/null
+++ b/resources/hooks-sample/gh-ost-on-stop-replication-hook
@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# Sample hook file for gh-ost-on-stop-replication
+
+echo "$(date) gh-ost-on-stop-replication $GH_OST_DATABASE_NAME.$GH_OST_TABLE_NAME $GH_OST_MIGRATED_HOST" >> /tmp/gh-ost.log
diff --git a/resources/hooks-sample/gh-ost-on-success-hook b/resources/hooks-sample/gh-ost-on-success-hook
new file mode 100755
index 0000000..aa4aedc
--- /dev/null
+++ b/resources/hooks-sample/gh-ost-on-success-hook
@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# Sample hook file for gh-ost-on-success
+
+echo "$(date) gh-ost-on-success $GH_OST_DATABASE_NAME.$GH_OST_TABLE_NAME" >> /tmp/gh-ost.log
diff --git a/resources/hooks-sample/gh-ost-on-success-hook-2 b/resources/hooks-sample/gh-ost-on-success-hook-2
new file mode 100755
index 0000000..aa4aedc
--- /dev/null
+++ b/resources/hooks-sample/gh-ost-on-success-hook-2
@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# Sample hook file for gh-ost-on-success
+
+echo "$(date) gh-ost-on-success $GH_OST_DATABASE_NAME.$GH_OST_TABLE_NAME" >> /tmp/gh-ost.log
diff --git a/resources/hooks-sample/gh-ost-on-validated-hook b/resources/hooks-sample/gh-ost-on-validated-hook
new file mode 100755
index 0000000..efef4e5
--- /dev/null
+++ b/resources/hooks-sample/gh-ost-on-validated-hook
@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# Sample hook file for gh-ost-on-validated
+
+echo "$(date) gh-ost-on-validated $GH_OST_DATABASE_NAME.$GH_OST_TABLE_NAME" >> /tmp/gh-ost.log

From cbdec6bd3921ca64227f9eef16c7ce27e6d47c8b Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Thu, 25 Aug 2016 13:58:36 +0200
Subject: [PATCH 10/20] supporting --hooks-path and --hooks-hint

---
 go/cmd/gh-ost/main.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/go/cmd/gh-ost/main.go b/go/cmd/gh-ost/main.go
index 480db68..6dafa45 100644
--- a/go/cmd/gh-ost/main.go
+++ b/go/cmd/gh-ost/main.go
@@ -89,6 +89,9 @@ 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")
 
+	flag.StringVar(&migrationContext.HooksPath, "hooks-path", "", "directory where hook files are found (default: empty, ie. hooks disabled). Hook files found on this path, and conforming to hook naming conventions will be executed")
+	flag.StringVar(&migrationContext.HooksHintMessage, "hooks-hint", "", "arbitrary message to be injected to hooks via GH_OST_HOOKS_HINT, for your convenience")
+
 	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")

From 2c9d71570f3cd9496db965ae9685d82faa6276a3 Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Thu, 25 Aug 2016 14:42:49 +0200
Subject: [PATCH 11/20] logging intented hook invocation

---
 go/logic/hooks.go | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/go/logic/hooks.go b/go/logic/hooks.go
index 7b831d8..ea1fa11 100644
--- a/go/logic/hooks.go
+++ b/go/logic/hooks.go
@@ -1,3 +1,4 @@
+/*
 /*
    Copyright 2016 GitHub Inc.
 	 See https://github.com/github/gh-ost/blob/master/LICENSE
@@ -89,6 +90,7 @@ func (this *HooksExecutor) executeHooks(baseName string, extraVariables ...strin
 		return err
 	}
 	for _, hook := range hooks {
+		log.Infof("executing %+v hook: %+v", baseName, hook)
 		if err := this.executeHook(hook, extraVariables...); err != nil {
 			return err
 		}
@@ -137,9 +139,11 @@ func (this *HooksExecutor) onFailure() error {
 }
 
 func (this *HooksExecutor) onStatus(statusMessage string, elapsedSeconds int64) error {
-	v0 := fmt.Sprintf("GH_OST_STATUS='%s'", statusMessage)
-	v1 := fmt.Sprintf("GH_OST_ELAPSED_SECONDS='%d'", elapsedSeconds)
-	return this.executeHooks(onStatus, v0, v1)
+	v := []string{
+		fmt.Sprintf("GH_OST_STATUS='%s'", statusMessage),
+		fmt.Sprintf("GH_OST_ELAPSED_SECONDS='%d'", elapsedSeconds),
+	}
+	return this.executeHooks(onStatus, v...)
 }
 
 func (this *HooksExecutor) onStopReplication() error {

From ebd53371d64a08388e1a663b54a7b18c65a25edb Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Thu, 25 Aug 2016 14:43:06 +0200
Subject: [PATCH 12/20] adding hooks documentation

---
 doc/hooks.md | 74 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)
 create mode 100644 doc/hooks.md

diff --git a/doc/hooks.md b/doc/hooks.md
new file mode 100644
index 0000000..48d3887
--- /dev/null
+++ b/doc/hooks.md
@@ -0,0 +1,74 @@
+# Hooks
+
+`gh-ost` supports _hooks_: external processes which `gh-ost` executes at particular points of interest.
+
+Use cases include:
+
+- You wish to be notified ny mail when a migration completes/fails
+- You wish to be notified when `gh-ost` postpones cut-over (at your demand), thus ready to complete (at your leisure)
+- RDS users who wish to `--test-on-replica`, but who cannot have `gh-ost` issue a `STOP SLAVE`, would use a hook to command RDS to stop replication
+- Send a status message to your chatops every hour
+- Perform cleanup on the _ghost_ table (drop/rename/nibble) once migration completes
+- etc.
+
+`gh-ost` defines certain points of interest (event types), and executes hooks at those points.
+
+Notes:
+
+- You may have more than one hook per event type.
+- `gh-ost` will invoke relevant hooks _sequentially_ and _synchronously_
+  - thus, you would generally like the hooks to execute as fast as possible, or otherwise issue tasks in the background
+- A hook returning with error code will propagate the error in `gh-ost`. Thus, you are able to force `gh-ost` to fail migration on your conditions.
+  - Make sure to only return an error code when you do indeed wish to fail the rest of the migration
+
+### Creating hooks
+
+All hooks are expected to reside in a single directory. This directory is indicated by `--hooks-path`. When not provided, no hooks are executed.
+
+`gh-ost` will dynamically search for hooks in said directory. You may add and remove hooks to/from this directory as `gh-ost` makes progress (though likely you don't want to). Hook files are expected to be executable processes.
+
+In an effort to simplify code and to standardize usage, `gh-ost` expects hooks in explicit naming conventions. As an example, the `onStartup` hook expects processes named `gh-ost-on-startup*`. It will match and accept files named:
+
+- `gh-ost-on-startup`
+- `gh-ost-on-startup--send-notification-mail`
+- `gh-ost-on-startup12345`
+- etc.
+
+The full list of supported hooks is best found in code: [hooks.go](https://github.com/github/gh-ost/blob/master/go/logic/hooks.go). Documentation will always be a bit behind. At this time, though, the following are recognized:
+
+- `gh-ost-on-startup`
+- `gh-ost-on-validated`
+- `gh-ost-on-rowcount-complete`
+- `gh-ost-on-before-row-copy`
+- `gh-ost-on-status`
+- `gh-ost-on-interactive-command`
+- `gh-ost-on-row-copy-complete`
+- `gh-ost-on-stop-replication`
+- `gh-ost-on-begin-postponed`
+- `gh-ost-on-before-cut-over`
+- `gh-ost-on-success`
+- `gh-ost-on-failure`
+
+### Context
+
+`gh-ost` will set environment variables per hook invocation. Hooks are then able to read those variables, indicating schema name, table name, `alter` statement, migrated host name etc. Some variables are available on all hooks, and some are available on relevant hooks.
+
+The following variables are available on all hooks:
+
+- `GH_OST_DATABASE_NAME`
+- `GH_OST_TABLE_NAME`
+- `GH_OST_GHOST_TABLE_NAME`
+- `GH_OST_OLD_TABLE_NAME`
+- `GH_OST_DDL`
+- `GH_OST_ELAPSED_SECONDS`
+- `GH_OST_MIGRATED_HOST`
+- `GH_OST_INSPECTED_HOST`
+- `GH_OST_EXECUTING_HOST`
+- `GH_OST_HOOKS_HINT`
+
+- `GH_OST_COMMAND` is only available in `gh-ost-on-interactive-command`
+- `GH_OST_STATUS` and `GH_OST_ELAPSED_SECONDS` are only available in `gh-ost-on-status`
+
+### Examples
+
+See [sample hooks](https://github.com/github/gh-ost/tree/master/resources/hooks-sample), as `bash` implementation samples.

From 398e1c75fff6af492a6a78109d1ce7ba35134e35 Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Thu, 25 Aug 2016 14:44:15 +0200
Subject: [PATCH 13/20] doc clarification

---
 doc/hooks.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/doc/hooks.md b/doc/hooks.md
index 48d3887..293435e 100644
--- a/doc/hooks.md
+++ b/doc/hooks.md
@@ -66,6 +66,8 @@ The following variables are available on all hooks:
 - `GH_OST_EXECUTING_HOST`
 - `GH_OST_HOOKS_HINT`
 
+The following variable are available on particular hooks:
+
 - `GH_OST_COMMAND` is only available in `gh-ost-on-interactive-command`
 - `GH_OST_STATUS` and `GH_OST_ELAPSED_SECONDS` are only available in `gh-ost-on-status`
 

From b967e6e96e5eb9cda3c13dcd30bfe1d5bb70626f Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Thu, 25 Aug 2016 14:46:43 +0200
Subject: [PATCH 14/20] doc clarification

---
 README.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/README.md b/README.md
index deb29b9..53d017a 100644
--- a/README.md
+++ b/README.md
@@ -29,6 +29,7 @@ In addition, it offers many [operational perks](doc/perks.md) that make it safer
 - Dynamic control: you can [interactively](doc/interactive-commands.md) reconfigure `gh-ost`, even as migration still runs. You may forcibly initiate throttling.
 - Auditing: you may query `gh-ost` for status. `gh-ost` listens on unix socket or TCP.
 - Control over cut-over phase: `gh-ost` can be instructed to postpone what is probably the most critical step: the swap of tables, until such time that you're comfortably available. No need to worry about ETA being outside office hours.
+- External [hooks](doc/hooks.md) can couple `gh-ost` with your particular environment.
 
 Please refer to the [docs](doc) for more information. No, really, read the [docs](doc).
 

From 676020000a210e977bae052394429a47aef2542b Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Thu, 25 Aug 2016 15:11:58 +0200
Subject: [PATCH 15/20] typo

---
 doc/hooks.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/hooks.md b/doc/hooks.md
index 293435e..169dfb2 100644
--- a/doc/hooks.md
+++ b/doc/hooks.md
@@ -4,7 +4,7 @@
 
 Use cases include:
 
-- You wish to be notified ny mail when a migration completes/fails
+- You wish to be notified by mail when a migration completes/fails
 - You wish to be notified when `gh-ost` postpones cut-over (at your demand), thus ready to complete (at your leisure)
 - RDS users who wish to `--test-on-replica`, but who cannot have `gh-ost` issue a `STOP SLAVE`, would use a hook to command RDS to stop replication
 - Send a status message to your chatops every hour

From ef386add5cd3171bb508b5ddc6003fedf4675b7f Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Thu, 25 Aug 2016 16:08:49 +0200
Subject: [PATCH 16/20] hook output and err are written to gh-ost's stderr

---
 go/logic/hooks.go                               | 8 ++++----
 resources/hooks-sample/gh-ost-on-success-hook-2 | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/go/logic/hooks.go b/go/logic/hooks.go
index ea1fa11..8906f62 100644
--- a/go/logic/hooks.go
+++ b/go/logic/hooks.go
@@ -65,14 +65,14 @@ func (this *HooksExecutor) applyEnvironmentVairables(extraVariables ...string) [
 }
 
 // executeHook executes a command, and sets relevant environment variables
+// combined output & error are printed to gh-ost's standard error.
 func (this *HooksExecutor) executeHook(hook string, extraVariables ...string) error {
 	cmd := exec.Command(hook)
 	cmd.Env = this.applyEnvironmentVairables(extraVariables...)
 
-	if err := cmd.Run(); err != nil {
-		return log.Errore(err)
-	}
-	return nil
+	combinedOutput, err := cmd.CombinedOutput()
+	fmt.Fprintln(os.Stderr, string(combinedOutput))
+	return log.Errore(err)
 }
 
 func (this *HooksExecutor) detectHooks(baseName string) (hooks []string, err error) {
diff --git a/resources/hooks-sample/gh-ost-on-success-hook-2 b/resources/hooks-sample/gh-ost-on-success-hook-2
index aa4aedc..29cba49 100755
--- a/resources/hooks-sample/gh-ost-on-success-hook-2
+++ b/resources/hooks-sample/gh-ost-on-success-hook-2
@@ -2,4 +2,4 @@
 
 # Sample hook file for gh-ost-on-success
 
-echo "$(date) gh-ost-on-success $GH_OST_DATABASE_NAME.$GH_OST_TABLE_NAME" >> /tmp/gh-ost.log
+echo "$(date) gh-ost-on-success $GH_OST_DATABASE_NAME.$GH_OST_TABLE_NAME -- this message should show on the gh-ost log"

From 89a3a261a85f04ca63dd8227255e0d90b700a506 Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Fri, 26 Aug 2016 08:39:32 +0200
Subject: [PATCH 17/20] updated version

---
 build.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/build.sh b/build.sh
index 20f127a..e00cb54 100755
--- a/build.sh
+++ b/build.sh
@@ -2,7 +2,7 @@
 #
 #
 
-RELEASE_VERSION="1.0.14"
+RELEASE_VERSION="1.0.15"
 
 function build {
     osname=$1

From 6e5db089c8740fec0be8895c4b85a16b34883992 Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Mon, 29 Aug 2016 09:58:31 +0200
Subject: [PATCH 18/20] supporting onRowCountComplete hook

---
 go/logic/migrator.go | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/go/logic/migrator.go b/go/logic/migrator.go
index e767455..c44d196 100644
--- a/go/logic/migrator.go
+++ b/go/logic/migrator.go
@@ -379,13 +379,24 @@ func (this *Migrator) countTableRows() (err error) {
 		log.Debugf("Noop operation; not really counting table rows")
 		return nil
 	}
+
+	countRowsFunc := func() error {
+		if err := this.inspector.CountTableRows(); err != nil {
+			return err
+		}
+		if err := this.hooksExecutor.onRowCountComplete(); err != nil {
+			return err
+		}
+		return nil
+	}
+
 	if this.migrationContext.ConcurrentCountTableRows {
-		go this.inspector.CountTableRows()
 		log.Infof("As instructed, counting rows in the background; meanwhile I will use an estimated count, and will update it later on")
+		go countRowsFunc()
 		// and we ignore errors, because this turns to be a background job
 		return nil
 	}
-	return this.inspector.CountTableRows()
+	return countRowsFunc()
 }
 
 // Migrate executes the complete migration logic. This is *the* major gh-ost function.

From 6dfa4873c296a7b0472e5b64aafd7902e74a973f Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Mon, 29 Aug 2016 10:44:43 +0200
Subject: [PATCH 19/20] removed excessive argument

---
 go/logic/hooks.go    | 9 +++------
 go/logic/migrator.go | 2 +-
 2 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/go/logic/hooks.go b/go/logic/hooks.go
index 8906f62..ad55b99 100644
--- a/go/logic/hooks.go
+++ b/go/logic/hooks.go
@@ -138,12 +138,9 @@ func (this *HooksExecutor) onFailure() error {
 	return this.executeHooks(onFailure)
 }
 
-func (this *HooksExecutor) onStatus(statusMessage string, elapsedSeconds int64) error {
-	v := []string{
-		fmt.Sprintf("GH_OST_STATUS='%s'", statusMessage),
-		fmt.Sprintf("GH_OST_ELAPSED_SECONDS='%d'", elapsedSeconds),
-	}
-	return this.executeHooks(onStatus, v...)
+func (this *HooksExecutor) onStatus(statusMessage string) error {
+	v := fmt.Sprintf("GH_OST_STATUS='%s'", statusMessage)
+	return this.executeHooks(onStatus, v)
 }
 
 func (this *HooksExecutor) onStopReplication() error {
diff --git a/go/logic/migrator.go b/go/logic/migrator.go
index c44d196..799e70b 100644
--- a/go/logic/migrator.go
+++ b/go/logic/migrator.go
@@ -1102,7 +1102,7 @@ func (this *Migrator) printStatus(rule PrintStatusRule, writers ...io.Writer) {
 	fmt.Fprintln(w, status)
 
 	if elapsedSeconds%60 == 0 {
-		this.hooksExecutor.onStatus(status, elapsedSeconds)
+		this.hooksExecutor.onStatus(status)
 	}
 }
 

From 7450910e707c4aaffa2397ae464d190ddfdeb965 Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Mon, 29 Aug 2016 12:47:15 +0200
Subject: [PATCH 20/20] fixed docs

---
 doc/hooks.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/hooks.md b/doc/hooks.md
index 169dfb2..44e59a7 100644
--- a/doc/hooks.md
+++ b/doc/hooks.md
@@ -69,7 +69,7 @@ The following variables are available on all hooks:
 The following variable are available on particular hooks:
 
 - `GH_OST_COMMAND` is only available in `gh-ost-on-interactive-command`
-- `GH_OST_STATUS` and `GH_OST_ELAPSED_SECONDS` are only available in `gh-ost-on-status`
+- `GH_OST_STATUS` is only available in `gh-ost-on-status`
 
 ### Examples