diff --git a/go.mod b/go.mod
index 0f123bcf694..9f72934af39 100644
--- a/go.mod
+++ b/go.mod
@@ -25,6 +25,7 @@ require (
 	github.com/cyberdelia/go-metrics-graphite v0.0.0-20161219230853-39f87cc3b432
 	github.com/dave/jennifer v1.4.1
 	github.com/evanphx/json-patch v4.5.0+incompatible
+	github.com/fsnotify/fsnotify v1.4.9
 	github.com/go-martini/martini v0.0.0-20170121215854-22fa46961aab
 	github.com/go-sql-driver/mysql v1.5.1-0.20210202043019-fe2230a8b20c
 	github.com/gogo/protobuf v1.3.1
diff --git a/go.sum b/go.sum
index 552aec1c7cd..4b9b554eb6e 100644
--- a/go.sum
+++ b/go.sum
@@ -182,6 +182,8 @@ github.com/felixge/httpsnoop v1.0.1 h1:lvB5Jl89CsZtGIWuTcDM1E/vkVs49/Ml7JJe07l8S
 github.com/felixge/httpsnoop v1.0.1/go.mod h1:m8KPJKqk1gH5J9DgRY2ASl2lWCfGKXixSwevea8zH2U=
 github.com/fsnotify/fsnotify v1.4.7 h1:IXs+QLmnXW2CcXuY+8Mzv/fWEsPGWxqefPtCP5CnV9I=
 github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
+github.com/fsnotify/fsnotify v1.4.9 h1:hsms1Qyu0jgnwNXIxa+/V/PDsU6CfLf6CNO8H7IWoS4=
+github.com/fsnotify/fsnotify v1.4.9/go.mod h1:znqG4EE+3YCdAaPaxE2ZRY/06pZUdp0tY4IgpuI1SZQ=
 github.com/ghodss/yaml v0.0.0-20150909031657-73d445a93680/go.mod h1:4dBDuWmgqj2HViK6kFavaiC9ZROes6MMH2rRYeMEF04=
 github.com/ghodss/yaml v1.0.0 h1:wQHKEahhL6wmXdzwWG11gIVCkOv05bNOh+Rxn0yngAk=
 github.com/ghodss/yaml v1.0.0/go.mod h1:4dBDuWmgqj2HViK6kFavaiC9ZROes6MMH2rRYeMEF04=
@@ -783,6 +785,7 @@ golang.org/x/sys v0.0.0-20190624142023-c5567b49c5d0/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20190826190057-c7b8b68b1456/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190922100055-0a153f010e69/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190924154521-2837fb4f24fe/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20191005200804-aed5e4c7ecf9/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191008105621-543471e840be/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191026070338-33540a1f6037/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200116001909-b77594299b42/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
diff --git a/go/cmd/rulesctl/cmd/add.go b/go/cmd/rulesctl/cmd/add.go
index 76e80999360..e83e494dc0a 100644
--- a/go/cmd/rulesctl/cmd/add.go
+++ b/go/cmd/rulesctl/cmd/add.go
@@ -13,13 +13,15 @@ import (
 )
 
 var (
-	addOptDryrun      bool
-	addOptName        string
-	addOptDescription string
-	addOptAction      string
-	addOptPlans       []string
-	addOptTables      []string
-	addOptQueryRE     string
+	addOptDryrun            bool
+	addOptName              string
+	addOptDescription       string
+	addOptAction            string
+	addOptPlans             []string
+	addOptTables            []string
+	addOptQueryRE           string
+	addOptLeadingCommentRE  string
+	addOptTrailingCommentRE string
 	// TODO: other stuff, bind vars etc
 )
 
@@ -36,8 +38,20 @@ func runAdd(cmd *cobra.Command, args []string) {
 		rule.AddTableCond(t)
 	}
 
-	if err := rule.SetQueryCond(addOptQueryRE); err != nil {
-		log.Fatalf("Query condition invalid '%v': %v", addOptQueryRE, err)
+	if addOptQueryRE != "" {
+		if err := rule.SetQueryCond(addOptQueryRE); err != nil {
+			log.Fatalf("Query condition invalid '%v': %v", addOptQueryRE, err)
+		}
+	}
+	if addOptLeadingCommentRE != "" {
+		if err := rule.SetLeadingCommentCond(addOptLeadingCommentRE); err != nil {
+			log.Fatalf("Leading comment condition invalid '%v': %v", addOptLeadingCommentRE, err)
+		}
+	}
+	if addOptTrailingCommentRE != "" {
+		if err := rule.SetTrailingCommentCond(addOptTrailingCommentRE); err != nil {
+			log.Fatalf("Trailing comment condition invalid '%v': %v", addOptTrailingCommentRE, err)
+		}
 	}
 
 	var rules *vtrules.Rules
@@ -141,6 +155,16 @@ func Add() *cobra.Command {
 		"query", "q",
 		"",
 		"A regexp that will be applied to a query in order to determine if it matches")
+	addCmd.Flags().StringVarP(
+		&addOptLeadingCommentRE,
+		"leading-comment", "l",
+		"",
+		"A regexp that will be applied to comments prefacing a SQL statement")
+	addCmd.Flags().StringVarP(
+		&addOptTrailingCommentRE,
+		"trailing-comment", "r",
+		"",
+		"A regexp that will be applied to comments after a SQL statement")
 
 	for _, f := range []string{"name", "action"} {
 		addCmd.MarkFlagRequired(f)
diff --git a/go/vt/vttablet/customrule/filecustomrule/filecustomrule.go b/go/vt/vttablet/customrule/filecustomrule/filecustomrule.go
index 4ad7b64da45..eb52f04d7f8 100644
--- a/go/vt/vttablet/customrule/filecustomrule/filecustomrule.go
+++ b/go/vt/vttablet/customrule/filecustomrule/filecustomrule.go
@@ -1,5 +1,5 @@
 /*
-Copyright 2019 The Vitess Authors.
+Copyright 2021 The Vitess Authors.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -20,9 +20,13 @@ package filecustomrule
 import (
 	"flag"
 	"io/ioutil"
+	"path"
 	"time"
 
+	"github.com/fsnotify/fsnotify"
+
 	"vitess.io/vitess/go/vt/log"
+	"vitess.io/vitess/go/vt/servenv"
 	"vitess.io/vitess/go/vt/vttablet/tabletserver"
 	"vitess.io/vitess/go/vt/vttablet/tabletserver/rules"
 )
@@ -32,6 +36,8 @@ var (
 	fileCustomRule = NewFileCustomRule()
 	// Commandline flag to specify rule path
 	fileRulePath = flag.String("filecustomrules", "", "file based custom rule path")
+
+	fileRuleShouldWatch = flag.Bool("filecustomrules_watch", false, "set up a watch on the target file and reload query rules when it changes")
 )
 
 // FileCustomRule is an implementation of CustomRuleManager, it reads custom query
@@ -102,6 +108,45 @@ func ActivateFileCustomRules(qsc tabletserver.Controller) {
 	if *fileRulePath != "" {
 		qsc.RegisterQueryRuleSource(FileCustomRuleSource)
 		fileCustomRule.Open(qsc, *fileRulePath)
+
+		if *fileRuleShouldWatch {
+			baseDir := path.Dir(*fileRulePath)
+			ruleFileName := path.Base(*fileRulePath)
+
+			watcher, err := fsnotify.NewWatcher()
+			if err != nil {
+				log.Fatalf("Unable create new fsnotify watcher: %v", err)
+			}
+			servenv.OnTerm(func() { watcher.Close() })
+
+			go func(tsc tabletserver.Controller) {
+				for {
+					select {
+					case evt, ok := <-watcher.Events:
+						if !ok {
+							return
+						}
+						if path.Base(evt.Name) != ruleFileName {
+							continue
+						}
+						if err := fileCustomRule.Open(tsc, *fileRulePath); err != nil {
+							log.Infof("Failed to load custom rules from %q: %v", *fileRulePath, err)
+						} else {
+							log.Infof("Loaded custom rules from %q", *fileRulePath)
+						}
+					case err, ok := <-watcher.Errors:
+						if !ok {
+							return
+						}
+						log.Errorf("Error watching %v: %v", *fileRulePath, err)
+					}
+				}
+			}(qsc)
+
+			if err = watcher.Add(baseDir); err != nil {
+				log.Fatalf("Unable to set up watcher for %v + %v: %v", baseDir, ruleFileName, err)
+			}
+		}
 	}
 }
 
diff --git a/go/vt/vttablet/tabletserver/query_executor.go b/go/vt/vttablet/tabletserver/query_executor.go
index 40aa2c6e65e..17ecb13ce79 100644
--- a/go/vt/vttablet/tabletserver/query_executor.go
+++ b/go/vt/vttablet/tabletserver/query_executor.go
@@ -382,7 +382,7 @@ func (qre *QueryExecutor) checkPermissions() error {
 		remoteAddr = ci.RemoteAddr()
 		username = ci.Username()
 	}
-	action, desc := qre.plan.Rules.GetAction(remoteAddr, username, qre.bindVars)
+	action, desc := qre.plan.Rules.GetAction(remoteAddr, username, qre.bindVars, qre.marginComments)
 	switch action {
 	case rules.QRFail:
 		return vterrors.Errorf(vtrpcpb.Code_INVALID_ARGUMENT, "disallowed due to rule: %s", desc)
diff --git a/go/vt/vttablet/tabletserver/rules/cached_size.go b/go/vt/vttablet/tabletserver/rules/cached_size.go
index 61cd23586c2..60403475105 100644
--- a/go/vt/vttablet/tabletserver/rules/cached_size.go
+++ b/go/vt/vttablet/tabletserver/rules/cached_size.go
@@ -43,7 +43,7 @@ func (cached *Rule) CachedSize(alloc bool) int64 {
 	}
 	size := int64(0)
 	if alloc {
-		size += int64(184)
+		size += int64(232)
 	}
 	// field Description string
 	size += int64(len(cached.Description))
@@ -55,6 +55,10 @@ func (cached *Rule) CachedSize(alloc bool) int64 {
 	size += cached.user.CachedSize(false)
 	// field query vitess.io/vitess/go/vt/vttablet/tabletserver/rules.namedRegexp
 	size += cached.query.CachedSize(false)
+	// field leadingComment vitess.io/vitess/go/vt/vttablet/tabletserver/rules.namedRegexp
+	size += cached.leadingComment.CachedSize(false)
+	// field trailingComment vitess.io/vitess/go/vt/vttablet/tabletserver/rules.namedRegexp
+	size += cached.trailingComment.CachedSize(false)
 	// field plans []vitess.io/vitess/go/vt/vttablet/tabletserver/planbuilder.PlanType
 	{
 		size += int64(cap(cached.plans)) * int64(8)
diff --git a/go/vt/vttablet/tabletserver/rules/rules.go b/go/vt/vttablet/tabletserver/rules/rules.go
index 3cca04cee31..5ba71791030 100644
--- a/go/vt/vttablet/tabletserver/rules/rules.go
+++ b/go/vt/vttablet/tabletserver/rules/rules.go
@@ -27,6 +27,7 @@ import (
 	"vitess.io/vitess/go/vt/vtgate/evalengine"
 
 	"vitess.io/vitess/go/sqltypes"
+	"vitess.io/vitess/go/vt/sqlparser"
 	"vitess.io/vitess/go/vt/vterrors"
 	"vitess.io/vitess/go/vt/vttablet/tabletserver/planbuilder"
 
@@ -166,9 +167,14 @@ func (qrs *Rules) FilterByPlan(query string, planid planbuilder.PlanType, tableN
 }
 
 // GetAction runs the input against the rules engine and returns the action to be performed.
-func (qrs *Rules) GetAction(ip, user string, bindVars map[string]*querypb.BindVariable) (action Action, desc string) {
+func (qrs *Rules) GetAction(
+	ip,
+	user string,
+	bindVars map[string]*querypb.BindVariable,
+	marginComments sqlparser.MarginComments,
+) (action Action, desc string) {
 	for _, qr := range qrs.rules {
-		if act := qr.GetAction(ip, user, bindVars); act != QRContinue {
+		if act := qr.GetAction(ip, user, bindVars, marginComments); act != QRContinue {
 			return act, qr.Description
 		}
 	}
@@ -192,7 +198,7 @@ type Rule struct {
 	// All defined conditions must match for the rule to fire (AND).
 
 	// Regexp conditions. nil conditions are ignored (TRUE).
-	requestIP, user, query namedRegexp
+	requestIP, user, query, leadingComment, trailingComment namedRegexp
 
 	// Any matched plan will make this condition true (OR)
 	plans []planbuilder.PlanType
@@ -241,6 +247,8 @@ func (qr *Rule) Equal(other *Rule) bool {
 		qr.requestIP.Equal(other.requestIP) &&
 		qr.user.Equal(other.user) &&
 		qr.query.Equal(other.query) &&
+		qr.leadingComment.Equal(other.leadingComment) &&
+		qr.trailingComment.Equal(other.trailingComment) &&
 		reflect.DeepEqual(qr.plans, other.plans) &&
 		reflect.DeepEqual(qr.tableNames, other.tableNames) &&
 		reflect.DeepEqual(qr.bindVarConds, other.bindVarConds) &&
@@ -250,12 +258,14 @@ func (qr *Rule) Equal(other *Rule) bool {
 // Copy performs a deep copy of a Rule.
 func (qr *Rule) Copy() (newqr *Rule) {
 	newqr = &Rule{
-		Description: qr.Description,
-		Name:        qr.Name,
-		requestIP:   qr.requestIP,
-		user:        qr.user,
-		query:       qr.query,
-		act:         qr.act,
+		Description:     qr.Description,
+		Name:            qr.Name,
+		requestIP:       qr.requestIP,
+		user:            qr.user,
+		query:           qr.query,
+		leadingComment:  qr.leadingComment,
+		trailingComment: qr.trailingComment,
+		act:             qr.act,
 	}
 	if qr.plans != nil {
 		newqr.plans = make([]planbuilder.PlanType, len(qr.plans))
@@ -286,6 +296,12 @@ func (qr *Rule) MarshalJSON() ([]byte, error) {
 	if qr.query.Regexp != nil {
 		safeEncode(b, `,"Query":`, qr.query)
 	}
+	if qr.leadingComment.Regexp != nil {
+		safeEncode(b, `,"LeadingComment":`, qr.leadingComment)
+	}
+	if qr.trailingComment.Regexp != nil {
+		safeEncode(b, `,"TrailingComment":`, qr.trailingComment)
+	}
 	if qr.plans != nil {
 		safeEncode(b, `,"Plans":`, qr.plans)
 	}
@@ -339,6 +355,20 @@ func (qr *Rule) SetQueryCond(pattern string) (err error) {
 	return
 }
 
+// SetLeadingCommentCond adds a regular expression condition for a leading query comment.
+func (qr *Rule) SetLeadingCommentCond(pattern string) (err error) {
+	qr.leadingComment.name = pattern
+	qr.leadingComment.Regexp, err = regexp.Compile(makeExact(pattern))
+	return
+}
+
+// SetTrailingCommentCond adds a regular expression condition for a trailing query comment.
+func (qr *Rule) SetTrailingCommentCond(pattern string) (err error) {
+	qr.trailingComment.name = pattern
+	qr.trailingComment.Regexp, err = regexp.Compile(makeExact(pattern))
+	return
+}
+
 // makeExact forces a full string match for the regex instead of substring
 func makeExact(pattern string) string {
 	return fmt.Sprintf("^%s$", pattern)
@@ -418,13 +448,26 @@ func (qr *Rule) FilterByPlan(query string, planid planbuilder.PlanType, tableNam
 	}
 	newqr = qr.Copy()
 	newqr.query = namedRegexp{}
+	// Note we explicitly don't remove the leading/trailing comments as they
+	// must be evaluated at execution time.
 	newqr.plans = nil
 	newqr.tableNames = nil
 	return newqr
 }
 
 // GetAction returns the action for a single rule.
-func (qr *Rule) GetAction(ip, user string, bindVars map[string]*querypb.BindVariable) Action {
+func (qr *Rule) GetAction(
+	ip,
+	user string,
+	bindVars map[string]*querypb.BindVariable,
+	marginComments sqlparser.MarginComments,
+) Action {
+	if !reMatch(qr.leadingComment.Regexp, marginComments.Leading) {
+		return QRContinue
+	}
+	if !reMatch(qr.trailingComment.Regexp, marginComments.Trailing) {
+		return QRContinue
+	}
 	if !reMatch(qr.requestIP.Regexp, ip) {
 		return QRContinue
 	}
@@ -791,7 +834,7 @@ func BuildQueryRule(ruleInfo map[string]interface{}) (qr *Rule, err error) {
 		var lv []interface{}
 		var ok bool
 		switch k {
-		case "Name", "Description", "RequestIP", "User", "Query", "Action":
+		case "Name", "Description", "RequestIP", "User", "Query", "Action", "LeadingComment", "TrailingComment":
 			sv, ok = v.(string)
 			if !ok {
 				return nil, vterrors.Errorf(vtrpcpb.Code_INVALID_ARGUMENT, "want string for %s", k)
@@ -824,6 +867,16 @@ func BuildQueryRule(ruleInfo map[string]interface{}) (qr *Rule, err error) {
 			if err != nil {
 				return nil, vterrors.Errorf(vtrpcpb.Code_INVALID_ARGUMENT, "could not set Query condition: %v", sv)
 			}
+		case "LeadingComment":
+			err = qr.SetLeadingCommentCond(sv)
+			if err != nil {
+				return nil, vterrors.Errorf(vtrpcpb.Code_INVALID_ARGUMENT, "could not set LeadingComment condition: %v", sv)
+			}
+		case "TrailingComment":
+			err = qr.SetTrailingCommentCond(sv)
+			if err != nil {
+				return nil, vterrors.Errorf(vtrpcpb.Code_INVALID_ARGUMENT, "could not set TrailingComment condition: %v", sv)
+			}
 		case "Plans":
 			for _, p := range lv {
 				pv, ok := p.(string)
diff --git a/go/vt/vttablet/tabletserver/rules/rules_test.go b/go/vt/vttablet/tabletserver/rules/rules_test.go
index 76bddebc10f..951f4146789 100644
--- a/go/vt/vttablet/tabletserver/rules/rules_test.go
+++ b/go/vt/vttablet/tabletserver/rules/rules_test.go
@@ -25,6 +25,7 @@ import (
 	"testing"
 
 	"vitess.io/vitess/go/sqltypes"
+	"vitess.io/vitess/go/vt/sqlparser"
 	"vitess.io/vitess/go/vt/vterrors"
 	"vitess.io/vitess/go/vt/vttablet/tabletserver/planbuilder"
 
@@ -496,31 +497,68 @@ func TestAction(t *testing.T) {
 
 	bv := make(map[string]*querypb.BindVariable)
 	bv["a"] = sqltypes.Uint64BindVariable(0)
-	action, desc := qrs.GetAction("123", "user1", bv)
+
+	mc := sqlparser.MarginComments{
+		Leading:  "some comments leading the query",
+		Trailing: "other trailing comments",
+	}
+
+	action, desc := qrs.GetAction("123", "user1", bv, mc)
 	if action != QRFail {
 		t.Errorf("want fail")
 	}
 	if desc != "rule 1" {
 		t.Errorf("want rule 1, got %s", desc)
 	}
-	action, desc = qrs.GetAction("1234", "user", bv)
+	action, desc = qrs.GetAction("1234", "user", bv, mc)
 	if action != QRFailRetry {
 		t.Errorf("want fail_retry")
 	}
 	if desc != "rule 2" {
 		t.Errorf("want rule 2, got %s", desc)
 	}
-	action, _ = qrs.GetAction("1234", "user1", bv)
+	action, _ = qrs.GetAction("1234", "user1", bv, mc)
 	if action != QRContinue {
 		t.Errorf("want continue")
 	}
+
 	bv["a"] = sqltypes.Uint64BindVariable(1)
-	action, desc = qrs.GetAction("1234", "user1", bv)
+	action, desc = qrs.GetAction("1234", "user1", bv, mc)
 	if action != QRFail {
 		t.Errorf("want fail")
 	}
 	if desc != "rule 3" {
-		t.Errorf("want rule 2, got %s", desc)
+		t.Errorf("want rule 3, got %s", desc)
+	}
+
+	// reset bound variable 'a' to 0 so it doesn't match rule 3
+	bv["a"] = sqltypes.Uint64BindVariable(0)
+
+	qr4 := NewQueryRule("rule 4", "r4", QRFail)
+	qr4.SetTrailingCommentCond(".*trailing.*")
+
+	newQrs := qrs.Copy()
+	newQrs.Add(qr4)
+
+	action, desc = newQrs.GetAction("1234", "user1", bv, mc)
+	if action != QRFail {
+		t.Errorf("want fail")
+	}
+	if desc != "rule 4" {
+		t.Errorf("want rule 4, got %s", desc)
+	}
+
+	qr5 := NewQueryRule("rule 5", "r4", QRFail)
+	qr5.SetLeadingCommentCond(".*leading.*")
+
+	newQrs = qrs.Copy()
+	newQrs.Add(qr5)
+	action, desc = newQrs.GetAction("1234", "user1", bv, mc)
+	if action != QRFail {
+		t.Errorf("want fail")
+	}
+	if desc != "rule 5" {
+		t.Errorf("want rule 5, got %s", desc)
 	}
 }