From 33ffee658c305e1a92093e8e977393d3c6fb8e7e Mon Sep 17 00:00:00 2001
From: pk910 <philipp@pk910.de>
Date: Sun, 1 Sep 2024 00:17:15 +0200
Subject: [PATCH] fix callstack extraction for timed out page calls

---
 go.mod                    |  1 +
 go.sum                    |  2 ++
 services/frontendcache.go | 33 +++++++++++++++++++--------------
 utils/debug.go            | 32 --------------------------------
 4 files changed, 22 insertions(+), 46 deletions(-)
 delete mode 100644 utils/debug.go

diff --git a/go.mod b/go.mod
index 597092c4..dcf043f5 100644
--- a/go.mod
+++ b/go.mod
@@ -29,6 +29,7 @@ require (
 	github.com/sirupsen/logrus v1.9.3
 	github.com/stdatiks/jdenticon-go v0.1.0
 	github.com/tdewolff/minify v2.3.6+incompatible
+	github.com/timandy/routine v1.1.4
 	github.com/urfave/negroni v1.0.0
 	golang.org/x/crypto v0.26.0
 	golang.org/x/exp v0.0.0-20240613232115-7f521ea00fb8
diff --git a/go.sum b/go.sum
index 55406583..092e8c74 100644
--- a/go.sum
+++ b/go.sum
@@ -412,6 +412,8 @@ github.com/tdewolff/parse v2.3.4+incompatible h1:x05/cnGwIMf4ceLuDMBOdQ1qGniMoxp
 github.com/tdewolff/parse v2.3.4+incompatible/go.mod h1:8oBwCsVmUkgHO8M5iCzSIDtpzXOT0WXX9cWhz+bIzJQ=
 github.com/tdewolff/test v1.0.9 h1:SswqJCmeN4B+9gEAi/5uqT0qpi1y2/2O47V/1hhGZT0=
 github.com/tdewolff/test v1.0.9/go.mod h1:6DAvZliBAAnD7rhVgwaM7DE5/d9NMOAJ09SqYqeK4QE=
+github.com/timandy/routine v1.1.4 h1:L9eAli/ROJcW6LhmwZcusYQcdAqxAXGOQhEXLQSNWOA=
+github.com/timandy/routine v1.1.4/go.mod h1:siBcl8iIsGmhLCajRGRcy7Y7FVcicNXkr97JODdt9fc=
 github.com/tklauser/go-sysconf v0.3.14 h1:g5vzr9iPFFz24v2KZXs/pvpvh8/V9Fw6vQK5ZZb78yU=
 github.com/tklauser/go-sysconf v0.3.14/go.mod h1:1ym4lWMLUOhuBOPGtRcJm7tEGX4SCYNEEEtghGG/8uY=
 github.com/tklauser/numcpus v0.8.0 h1:Mx4Wwe/FjZLeQsK/6kt2EOepwwSl7SmJrK5bV/dXYgY=
diff --git a/services/frontendcache.go b/services/frontendcache.go
index f2367091..428823f9 100644
--- a/services/frontendcache.go
+++ b/services/frontendcache.go
@@ -14,6 +14,7 @@ import (
 	"github.com/ethpandaops/dora/cache"
 	"github.com/ethpandaops/dora/utils"
 	"github.com/sirupsen/logrus"
+	"github.com/timandy/routine"
 )
 
 type FrontendCacheService struct {
@@ -119,6 +120,8 @@ func (fc *FrontendCacheService) processPageCall(pageKey string, caching bool, pa
 	callIdx := fc.pageCallCounter
 	fc.pageCallCounterMutex.Unlock()
 
+	callGoId := int64(0)
+
 	go func(callIdx uint64) {
 		defer func() {
 			if err := recover(); err != nil {
@@ -130,6 +133,8 @@ func (fc *FrontendCacheService) processPageCall(pageKey string, caching bool, pa
 			}
 		}()
 
+		callGoId = routine.Goid()
+
 		// check cache
 		if !utils.Config.Frontend.Debug && caching && fc.getFrontendCache(pageKey, pageData) == nil {
 			logrus.Debugf("page served from cache: %v", pageKey)
@@ -169,7 +174,7 @@ func (fc *FrontendCacheService) processPageCall(pageKey string, caching bool, pa
 		return nil, &FrontendCachePageError{
 			name:  "page timeout",
 			err:   fmt.Errorf("page call %v timeout", callIdx),
-			stack: fc.extractPageCallStack(callIdx),
+			stack: fc.extractPageCallStack(callGoId),
 		}
 	}
 }
@@ -190,7 +195,7 @@ func (fc *FrontendCacheService) completePageLoad(pageKey string, processingPage
 	fc.processingMutex.Unlock()
 }
 
-func (fc *FrontendCacheService) extractPageCallStack(callIdx uint64) string {
+func (fc *FrontendCacheService) extractPageCallStack(callGoid int64) string {
 	if fc.callStackMutex.TryLock() {
 		runtime.Stack(fc.callStackBuffer, true)
 		fc.callStackMutex.Unlock()
@@ -198,27 +203,27 @@ func (fc *FrontendCacheService) extractPageCallStack(callIdx uint64) string {
 	fc.callStackMutex.RLock()
 	defer fc.callStackMutex.RUnlock()
 
-	callFnName := fmt.Sprintf("processPageCall.func1(0x%x)", callIdx)
 	scanner := bufio.NewScanner(bytes.NewReader(fc.callStackBuffer))
-	lastBlock := []string{}
-	isPageCall := false
+	stackTrace := []string{}
+	isRelevantCall := false
 	for scanner.Scan() {
 		line := scanner.Text()
 		if strings.HasPrefix(line, "goroutine ") {
-			if isPageCall {
+			if isRelevantCall {
 				break
 			}
-			lastBlock = []string{}
-		} else {
-			lastBlock = append(lastBlock, line)
 
-			if strings.Contains(line, callFnName) {
-				isPageCall = true
-			}
+			isRelevantCall = strings.HasPrefix(line, fmt.Sprintf("goroutine %v ", callGoid))
+		}
+
+		if isRelevantCall {
+			stackTrace = append(stackTrace, line)
 		}
 	}
-	if !isPageCall {
+
+	if !isRelevantCall {
 		return "call stack not found"
 	}
-	return strings.Join(lastBlock, "\n")
+
+	return strings.Join(stackTrace, "\n")
 }
diff --git a/utils/debug.go b/utils/debug.go
deleted file mode 100644
index ddd63228..00000000
--- a/utils/debug.go
+++ /dev/null
@@ -1,32 +0,0 @@
-package utils
-
-import (
-	"bytes"
-	"runtime"
-	"strconv"
-)
-
-var (
-	goroutinePrefix = []byte("goroutine ")
-)
-
-// This is terrible, slow, and should never be used.
-func Goid() int {
-	buf := make([]byte, 32)
-	n := runtime.Stack(buf, false)
-	buf = buf[:n]
-	// goroutine 1 [running]: ...
-
-	buf, ok := bytes.CutPrefix(buf, goroutinePrefix)
-	if !ok {
-		return 0
-	}
-
-	i := bytes.IndexByte(buf, ' ')
-	if i < 0 {
-		return 0
-	}
-
-	res, _ := strconv.Atoi(string(buf[:i]))
-	return res
-}