fix symlink broken in container log filepath

pkg/go.mod

@@ -136,7 +136,7 @@ require (
 )
 
 replace (
-	github.com/VictoriaMetrics/VictoriaMetrics => github.com/iLogtail/VictoriaMetrics v1.83.3-ilogtail
+	github.com/VictoriaMetrics/VictoriaMetrics => github.com/iLogtail/VictoriaMetrics v1.83.4-ilogtail
 	github.com/VictoriaMetrics/metrics => github.com/iLogtail/metrics v1.23.0-ilogtail
 	github.com/aliyun/alibaba-cloud-sdk-go/services/sls_inner => ../external/github.com/aliyun/alibaba-cloud-sdk-go/services/sls_inner
 	github.com/elastic/beats/v7 => ../external/github.com/elastic/beats/v7

pkg/helper/mount_others.go

@@ -18,7 +18,9 @@
 package helper
 
 import (
+	"io/fs"
 	"os"
+	"strings"
 )
 
 var DefaultLogtailMountPath string
@@ -31,6 +33,43 @@ func GetMountedFilePathWithBasePath(basePath, logPath string) string {
 	return basePath + logPath
 }
 
+func TryGetRealPath(path string) (string, fs.FileInfo) {
+	sepLen := len(string(os.PathSeparator))
+	index := 0 // assume path is absolute
+	for i := 0; i < 10; i++ {
+		if f, err := os.Stat(path); err == nil {
+			return path, f
+		}
+		for {
+			j := strings.IndexRune(path[index+sepLen:], os.PathSeparator)
+			if j == -1 {
+				index = len(path)
+			} else {
+				index += j + sepLen
+			}
+
+			f, err := os.Lstat(path[:index])
+			if err != nil {
+				return "", nil
+			}
+			if f.Mode()&os.ModeSymlink != 0 {
+				// path[:index] is a symlink
+				target, _ := os.Readlink(path[:index])
+				partialPath := GetMountedFilePath(target)
+				path = partialPath + path[index:]
+				if _, err := os.Stat(partialPath); err != nil {
+					// path referenced by partialPath does not exist or has symlink
+					index = 0
+				} else {
+					index = len(partialPath)
+				}
+				break
+			}
+		}
+	}
+	return "", nil
+}
+
 func init() {
 	defaultPath := "/logtail_host"
 	_, err := os.Stat(defaultPath)

pkg/helper/mount_windows.go

@@ -17,6 +17,7 @@ package helper
 import (
 	"flag"
 	"fmt"
+	"io/fs"
 	"os"
 	"strings"
 
@@ -118,3 +119,10 @@ func GetMountedFilePathWithBasePath(basePath, filePath string) string {
 	}
 	return basePath + filePath[colonPos+1:]
 }
+
+func TryGetRealPath(path string) (string, fs.FileInfo) {
+	if f, err := os.Stat(path); err == nil {
+		return path, f
+	}
+	return "", nil
+}

plugins/input/docker/stdout/input_docker_stdout.go

@@ -16,7 +16,6 @@ package stdout
 
 import (
 	"fmt"
-	"os"
 	"regexp"
 	"sync"
 	"time"
@@ -85,9 +84,9 @@ func NewDockerFileSyner(sds *ServiceDockerStdout,
 		}
 
 		// first watch this container
-		stat, err := os.Stat(checkpoint.Path)
-		if err != nil {
-			logger.Warning(sds.context.GetRuntimeContext(), "DOCKER_STDOUT_STAT_ALARM", "stat log file error, path", checkpoint.Path, "error", err.Error())
+		realPath, stat := helper.TryGetRealPath(checkpoint.Path)
+		if realPath == "" {
+			logger.Warning(sds.context.GetRuntimeContext(), "DOCKER_STDOUT_STAT_ALARM", "stat log file error, path", checkpoint.Path, "error", "path not found")
 		} else {
 			checkpoint.Offset = stat.Size()
 			if checkpoint.Offset > sds.StartLogMaxOffset {