From 760be655e914898a164736cca8a82861bc79fe4c Mon Sep 17 00:00:00 2001
From: Jose Diaz-Gonzalez <email@josediazgonzalez.com>
Date: Sun, 24 Oct 2021 20:20:35 -0400
Subject: [PATCH] fix: handle both stderr and stdout when tailing container
 logs

Previously, stderr was ignored when tailing container log output in golang. This change ensures we capture it and also use the correct helper for that output method.
---
 plugins/common/log.go | 91 ++++++++++++++++++++++++++++++-------------
 1 file changed, 64 insertions(+), 27 deletions(-)

diff --git a/plugins/common/log.go b/plugins/common/log.go
index 7cfc87b62..d45f26e48 100644
--- a/plugins/common/log.go
+++ b/plugins/common/log.go
@@ -1,11 +1,11 @@
 package common
 
 import (
-	"bufio"
 	"fmt"
 	"os"
 	"strconv"
 	"strings"
+	"sync"
 )
 
 // ErrWithExitCode wraps error and exposes an ExitCode method
@@ -13,6 +13,37 @@ type ErrWithExitCode interface {
 	ExitCode() int
 }
 
+type writer struct {
+	mu     *sync.Mutex
+	source string
+}
+
+// Write prints the data to either stdout or stderr using the log helper functions
+func (w *writer) Write(bytes []byte) (int, error) {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+
+	if w.source == "stdout" {
+		for _, line := range strings.Split(string(bytes), "\n") {
+			if line == "" {
+				continue
+			}
+
+			LogVerboseQuiet(line)
+		}
+	} else {
+		for _, line := range strings.Split(string(bytes), "\n") {
+			if line == "" {
+				continue
+			}
+
+			LogVerboseStderrQuiet(line)
+		}
+	}
+
+	return len(bytes), nil
+}
+
 // LogFail is the failure log formatter
 // prints text to stderr and exits with status 1
 func LogFail(text string) {
@@ -81,6 +112,12 @@ func LogVerbose(text string) {
 	fmt.Println(fmt.Sprintf("       %s", text))
 }
 
+// LogVerboseStderr is the verbose log formatter
+// prints indented text to stderr
+func LogVerboseStderr(text string) {
+	fmt.Fprintln(os.Stderr, fmt.Sprintf(" !     %s", text))
+}
+
 // LogVerboseQuiet is the verbose log formatter
 // prints indented text to stdout (with quiet option)
 func LogVerboseQuiet(text string) {
@@ -89,25 +126,17 @@ func LogVerboseQuiet(text string) {
 	}
 }
 
+// LogVerboseStderrQuiet is the verbose log formatter
+// prints indented text to stderr (with quiet option)
+func LogVerboseStderrQuiet(text string) {
+	if os.Getenv("DOKKU_QUIET_OUTPUT") == "" {
+		LogVerboseStderr(text)
+	}
+}
+
 // LogVerboseQuietContainerLogs is the verbose log formatter for container logs
 func LogVerboseQuietContainerLogs(containerID string) {
-	sc := NewShellCmdWithArgs(DockerBin(), "container", "logs", containerID)
-	sc.ShowOutput = false
-	b, err := sc.CombinedOutput()
-	if err != nil {
-		LogExclaim(fmt.Sprintf("Failed to fetch container logs: %s", containerID))
-	}
-
-	output := strings.TrimSpace(string(b))
-	if len(output) == 0 {
-		return
-	}
-
-	for _, line := range strings.Split(output, "\n") {
-		if line != "" {
-			LogVerboseQuiet(line)
-		}
-	}
+	LogVerboseQuietContainerLogsTail(containerID, 0, false)
 }
 
 // LogVerboseQuietContainerLogsTail is the verbose log formatter for container logs with tail mode enabled
@@ -119,17 +148,25 @@ func LogVerboseQuietContainerLogsTail(containerID string, lines int, tail bool)
 	if tail {
 		args = append(args, "--follow")
 	}
-	sc := NewShellCmdWithArgs(DockerBin(), args...)
-	stdout, _ := sc.Command.StdoutPipe()
-	sc.Command.Start()
 
-	scanner := bufio.NewScanner(stdout)
-	scanner.Split(bufio.ScanLines)
-	for scanner.Scan() {
-		m := scanner.Text()
-		LogVerboseQuiet(m)
+	sc := NewShellCmdWithArgs(DockerBin(), args...)
+	var mu sync.Mutex
+	sc.Command.Stdout = &writer{
+		mu:     &mu,
+		source: "stdout",
+	}
+	sc.Command.Stderr = &writer{
+		mu:     &mu,
+		source: "stderr",
+	}
+
+	if err := sc.Command.Start(); err != nil {
+		LogExclaim(fmt.Sprintf("Failed to fetch container logs: %s", containerID))
+	}
+
+	if err := sc.Command.Wait(); err != nil {
+		LogExclaim(fmt.Sprintf("Failed to fetch container logs: %s", containerID))
 	}
-	sc.Command.Wait()
 }
 
 // LogWarn is the warning log formatter