From 5c146ca57ad5bc8e91d8af9ea59bd5b0f49d6361 Mon Sep 17 00:00:00 2001
From: Denis Bilenko <denis.bilenko@databricks.com>
Date: Mon, 3 Mar 2025 14:42:43 +0100
Subject: [PATCH] Synchronize logging in cmdio (#2418)
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## Changes
Add mutex synchronization in cmdio logger Log() method.

## Why

Since we issue multiple calls to underlying writer, we should lock the
whole method, otherwise we can get broken messages. One that can be
easily reproduced today is

```
 hyperfine -m 100 --show-output 'go test ./acceptance -run ^TestAccept$/^bundle$/^artifacts$/^whl_multiple$ -count=1'
...
            -Uploading my_test_code-0.0.1-py3-none-any.whl...
            -Uploading my_test_code_2-0.0.1-py3-none-any.whl...
            +Uploading my_test_code-0.0.1-py3-none-any.whl...Uploading my_test_code_2-0.0.1-py3-none-any.whl...

Error: Command terminated with non-zero exit code 1 in benchmark iteration 54. Use the '-i'/'--ignore-failure' option if you want to ignore this. Alternatively, use the '--show-output' option to debug what went wrong.
```

An alternative could be to prepare a message fully in a local buffer and
write it in one call (I’m assuming underlying writer is still
synchronized). However, that’s more complicated and unclear if it’s
worth it, perf-wise.

## Tests
With this change I’m running the same hyperfine command with 1000
iterations with no failures.
---
 libs/cmdio/logger.go | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libs/cmdio/logger.go b/libs/cmdio/logger.go
index 48b76ce42..7d369a8a0 100644
--- a/libs/cmdio/logger.go
+++ b/libs/cmdio/logger.go
@@ -9,6 +9,7 @@ import (
 	"io"
 	"os"
 	"strings"
+	"sync"
 
 	"github.com/databricks/cli/libs/flags"
 	"github.com/manifoldco/promptui"
@@ -29,6 +30,8 @@ type Logger struct {
 	// If true, indicates no events have been printed by the logger yet. Used
 	// by inplace logging for formatting
 	isFirstEvent bool
+
+	mutex sync.Mutex
 }
 
 func NewLogger(mode flags.ProgressLogFormat) *Logger {
@@ -216,6 +219,8 @@ func (l *Logger) writeInplace(event Event) {
 }
 
 func (l *Logger) Log(event Event) {
+	l.mutex.Lock()
+	defer l.mutex.Unlock()
 	switch l.Mode {
 	case flags.ModeInplace:
 		if event.IsInplaceSupported() {