From 86640ceae052242787a1efb185d9b547ded41d68 Mon Sep 17 00:00:00 2001
From: Corentin <33163342+corentinmusard@users.noreply.github.com>
Date: Wed, 9 Jul 2025 09:18:17 +0000
Subject: [PATCH] Clarify DefaultMaxQueueSize and DefaultScheduleDelay usage
 (#6974)
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### Description

OpenTelemetry uses `DefaultScheduleDelay` and `DefaultExportTimeout`
values as milliseconds but Go time package will understand them as
nanoseconds.

I understand that this is a stable library and that those value will
probably never change, so can we at least clarify their usage?

Right above the defaults declaration it says `// Defaults for
BatchSpanProcessorOptions.` which is confusing.

We used `trace.DefaultScheduleDelay` as a fallback value for our tracing
setup.
This confusion led to high CPU usage due to the frequent batch exports.

### Confusing behavior

```go
processor := trace.NewBatchSpanProcessor(exporter,
    // set timeout to 5000 ns instead of the expected 5000 ms
    trace.WithBatchTimeout(trace.DefaultScheduleDelay),
    // set timeout to 30000 ns instead of the expected 30000 ms
    trace.WithExportTimeout(trace.DefaultExportTimeout),
)
```

### Correct way to use those values

```go
processor := trace.NewBatchSpanProcessor(exporter,
    trace.WithBatchTimeout(trace.DefaultScheduleDelay * time.Millisecond),
    trace.WithExportTimeout(trace.DefaultExportTimeout * time.Millisecond),
)
```

---------

Co-authored-by: Damien Mathieu <42@dmathieu.com>
Co-authored-by: Robert Pająk <pellared@hotmail.com>
---
 sdk/trace/batch_span_processor.go | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/sdk/trace/batch_span_processor.go b/sdk/trace/batch_span_processor.go
index 6966ed861..b6e93dea0 100644
--- a/sdk/trace/batch_span_processor.go
+++ b/sdk/trace/batch_span_processor.go
@@ -18,8 +18,10 @@ import (
 
 // Defaults for BatchSpanProcessorOptions.
 const (
-	DefaultMaxQueueSize       = 2048
-	DefaultScheduleDelay      = 5000
+	DefaultMaxQueueSize = 2048
+	// DefaultScheduleDelay is the delay interval between two consecutive exports, in milliseconds.
+	DefaultScheduleDelay = 5000
+	// DefaultExportTimeout is the duration after which an export is cancelled, in milliseconds.
 	DefaultExportTimeout      = 30000
 	DefaultMaxExportBatchSize = 512
 )