Make output window configurable: BUILDKIT_TTY_LOG_LINES

The output window was previously hard-coded to a height of 6; this patch makes it configurable at run-time by setting the BUILDKIT_TTY_LOG_LINES environment variable. Signed-off-by: Burt Holzman <[email protected]>
pmengelbert · Sep 28, 2023 · 2677a22 · 2677a22
1 parent 4c89091
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diff --git a/README.md b/README.md
@@ -81,6 +81,7 @@ Join `#buildkit` channel on [Docker Community Slack](https://dockr.ly/comm-slack
 - [Building multi-platform images](#building-multi-platform-images)
   - [Configuring `buildctl`](#configuring-buildctl)
     - [Color Output Controls](#color-output-controls)
+    - [Number of log lines (for active steps in tty mode)](#number-of-log-lines-for-active-steps-in-tty-mode)
 - [Contributing](#contributing)
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
@@ -791,6 +792,9 @@ Parsing errors will be reported but ignored. This will result in default color v
 
 - [The list of pre-defined colors](https://github.com/moby/buildkit/blob/master/util/progress/progressui/colors.go).
 
+#### Number of log lines (for active steps in tty mode)
+You can change how many log lines are visible for active steps in tty mode by setting `BUILDKIT_TTY_LOG_LINES` to a number (default: 6).
+
 ## Contributing
 
 Want to contribute to BuildKit? Awesome! You can find information about contributing to this project in the [CONTRIBUTING.md](/.github/CONTRIBUTING.md)
diff --git a/util/progress/progressui/display.go b/util/progress/progressui/display.go
@@ -310,7 +310,6 @@ func (d *rawJSONDisplay) done() {
 	// No actions needed.
 }
 
-const termHeight = 6
 const termPad = 10
 
 type displayInfo struct {

diff --git a/util/progress/progressui/init.go b/util/progress/progressui/init.go
@@ -3,6 +3,7 @@ package progressui
 import (
 	"os"
 	"runtime"
+	"strconv"
 
 	"github.com/morikuni/aec"
 )
@@ -12,6 +13,8 @@ var colorCancel aec.ANSI
 var colorWarning aec.ANSI
 var colorError aec.ANSI
 
+var termHeight = 6
+
 func init() {
 	// As recommended on https://no-color.org/
 	if v := os.Getenv("NO_COLOR"); v != "" {
@@ -34,4 +37,13 @@ func init() {
 		envColorString := os.Getenv("BUILDKIT_COLORS")
 		setUserDefinedTermColors(envColorString)
 	}
+
+	// Make the terminal height configurable at runtime.
+	termHeightStr := os.Getenv("BUILDKIT_TTY_LOG_LINES")
+	if termHeightStr != "" {
+		termHeightVal, err := strconv.Atoi(termHeightStr)
+		if err == nil && termHeightVal > 0 {
+			termHeight = termHeightVal
+		}
+	}
 }