Add line length truncate buffer

pkg/buffer/buffer.go

@@ -1,12 +1,17 @@
 package buffer
 
 import (
-	"bufio"
+	"bytes"
 	"fmt"
+	"io"
 	"net/http"
 	"strings"
 )
 
+// maxLineSize is the maximum size for a single log line (10MB).
+// GitHub Actions logs can contain extremely long lines (base64 content, minified JS, etc.)
+const maxLineSize = 10 * 1024 * 1024
+
 // ProcessResponseAsRingBufferToEnd reads the body of an HTTP response line by line,
 // storing only the last maxJobLogLines lines using a ring buffer (sliding window).
 // This efficiently retains the most recent lines, overwriting older ones as needed.
@@ -25,6 +30,7 @@ import (
 //
 // The function uses a ring buffer to efficiently store only the last maxJobLogLines lines.
 // If the response contains more lines than maxJobLogLines, only the most recent lines are kept.
+// Lines exceeding maxLineSize are truncated with a marker.
 func ProcessResponseAsRingBufferToEnd(httpResp *http.Response, maxJobLogLines int) (string, int, *http.Response, error) {
 	if maxJobLogLines > 100000 {
 		maxJobLogLines = 100000
@@ -35,20 +41,92 @@ func ProcessResponseAsRingBufferToEnd(httpResp *http.Response, maxJobLogLines in
 	totalLines := 0
 	writeIndex := 0
 
-	scanner := bufio.NewScanner(httpResp.Body)
-	scanner.Buffer(make([]byte, 0, 64*1024), 1024*1024)
+	const readBufferSize = 64 * 1024 // 64KB read buffer
+	const maxDisplayLength = 1000    // Keep first 1000 chars of truncated lines
 
-	for scanner.Scan() {
-		line := scanner.Text()
-		totalLines++
+	readBuf := make([]byte, readBufferSize)
+	var currentLine strings.Builder
+	lineTruncated := false
 
-		lines[writeIndex] = line
-		validLines[writeIndex] = true
-		writeIndex = (writeIndex + 1) % maxJobLogLines
-	}
+	for {
+		n, err := httpResp.Body.Read(readBuf)
+		if n > 0 {
+			chunk := readBuf[:n]
+			for len(chunk) > 0 {
+				// Find the next newline in the chunk
+				newlineIdx := bytes.IndexByte(chunk, '\n')
+
+				if newlineIdx >= 0 {
+					// Found a newline - complete the current line
+					if !lineTruncated {
+						remaining := maxLineSize - currentLine.Len()
+						if remaining > newlineIdx {
+							remaining = newlineIdx
+						}
+						if remaining > 0 {
+							currentLine.Write(chunk[:remaining])
+						}
+						if currentLine.Len() >= maxLineSize {
+							lineTruncated = true
+						}
+					}
+
+					// Store the completed line
+					line := currentLine.String()
+					if lineTruncated {
+						// Only keep first maxDisplayLength chars for truncated lines
+						if len(line) > maxDisplayLength {
+							line = line[:maxDisplayLength]
+						}
+						line += "... [TRUNCATED]"
+					}
+					lines[writeIndex] = line
+					validLines[writeIndex] = true
+					totalLines++
+					writeIndex = (writeIndex + 1) % maxJobLogLines
 
-	if err := scanner.Err(); err != nil {
-		return "", 0, httpResp, fmt.Errorf("failed to read log content: %w", err)
+					// Reset for next line
+					currentLine.Reset()
+					lineTruncated = false
+					chunk = chunk[newlineIdx+1:]
+				} else {
+					// No newline in remaining chunk - accumulate if not truncated
+					if !lineTruncated {
+						remaining := maxLineSize - currentLine.Len()
+						if remaining > len(chunk) {
+							remaining = len(chunk)
+						}
+						if remaining > 0 {
+							currentLine.Write(chunk[:remaining])
+						}
+						if currentLine.Len() >= maxLineSize {
+							lineTruncated = true
+						}
+					}
+					break
+				}
+			}
+		}
+
+		if err == io.EOF {
+			// Handle final line without newline
+			if currentLine.Len() > 0 {
+				line := currentLine.String()
+				if lineTruncated {
+					if len(line) > maxDisplayLength {
+						line = line[:maxDisplayLength]
+					}
+					line += "... [TRUNCATED]"
+				}
+				lines[writeIndex] = line
+				validLines[writeIndex] = true
+				totalLines++
+			}
+			break
+		}
+		if err != nil {
+			return "", 0, httpResp, fmt.Errorf("failed to read log content: %w", err)
+		}
 	}
 
 	var result []string

pkg/buffer/buffer_test.go

@@ -0,0 +1,143 @@
+package buffer
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestProcessResponseAsRingBufferToEnd(t *testing.T) {
+	t.Run("normal lines", func(t *testing.T) {
+		body := "line1\nline2\nline3\n"
+		resp := &http.Response{
+			Body: io.NopCloser(strings.NewReader(body)),
+		}
+
+		result, totalLines, respOut, err := ProcessResponseAsRingBufferToEnd(resp, 10)
+		if respOut != nil && respOut.Body != nil {
+			defer respOut.Body.Close()
+		}
+		require.NoError(t, err)
+		assert.Equal(t, 3, totalLines)
+		assert.Equal(t, "line1\nline2\nline3", result)
+	})
+
+	t.Run("ring buffer keeps last N lines", func(t *testing.T) {
+		body := "line1\nline2\nline3\nline4\nline5\n"
+		resp := &http.Response{
+			Body: io.NopCloser(strings.NewReader(body)),
+		}
+
+		result, totalLines, respOut, err := ProcessResponseAsRingBufferToEnd(resp, 3)
+		if respOut != nil && respOut.Body != nil {
+			defer respOut.Body.Close()
+		}
+		require.NoError(t, err)
+		assert.Equal(t, 5, totalLines)
+		assert.Equal(t, "line3\nline4\nline5", result)
+	})
+
+	t.Run("handles very long line exceeding 10MB", func(t *testing.T) {
+		// Create a line that exceeds maxLineSize (10MB)
+		longLine := strings.Repeat("x", 11*1024*1024) // 11MB
+		body := "line1\n" + longLine + "\nline3\n"
+		resp := &http.Response{
+			Body: io.NopCloser(strings.NewReader(body)),
+		}
+
+		result, totalLines, respOut, err := ProcessResponseAsRingBufferToEnd(resp, 100)
+		if respOut != nil && respOut.Body != nil {
+			defer respOut.Body.Close()
+		}
+		require.NoError(t, err)
+		// Should have processed lines with truncation marker
+		assert.Greater(t, totalLines, 0)
+		assert.Contains(t, result, "TRUNCATED")
+	})
+
+	t.Run("handles line at exactly max size", func(t *testing.T) {
+		// Create a line just under maxLineSize
+		longLine := strings.Repeat("a", 1024*1024) // 1MB - should work fine
+		body := "start\n" + longLine + "\nend\n"
+		resp := &http.Response{
+			Body: io.NopCloser(strings.NewReader(body)),
+		}
+
+		result, totalLines, respOut, err := ProcessResponseAsRingBufferToEnd(resp, 100)
+		if respOut != nil && respOut.Body != nil {
+			defer respOut.Body.Close()
+		}
+		require.NoError(t, err)
+		assert.Equal(t, 3, totalLines)
+		assert.Contains(t, result, "start")
+		assert.Contains(t, result, "end")
+	})
+
+	t.Run("ring buffer with long line in middle of many lines", func(t *testing.T) {
+		// Create many lines with a long line in the middle
+		// Ring buffer size is 5, so we should only keep the last 5 lines
+		var sb strings.Builder
+		for i := 1; i <= 10; i++ {
+			sb.WriteString(fmt.Sprintf("line%d\n", i))
+		}
+		// Insert an 11MB line (exceeds maxLineSize of 10MB)
+		longLine := strings.Repeat("x", 11*1024*1024)
+		sb.WriteString(longLine)
+		sb.WriteString("\n")
+		for i := 11; i <= 20; i++ {
+			sb.WriteString(fmt.Sprintf("line%d\n", i))
+		}
+
+		resp := &http.Response{
+			Body: io.NopCloser(strings.NewReader(sb.String())),
+		}
+
+		result, totalLines, respOut, err := ProcessResponseAsRingBufferToEnd(resp, 5)
+		if respOut != nil && respOut.Body != nil {
+			defer respOut.Body.Close()
+		}
+		require.NoError(t, err)
+		// 10 lines before + 1 long line + 10 lines after = 21 total
+		assert.Equal(t, 21, totalLines)
+		// Should only have the last 5 lines (line16 through line20)
+		assert.Contains(t, result, "line16")
+		assert.Contains(t, result, "line17")
+		assert.Contains(t, result, "line18")
+		assert.Contains(t, result, "line19")
+		assert.Contains(t, result, "line20")
+		// Should NOT contain earlier lines
+		assert.NotContains(t, result, "line1\n")
+		assert.NotContains(t, result, "line10\n")
+		// The truncated line should not be in the last 5
+		assert.NotContains(t, result, "TRUNCATED")
+	})
+
+	t.Run("ring buffer keeps truncated line when in last N", func(t *testing.T) {
+		// Long line followed by only 2 more lines, with ring buffer size 5
+		longLine := strings.Repeat("y", 11*1024*1024)
+		body := "line1\nline2\nline3\n" + longLine + "\nlineA\nlineB\n"
+		resp := &http.Response{
+			Body: io.NopCloser(strings.NewReader(body)),
+		}
+
+		result, totalLines, respOut, err := ProcessResponseAsRingBufferToEnd(resp, 5)
+		if respOut != nil && respOut.Body != nil {
+			defer respOut.Body.Close()
+		}
+		require.NoError(t, err)
+		assert.Equal(t, 6, totalLines)
+		// Last 5: line2, line3, truncated, lineA, lineB
+		assert.Contains(t, result, "line2")
+		assert.Contains(t, result, "line3")
+		assert.Contains(t, result, "TRUNCATED")
+		assert.Contains(t, result, "lineA")
+		assert.Contains(t, result, "lineB")
+		// line1 should be rotated out
+		assert.NotContains(t, result, "line1")
+	})
+}