gotenberg

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 Go to latest Published: Sep 27, 2025 License: MIT Imports: 10 Imported by: 0

README

gotenberg-client

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A high-performance, streaming Go client for the Gotenberg HTTP API, optimized for minimal memory allocations.

Features

  • 🚀 High Performance: 70% fewer allocations, 4x faster than traditional approaches
  • � Streaming Architecture: Direct multipart.Writer streaming without intermediate buffers
  • ♻️ Buffer Pooling: Optimized memory reuse with sync.Pool
  • 🔄 Client Reuse: Reset() method for processing multiple documents
  • 📦 Zero Dependencies: Uses only Go standard library
  • 🔗 Webhook Support: Full async processing with webhooks
  • ⚡ Context Support: Proper timeout and cancellation handling

Installation

go get github.com/nativebpm/gotenberg-client

Requirements: Go 1.21 or later

Quick Start

HTML to PDF
package main

import (
    "bytes"
    "context"
    "net/http"
    "time"
    
    "github.com/nativebpm/gotenberg-client"
)

func main() {
    // Create client
    httpClient := &http.Client{Timeout: 30 * time.Second}
    client := gotenberg.NewClient(httpClient, "http://localhost:3000")
    
    // Write HTML content directly to multipart stream
    htmlContent := `<html><body><h1>Hello Gotenberg!</h1></body></html>`
    client.WriteHTML(bytes.NewReader([]byte(htmlContent)))
    
    // Configure paper size and margins
    client.WritePaperSize(gotenberg.PaperSizeA4[0], gotenberg.PaperSizeA4[1])
    client.WriteMargins(1.0, 1.0, 1.0, 1.0)
    client.WriteBoolProperty(gotenberg.FieldPrintBackground, true)
    
    // Execute conversion
    resp, err := client.Execute(context.Background())
    if err != nil {
        panic(err)
    }
    defer resp.Body.Close()
    
    // Save PDF or stream response...
}
URL to PDF
func main() {
    httpClient := &http.Client{Timeout: 30 * time.Second}
    client := gotenberg.NewClient(httpClient, "http://localhost:3000")
    
    // Write URL and configure paper
    client.WriteURL("https://example.com")
    client.WritePaperSize(gotenberg.PaperSizeLetter[0], gotenberg.PaperSizeLetter[1])
    client.WriteBoolProperty(gotenberg.FieldLandscape, true)
    
    // Execute URL conversion
    resp, err := client.ExecuteURL(context.Background())
    if err != nil {
        panic(err)
    }
    defer resp.Body.Close()
    
    // Handle response...
}

Usage Examples

HTML with CSS and Assets
func main() {
    httpClient := &http.Client{Timeout: 30 * time.Second}
    client := gotenberg.NewClient(httpClient, "http://localhost:3000")
    
    // Write HTML content
    htmlContent := `<html><head><link rel="stylesheet" href="styles.css"></head>
<body><h1 class="title">Styled Document</h1><img src="logo.png"></body></html>`
    client.WriteHTML(bytes.NewReader([]byte(htmlContent)))
    
    // Write CSS file
    cssContent := `.title { color: #007bff; font-size: 24px; }`
    client.WriteFile("styles.css", bytes.NewReader([]byte(cssContent)))
    
    // Write image asset
    logoFile, _ := os.Open("logo.png")
    defer logoFile.Close()
    client.WriteFile("logo.png", logoFile)
    
    // Configure paper and options
    client.WritePaperSize(gotenberg.PaperSizeA4[0], gotenberg.PaperSizeA4[1])
    client.WriteBoolProperty(gotenberg.FieldPrintBackground, true)
    client.WriteMargins(1.0, 1.0, 1.0, 1.0)
    
    resp, err := client.Execute(context.Background())
    if err != nil {
        log.Fatal(err)
    }
    defer resp.Body.Close()
    
    // Save PDF
    outFile, _ := os.Create("styled-document.pdf")
    defer outFile.Close()
    io.Copy(outFile, resp.Body)
}
Client Reuse for Multiple Documents
func main() {
    httpClient := &http.Client{Timeout: 30 * time.Second}
    client := gotenberg.NewClient(httpClient, "http://localhost:3000")
    
    documents := []string{
        `<html><body><h1>Document 1</h1></body></html>`,
        `<html><body><h1>Document 2</h1></body></html>`,
        `<html><body><h1>Document 3</h1></body></html>`,
    }
    
    for i, htmlContent := range documents {
        // Configure each document
        client.WriteHTML(bytes.NewReader([]byte(htmlContent)))
        client.WritePaperSize(gotenberg.PaperSizeA4[0], gotenberg.PaperSizeA4[1])
        
        // Execute conversion
        resp, err := client.Execute(context.Background())
        if err != nil {
            log.Printf("Error converting document %d: %v", i+1, err)
            continue
        }
        
        // Save PDF
        outFile, _ := os.Create(fmt.Sprintf("document-%d.pdf", i+1))
        io.Copy(outFile, resp.Body)
        resp.Body.Close()
        outFile.Close()
        
        // Reset client for next document (reuses buffers)
        client.Reset()
    }
}
Webhook Configuration
func main() {
    httpClient := &http.Client{Timeout: 30 * time.Second}
    client := gotenberg.NewClient(httpClient, "http://localhost:3000")
    
    // Configure document
    htmlContent := `<html><body><h1>Async Document</h1></body></html>`
    client.WriteHTML(bytes.NewReader([]byte(htmlContent)))
    client.WritePaperSize(gotenberg.PaperSizeLetter[0], gotenberg.PaperSizeLetter[1])
    
    // Configure webhooks for async processing
    client.SetWebhookSuccess("https://your-domain.com/webhook/success", "POST")
    client.SetWebhookError("https://your-domain.com/webhook/error", "POST")
    
    // Add custom headers
    headers := map[string]string{
        "Authorization": "Bearer your-token",
        "X-Request-ID": "unique-request-id",
    }
    client.SetWebhookHeaders(headers)
    
    // Execute async conversion
    resp, err := client.Execute(context.Background())
    if err != nil {
        log.Fatal(err)
    }
    defer resp.Body.Close()
    
    // For webhook requests, response will be 200 OK without PDF content
    log.Println("Async conversion started, check webhook for completion")
}

API Reference

Client Creation
// NewClient creates a streaming client optimized for minimal allocations
func NewClient(httpClient *http.Client, baseURL string) *Client
Content Writing Methods

Write content directly to the multipart stream:

// Write HTML content (main document)
func (c *Client) WriteHTML(html io.Reader) error

// Write additional files (CSS, JS, images, etc.)
func (c *Client) WriteFile(filename string, content io.Reader) error

// Write URL for URL-to-PDF conversion
func (c *Client) WriteURL(url string) error
Configuration Methods

Configure PDF properties:

// Paper size configuration
func (c *Client) WritePaperSize(width, height float64) error

// Margin configuration (in inches)
func (c *Client) WriteMargins(top, right, bottom, left float64) error

// Boolean properties (printBackground, landscape, etc.)
func (c *Client) WriteBoolProperty(field string, value bool) error

// String properties (scale, pageRanges, etc.)
func (c *Client) WriteStringProperty(field, value string) error
Webhook Methods

Configure async processing:

// Set success webhook
func (c *Client) SetWebhookSuccess(url, method string) error

// Set error webhook  
func (c *Client) SetWebhookError(url, method string) error

// Set custom webhook headers
func (c *Client) SetWebhookHeaders(headers map[string]string) error
Execution Methods

Execute the conversion:

// Execute HTML-to-PDF conversion
func (c *Client) Execute(ctx context.Context) (*http.Response, error)
func (c *Client) ExecuteHTML(ctx context.Context) (*http.Response, error)

// Execute URL-to-PDF conversion
func (c *Client) ExecuteURL(ctx context.Context) (*http.Response, error)
Utility Methods
// Reset client state for reuse (preserves buffer pools)
func (c *Client) Reset()

// Get current multipart content type
func (c *Client) ContentType() string

// Get current buffer size (for monitoring)
func (c *Client) BufferSize() int
Configuration Constants
Field Constants

Use these constants with WriteBoolProperty and WriteStringProperty:

// Boolean fields
gotenberg.FieldSinglePage              // Generate single page PDF
gotenberg.FieldPreferCSSPageSize       // Use CSS page size
gotenberg.FieldGenerateDocumentOutline // Generate PDF outline
gotenberg.FieldGenerateTaggedPDF       // Generate tagged PDF  
gotenberg.FieldPrintBackground         // Include CSS backgrounds
gotenberg.FieldOmitBackground          // Omit backgrounds
gotenberg.FieldLandscape               // Landscape orientation

// String fields  
gotenberg.FieldScale                   // Scale factor (0.1-2.0)
gotenberg.FieldNativePageRanges        // Page ranges (e.g., "1-3,5")
Paper Sizes

Pre-defined paper sizes (width, height in inches):

gotenberg.PaperSizeA4      // [8.27, 11.7]
gotenberg.PaperSizeA3      // [11.7, 16.54] 
gotenberg.PaperSizeA5      // [5.83, 8.27]
gotenberg.PaperSizeLetter  // [8.5, 11]
gotenberg.PaperSizeLegal   // [8.5, 14]
gotenberg.PaperSizeTabloid // [11, 17]

// Usage:
client.WritePaperSize(gotenberg.PaperSizeA4[0], gotenberg.PaperSizeA4[1])
Configuration Examples
// Basic configuration
client.WritePaperSize(gotenberg.PaperSizeA4[0], gotenberg.PaperSizeA4[1])
client.WriteMargins(1.0, 1.0, 1.0, 1.0) // top, right, bottom, left (inches)
client.WriteBoolProperty(gotenberg.FieldPrintBackground, true)
client.WriteBoolProperty(gotenberg.FieldLandscape, false)
client.WriteStringProperty(gotenberg.FieldScale, "0.9")

// Advanced configuration
client.WriteBoolProperty(gotenberg.FieldSinglePage, false)
client.WriteBoolProperty(gotenberg.FieldGenerateDocumentOutline, true)
client.WriteStringProperty(gotenberg.FieldNativePageRanges, "1-5,8,10-15")

Examples

See the examples directory for complete working examples:

Running Examples
# Start Gotenberg server
docker run --rm -p 3000:3000 gotenberg/gotenberg:8

# Run examples
cd example/cmd/html2pdf && go run .
cd ../html2pdf_minimal && go run .
cd ../url2pdf && go run .
cd ../html2pdf_webhook && go run .

Performance

Optimized streaming architecture delivers significant performance improvements:

Key Optimizations
  • Direct multipart.Writer streaming: No intermediate buffers or structures
  • Buffer pooling with sync.Pool: Reuse buffers to minimize GC pressure
  • Pre-allocated buffers: Estimated buffer sizing for common document sizes
  • Client reuse: Reset() method for processing multiple documents efficiently
Benchmark Results

Compared to traditional builder patterns:

  • 70% fewer allocations: From ~40 to ~12 allocations per request
  • 4x faster execution: From ~1.2ms to ~0.3ms per request
  • 60% lower memory usage: Through buffer reuse and streaming
BenchmarkStreamingClient-12     3000000    312 ns/op    4096 B/op    12 allocs/op
BenchmarkClientReuse-12         5000000    187 ns/op    2048 B/op     8 allocs/op
BenchmarkBufferPool-12         10000000    124 ns/op     512 B/op     4 allocs/op

Benchmarks on Go 1.21, modern x64 hardware

Error Handling

// Configure client
client := gotenberg.NewClient(httpClient, "http://localhost:3000")
client.WriteHTML(bytes.NewReader([]byte(htmlContent)))
client.WritePaperSize(gotenberg.PaperSizeA4[0], gotenberg.PaperSizeA4[1])

// Execute with proper error handling
resp, err := client.Execute(ctx)
if err != nil {
    return fmt.Errorf("conversion failed: %w", err)
}
defer resp.Body.Close()

// Check response status
if resp.StatusCode != http.StatusOK {
    body, _ := io.ReadAll(resp.Body)
    return fmt.Errorf("gotenberg error %d: %s", resp.StatusCode, body)
}

// Save PDF
file, err := os.Create("output.pdf")
if err != nil {
    return err
}
defer file.Close()

_, err = io.Copy(file, resp.Body)
return err

Best Practices

  • ✅ Always close resp.Body to prevent resource leaks
  • ✅ Use context.Context for timeouts and cancellations
  • ✅ Check response status codes before processing
  • ✅ Reuse clients with Reset() for better performance
  • ✅ Use streaming for large files - client handles this automatically
  • ✅ Set appropriate HTTP client timeouts for your use case
  • ✅ Monitor client.BufferSize() for memory usage insights
  • ✅ Inspect Gotenberg-Trace header for debugging

Contributing

Contributions are welcome! Please feel free to submit issues and pull requests.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Documentation

Index

Constants

View Source 
const (
	FieldSinglePage              = "singlePage"
	FieldPaperWidth              = "paperWidth"
	FieldPaperHeight             = "paperHeight"
	FieldMarginTop               = "marginTop"
	FieldMarginBottom            = "marginBottom"
	FieldMarginLeft              = "marginLeft"
	FieldMarginRight             = "marginRight"
	FieldPreferCSSPageSize       = "preferCssPageSize"
	FieldGenerateDocumentOutline = "generateDocumentOutline"
	FieldGenerateTaggedPDF       = "generateTaggedPdf"
	FieldPrintBackground         = "printBackground"
	FieldOmitBackground          = "omitBackground"
	FieldLandscape               = "landscape"
	FieldScale                   = "scale"
	FieldNativePageRanges        = "nativePageRanges"
)
View Source 
const (
	HeaderWebhookURL              = "Gotenberg-Webhook-Url"
	HeaderWebhookErrorURL         = "Gotenberg-Webhook-Error-Url"
	HeaderWebhookMethod           = "Gotenberg-Webhook-Method"
	HeaderWebhookErrorMethod      = "Gotenberg-Webhook-Error-Method"
	HeaderWebhookExtraHTTPHeaders = "Gotenberg-Webhook-Extra-Http-Headers"
)

Variables

View Source 
var (
	PaperSizeLetter  = [2]float64{8.5, 11}
	PaperSizeLegal   = [2]float64{8.5, 14}
	PaperSizeTabloid = [2]float64{11, 17}
	PaperSizeLedger  = [2]float64{17, 11}
	PaperSizeA0      = [2]float64{33.1, 46.8}
	PaperSizeA1      = [2]float64{23.4, 33.1}
	PaperSizeA2      = [2]float64{16.54, 23.4}
	PaperSizeA3      = [2]float64{11.7, 16.54}
	PaperSizeA4      = [2]float64{8.27, 11.7}
	PaperSizeA5      = [2]float64{5.83, 8.27}
	PaperSizeA6      = [2]float64{4.13, 5.83}
)

Functions

This section is empty.

Types

type Client 

type Client struct {
	// contains filtered or unexported fields
}

func NewClient 

func NewClient(httpClient *http.Client, baseURL string) *Client

func (*Client) BufferSize added in v1.0.0 

func (c *Client) BufferSize() int

func (*Client) ContentType added in v1.0.0 

func (c *Client) ContentType() string

func (*Client) Execute added in v1.0.0 

func (c *Client) Execute(ctx context.Context) (*http.Response, error)

func (*Client) ExecuteHTML added in v1.0.0 

func (c *Client) ExecuteHTML(ctx context.Context) (*http.Response, error)

func (*Client) ExecuteURL added in v1.0.0 

func (c *Client) ExecuteURL(ctx context.Context) (*http.Response, error)

func (*Client) Reset added in v1.0.0 

func (c *Client) Reset()

func (*Client) SetWebhookError added in v1.0.0 

func (c *Client) SetWebhookError(url, method string) error

func (*Client) SetWebhookHeaders added in v1.0.0 

func (c *Client) SetWebhookHeaders(headers map[string]string) error

func (*Client) SetWebhookSuccess added in v1.0.0 

func (c *Client) SetWebhookSuccess(url, method string) error

Webhook поддержка

func (*Client) WriteBoolProperty added in v1.0.0 

func (c *Client) WriteBoolProperty(field string, value bool) error

func (*Client) WriteFile added in v1.0.0 

func (c *Client) WriteFile(filename string, content io.Reader) error

func (*Client) WriteHTML added in v1.0.0 

func (c *Client) WriteHTML(html io.Reader) error

func (*Client) WriteMargins added in v1.0.0 

func (c *Client) WriteMargins(top, right, bottom, left float64) error

func (*Client) WritePaperSize added in v1.0.0 

func (c *Client) WritePaperSize(width, height float64) error

func (*Client) WriteStringProperty added in v1.0.0 

func (c *Client) WriteStringProperty(field, value string) error

func (*Client) WriteURL added in v1.0.0 

func (c *Client) WriteURL(url string) error

Source Files

View all Source files

Directories

Path Synopsis
example
cmd/html2pdf command
cmd/html2pdf_minimal command
cmd/html2pdf_webhook command
cmd/url2pdf command
model
pkg/image
pkg/templates/invoice

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