Vary

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Overview

• Proper cache control
• Content negotiation
• CDN configuration

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Installation

import "github.com/go-mizu/mizu/middlewares/vary"

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Quick Start

app := mizu.New()

// Vary by Accept-Encoding
app.Use(vary.New("Accept-Encoding"))

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Configuration

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Options

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Examples

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Single Header

app.Use(vary.New("Accept-Encoding"))
// Vary: Accept-Encoding

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Multiple Headers

app.Use(vary.New("Accept-Encoding", "Accept-Language", "Authorization"))
// Vary: Accept-Encoding, Accept-Language, Authorization

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Common Patterns

// API with auth
app.Use(vary.New("Authorization"))

// Multilingual site
app.Use(vary.New("Accept-Language"))

// Compression
app.Use(vary.New("Accept-Encoding"))

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API Reference

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Functions

// New creates vary middleware
func New(headers ...string) mizu.Middleware

// Add adds to existing Vary header
func Add(c *mizu.Ctx, header string)

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Technical Details

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Implementation Overview

1. Header Management: Maintains a set of headers that affect response content
2. Duplicate Prevention: Uses case-insensitive comparison to prevent duplicate headers
3. Header Merging: Combines new Vary headers with existing ones from the response
4. Execution Order: Processes after the handler executes to capture all Vary requirements

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Key Functions

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add(c *mizu.Ctx, headers ...string)

• Adds headers to the Vary response header
• Parses existing Vary header and creates a set for deduplication
• Uses case-insensitive comparison (strings.ToLower)
• Joins headers with comma-space separator

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autoDetect(c *mizu.Ctx)

• Automatically detects content negotiation headers from the request
• Checks for: Accept, Accept-Encoding, Accept-Language
• Only adds headers that are present in the request

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Options Structure

type Options struct {
    Headers []string  // Explicit headers to add to Vary
    Auto    bool      // Enable automatic detection
}

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Convenience Functions

• AcceptEncoding(): Adds Accept-Encoding to Vary
• Accept(): Adds Accept to Vary
• AcceptLanguage(): Adds Accept-Language to Vary
• Origin(): Adds Origin to Vary (useful for CORS)
• All(): Adds common headers: Accept, Accept-Encoding, Accept-Language
• Auto(): Enables automatic header detection

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Best Practices

• Include all headers that affect response
• Use with compression middleware
• Consider CDN caching implications
• Don’t over-vary (reduces cache effectiveness)

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Testing

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Related Middlewares

• compress - Response compression
• cache - Cache-Control headers
• language - Language detection