Compress

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Overview

• Reduced bandwidth for API responses
• Faster page loads for web applications
• Compression for JSON, HTML, CSS, and JavaScript

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Installation

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

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Quick Start

app := mizu.New()

// Enable gzip compression
app.Use(compress.Gzip())

// Or enable deflate
app.Use(compress.Deflate())

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Configuration

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Options

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Examples

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Gzip Compression

app.Use(compress.Gzip())

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Custom Compression Level

// Best compression (slower)
app.Use(compress.GzipLevel(9))

// Fastest compression
app.Use(compress.GzipLevel(1))

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With Options

app.Use(compress.New(compress.Options{
    MinSize: 1000, // Only compress responses > 1KB
    ContentTypes: []string{
        "text/plain",
        "text/html",
        "text/css",
        "application/json",
        "application/javascript",
    },
}))

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Auto-Select Encoding

// Automatically selects gzip or deflate based on Accept-Encoding
app.Use(compress.New(compress.Options{
    MinSize: 512,
}))

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API Reference

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Functions

// Gzip creates gzip compression middleware
func Gzip() mizu.Middleware

// GzipLevel creates gzip middleware with specific level
func GzipLevel(level int) mizu.Middleware

// Deflate creates deflate compression middleware
func Deflate() mizu.Middleware

// New creates compression middleware with options
func New(opts Options) mizu.Middleware

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Compression Levels

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Behavior

• Automatically sets Content-Encoding header
• Adds Vary: Accept-Encoding header
• Skips compression if client doesn’t support it
• Skips already-encoded responses
• Skips responses smaller than MinSize

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Technical Details

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Implementation Overview

1. Buffering Phase: Responses are buffered until they reach the MinSize threshold
2. Decision Point: Once the threshold is reached, the middleware checks:
   • If the client supports the requested encoding (via Accept-Encoding header)
   • If the content type is compressible (matches ContentTypes list)
   • If the response is not already encoded (no existing Content-Encoding header)
3. Compression Phase: If all checks pass, the appropriate compression writer is applied

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Writer Pooling

• Gzip Pool: Maintains a pool of gzip.Writer instances
• Deflate Pool: Maintains a pool of flate.Writer instances
• Writers are reset and returned to the pool after each request
• This reduces garbage collection pressure and improves performance

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Custom Response Writer

• Buffering: Accumulates response data until compression decision is made
• Lazy Header Writing: Delays header writing until compression status is determined
• Automatic Cleanup: Ensures compression writers are properly closed and returned to pool
• Flush Support: Implements http.Flusher for streaming responses

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Encoding Selection

1. Checks for gzip in Accept-Encoding header first (preferred)
2. Falls back to deflate if gzip is not supported
3. Uses no compression if neither is supported

• Only applies compression if the client explicitly supports the selected encoding

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Default Content Types

• text/html, text/css, text/plain, text/javascript, text/xml
• application/json, application/javascript, application/xml
• application/xhtml+xml, application/rss+xml, application/atom+xml
• image/svg+xml

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Best Practices

• Use level 6 for most applications (good balance)
• Set appropriate MinSize to avoid compressing tiny responses
• Only compress text-based content types
• Place before other response-modifying middleware

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Testing

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Related Middlewares

• cache - HTTP caching
• etag - ETag generation
• vary - Vary header management