Loading documentation...

ETag Middleware

Generates ETag headers for responses and handles If-None-Match requests. Returns 304 Not Modified when appropriate.

Basic Usage

// Strong ETags
s.Use(middleware.ETag())

// Weak ETags
s.Use(middleware.ETagWeak())

Configuration

s.Use(middleware.ETagWithConfig(middleware.ETagConfig{
    Weak: false, // Strong ETags
    SkipFunc: func(r *http.Request) bool {
        // Skip ETag for dynamic content
        return r.URL.Path == "/api/dynamic"
    },
}))

Features

Automatic ETag generation from response body
Handles If-None-Match header
Returns 304 Not Modified when appropriate
Supports weak ETags

How It Works

Middleware buffers the response body
Generates ETag hash from body content
Checks If-None-Match header from request
If ETag matches, returns 304 Not Modified
Otherwise, sets ETag header and sends full response

Strong vs Weak ETags

Strong ETags (default):

Indicate exact byte-for-byte match
Format: "abc123..."
Use when content is identical

Weak ETags:

Indicate semantic equivalence
Format: W/"abc123..."
Use when content is semantically same but may differ

// Strong ETags (default)
s.Use(middleware.ETag())

// Weak ETags
s.Use(middleware.ETagWeak())

Skipping ETag

Skip ETag generation for dynamic content:

s.Use(middleware.ETagWithConfig(middleware.ETagConfig{
    SkipFunc: func(r *http.Request) bool {
        // Skip for dynamic or personalized content
        return r.URL.Path == "/api/user/profile" ||
               r.URL.Path == "/api/dynamic"
    },
}))

Helper Functions

Generate ETags manually:

// Generate ETag from content
etag := middleware.ETagFromContent([]byte("content"), false)

// Generate ETag from string
etag := middleware.ETagFromString("content", false)

// Generate ETag from version number
etag := middleware.ETagFromVersion(123, false)

Client Usage

Clients can use ETags for caching:

GET /api/users HTTP/1.1
If-None-Match: "abc123def456"

If content hasn't changed, server responds:

HTTP/1.1 304 Not Modified
ETag: "abc123def456"

Example

s := helix.New(nil)

// Enable ETag for all GET requests
s.Use(middleware.ETag())

// Handler that benefits from ETag
s.GET("/api/users", helix.HandleCtx(func(c *helix.Ctx) error {
    users, err := userService.List(c.Context())
    if err != nil {
        return err
    }
    // ETag is automatically generated and checked
    return c.OK(users)
}))

Best Practices

Use ETags for cacheable content (GET requests)
Skip ETags for dynamic or personalized content
Use weak ETags when content is semantically equivalent but may differ
Combine with Cache middleware for optimal caching

Loading documentation...

ETag Middleware

Generates ETag headers for responses and handles If-None-Match requests. Returns 304 Not Modified when appropriate.

Basic Usage

// Strong ETags
s.Use(middleware.ETag())

// Weak ETags
s.Use(middleware.ETagWeak())

Configuration

s.Use(middleware.ETagWithConfig(middleware.ETagConfig{
    Weak: false, // Strong ETags
    SkipFunc: func(r *http.Request) bool {
        // Skip ETag for dynamic content
        return r.URL.Path == "/api/dynamic"
    },
}))

Features

Automatic ETag generation from response body
Handles If-None-Match header
Returns 304 Not Modified when appropriate
Supports weak ETags

How It Works

Middleware buffers the response body
Generates ETag hash from body content
Checks If-None-Match header from request
If ETag matches, returns 304 Not Modified
Otherwise, sets ETag header and sends full response

Strong vs Weak ETags

Strong ETags (default):

Indicate exact byte-for-byte match
Format: "abc123..."
Use when content is identical

Weak ETags:

Indicate semantic equivalence
Format: W/"abc123..."
Use when content is semantically same but may differ

// Strong ETags (default)
s.Use(middleware.ETag())

// Weak ETags
s.Use(middleware.ETagWeak())

Skipping ETag

Skip ETag generation for dynamic content:

s.Use(middleware.ETagWithConfig(middleware.ETagConfig{
    SkipFunc: func(r *http.Request) bool {
        // Skip for dynamic or personalized content
        return r.URL.Path == "/api/user/profile" ||
               r.URL.Path == "/api/dynamic"
    },
}))

Helper Functions

Generate ETags manually:

// Generate ETag from content
etag := middleware.ETagFromContent([]byte("content"), false)

// Generate ETag from string
etag := middleware.ETagFromString("content", false)

// Generate ETag from version number
etag := middleware.ETagFromVersion(123, false)

Client Usage

Clients can use ETags for caching:

GET /api/users HTTP/1.1
If-None-Match: "abc123def456"

If content hasn't changed, server responds:

HTTP/1.1 304 Not Modified
ETag: "abc123def456"

Example

s := helix.New(nil)

// Enable ETag for all GET requests
s.Use(middleware.ETag())

// Handler that benefits from ETag
s.GET("/api/users", helix.HandleCtx(func(c *helix.Ctx) error {
    users, err := userService.List(c.Context())
    if err != nil {
        return err
    }
    // ETag is automatically generated and checked
    return c.OK(users)
}))

Best Practices

Use ETags for cacheable content (GET requests)
Skip ETags for dynamic or personalized content
Use weak ETags when content is semantically equivalent but may differ
Combine with Cache middleware for optimal caching

Loading documentation...

ETag Middleware

Generates ETag headers for responses and handles If-None-Match requests. Returns 304 Not Modified when appropriate.

Basic Usage

// Strong ETags
s.Use(middleware.ETag())

// Weak ETags
s.Use(middleware.ETagWeak())

// Strong ETags
s.Use(middleware.ETag())

// Weak ETags
s.Use(middleware.ETagWeak())

Configuration

s.Use(middleware.ETagWithConfig(middleware.ETagConfig{
    Weak: false, // Strong ETags
    SkipFunc: func(r *http.Request) bool {
        // Skip ETag for dynamic content
        return r.URL.Path == "/api/dynamic"
    },
}))

s.Use(middleware.ETagWithConfig(middleware.ETagConfig{
    Weak: false, // Strong ETags
    SkipFunc: func(r *http.Request) bool {
        // Skip ETag for dynamic content
        return r.URL.Path == "/api/dynamic"
    },
}))

Features

Automatic ETag generation from response body
Handles If-None-Match header
Returns 304 Not Modified when appropriate
Supports weak ETags

How It Works

Middleware buffers the response body
Generates ETag hash from body content
Checks If-None-Match header from request
If ETag matches, returns 304 Not Modified
Otherwise, sets ETag header and sends full response

Strong vs Weak ETags

Strong ETags (default):

Indicate exact byte-for-byte match
Format: "abc123..."
Use when content is identical

Weak ETags:

Indicate semantic equivalence
Format: W/"abc123..."
Use when content is semantically same but may differ

// Strong ETags (default)
s.Use(middleware.ETag())

// Weak ETags
s.Use(middleware.ETagWeak())

// Strong ETags (default)
s.Use(middleware.ETag())

// Weak ETags
s.Use(middleware.ETagWeak())

Skipping ETag

Skip ETag generation for dynamic content:

s.Use(middleware.ETagWithConfig(middleware.ETagConfig{
    SkipFunc: func(r *http.Request) bool {
        // Skip for dynamic or personalized content
        return r.URL.Path == "/api/user/profile" ||
               r.URL.Path == "/api/dynamic"
    },
}))

s.Use(middleware.ETagWithConfig(middleware.ETagConfig{
    SkipFunc: func(r *http.Request) bool {
        // Skip for dynamic or personalized content
        return r.URL.Path == "/api/user/profile" ||
               r.URL.Path == "/api/dynamic"
    },
}))

Helper Functions

Generate ETags manually:

// Generate ETag from content
etag := middleware.ETagFromContent([]byte("content"), false)

// Generate ETag from string
etag := middleware.ETagFromString("content", false)

// Generate ETag from version number
etag := middleware.ETagFromVersion(123, false)

// Generate ETag from content
etag := middleware.ETagFromContent([]byte("content"), false)

// Generate ETag from string
etag := middleware.ETagFromString("content", false)

// Generate ETag from version number
etag := middleware.ETagFromVersion(123, false)

Client Usage

Clients can use ETags for caching:

http

GET /api/users HTTP/1.1
If-None-Match: "abc123def456"

GET /api/users HTTP/1.1
If-None-Match: "abc123def456"

If content hasn't changed, server responds:

http

HTTP/1.1 304 Not Modified
ETag: "abc123def456"

HTTP/1.1 304 Not Modified
ETag: "abc123def456"

Example

s := helix.New(nil)

// Enable ETag for all GET requests
s.Use(middleware.ETag())

// Handler that benefits from ETag
s.GET("/api/users", helix.HandleCtx(func(c *helix.Ctx) error {
    users, err := userService.List(c.Context())
    if err != nil {
        return err
    }
    // ETag is automatically generated and checked
    return c.OK(users)
}))

s := helix.New(nil)

// Enable ETag for all GET requests
s.Use(middleware.ETag())

// Handler that benefits from ETag
s.GET("/api/users", helix.HandleCtx(func(c *helix.Ctx) error {
    users, err := userService.List(c.Context())
    if err != nil {
        return err
    }
    // ETag is automatically generated and checked
    return c.OK(users)
}))

Best Practices

Use ETags for cacheable content (GET requests)
Skip ETags for dynamic or personalized content
Use weak ETags when content is semantically equivalent but may differ
Combine with Cache middleware for optimal caching

ETag Middleware

Generates ETag headers for responses and handles If-None-Match requests. Returns 304 Not Modified when appropriate.

Basic Usage

// Strong ETags
s.Use(middleware.ETag())

// Weak ETags
s.Use(middleware.ETagWeak())

// Strong ETags
s.Use(middleware.ETag())

// Weak ETags
s.Use(middleware.ETagWeak())

Configuration

s.Use(middleware.ETagWithConfig(middleware.ETagConfig{
    Weak: false, // Strong ETags
    SkipFunc: func(r *http.Request) bool {
        // Skip ETag for dynamic content
        return r.URL.Path == "/api/dynamic"
    },
}))

s.Use(middleware.ETagWithConfig(middleware.ETagConfig{
    Weak: false, // Strong ETags
    SkipFunc: func(r *http.Request) bool {
        // Skip ETag for dynamic content
        return r.URL.Path == "/api/dynamic"
    },
}))

Features

Automatic ETag generation from response body
Handles If-None-Match header
Returns 304 Not Modified when appropriate
Supports weak ETags

How It Works

Middleware buffers the response body
Generates ETag hash from body content
Checks If-None-Match header from request
If ETag matches, returns 304 Not Modified
Otherwise, sets ETag header and sends full response

Strong vs Weak ETags

Strong ETags (default):

Indicate exact byte-for-byte match
Format: "abc123..."
Use when content is identical

Weak ETags:

Indicate semantic equivalence
Format: W/"abc123..."
Use when content is semantically same but may differ

// Strong ETags (default)
s.Use(middleware.ETag())

// Weak ETags
s.Use(middleware.ETagWeak())

// Strong ETags (default)
s.Use(middleware.ETag())

// Weak ETags
s.Use(middleware.ETagWeak())

Skipping ETag

Skip ETag generation for dynamic content:

s.Use(middleware.ETagWithConfig(middleware.ETagConfig{
    SkipFunc: func(r *http.Request) bool {
        // Skip for dynamic or personalized content
        return r.URL.Path == "/api/user/profile" ||
               r.URL.Path == "/api/dynamic"
    },
}))

s.Use(middleware.ETagWithConfig(middleware.ETagConfig{
    SkipFunc: func(r *http.Request) bool {
        // Skip for dynamic or personalized content
        return r.URL.Path == "/api/user/profile" ||
               r.URL.Path == "/api/dynamic"
    },
}))

Helper Functions

Generate ETags manually:

// Generate ETag from content
etag := middleware.ETagFromContent([]byte("content"), false)

// Generate ETag from string
etag := middleware.ETagFromString("content", false)

// Generate ETag from version number
etag := middleware.ETagFromVersion(123, false)

// Generate ETag from content
etag := middleware.ETagFromContent([]byte("content"), false)

// Generate ETag from string
etag := middleware.ETagFromString("content", false)

// Generate ETag from version number
etag := middleware.ETagFromVersion(123, false)

Client Usage

Clients can use ETags for caching:

http

GET /api/users HTTP/1.1
If-None-Match: "abc123def456"

GET /api/users HTTP/1.1
If-None-Match: "abc123def456"

If content hasn't changed, server responds:

http

HTTP/1.1 304 Not Modified
ETag: "abc123def456"

HTTP/1.1 304 Not Modified
ETag: "abc123def456"

Example

s := helix.New(nil)

// Enable ETag for all GET requests
s.Use(middleware.ETag())

// Handler that benefits from ETag
s.GET("/api/users", helix.HandleCtx(func(c *helix.Ctx) error {
    users, err := userService.List(c.Context())
    if err != nil {
        return err
    }
    // ETag is automatically generated and checked
    return c.OK(users)
}))

s := helix.New(nil)

// Enable ETag for all GET requests
s.Use(middleware.ETag())

// Handler that benefits from ETag
s.GET("/api/users", helix.HandleCtx(func(c *helix.Ctx) error {
    users, err := userService.List(c.Context())
    if err != nil {
        return err
    }
    // ETag is automatically generated and checked
    return c.OK(users)
}))

Best Practices

Use ETags for cacheable content (GET requests)
Skip ETags for dynamic or personalized content
Use weak ETags when content is semantically equivalent but may differ
Combine with Cache middleware for optimal caching