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The Transport API defines the core interfaces for transport layer implementations in Kratos, supporting both HTTP and gRPC protocols.

​
Interfaces

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Server

Transport server interface that all transport implementations must satisfy. 
type Server interface {
    Start(context.Context) error
    Stop(context.Context) error
}
​
Start
func(context.Context) error
Starts the transport server. Blocks until the server stops or context is canceled.
​
Stop
func(context.Context) error
Gracefully stops the transport server within the context deadline.

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Endpointer

Interface for services that can provide their endpoint URL. 
type Endpointer interface {
    Endpoint() (*url.URL, error)
}
​
Endpoint
func() (*url.URL, error)
Returns the endpoint URL of the service (e.g., http://127.0.0.1:8000 or grpc://127.0.0.1:9000)
Storage interface for transport headers. 
type Header interface {
    Get(key string) string
    Set(key string, value string)
    Add(key string, value string)
    Keys() []string
    Values(key string) []string
}
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Get
func(key string) string
Returns the first value associated with the key
​
Set
func(key string, value string)
Sets the header entry, replacing any existing values
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Add
func(key string, value string)
Adds a value to the header entry
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Keys
func() []string
Returns all header keys
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Values
func(key string) []string
Returns all values associated with the key

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Transporter

Transport context value interface providing access to transport information. 
type Transporter interface {
    Kind() Kind
    Endpoint() string
    Operation() string
    RequestHeader() Header
    ReplyHeader() Header
}
​
Kind
func() Kind
Returns the transport kind (“grpc” or “http”)
​
Endpoint
func() string
Returns the server or client endpoint.
  • Server: grpc://127.0.0.1:9000 or http://127.0.0.1:8000
  • Client: discovery:///provider-demo
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Operation
func() string
Returns the service full method selector generated by protobuf. Example: /helloworld.Greeter/SayHello
​
RequestHeader
func() Header
Returns the transport request header (http.Header for HTTP, metadata.MD for gRPC)
​
ReplyHeader
func() Header
Returns the transport reply/response header. Only valid for server transport. (http.Header for HTTP, metadata.MD for gRPC)

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Types

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Kind

Defines the type of transport. 
type Kind string

const (
    KindGRPC Kind = "grpc"
    KindHTTP Kind = "http"
)
​
KindGRPC
Kind
gRPC transport kind
​
KindHTTP
Kind
HTTP transport kind
Methods: 
func (k Kind) String() string

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Context Functions

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NewServerContext

Returns a new Context that carries the server Transporter value. 
func NewServerContext(ctx context.Context, tr Transporter) context.Context
​
ctx
context.Context
The parent context
​
tr
Transporter
The Transporter to attach
​
context
context.Context
Context with server Transporter attached

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FromServerContext

Returns the server Transporter value stored in context. 
func FromServerContext(ctx context.Context) (tr Transporter, ok bool)
​
ctx
context.Context
Context to retrieve Transporter from
​
tr
Transporter
The retrieved Transporter instance
​
ok
bool
Whether the Transporter was found
Example: 
if tr, ok := transport.FromServerContext(ctx); ok {
    fmt.Println("Transport kind:", tr.Kind())
    fmt.Println("Operation:", tr.Operation())
}

​
NewClientContext

Returns a new Context that carries the client Transporter value. 
func NewClientContext(ctx context.Context, tr Transporter) context.Context
​
ctx
context.Context
The parent context
​
tr
Transporter
The Transporter to attach
​
context
context.Context
Context with client Transporter attached

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FromClientContext

Returns the client Transporter value stored in context. 
func FromClientContext(ctx context.Context) (tr Transporter, ok bool)
​
ctx
context.Context
Context to retrieve Transporter from
​
tr
Transporter
The retrieved Transporter instance
​
ok
bool
Whether the Transporter was found

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Usage Example

package main

import (
    "context"
    "fmt"
    "github.com/go-kratos/kratos/v2/transport"
)

func middleware(next Handler) Handler {
    return func(ctx context.Context, req interface{}) (interface{}, error) {
        if tr, ok := transport.FromServerContext(ctx); ok {
            // Access transport information
            fmt.Printf("Kind: %s\n", tr.Kind())
            fmt.Printf("Operation: %s\n", tr.Operation())
            fmt.Printf("Endpoint: %s\n", tr.Endpoint())
            
            // Access headers
            header := tr.RequestHeader()
            authToken := header.Get("authorization")
            fmt.Printf("Auth: %s\n", authToken)
        }
        return next(ctx, req)
    }
}

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