Dubbo-go Filter Samples

Background

Dubbo-go designs and implements the filter mode, which helps the provider/consumer to process some actions before sending/processing requests. Dubbo-go has some built-in filter implementations, such as tps limiter, token, etc., and also supports user-defined implementations filter, please refer to the custom module.

Instructions

1. Built-in Filter

1.1 Background

Dubbo-go has built-in implementations of various filters, and the following types are connected by default during the running phase of the provider/consumer. Provider：

• echo
• metrics
• token
• accesslog
• tps
• generic_service
• execute
• pshutdown

Consumer：

• cshutdown

For more built-in implementations of filter, please refer to the filter module of dubbo-go.

1.2 Filter Confugration

Just configure the name of the filter under the corresponding provider or consumer, refer to Section 2.2.

2. Custom Filter

Take the consumer as an example, refer to the custom module for more specific code.

2.1 Implement Custom Filter

Implement Filter interface.

type Filter interface {
	Invoke(context.Context, protocol.Invoker, protocol.Invocation) protocol.Result
	OnResponse(context.Context, protocol.Result, protocol.Invoker, protocol.Invocation) protocol.Result
}

and inject it into the environment via extension.SetFilter：

func init() {
	extension.SetFilter("myClientFilter", NewMyClientFilter)
}

func NewMyClientFilter() filter.Filter {
	return &MyClientFilter{}
}

type MyClientFilter struct {
}

func (f *MyClientFilter) Invoke(ctx context.Context, invoker protocol.Invoker, invocation protocol.Invocation) protocol.Result {
	fmt.Println("MyClientFilter Invoke is called, method Name = ", invocation.MethodName())
	invocation.SetAttachment("request-key1", "request-value1")
	invocation.SetAttachment("request-key2", []string{"request-value2.1", "request-value2.2"})
	return invoker.Invoke(ctx, invocation)
}

func (f *MyClientFilter) OnResponse(ctx context.Context, result protocol.Result, invoker protocol.Invoker, protocol protocol.Invocation) protocol.Result {
	fmt.Println("MyClientFilter OnResponse is called")
	fmt.Println("result attachment = ", result.Attachments())
	return result
}

2.2 Filter Confugration

# service config
dubbo:
  registries:
    demoZK:
      protocol: zookeeper
      timeout: 3s
      address: 127.0.0.1:2181
  consumer:
    filter: myClientFilter
    check: true
    request_timeout: 3s
    connect_timeout: 3s
    references:
      GreeterClientImpl:
        protocol: tri

3. Running

See HOWTO.md in the root directory to run this example.

Observe the output of the client:

MyClientFilter Invoke is called, method Name =  SayHello
MyClientFilter OnResponse is called