Dubbo-go Filter Samples

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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 Configuration

Use server.WithFilter() for provider side or client.WithFilter() for consumer side. See examples in the token, sentinel, and custom modules.

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 Configuration

For provider side:

if err := greet.RegisterGreetServiceHandler(srv, &GreetTripleServer{},
	server.WithFilter("myServerFilter"),
); err != nil {
	panic(err)
}

For consumer side:

svc, err := greet.NewGreetService(cli, client.WithFilter("myClientFilter"))
if err != nil {
	panic(err)
}

Examples

This directory contains the following filter examples:

• custom: Custom filter implementation example (client and server)
• token: Token filter example
• sentinel: Sentinel filter example for flow control and circuit breaking
• polaris/limit: Polaris TPS limiter example
• tpslimit: Custom TPS limit strategy and rejected execution handler example