[Master] Improve decoding performance for remoting commands

[czah]

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BUG REPORT

1. Please describe the issue you observed:

Recently we've benchmarked our service which act as a RocketMQ consumer and I noticed that it spends much time on reflection while decoding remoting commands (as shown below):

After some investigations, I found it was caused by passing a byte slice pointer to binary.Read(). It makes binary.Read() to fallback to reflect-based decoding, consuming more CPU cycles.

rocketmq-client-go/internal/remote/codec.go

Lines 227 to 231 in d6e66a2

	headerData := make([]byte, headerLength)
	err = binary.Read(buf, binary.BigEndian, &headerData)
	if err != nil {
	return nil, err
	}

There're two ways to solve this issue.

• pass an initialized byte slice instead of a slice pointer to binary.Read()
• just use io.ReadFull() instead

I've tried the second way and got a ~1.9x performance boost on remoting command decoding:

before:

goos: linux
goarch: amd64
pkg: github.com/apache/rocketmq-client-go/v2/internal/remote
Benchmark_decode-8   	  141375	      7141 ns/op	    2334 B/op	      60 allocs/op
PASS
ok  	github.com/apache/rocketmq-client-go/v2/internal/remote	1.102s

after:

goos: linux
goarch: amd64
pkg: github.com/apache/rocketmq-client-go/v2/internal/remote
Benchmark_decode-8   	  286480	      3724 ns/op	    1950 B/op	      56 allocs/op
PASS
ok  	github.com/apache/rocketmq-client-go/v2/internal/remote	1.116s