Add new package instrument: go-redis

[minimAluminiumalism]

Ref #1053

This project currently does not support Redis, and this PR aims to support it.

Instrumentation for the library github.com/go-redis/redis/v8 is quite difficult, primarily because some of the available instrument functions include input params of type interface{} (this issue is also mentioned in #1209) like this:

func (c *baseClient) process(ctx context.Context, cmd Cmder)

A possible solution (found to be unfeasible after attempting)

I want to get the type of these interface{} type input params, then try to retrieving the corresponding value based on that type. The type field's position of eface is:

type eface struct {
    _type *_type
    data  unsafe.Pointer
}
type _type struct {
    size       uintptr
    ptrdata    uintptr
    hash       uint32
    tflag      uint8
    align      uint8
    fieldalign uint8
    kind       uint8
    equal      func(unsafe.Pointer, unsafe.Pointer) bool
    gcdata     *byte
    str        nameOff
    ptrToThis  typeOff
}

The biggest issue with this solution is its high level of complexity, which will exceed the instruction limit of eBPF(100W) with error program uprobe_process: load program: argument list too long: BPF program is too large. Processed 1000001 insn (4760 line(s) omitted)

The implementation is the closed PR #1522

Final selected solution

So I suppose we cannot directly start from the interface{} input parameters of instrument function. I decided to start with the RESP protocol. Redis cmds will be encoded to bytes stream(RESP), so I chose the instrument func:

func (cn *Conn) WithWriter(ctx context.Context, timeout time.Duration, fn func(wr *proto.Writer)

But the bufio uses write-back buffer strategy. It makes me cannot determine the boundaries of a valid RESP byte stream which is significant for redis pipelining mode with multiple cmds. So I pre-fetched the segments of command through func:

func (c *baseClient) generalProcessPipeline(ctx context.Context, cmds []Cmder, p pipelineProcessor)

I also added a example httpRedis to validate the new instrumentation.

[minimAluminiumalism]

CR @damemi @RonFed