Discussion of a new observable

[MalikHou]

Hi All
There is a trace sampling requirement in our business, the purpose is to understand what a query request has experienced throughout its life cycle. The existing trace solution is obviously not very satisfactory. My initial idea is as follows:

1. Add trace strcut, which includes some data:

• bool hit_mem_table;
• bool hit_row_cache;
• bool hit_block_cache;
• bool hit_sys_disk;
• uint64_t read_disk_us;
  ...

2. Overload the new Get method and add the parameter trace struct to the function signature;
3. If the trace object exists, write the statistical information to the trace in the key path of the code.

Note that the generation of trace has a certain sampling rate, and not every request calls this method.

I haven't received a timely reply in the mail group & hope to hear from everyone