Badrish Chandramouli

### How to test out-of-band responses 1. Launch GarnetServer in low memory mode (only 2 pages of 4k size each) with storage tier enabled `GarnetServer --memory 8k --page 4k --logger-level...

> awesome to see this being investigated, and I fully understand this is very early! probably the main thing to describe somewhere is: what exactly is the expected usage, in...

> IMO that single-connection approach **cannot** be done safely before RESP3, which adds a token prefix to specify an out-of-band message. I do not believe it is 100% safe or...

As first step, added basic `HELLO` support here: https://github.com/microsoft/garnet/pull/398

For ASYNC barrier, note that the push comes in between the BARRIER request and its +OK response: Request: ``` *2 $5 async $7 barrier ``` First come all the ongoing...

Is it fine to support RESP3 (specifically, `HELLO 3`) for the purposes of adding this `async` feature, but then the other existing commands like `HGETALL` continue to return results in...

What happens when async is called in RESP2? ``` 127.0.0.1:6379> async on (error) ERR command not supported in RESP2 127.0.0.1:6379> async off (error) ERR command not supported in RESP2 127.0.0.1:6379>...

@mgravell - this work item is now complete and ready to review. Would be great to see sample client integration for end-to-end async wiring.

cc @kevin-montrose

Great work overall. Shaping up really nicely, thanks!