Re: [TCLCORE] tcltls: unexpected 0-bytes [read], then nothing

[Colin M. <col...@ya...>]

Hello all, here is a follow-up on this issue.

I consulted Upstash.com support, I will attach a transcript of our 
messages.  On 20th June they added a reply which I did not see until now 
because it did not get emailed to me.  Part of this says:

Normally server doesn't buffer response unless a pipeline is detected. A 
pipeline is when a client sends multiple consequent requests without 
waiting response of earlier requests.

This makes me suspect that the Redis server wrongly gets into its 
pipeline mode (https://redis.io/docs/latest/develop/use/pipelining/) and 
so buffers its replies.  However I'm not going to spend more time 
investigating this myself because I'm now using redis-cloud.com which 
does not require TLS and works fine with Retcl.

Colin.

On 05/06/2024 14:22, Pietro Cerutti wrote:
> Hi,
>
> I and Colin have been investigating an issue when using the TLS 
> extension (https://core.tcl-lang.org/tcltls) to interact with a Redis 
> server using retcl (https://code.ptrcrt.ch/retcl/).
>
> I have a small reproducer here, which I have trimmed down to a 
> minimum.  It doesn't include any retcl code, just TLS sockets:
> https://gist.github.com/gahr/a9258f0f9cdd20ec0479a409e0db49fd
>
> The protocol is line-oriented, with \r\n as terminators.
>
> The setup is as follows:
>
> 1. we connect to a Redis instance using [tls::socket]
> 2. we [chan configure $sock -blocking 0 -translation binary]
> 3. we send a command string, and we [chan flush $sock]
> 4. we get a read event on the $sock
> 5. we [read $sock] in the event handler and expect to get a response
>
> Point 5. works fine against a local Redis instance w/o TLS.
>
> When we turn TLS on, we see weird things:
>
> 1. we get a number of read events where [read $sock] returns ""
> 2. sometimes we get meaningful read events afterwards, where a [read 
> $sock] returns the expected response
> 3. sometimes we don't get any meaningful read events after the empty ones
>
> Under the gist, I have included two comments with sample runs against 
> my local Redis server and against an intance on upstash.com. You can 
> see the randomness of the empty / meaningful responses.
>
> I can provide the output when tcltls is compiled with 
> -DTCLEXT_TCLTLS_DEBUG, if anyone wants to take a look.
>
> Any pointers would be appreciated.
>