Async queries start failing with "C++ exception"

[wyozi]

Quite hard to pinpoint the exact cause but this starts randomly happening at some point

local q = db:query("SELECT 1")
print("r", pcall(function()q:run() end ))

prints r false C++ exception

I think this is a data race issue. The whole DatabaseQuery::last_query thing seems quite susceptible to dataraces. I believe adding a ConcurrentQueue for incoming async queries would improve that. I can see if I can create a patch for it at some point later.

[Meow]

Thanks for reporting all the issues, it's really appreciated.

I'll try to reproduce this in my testing environment sometime over the weekend. I haven't experienced anything like this in all of my testing before.

[wyozi]

Not sure if relevant to this issue and there's no way I can reproduce this specific error anymore, but I found out that coroutines cause issues.

mcountryman/gloo#5

[Meow]

I have confirmed that this bug exists and will work on fixing it asap. This is critical, thanks for reporting.

[Meow]

Update:
I will probably rewrite the entire module in ANSI C using libpq.

It is to improve compatibility and speed, as well as make the code more maintainable, because C++ (especially the later standards) is hell to maintain.

[xaviergmail]

I'll be keeping an eye out for this, would love to use the json capabilities of postgres

[xaviergmail]

I may be misunderstanding- Is the module currently considered unreliable / unpredictable for use in production, or is there a known way to avoid this?

[Meow]

@xaviergmail Linux build is unreliable and crashes under certain conditions, Windows build is stable.
I'm rewriting the module in C to hopefully fix the issues.