Re: [BuildStream] Proposal: Moving UI into a subprocess

[Tristan Van Berkom <tristan vanberkom codethink co uk>]

Hi again,

There is one detail I meant to mention in the last followup but forgot:

On Wed, 2019-05-22 at 14:48 +0100, Phil Dawson wrote:
> # Tldr: 
[...]
> # Message handling
>
> The message handler in `Context` will send messages over a queue to the
> front-end to handle. Currently, the front-end uses global state to gain
> some of the information it renders. After the split, all state needed
> by the front-end will be passed as explicit parameters of each `Message`
> object (with the exception of any BuildStream configuration, which
> will be still loaded and available before the `Stream` process is
> spawned and therefore available to the front-end without any changes
> needed).

Here, we want job processes to issue logs directly to the frontend
process, without having to make a pit stops in the scheduling processes
(this may have some implications, like ensuring job completion messages
are queued up for the frontend before sending a message to the frontend
to inform it that a job has completed, and with which exit status).

Cheers,
    -Tristan