Re: Pause and Resume

Alexey Zakhlestin <[email protected]> Mon, 18 Nov 2013 16:49:06 +0400
Newsgroups	gmane.text.yaml.general
Message-ID	<[email protected]>
On 18.11.13, 16:08, Trans wrote:
> I've been working with YAML streams the last couple of days and I've run
> into an issue/question I could use some help with.
>
> The program I am working on passes a YAML stream through a pipe. At any
> point during the stream the producing program may need to halt the YAML
> stream and somehow instruct the program at the end of the pipe that the
> YAML is "paused". From there it expects the consuming program to dump
> what comes across the pipe to stdout as given until such time it
> receives a special instruction to "resume" processing the YAML stream.
>
> Initially I thought this should be easy, I can just send a `...` to
> signal the pause and a `---` to restart. But this morning I realized,
> though I might be able to get away with in my particular case, it's not
> technically quite right b/c there could be a situation where the pause
> needs to occur mid-document.
>
> So this leads me to wonder, should YAML have markers for pause and
> resume, in addition to the current boundary markers?

This doesn't sound right to me. This is an application-specific task and
should be handled on the level of protocol.

YAML documents -> [Protocol encoding] -> [Transport = Pipe] ->
  -> [Protocol decoding] -> [Receiver]

So, you are looking for some protocol, which allows you to send
control-flow information in addition to data packets.

> Also, are there any standards for this kind of thing when using pipes in
> general? If there are maybe that would be sufficient.

I don't think there's anything specific to pipes (I might be wrong).

The simplest low-level solution is to send data via packets prefixing
them with packet-type (data or control) followed by length of payload
and payload itself.

High-level solution would be to replace pipes by 0mq


-- 
Alexey Zakhlestin
CTO at Grids.by/you
https://github.com/indeyets
PGP key: http://indeyets.ru/alexey.zakhlestin.pgp.asc

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