Re: [PATCH] qemu-nbd: Document benefit of --pid-file

From: Eric Blake <eblake@redhat.com>
To: "Vladimir Sementsov-Ogievskiy" <vsementsov@virtuozzo.com>,
	"Daniel P. Berrangé" <berrange@redhat.com>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
	"qemu-block@nongnu.org" <qemu-block@nongnu.org>
Subject: Re: [PATCH] qemu-nbd: Document benefit of --pid-file
Date: Tue, 8 Oct 2019 08:56:22 -0500	[thread overview]
Message-ID: <de461851-39a3-0c48-9270-85e0f0859603@redhat.com> (raw)
In-Reply-To: <99240aec-6d19-cea6-5b95-6bbf5a9106e8@virtuozzo.com>

On 10/8/19 8:53 AM, Vladimir Sementsov-Ogievskiy wrote:

> 
> I've already implemented loop of attempting to connect in my series (patch 4/3).
> It's a bit more difficult to implement, but it's done. And it's a bit better,
> as it test exactly what we want to test. Can we proceed with it?
> 

For test purposes, yes, that's fine (a test doesn't have to be clean, 
just work).

>>
>> We shouldn't need todo any of those tricks IIUC.  The --fork argument is
>> supposed to only let the parent process exit once the server is running.
>>
>> IOW, if you run qemu-nbd --fork, in the foreground, then when execution
>> continues the sockets should be present & accepting connections. No need
>> to check for existance of any files or check connecting, etc.
>>
>>
>> Except that AFAICT, --fork isn't actually implemented with this semantics
>> in qemu-nbd. It looks like we only listen on the sockets after the parent
>> has already exited :-( Can we fix that to synchronize wrt socket listeners ?

Yes, sounds like something good to have.  I'll take a look at doing that.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org