Re: [RFC 4/6] migration: Deprecate -incoming <uri>

[Juan Quintela <quintela@redhat.com>]

Peter Xu <peterx@redhat.com> wrote:
> On Mon, Jun 12, 2023 at 09:33:42PM +0200, Juan Quintela wrote:
>> Only "defer" is recommended.  After setting all migation parameters,
>> start incoming migration with "migrate-incoming uri" command.
>> 
>> Signed-off-by: Juan Quintela <quintela@redhat.com>
>> ---
>>  docs/about/deprecated.rst | 7 +++++++
>>  softmmu/vl.c              | 2 ++
>>  2 files changed, 9 insertions(+)
>> 
>> diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
>> index 47e98dc95e..518672722d 100644
>> --- a/docs/about/deprecated.rst
>> +++ b/docs/about/deprecated.rst
>> @@ -447,3 +447,10 @@ The new way to modify migration is using migration parameters.
>>  ``blk`` functionality can be acchieved using
>>  ``migrate_set_parameter block-incremental true``.
>>  
>> +``-incoming uri`` (since 8.1)
>> +'''''''''''''''''''''''''''''
>> +
>> +Everything except ``-incoming defer`` are deprecated.  This allows to
>> +setup parameters before launching the proper migration with
>> +``migrate-incoming uri``.
>> +
>> diff --git a/softmmu/vl.c b/softmmu/vl.c
>> index b0b96f67fa..7fe865ab59 100644
>> --- a/softmmu/vl.c
>> +++ b/softmmu/vl.c
>> @@ -2651,6 +2651,8 @@ void qmp_x_exit_preconfig(Error **errp)
>>      if (incoming) {
>>          Error *local_err = NULL;
>>          if (strcmp(incoming, "defer") != 0) {
>> +            warn_report("-incoming %s is deprecated, use -incoming defer and "
>> +                        " set the uri with migrate-incoming.", incoming);
>
> I still use uri for all my scripts, alongside with "-global migration.xxx"
> and it works.

You know what you are doing (TM).
And remember that we don't support -gobal migration.x-foo.
Yes, I know, we should drop the "x-" prefixes.

> Shall we just leave it there?  Or is deprecating it helps us in any form?

See the patches two weeks ago when people complained that lisen(.., num)
was too low.  And there are other parameters that work the same way
(that I convenientely had forgotten).  So the easiest way to get things
right is to use "defer" always.  Using -incoming "uri" should only be
for people that "know what they are doing", so we had to ways to do it:
- review all migration options and see which ones work without defer
  and document it
- deprecate everything that is not defer.

Anything else is not going to be very user unfriendly.
What do you think.

Later, Juan.

PD.  This series are RFC for multiple reasons O:-)