On Thu, Apr 10, 2025 at 12:10:13PM +0100, brendan.do...@oracle.com wrote:
> Hi Dumitru/Adrian,
>
>
>
> I'm working my way through IPFIX test in system-ovn.at, just a couple of
> questions.
>
> > collector1=$(ovn-nbctl create Sample_Collector id=1 name=c1
> > probability=65535 set_id=100)
> > collector2=$(ovn-nbctl create Sample_Collector id=2 name=c2
> > probability=65535 set_id=200)
> > check_row_count nb:Sample_Collector 2
> >
> > check_uuid ovn-nbctl create Sampling_App type="acl-new" id="42"
> > check_uuid ovn-nbctl create Sampling_App type="acl-est" id="43"
> > check_row_count nb:Sampling_App 2
> >
> > dnl Create ACLs that match the 3 types of traffic in all 3 possible
> > stages:
> > dnl from-lport, from-lport-after-lb, to-lport.
> > check_uuid ovn-nbctl \
> > -- --id=@sample_in_1c_new create Sample collector="$collector1"
> > metadata=1001 \
> I don't follow this syntax, it is not described in the ovn-nbctl man page,
> there we just
> have
> ovn-nbctl --sample-new=<uuid of a row of the Sample table> acl-add
>
> So what is 'id' above?
>
> what is '@sample_in_1c_new' is it "42"?
All OVS and OVN commands that interact with an OVSDB (such as ovn-nbctl
or ovs-vsctl), apart from some specific "high level" commands,
(such as "acl-add [---sample-new]..."), support interacting with the
OVSDB directly,
See "Database Commands" section in ovn-nbctl(8).
This part of the command is creating an entry in the Sample action and
_storing_ its id in a temporary reference called "sample_in_1c_new"
which can be used in the same OVSDB transaction futher below.
>
> Is it required to also specify 'create Sample collector', it is not
> described in the ovn-nbctl man page.
>
From manpage:
ovn-nbctl [--id=(@name|uuid)] create table column[:key]=value...
> Is '$collector1' the UUID of the Sample_Collector table row we created with
> set_id=100 ?
>
Yes
> What is 'metadata' - Is it arbitrary?
>
Since the command is editing the DB directly, you should look at the
ovn-nb(5) for the documentation of each column in the table. Quoting
such manpage:
"""
metadata: integer, in range 1 to 4,294,967,295 (must be unique within table)
Will be used as Observation Point ID in every sample. The
Observation Domain ID will be generated by ovn-northd and includes the
logical datapath key as the least significant 24 bits and the sampling
application type (e.g., drop debugging) as the 8 most significant
bits.
"""
> Also I see in the ovn-nbctl man page, we have --sample-new and --sample-est,
> but no
> --sample-drop, even though the ovn-nb man pages says the 'type' in the
> Sampling_App
> Table can be acl-est, acl-new, or drop
>
You are right. "--sample-{new,est}" are options to "acl-add". If you
enable those options, _only_ ACL drops will be sampled.
In order to sample _all_ drops (including implicit ones), we used to
have two flags in NB_Global:options but those got superceeded by just
configuring the Sampling_App table. Nevertheless, this was not added as
a "high level" command to ovn-nbctl. Global options tend not to be, plus
this is a debugging-oriented feature.
Thanks.
Adrián
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