On 10/30/25 12:57 PM, Brendan Doyle via discuss wrote:
>
> As a follow up, the man page for Sampling_App states...
>
> *i**d*: integer, in range 1 to 255
>
> This identifier is used as part of the sample’s observation
> domain ID.
>
> So in my generated samples I have:
>
> "observationDomainID" : 704643079,
> "observationPointID" : 1003,
>
> My Sample collector:
> ovn-nbctl list Sampling_App
> _uuid : daa18e34-7705-42c4-bed7-afc4497e0a21
> external_ids : {}
> id : 42
> type : acl-new
>
>
> But I can't find '42' in '704643079' binary/hex or decimal, so how is the
> observationDomainID generated?
>>> hex(704643079)
'0x2a000007'
>>> 0x2a
42
The 7 is a datapath key.
This is documented in the description for debug_drop_domain_id.
But the docs could be better indeed...
>
> Brendan.
>
>
> On 30/10/2025 11:09, Brendan Doyle via discuss wrote:
>> Hi,
>>
>> I've asked this before but perhaps the question or response got lost, I'm
>> struggling
>> to understand the relationship between Sampling_App, Sample_Collector and
>> Sample
>> when creating ACLs with samples. I can't find any good documentation/blog or
>> tutorial
>> so I'm working off the unit tests.
>>
>> So what's the purpose of Sampling_App type="drop", it seems you don't need
>> it to
>> sample dropped packets. I have
>>
>> collector1=$(ovn-nbctl create Sample_Collector id=1 name=c1
>> probability=65535 set_id=100)
>>
>> ovn-nbctl create Sampling_App type="acl-new" id="42"
>>
>> ovn-nbctl acl-add ls_vcn1_net1 from-lport 32767 "inport ==
>> \"00bff7c0-2e2d-41ba-9485-3b5fa9801365\" && arp" allow-related
>> ovn-nbctl acl-add ls_vcn1_net1 from-lport 14000 "inport ==
>> \"00bff7c0-2e2d-41ba-9485-3b5fa9801365\" && ip.proto == 6" allow-related
>>
>> ovn-nbctl \
>> -- --id=@sample_in_1c_new create Sample collector="$collector1"
>> metadata=1003 \
>> -- --sample-new=@sample_in_1c_new \
>> acl-add ls_vcn1_net1 from-lport 0 "inport ==
>> \"00bff7c0-2e2d-41ba-9485-3b5fa9801365\"" drop
>>
>>
>> And this generates samples for dropped pkts, I don't need to create:
>>
>> ovn-nbctl create Sampling_App type="drop" id="44"
>>
>> And in any case there is no "--sample-drop=sample" option for ovn-nbctl
>> acl_add so how would I use it?
IIRC, the drop sampling app is for any packet drops in the system that OVN
is responsible for, it's not tied to ACLs. E.g. if the packet is dropped
due to routing or there is no port to deliver, it will be sampled using the
"drop" sampling app. This behavior may need to be enabled separately, see
the docs for debug_drop_collector_set.
Dumitru or Adrian may correct me if I'm wrong.
Best regards, Ilya Maximets.
_______________________________________________
discuss mailing list
[email protected]
https://mail.openvswitch.org/mailman/listinfo/ovs-discuss
