On Thu, Apr 30, 2020 at 4:07 AM Dumitru Ceara <dce...@redhat.com> wrote:
>
> On 4/30/20 12:06 PM, Numan Siddique wrote:
> > On Thu, Apr 30, 2020 at 1:41 PM Numan Siddique <num...@ovn.org> wrote:
> >
> >>
> >>
> >> On Thu, Apr 30, 2020 at 8:43 AM Han Zhou <hz...@ovn.org> wrote:
> >>
> >>> On Wed, Apr 29, 2020 at 4:50 PM Han Zhou <hz...@ovn.org> wrote:
> >>>>
> >>>>
> >>>>
> >>>> On Wed, Apr 29, 2020 at 2:45 PM Dumitru Ceara <dce...@redhat.com>
> >>> wrote:
> >>>>>
> >>>>> On 4/29/20 9:57 PM, Han Zhou wrote:
> >>>>>>
> >>>>>>
> >>>>>> On Wed, Apr 29, 2020 at 12:17 PM Numan Siddique <num...@ovn.org
> >>>>>> <mailto:num...@ovn.org>> wrote:
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> On Wed, Apr 29, 2020 at 9:57 PM Dumitru Ceara <dce...@redhat.com
> >>>>>> <mailto:dce...@redhat.com>> wrote:
> >>>>>>>>
> >>>>>>>> In some cases, if the NB/SB databases ovn-northd connects to are
> >>>>>>>> inconsistent, ovn-northd might generate transactions that fail
> >>>>>>>> continuously due to failed integrity checks on the SB database
> >>> server.
> >>>>>>>>
> >>>>>>>> The first patch of the series addresses inconsistencies due to
> >>> stale
> >>>>>>>> Datapath_Binding records in the SB database.
> >>>>>>>>
> >>>>>>>> The second patch of the series addresses inconsistencies due to
> >>> stale
> >>>>>>>> tunnel_key values in various SB database table records.
> >>>>>>>>
> >>>>>>>> Reported-by: Dan Williams <d...@redhat.com <mailto:
> >>> d...@redhat.com>>
> >>>>>>>> Reported-at: https://bugzilla.redhat.com/1828637
> >>>>>>>> Signed-off-by: Dumitru Ceara <dce...@redhat.com
> >>>>>> <mailto:dce...@redhat.com>>
> >>>>>>>>
> >>>>>>>> Dumitru Ceara (2):
> >>>>>>>> ovn-northd: Clear SB records depending on stale datapaths.
> >>>>>>>> ovn-northd: Fix tunnel_key allocation for SB records.
> >>>>>>>
> >>>>>>>
> >>>>>>> Hi Dumitru,
> >>>>>>>
> >>>>>>> I did some testing in my ovn-fake-multinode setup. These are my
> >>>>>> observations.
> >>>>>>>
> >>>>>>> I created a logical switch sw0 with 4 logical ports. So the next
> >>>>>> tunnel key should be 5.
> >>>>>>> I stopped ovn-northd and created a couple of port_binding entries
> >>>>>> manually using
> >>>>>>> "ovn-sbctl create port_binding" with tunnel keys 5 and 6.
> >>>>>>> I also created a logical port in sw0. Then I started ovn-northd.
> >>>>>> ovn-northd deletes the port binding
> >>>>>>> entries added by me and creates the port_binding entry for the
> >>> logical
> >>>>>> port with the tunnel_key=5
> >>>>>>> in the same transaction.
> >>>>>>>
> >>>>>>> I think ovn-northd syncs the south db based on the contents of the
> >>>>>> north db.
> >>>>>>>
> >>>>>>> There's no harm in having your patches. But I'm not really sure if
> >>> it
> >>>>>> resolves the issue we have observed.
> >>>>>>>
> >>>>>>> Just to brief everyone about the issue we are seeing, we see below
> >>>>>> logs in ovn-northd.
> >>>>>>>
> >>>>>>> *******
> >>>>>>> 2020-04-16T23:02:33Z|00127|ovsdb_idl|WARN|transaction error:
> >>>>>> {"details":"Transaction causes multiple rows in \"Port_Binding\"
> >>> table
> >>>>>> to have identical values (23eb9016-45f9-4158-be35-77b2713b9a0f and
> >>> 7)
> >>>>>> for index on columns \"datapath\" and \"tunnel_key\". First row,
> >>> with
> >>>>>> UUID e4f11a7b-09b6-454f-a125-34cc4b144ef6, had the following index
> >>>>>> values before the transaction: bdbb436e-f98c-4651-9b80-6e8b95044560
> >>> and
> >>>>>> 7. Second row, with UUID d37cc3f1-8633-440f-b145-8222a0d4723c,
> >>> existed
> >>>>>> in the database before this transaction and was not modified by the
> >>>>>> transaction.","error":"constraint violation"}
> >>>>>>> ******
> >>>>>>>
> >>>>>>> And because of this constraint violation error, ovn-northd cannot
> >>>>>> further write to the sb db until it is restarted.
> >>>>>>>
> >>>>>>> In my opinion this can only happen if ovn-northd doesn't see the
> >>> port
> >>>>>> binding row (which is actually present in the DB) in its IDL
> >>> in-memory db.
> >>>>>>> I suspect this could have happened when ovn-northd reconnects to
> >>> the
> >>>>>> same master or connects to the new master and it doesn't get the
> >>> proper
> >>>>>>> updates.
> >>>>>>>
> >>>>>>> Maybe in this case, the IDL should request the db contents with
txn
> >>> id
> >>>>>> =0, so that it receives the complete dump of the db.
> >>>>>>>
> >>>>>>> Is it possible that ovn-northd sees a port binding with a tunnel
> >>> key
> >>>>>> 'x' and still allocates the same tunnel id 'x' to a new logical
> >>> port ?
> >>>>>>> If so, then definitely your patches makes sense.
> >>>>>>>
> >>>>>>> @Han - Have you seen this issue in your deployments ? Do you have
> >>>>>> comments here ?
> >>>>>>>
> >>>>>>> Thanks
> >>>>>>> Numan
> >>>>>>>
> >>>>>> I never saw such issue before, but I am not sure if this is
possible
> >>> due
> >>>>>> to bugs. Currently there is a bug fix under review:
> >>>>>>
> >>>
> >>>
https://patchwork.ozlabs.org/project/openvswitch/patch/20200422183842.6303.99600.st...@dceara.remote.csb/
> >>> .
> >>>>>> However, northd doesn't conditionally monitor the rows so I am not
> >>> sure
> >>>>>> if this is the root cause of the northd inconsistency issue
> >>> discussed
> >>> here.
> >>>>>>
> >>>>>> I don't think we should fix in northd (or ovn-controller) to handle
> >>> the
> >>>>>> inconsistency of ovsdb. The consistency should be expected from
> >>> ovsdb
> >>>>>> and we should fix ovsdb/IDL when there is such kind of bug.
> >>> Otherwise,
> >>>>>> there might be too many places to fix and even re-design. My
> >>>>>> understanding is, if the ovsdb IDL sees a temporarily stale data,
> >>> the
> >>>>>> current northd/ovn-controller logic should be able to correct
> >>> themselves
> >>>>>> once the data is up-to-date. Moreover, for northd, it is connected
> >>> to
> >>>>>> leader-only in clustered mode, which avoids the possibility of
> >>> seeing
> >>>>>> staled data in northd (unless there is a bug).
> >>>>>>
> >>>>>> To summarize, I think we need to find the root cause of the
> >>>>>> inconsistency between IDL and server and fix it there, instead of
> >>>>>> changing ovn-northd to accommodate the inconsistency. (consistency
> >>> is
> >>>>>> the biggest advantage of OVSDB, to ease the application
> >>> implementation).
> >>>>>>
> >>>>>> Thanks,
> >>>>>> Han
> >>>>>
> >>>>> Hi Han, Numan,
> >>>>>
> >>>>> I might have misused "inconsistency" in this context. What I meant
was
> >>>>> more on the note of "discrepancies between NB and SB databases".
> >>>>>
> >>>>> This is a very simple reproducer for the port_binding tunnel_key
> >>> issue,
> >>>>> no clustering of NB/SB dbs involved:
> >>>>>
> >>>>> # Create two logical switches with one port each.
> >>>>> $ ovn-nbctl ls-add ls1
> >>>>> $ ovn-nbctl lsp-add ls1 p1
> >>>>> $ ovn-nbctl ls-add ls2
> >>>>> $ ovn-nbctl lsp-add ls2 p2
> >>>>> $ ovn-nbctl --wait=sb sync
> >>>>>
> >>>>> # At this point PB for p1 has tunnel_key=1
> >>>>> # At this point PB for p2 has tunnel_key=2
> >>>>>
> >>>>> # Simulate the SB db going away (could be network
> >>>>> # issues or crash or some other event).
> >>>>> $ ovn-ctl stop_sb_ovsdb
> >>>>>
> >>>>> # CMS decides to move p2 from ls2 to ls1 and removes
> >>>>> # ls2 completely.
> >>>>> $ ovn-nbctl ls-del ls2
> >>>>> $ ovn-nbctl lsp-add ls1 p2
> >>>>>
> >>>>> # Simulate SB DB coming back online.
> >>>>> $ ovn-ctl start_sb_ovsdb
> >>>>>
> >>>>> At this point ovn-northd will try to set the datapath field in PB2
to
> >>>>> point to datapath_binding corresponding to ls1 but will *not* change
> >>>>> tunnel_key.
> >>>>>
> >>>>> We get:
> >>>>> 2020-04-29T20:52:41.327Z|00016|ovsdb_idl|WARN|transaction error:
> >>>>> {"details":"Transaction causes multiple rows in \"Port_Binding\"
table
> >>>>> to have identical values (1b1c4b39-c045-448d-a532-8edbe5544e13 and
1)
> >>>>> for index on columns \"datapath\" and \"tunnel_key\". First row,
with
> >>>>> UUID e20219fa-ef67-49a2-81cd-739fa80d2bd4, existed in the database
> >>>>> before this transaction and was not modified by the transaction.
> >>> Second
> >>>>> row, with UUID 50b0e240-8a4d-4e98-8e2f-97c94811d1b1, had the
following
> >>>>> index values before the transaction:
> >>>>> a9b5959f-2f48-44e7-b6bb-f7148c28e4b5 and 1.","error":"constraint
> >>> violation"}
> >>>>>
> >>>>> And ovn-northd keeps retrying the same transaction at every
iteration
> >>>>> from this point on and fails continuously.
> >>>>>
> >>>>> For the stale datapath issue (patch #1 in the series) a similar
> >>>>> reproducer is:
> >>>>>
> >>>>> # Create a logical router with on router port.
> >>>>> $ ovn-nbctl lr-add lr
> >>>>> $ ovn-nbctl lrp-add lr p 00:00:00:00:00:01 1.1.1.1/24
> >>>>>
> >>>>> # Simulate that a mac binding was created for the router
> >>>>> # port.
> >>>>> $ dp=$(ovn-sbctl --bare --columns _uuid list datapath .)
> >>>>> $ ovn-sbctl create mac_binding logical_port="p" ip="1.1.1.2"
> >>> datapath="$dp"
> >>>>> $ ovn-nbctl --wait=sb sync
> >>>>>
> >>>>> # Simulate the SB db going away (could be network
> >>>>> # issues or crash or some other event).
> >>>>> $ ovn-ctl stop_sb_ovsdb
> >>>>>
> >>>>> # CMS decides to delete lr.
> >>>>> $ ovn-nbctl lr-del lr
> >>>>>
> >>>>> # CMS decides to readd lr and router port.
> >>>>> $ ovn-nbctl lr-add lr
> >>>>> $ ovn-nbctl lrp-add lr p 00:00:00:00:00:01 1.1.1.1/24
> >>>>>
> >>>>> # Simulate SB DB coming back online.
> >>>>> $ ovn-ctl start_sb_ovsdb
> >>>>>
> >>>>> At this point ovn-northd will try to clear the old datapath record
> >>> from
> >>>>> SB DB *without* destroying the mac binding record.
> >>>>>
> >>>>> We get:
> >>>>> 2020-04-29T21:41:42.145Z|00013|ovsdb_idl|WARN|transaction error:
> >>>>> {"details":"cannot delete Datapath_Binding row
> >>>>> de8d19d6-d67b-499b-8825-12d34ec60946 because of 1 remaining
> >>>>> reference(s)","error":"referential integrity violation"}
> >>>>>
> >>>>> I think both situations above should be addressed by ovn-northd and
> >>>>> stale datapath/mac_binding/port_binding/etc records should be
purged.
> >>> I
> >>>>> guess there might be other scenarios that would trigger constraint
> >>>>> violations too but this is what I found so far.
> >>>>>
> >>>>> If you agree, I can send a v2 and add tests for the two simplified
> >>>>> scenarios I mentioned above.
> >>>>>
> >>>>> What do you think?
> >>>
> >>
> >> Thanks Dumitru. for the explanation. It would be great to add these
tests
> >> in v2.
> >>
> >> Thanks
> >> Numan
> >>
> >>
> >>>>>
> >>>>> Thanks,
> >>>>> Dumitru
> >>>>>
> >>>>
> >>>> Thanks Dumitru for explaining. Now I understand the problem. So it
has
> >>> nothing to do with OVSDB consistency itself, but just northd'd logic.
I
> >>> don't even need to stop SB to reproduce. Here is how I reproduced it:
> >>>> $ ovn-nbctl ls-add ls1
> >>>> $ ovn-nbctl ls-add ls2
> >>>> $ ovn-nbctl lsp-add ls1 lsp1
> >>>> $ ovn-nbctl lsp-add ls2 lsp2
> >>>> $ ovn-nbctl lsp-del ls2 -- lsp-add ls1 lsp2
> >>>
> >>> Sorry for the typo. The last command was:
> >>> $ ovn-nbctl lsp-del lsp2 -- lsp-add ls1 lsp2
> >>>
> >>
> > I applied these 2 patches locally and I ran the below commands, which is
> > the same as the above
> > commands shared by Han.
> >
> > $ovn-nbctl ls-add ls1
> > $ovn-nbctl ls-add ls2
> > $ovn-nbctl lsp-add ls1 lsp1
> > $ovn-nbctl lsp-add ls2 lsp2
> > $ovs-vsctl add-port br-int p1 -- set Interface p1
external_ids:iface-id=lsp2
> > $ovn-sbctl list port_binding
> >
> > $ovn-sbctl list port_binding
> > _uuid : bbf2f7e4-b61b-4ce8-adb6-4d17e410b87b
> > chassis : ff506354-ac7b-4463-b42d-d89bddf319c7
> > datapath : ef316369-0f2c-4246-adbd-8c187bd95e41
> > ...
> > ...
> > tunnel_key : 1
> > type : ""
> > virtual_parent : []
> >
> > _uuid : 7cca89fa-55f9-4326-8188-6678838467bb
> > chassis : []
> > datapath : 21263028-a511-457a-824b-39a1219084c8
> > ...
> > logical_port : lsp1
> > ...
> > tunnel_key : 1
> > type : ""
> > virtual_parent : []
> >
> > $ovn-nbctl lsp-del lsp2 -- lsp-add ls1 lsp2
> >
> > $ovn-sbctl list port_binding
> > _uuid : bbf2f7e4-b61b-4ce8-adb6-4d17e410b87b
> > chassis : ff506354-ac7b-4463-b42d-d89bddf319c7
> > datapath : 21263028-a511-457a-824b-39a1219084c8
> > ...
> > logical_port : lsp2
> > ...
> > tunnel_key : 1
> > type : ""
> > virtual_parent : []
> >
> > _uuid : 7cca89fa-55f9-4326-8188-6678838467bb
> > chassis : []
> > datapath : 21263028-a511-457a-824b-39a1219084c8
> > ...
> > logical_port : lsp1
> > ...
> > tunnel_key : 2
> > type : ""
> > virtual_parent : []
> >
> >
> > I notice that the same port_binding record for lsp2 is being reused.
> > Is that intentional ?
>
> This happens because the order in which ovn_port entries will be
processed:
>
> https://github.com/ovn-org/ovn/blob/master/northd/ovn-northd.c#L3453
>
> The "both" list is populated in join_logical_ports() and depends on the
> order of Logical_Switch/Router_Port records in
> od->nbs->ports/od->nbr->ports arrays which is not under ovn-northd's
> control.
>
> https://github.com/ovn-org/ovn/blob/master/northd/ovn-northd.c#L2022
> https://github.com/ovn-org/ovn/blob/master/northd/ovn-northd.c#L2103
>
> >
> > Ideally the old port binding record lsp2 should get deleted and
> > new one should get created.
>
> So even if we delete the old port binding and recreate it we'd still get
> a conflict in some cases because lsp2 would be processed before lsp1.
>
I was thinking about the same thing as Numan. I think OVN is not designed
to handle "moving a LSP from one LS to another", but the OVSDB schema
allows user to do so. In reality, I don't think it is a real world use case
for such support (correct me if I am wrong). So, for ovn-northd it should
detect the change of LSP - LS mapping and treat it as a deletion (delete
the related PB as well) and recreation (recreate a new PB). @Dumitru Ceara
<dce...@redhat.com> wouldn't this solve the problem?
> >
> > I found another issue with the below commands (tested in sandbox env)
> >
> > $ovn-nbctl ls-add ls1
> > $ovn-nbctl ls-add ls2
> > $ovn-nbctl lsp-add ls1 lsp1
> > $ovn-nbctl lsp-add ls2 lsp2
> > $ovn-nbctl lsp-set-type lsp2 external
> > $ovn-nbctl ha-chassis-group-add chg1
> > $ovn-nbctl ha-chassis-group-add-chassis chg1 chassis-1 30
> > $ovn-nbctl set logical_switch_port lsp2 ha_chassis_group=<chg1_uuid>
> > $ovn-nbctl lsp-del lsp2 -- lsp-add ls1 lsp2 -> This fails with the below
> > logs in ovn-northd
> >
> > *******
> > 2020-04-30T09:59:48.319Z|00007|ovsdb_idl|WARN|transaction error:
> > {"details":"cannot delete HA_Chassis_Group row
> > 6e0c88d7-20f6-473a-bd0a-9eea60b639e6 because of 1 remaining
> > reference(s)","error":"referential integrity violation"}
> > *******
>
> I'll look into this. Looks like patch #2 of the series should take care
> of HA_Chassis_Group too.
>
> >
> > I think it's better if the stale port binding entry is deleted instead
of
> > reusing it. What do you think ?
>
> As mentioned above, this wouldn't help too much and it would actually
> create larger transactions so it seems inefficient.
>
> Thanks,
> Dumitru
>
> >
> > Thanks
> > Numan
> >
> >
> >
> >
> >>>>
> >>>> 2020-04-29T23:46:17.675Z|00007|ovsdb_idl|WARN|transaction error:
> >>> {"details":"Transaction causes multiple rows in \"Port_Binding\"
table to
> >>> have identical values (be595a3b-3904-4229-9ba2-884b27a86b75 and 1) for
> >>> index on columns \"datapath\" and \"tunnel_key\". First row, with
UUID
> >>> d4cc6ec5-4817-47c9-aa83-9985d3b7b452, existed in the database before
this
> >>> transaction and was not modified by the transaction. Second row, with
> >>> UUID
> >>> b874ab93-d97a-4583-8ac3-c353a40b180d, had the following index values
> >>> before
> >>> the transaction: 6940ad91-83c5-4fe9-bab5-4fbec6714b0d and
> >>> 1.","error":"constraint violation"}
> >>>>
> >>>> I will take a closer look at the fix.
> >>>>
> >>>> Thanks,
> >>>> Han
> >>> _______________________________________________
> >>> dev mailing list
> >>> d...@openvswitch.org
> >>> https://mail.openvswitch.org/mailman/listinfo/ovs-dev
> >>>
> >>>
> > _______________________________________________
> > dev mailing list
> > d...@openvswitch.org
> > https://mail.openvswitch.org/mailman/listinfo/ovs-dev
> >
>
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