[ovs-dev] [PATCH v3] Revert "ovsdb-idl: Avoid sending redundant conditional monitoring updates"

[Han Zhou]

On Wed, Mar 25, 2020 at 1:15 PM Dumitru Ceara <dceara at redhat.com> wrote:
>
> This reverts commit 5351980b047f4dd40be7a59a1e4b910df21eca0a.
>
> If the ovsdb-server reply to "monitor_cond_since" requests has
> "found" == false then ovsdb_idl_db_parse_monitor_reply() calls
> ovsdb_idl_db_clear() which iterates through all tables and
> unconditionally sets table->cond_changed to false.
>
> However, if the client had already set a new condition for some of the
> tables, this new condition request will never be sent to ovsdb-server
> until the condition is reset to a different value. This is due to the
> check in ovsdb_idl_db_set_condition().
>
> One way to replicate the issue is described in the bugzilla reporting
> the bug, when ovn-controller is configured to use "ovn-monitor-all":
> https://bugzilla.redhat.com/show_bug.cgi?id=1808125#c6
>
> Commit 5351980b047f tried to optimize sending redundant conditional
> monitoring updates but the chances that this scenario happens with the
> latest code is quite low since commit 403a6a0cb003 ("ovsdb-idl: Fast
> resync from server when connection reset.") changed the behavior of
> ovsdb_idl_db_parse_monitor_reply() to avoid calling ovsdb_idl_db_clear()
> in most cases.
>
> Reported-by: Dan Williams <dcbw at redhat.com>
> Reported-at: https://bugzilla.redhat.com/1808125
> CC: Andy Zhou <azhou at ovn.org>
> Fixes: 5351980b047f ("ovsdb-idl: Avoid sending redundant conditional
monitoring updates")
> Signed-off-by: Dumitru Ceara <dceara at redhat.com>
>
> ---
> v3:
> - Changed commit summary from "ovsdb-idl.c: Clear conditions when
>   clearing IDL.". Also updated the commit description.
> - Instead of clearing IDL conditions, revert 5351980b047f as suggested
>   by Ilya when reviewing v2:
>   https://mail.openvswitch.org/pipermail/ovs-dev/2020-March/369144.html
> v2:
> - Updated commit log so that the "Fixes:" tag reflects the correct
>   commit that introduced the issue.
> ---
>  lib/ovsdb-idl.c | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/lib/ovsdb-idl.c b/lib/ovsdb-idl.c
> index 190143f..1535ad7 100644
> --- a/lib/ovsdb-idl.c
> +++ b/lib/ovsdb-idl.c
> @@ -610,7 +610,6 @@ ovsdb_idl_db_clear(struct ovsdb_idl_db *db)
>          struct ovsdb_idl_table *table = &db->tables[i];
>          struct ovsdb_idl_row *row, *next_row;
>
> -        table->cond_changed = false;
>          if (hmap_is_empty(&table->rows)) {
>              continue;
>          }
> @@ -634,7 +633,6 @@ ovsdb_idl_db_clear(struct ovsdb_idl_db *db)
>      }
>      ovsdb_idl_row_destroy_postprocess(db);
>
> -    db->cond_changed = false;
>      db->cond_seqno = 0;
>      ovsdb_idl_db_track_clear(db);
>
> --
> 1.8.3.1
>
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Acked-by: Han Zhou <hzhou at ovn.org>