[ovs-dev] [PATCH v2 2/2] ovsdb-idl: Preserve references for deleted rows.
Ilya Maximets
i.maximets at ovn.org
Tue Mar 9 15:07:51 UTC 2021
On 3/3/21 3:40 PM, Dumitru Ceara wrote:
> Considering two DB rows, 'a' from table A and 'b' from table B (with
> column 'ref_a' a reference to table A):
> a = {A._uuid=<U1>}
> b = {B._uuid=<U2>, B.ref_a=<U1>}
>
> Assuming both records are present in the IDL client's in-memory view of
> the database, depending whether row 'b' is also deleted in the same
> transaction or not, deletion of row 'a' should generate the following
> tracked changes:
>
> 1. only row 'a' is deleted:
> - for table A:
> - deleted records: a = {A._uuid=<U1>}
> - for table B:
> - updated records: b = {B._uuid=<U2>, B.ref_a=[]}
>
> 2. row 'a' and row 'b' are deleted in the same update:
> - for table A:
> - deleted records: a = {A._uuid=<U1>}
> - for table B:
> - deleted records: b = {B._uuid=<U2>, B.ref_a=<U1>}
>
> To ensure this, we now delay reparsing row backrefs until the row has
> been removed from the table's hmap and until the IDL client has
> processed all tracked changes (ovsdb_idl_track_clear() was called).
>
> Without this change, in scenario 2 above, the tracked changes for table
> B would be:
> - deleted records: b = {B._uuid=<U2>, B.ref_a=[]}
>
> In particular, for strong references, row 'a' can never be deleted in
> a transaction that happens strictly before row 'b' is deleted. In some
> cases [0] both rows are deleted in the same transaction and having
> B.ref_a=[] would violate the integrity of the database from client
> perspective. This would force the client to always validate that
> strong reference fields are non-NULL. This is not really an option
> because the information in the original reference is required for
> incrementally processing the record deletion.
>
> [0] with ovn-monitor-all=true, the following command triggers a crash
> in ovn-controller because a strong reference field becomes NULL:
> $ ovn-nbctl --wait=hv -- lr-add r -- lrp-add r rp 00:00:00:00:00:01 1.0.0.1/24
> $ ovn-nbctl lr-del r
>
> Reported-at: https://bugzilla.redhat.com/1932642
> Fixes: 72aeb243a52a ("ovsdb-idl: Tracking - preserve data for deleted rows.")
> Signed-off-by: Dumitru Ceara <dceara at redhat.com>
> ---
> v2:
> - Added ovsdb-idl.at test for strong references.
> ---
> lib/ovsdb-idl.c | 6 ++-
> tests/ovsdb-idl.at | 118 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> tests/test-ovsdb.c | 45 ++++++++++++++++++++
> 3 files changed, 167 insertions(+), 2 deletions(-)
>
> diff --git a/lib/ovsdb-idl.c b/lib/ovsdb-idl.c
> index 9e1e787..ecd4924 100644
> --- a/lib/ovsdb-idl.c
> +++ b/lib/ovsdb-idl.c
> @@ -163,6 +163,7 @@ static void ovsdb_idl_row_unparse(struct ovsdb_idl_row *);
> static void ovsdb_idl_row_clear_old(struct ovsdb_idl_row *);
> static void ovsdb_idl_row_clear_new(struct ovsdb_idl_row *);
> static void ovsdb_idl_row_clear_arcs(struct ovsdb_idl_row *, bool destroy_dsts);
> +static void ovsdb_idl_row_reparse_backrefs(struct ovsdb_idl_row *row);
>
> static void ovsdb_idl_txn_abort_all(struct ovsdb_idl *);
> static bool ovsdb_idl_txn_extract_mutations(struct ovsdb_idl_row *,
> @@ -367,6 +368,8 @@ ovsdb_idl_clear(struct ovsdb_idl *db)
> ovsdb_idl_row_unparse(row);
> }
> LIST_FOR_EACH_SAFE (arc, next_arc, src_node, &row->src_arcs) {
> + ovs_list_remove(&arc->src_node);
> + ovs_list_remove(&arc->dst_node);
> free(arc);
> }
> /* No need to do anything with dst_arcs: some node has those arcs
> @@ -1234,6 +1237,7 @@ ovsdb_idl_track_clear__(struct ovsdb_idl *idl, bool flush_all)
> ovs_list_remove(&row->track_node);
> ovs_list_init(&row->track_node);
> if (ovsdb_idl_row_is_orphan(row)) {
> + ovsdb_idl_row_reparse_backrefs(row);
> ovsdb_idl_row_unparse(row);
> if (row->tracked_old_datum) {
> const struct ovsdb_idl_table_class *class =
> @@ -2156,8 +2160,6 @@ ovsdb_idl_delete_row(struct ovsdb_idl_row *row)
> ovsdb_idl_row_clear_old(row);
> if (ovs_list_is_empty(&row->dst_arcs)) {
> ovsdb_idl_row_destroy(row);
> - } else {
> - ovsdb_idl_row_reparse_backrefs(row);
> }
By removing the ovsdb_idl_row_reparse_backrefs() you're making an assumption
that we always have a modification event for all rows that are referencing
this one. But that is not always the case.
There is scenario where this re-parsing is needed. In short, if you're
reducing the scope of conditional monitoring and some rows becomes
orphan rows. In this case ovsdb-server will not generate 'modify' event
for the row that references our newly orphan row, so it will not be
re-parsed and these orphan rows will be accessible the row that references
them.
Here is a quick'n'dirty testcase, how to reproduce:
diff --git a/tests/ovsdb-idl.at b/tests/ovsdb-idl.at
index 702502280..c6bb3f348 100644
--- a/tests/ovsdb-idl.at
+++ b/tests/ovsdb-idl.at
@@ -1174,7 +1174,7 @@ OVSDB_CHECK_IDL_TRACK([track, simple idl, initially populated],
dnl This test creates database with weak references and checks that orphan
dnl rows created for weak references are not available for iteration via
dnl list of tracked changes.
-OVSDB_CHECK_IDL_TRACK([track, simple idl, initially populated, orphan weak references],
+OVSDB_CHECK_IDL_TRACK([track, simple idl, initially populated, orphan weak references quickndirty],
[['["idltest",
{"op": "insert",
"table": "simple",
@@ -1196,7 +1196,7 @@ OVSDB_CHECK_IDL_TRACK([track, simple idl, initially populated, orphan weak refer
["named-uuid", "weak_row1"],
["named-uuid", "weak_row2"]]
]}}]']],
- [['condition simple []' \
+ [['condition simple [true]' \
'condition simple [["s","==","row1_s"]]' \
'["idltest",
{"op": "update",
diff --git a/tests/test-ovsdb.c b/tests/test-ovsdb.c
index 36fb9cc08..ace87b13d 100644
--- a/tests/test-ovsdb.c
+++ b/tests/test-ovsdb.c
@@ -2157,6 +2157,7 @@ print_idl_row_singleton(const struct idltest_singleton *sng, int step)
static void
print_idl(struct ovsdb_idl *idl, int step)
{
+ const struct idltest_simple6 *s6;
const struct idltest_simple *s;
const struct idltest_link1 *l1;
const struct idltest_link2 *l2;
@@ -2175,6 +2176,10 @@ print_idl(struct ovsdb_idl *idl, int step)
print_idl_row_link2(l2, step);
n++;
}
+ IDLTEST_SIMPLE6_FOR_EACH (s6, idl) {
+ print_idl_row_simple6(s6, step);
+ n++;
+ }
IDLTEST_SINGLETON_FOR_EACH (sng, idl) {
print_idl_row_singleton(sng, step);
n++;
@@ -2638,8 +2643,12 @@ do_idl(struct ovs_cmdl_context *ctx)
/* Print update. */
if (track) {
- print_idl_track(idl, step++);
+ print_idl_track(idl, step);
+ print_and_log("%03d: print_idl[1]", step);
+ print_idl(idl, step);
ovsdb_idl_track_clear(idl);
+ print_and_log("%03d: print_idl[2]", step);
+ print_idl(idl, step++);
} else {
print_idl(idl, step++);
}
---
By running make -j8 check TESTSUITEFLAGS='-k quickndirty -v', you will have
some output for the commands in the log.
The first condition for a 'simple' table is 'true', so we will receive all
3 rows from this table and also row from the 'simple6'.
All 3 rows are in a weak references:
test-ovsdb|test_ovsdb|001: table simple: inserted row: s=row0_s <> uuid=2309fce8-a6dd-46e5-a603-fe1ea1ab6bb0
test-ovsdb|test_ovsdb|001: table simple: updated columns: s
test-ovsdb|test_ovsdb|001: table simple: inserted row: s=row2_s <> uuid=1fd88ded-06f0-4fee-a21b-4e552d8a2f50
test-ovsdb|test_ovsdb|001: table simple: updated columns: s
test-ovsdb|test_ovsdb|001: table simple: inserted row: s=row1_s <> uuid=124ddccb-7eb8-4def-b768-887cb8d84ada
test-ovsdb|test_ovsdb|001: table simple: updated columns: s
test-ovsdb|test_ovsdb|001: table simple6: inserted row: name=first_row weak_ref=[124ddccb-7eb8-4def-b768-887cb8d84ada 1fd88ded-06f0-4fee-a21b-4e552d8a2f50 2309fce8-a6dd-46e5-a603-fe1ea1ab6bb0]
test-ovsdb|test_ovsdb|001: table simple6: updated columns: name weak_ref
All of them are accessible for a user before the track_clear():
test-ovsdb|test_ovsdb|001: print_idl[1]
test-ovsdb|test_ovsdb|001: table simple: inserted row: s=row0_s <> uuid=2309fce8-a6dd-46e5-a603-fe1ea1ab6bb0
test-ovsdb|test_ovsdb|001: table simple: updated columns: s
test-ovsdb|test_ovsdb|001: table simple: inserted row: s=row2_s <> uuid=1fd88ded-06f0-4fee-a21b-4e552d8a2f50
test-ovsdb|test_ovsdb|001: table simple: updated columns: s
test-ovsdb|test_ovsdb|001: table simple: inserted row: s=row1_s <> uuid=124ddccb-7eb8-4def-b768-887cb8d84ada
test-ovsdb|test_ovsdb|001: table simple: updated columns: s
test-ovsdb|test_ovsdb|001: table simple6: inserted row: name=first_row weak_ref=[124ddccb-7eb8-4def-b768-887cb8d84ada 1fd88ded-06f0-4fee-a21b-4e552d8a2f50 2309fce8-a6dd-46e5-a603-fe1ea1ab6bb0]
test-ovsdb|test_ovsdb|001: table simple6: updated columns: name weak_ref
And after:
test-ovsdb|test_ovsdb|001: print_idl[2]
test-ovsdb|test_ovsdb|001: table simple: inserted row: s=row0_s <> uuid=2309fce8-a6dd-46e5-a603-fe1ea1ab6bb0
test-ovsdb|test_ovsdb|001: table simple: inserted row: s=row2_s <> uuid=1fd88ded-06f0-4fee-a21b-4e552d8a2f50
test-ovsdb|test_ovsdb|001: table simple: inserted row: s=row1_s <> uuid=124ddccb-7eb8-4def-b768-887cb8d84ada
test-ovsdb|test_ovsdb|001: table simple6: name=first_row weak_ref=[124ddccb-7eb8-4def-b768-887cb8d84ada 1fd88ded-06f0-4fee-a21b-4e552d8a2f50 2309fce8-a6dd-46e5-a603-fe1ea1ab6bb0]
Now condition is changed. This makes 2 of 3 rows to become orphan rows.
Note that the update notification only removes orphan rows, but doesn't
modify the row in simple6, because rows wasn't actually removed, just
not needed anymore:
test-ovsdb|jsonrpc|unix:socket: send request, method="monitor_cond_change", params=[["monid","idltest"],["monid","idltest"],{"simple":[{"where":[["s","==","row1_s"]]}]}], id=5
test-ovsdb|jsonrpc|unix:socket: received notification, method="update3", params=[["monid","idltest"],"00000000-0000-0000-0000-000000000000",{"simple":{"3aa79e4a-d752-4d53-8e16-b62887d73ad8":{"delete":null},"d1b023f3-3b4d-4bb5-b4d9-cc9791afde7a":{"delete":null}}}]
test-ovsdb|jsonrpc|unix:socket: received reply, result={}, id=5
Track list is empty, but 2 orphan rows should be on a track list as deleted:
test-ovsdb|test_ovsdb|003: empty
But all 3 rows are still accessible for a user from the row in 'simple6' even
though table 'simple' has only 1 row accessible:
test-ovsdb|test_ovsdb|003: print_idl[1]
test-ovsdb|test_ovsdb|003: table simple: s=row1_s <> uuid=b8315694-7855-43e7-a963-ca9a8666682a
test-ovsdb|test_ovsdb|003: table simple6: name=first_row weak_ref=[3aa79e4a-d752-4d53-8e16-b62887d73ad8 b8315694-7855-43e7-a963-ca9a8666682a d1b023f3-3b4d-4bb5-b4d9-cc9791afde7a]
And they are still here after the track_clear():
test-ovsdb|test_ovsdb|003: print_idl[2]
test-ovsdb|test_ovsdb|003: table simple: s=row1_s <> uuid=b8315694-7855-43e7-a963-ca9a8666682a
test-ovsdb|test_ovsdb|003: table simple6: name=first_row weak_ref=[3aa79e4a-d752-4d53-8e16-b62887d73ad8 b8315694-7855-43e7-a963-ca9a8666682a d1b023f3-3b4d-4bb5-b4d9-cc9791afde7a]
When we have unrelated update on a row in 'simple6' it finally gets
re-parsed and we have tracked orphan rows as deleted and they are
no longer accessible for a user from a row in 'simple6':
test-ovsdb|jsonrpc|unix:socket: received notification, method="update3", params=[["monid","idltest"],"00000000-0000-0000-0000-000000000000",{"simple6":{"6fcb8599-4161-4314-901c-2ca4a18686c3":{"modify":{"name":"new_name"}}}}]
Tracked:
test-ovsdb|test_ovsdb|005: table simple: deleted row: s=row0_s <> uuid=d1b023f3-3b4d-4bb5-b4d9-cc9791afde7a
test-ovsdb|test_ovsdb|005: table simple: deleted row: s=row2_s <> uuid=3aa79e4a-d752-4d53-8e16-b62887d73ad8
test-ovsdb|test_ovsdb|005: table simple6: name=new_name weak_ref=[b8315694-7855-43e7-a963-ca9a8666682a]
test-ovsdb|test_ovsdb|005: table simple6: updated columns: name
Before track_clear():
test-ovsdb|test_ovsdb|005: print_idl[1]
test-ovsdb|test_ovsdb|005: table simple: s=row1_s <> uuid=b8315694-7855-43e7-a963-ca9a8666682a
test-ovsdb|test_ovsdb|005: table simple6: name=new_name weak_ref=[b8315694-7855-43e7-a963-ca9a8666682a]
test-ovsdb|test_ovsdb|005: table simple6: updated columns: name
After:
test-ovsdb|test_ovsdb|005: print_idl[2]
test-ovsdb|test_ovsdb|005: table simple: s=row1_s <> uuid=b8315694-7855-43e7-a963-ca9a8666682a
test-ovsdb|test_ovsdb|005: table simple6: name=new_name weak_ref=[b8315694-7855-43e7-a963-ca9a8666682a]
Best regards, Ilya Maximets.
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