Re: [PATCH] migration: do not exit on incoming failure

[Vladimir Sementsov-Ogievskiy]

On 18.04.24 17:37, Daniel P. Berrangé wrote:

On Thu, Apr 18, 2024 at 01:13:29AM +0300, Vladimir Sementsov-Ogievskiy wrote:

We do set MIGRATION_FAILED state, but don't give a chance to
orchestrator to query migration state and get the error.

Let's report an error through QAPI like we do on outgoing migration.

migration-test is updated correspondingly.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@yandex-team.ru>
---

Doubt: is exiting on failure a contract? Will this commit break
something in Libvirt? Finally, could we just change the logic, or I need
and additional migration-parameter for new behavior?

There's a decent risk that this could break apps, whether
libvirt or something else, especially if the app is just
launching QEMU with '-incoming URI', rather than using
'-incoming defer' and then explicitly using QMP to start the
incoming migration.

I'd say that with '-incoming defer' we should *not* exit on
migration error, because that arg implies the app explicitly
wants to be using QMP to control migration.

With the legacy '-incoming URI' it is probably best to keep
exit on error, as that's comparatively more likely to be used
in adhoc scenarios where the app/user is ignoring QMP on the
dst side.

None the less, I think we need to check how libvirt behaves
with this patch to be sure of no surprises.

Sounds reasonable, thanks! I'll rework it to behave the new way only with "-incoming 
defer", and check how libvirt behave with it.

  migration/migration.c           | 22 +++++++---------------
  tests/qtest/migration-helpers.c | 13 ++++++++++---
  tests/qtest/migration-helpers.h |  3 ++-
  tests/qtest/migration-test.c    | 14 +++++++-------
  4 files changed, 26 insertions(+), 26 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 86bf76e925..3c203e767d 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -738,11 +738,12 @@ process_incoming_migration_co(void *opaque)
      MigrationIncomingState *mis = migration_incoming_get_current();
      PostcopyState ps;
      int ret;
+    Error *local_err = NULL;

assert(mis->from_src_file); if (compress_threads_load_setup(mis->from_src_file)) {

-        error_report("Failed to setup decompress threads");
+        error_setg(&local_err, "Failed to setup decompress threads");
          goto fail;
      }

@@ -779,32 +780,23 @@ process_incoming_migration_co(void *opaque)

      }

if (ret < 0) {

-        MigrationState *s = migrate_get_current();
-
-        if (migrate_has_error(s)) {
-            WITH_QEMU_LOCK_GUARD(&s->error_mutex) {
-                error_report_err(s->error);
-            }
-        }
-        error_report("load of migration failed: %s", strerror(-ret));
+        error_setg(&local_err, "load of migration failed: %s", strerror(-ret));
          goto fail;
      }

if (colo_incoming_co() < 0) {

+        error_setg(&local_err, "colo incoming failed");
          goto fail;
      }

migration_bh_schedule(process_incoming_migration_bh, mis);

      return;
  fail:
+    migrate_set_error(migrate_get_current(), local_err);
+    error_report_err(local_err);
      migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
                        MIGRATION_STATUS_FAILED);
-    qemu_fclose(mis->from_src_file);
-
-    multifd_recv_cleanup();
-    compress_threads_load_cleanup();
-
-    exit(EXIT_FAILURE);
+    migration_incoming_state_destroy();
  }

/**

diff --git a/tests/qtest/migration-helpers.c b/tests/qtest/migration-helpers.c
index e451dbdbed..91c13bd566 100644
--- a/tests/qtest/migration-helpers.c
+++ b/tests/qtest/migration-helpers.c
@@ -211,7 +211,8 @@ void wait_for_migration_complete(QTestState *who)
      wait_for_migration_status(who, "completed", NULL);
  }

-void wait_for_migration_fail(QTestState *from, bool allow_active)

+void wait_for_migration_fail(QTestState *from, bool allow_active,
+                             bool is_incoming)
  {
      g_test_timer_start();
      QDict *rsp_return;
@@ -236,8 +237,14 @@ void wait_for_migration_fail(QTestState *from, bool 
allow_active)
      /* Is the machine currently running? */
      rsp_return = qtest_qmp_assert_success_ref(from,
                                                "{ 'execute': 'query-status' 
}");
-    g_assert(qdict_haskey(rsp_return, "running"));
-    g_assert(qdict_get_bool(rsp_return, "running"));
+    if (is_incoming) {
+        if (qdict_haskey(rsp_return, "running")) {
+            g_assert(!qdict_get_bool(rsp_return, "running"));
+        }
+    } else {
+        g_assert(qdict_haskey(rsp_return, "running"));
+        g_assert(qdict_get_bool(rsp_return, "running"));
+    }
      qobject_unref(rsp_return);
  }

diff --git a/tests/qtest/migration-helpers.h b/tests/qtest/migration-helpers.h

index 3bf7ded1b9..7bd07059ae 100644
--- a/tests/qtest/migration-helpers.h
+++ b/tests/qtest/migration-helpers.h
@@ -46,7 +46,8 @@ void wait_for_migration_status(QTestState *who,

void wait_for_migration_complete(QTestState *who); -void wait_for_migration_fail(QTestState *from, bool allow_active);

+void wait_for_migration_fail(QTestState *from, bool allow_active,
+                             bool is_incoming);

char *find_common_machine_version(const char *mtype, const char *var1,

                                    const char *var2);
diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c
index 1d2cee87ea..e00b755f05 100644
--- a/tests/qtest/migration-test.c
+++ b/tests/qtest/migration-test.c
@@ -1670,7 +1670,7 @@ static void test_baddest(void)
          return;
      }
      migrate_qmp(from, "tcp:127.0.0.1:0", "{}");
-    wait_for_migration_fail(from, false);
+    wait_for_migration_fail(from, false, false);
      test_migrate_end(from, to, false);
  }

@@ -1781,10 +1781,10 @@ static void test_precopy_common(MigrateCommon *args) if (args->result != MIG_TEST_SUCCEED) {

          bool allow_active = args->result == MIG_TEST_FAIL;
-        wait_for_migration_fail(from, allow_active);
+        wait_for_migration_fail(from, allow_active, false);

if (args->result == MIG_TEST_FAIL_DEST_QUIT_ERR) {

-            qtest_set_expected_status(to, EXIT_FAILURE);
+            wait_for_migration_fail(to, true, true);
          }
      } else {
          if (args->live) {
@@ -2571,8 +2571,8 @@ static void do_test_validate_uuid(MigrateStart *args, 
bool should_fail)
      migrate_qmp(from, uri, "{}");

if (should_fail) {

-        qtest_set_expected_status(to, EXIT_FAILURE);
-        wait_for_migration_fail(from, true);
+        wait_for_migration_fail(to, true, true);
+        wait_for_migration_fail(from, true, false);
      } else {
          wait_for_migration_complete(from);
      }
@@ -3047,8 +3047,8 @@ static void test_multifd_tcp_cancel(void)
      migrate_cancel(from);

/* Make sure QEMU process "to" exited */

-    qtest_set_expected_status(to, EXIT_FAILURE);
-    qtest_wait_qemu(to);
+    wait_for_migration_fail(to, true, true);
+    qtest_quit(to);

args = (MigrateStart){

          .only_target = true,
--
2.34.1

With regards,
Daniel

--
Best regards,
Vladimir