[Qemu-devel] [PATCH COLO-Frame v15 21/38] qmp event: Add COLO_EXIT event to notify users while exited from COLO

[zhanghailiang <zhang.zhanghailiang@huawei.com>]

If some errors happen during VM's COLO FT stage, it's important to notify the users
of this event. Together with 'x_colo_lost_heartbeat', users can intervene in COLO's
failover work immediately.
If users don't want to get involved in COLO's failover verdict,
it is still necessary to notify users that we exited COLO mode.

Cc: Markus Armbruster <armbru@redhat.com>
Cc: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
---
v13:
- Remove optional 'error' string for this event.
  (I doubted it was usefull for users, Since users shouldn't
   interpret it and can't depend on it to decide what happened
   exaclty. Besides it is really hard to organize.)
- Remove unused 'unknown' member for enum COLOExitReason.
 (Eric's suggestion)
- Fix comment for COLO_EXIT
v11:
- Fix several typos found by Eric
---
 docs/qmp-events.txt | 16 ++++++++++++++++
 migration/colo.c    | 20 ++++++++++++++++++++
 qapi-schema.json    | 14 ++++++++++++++
 qapi/event.json     | 15 +++++++++++++++
 4 files changed, 65 insertions(+)

diff --git a/docs/qmp-events.txt b/docs/qmp-events.txt
index 52eb7e2..b6e8937 100644
--- a/docs/qmp-events.txt
+++ b/docs/qmp-events.txt
@@ -184,6 +184,22 @@ Example:
 Note: The "ready to complete" status is always reset by a BLOCK_JOB_ERROR
 event.
 
+COLO_EXIT
+---------
+
+Emitted when VM finishes COLO mode due to some errors happening or
+at the request of users.
+
+Data:
+
+ - "mode": COLO mode, primary or secondary side (json-string)
+ - "reason": the exit reason, internal error or external request. (json-string)
+
+Example:
+
+{"timestamp": {"seconds": 2032141960, "microseconds": 417172},
+ "event": "COLO_EXIT", "data": {"mode": "primary", "reason": "request" } }
+
 DEVICE_DELETED
 --------------
 
diff --git a/migration/colo.c b/migration/colo.c
index a65b22b..814480c 100644
--- a/migration/colo.c
+++ b/migration/colo.c
@@ -17,6 +17,7 @@
 #include "trace.h"
 #include "qemu/error-report.h"
 #include "migration/failover.h"
+#include "qapi-event.h"
 
 /* colo buffer */
 #define COLO_BUFFER_BASE_SIZE (4 * 1024 * 1024)
@@ -367,6 +368,18 @@ out:
     if (local_err) {
         error_report_err(local_err);
     }
+    /*
+    * There are only two reasons we can go here, something error happened,
+    * Or users triggered failover.
+    */
+    if (!failover_request_is_active()) {
+        qapi_event_send_colo_exit(COLO_MODE_PRIMARY,
+                                  COLO_EXIT_REASON_ERROR, NULL);
+    } else {
+        qapi_event_send_colo_exit(COLO_MODE_PRIMARY,
+                                  COLO_EXIT_REASON_REQUEST, NULL);
+    }
+
     qsb_free(buffer);
     buffer = NULL;
 
@@ -530,6 +543,13 @@ out:
     if (local_err) {
         error_report_err(local_err);
     }
+    if (!failover_request_is_active()) {
+        qapi_event_send_colo_exit(COLO_MODE_SECONDARY,
+                                  COLO_EXIT_REASON_ERROR, NULL);
+    } else {
+        qapi_event_send_colo_exit(COLO_MODE_SECONDARY,
+                                  COLO_EXIT_REASON_REQUEST, NULL);
+    }
 
     if (fb) {
         qemu_fclose(fb);
diff --git a/qapi-schema.json b/qapi-schema.json
index 73325ed..7fec696 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -776,6 +776,20 @@
   'data': [ 'unknown', 'primary', 'secondary'] }
 
 ##
+# @COLOExitReason
+#
+# The reason for a COLO exit
+#
+# @request: COLO exit is due to an external request
+#
+# @error: COLO exit is due to an internal error
+#
+# Since: 2.6
+##
+{ 'enum': 'COLOExitReason',
+  'data': [ 'request', 'error' ] }
+
+##
 # @x-colo-lost-heartbeat
 #
 # Tell qemu that heartbeat is lost, request it to do takeover procedures.
diff --git a/qapi/event.json b/qapi/event.json
index 390fd45..cfcc887 100644
--- a/qapi/event.json
+++ b/qapi/event.json
@@ -268,6 +268,21 @@
   'data': { 'pass': 'int' } }
 
 ##
+# @COLO_EXIT
+#
+# Emitted when VM finishes COLO mode due to some errors happening or
+# at the request of users.
+#
+# @mode: which COLO mode the VM was in when it exited.
+#
+# @reason: describes the reason for the COLO exit.
+#
+# Since: 2.6
+##
+{ 'event': 'COLO_EXIT',
+  'data': {'mode': 'COLOMode', 'reason': 'COLOExitReason' } }
+
+##
 # @ACPI_DEVICE_OST
 #
 # Emitted when guest executes ACPI _OST method.
-- 
1.8.3.1