Document timer task page tokens' risky serialization needs (#6821)

Groxx · web-flow · commit 6ab886b07ed8 · 2025-04-16T01:37:03.000Z
Discovered due to a changed test in #6800 So I am writing this down so an accidental cleanup doesn't break task replication. This _can probably_ be changed at some point, and it'd probably be worth it, but it'd need to be done in two or three fully-deployed-and-all-data-updated stages (support both, create in new format, remove old support) and I don't feel like doing that right now.
diff --git a/common/persistence/sql/sql_execution_store.go b/common/persistence/sql/sql_execution_store.go
@@ -1007,8 +1007,8 @@ func (m *sqlExecutionStore) CreateFailoverMarkerTasks(
 }
 
 type timerTaskPageToken struct {
-	TaskID    int64
-	Timestamp time.Time
+	TaskID    int64     `json:"TaskID"`    // CAUTION: JSON format is used in replication, this should not be changed without great care
+	Timestamp time.Time `json:"Timestamp"` // CAUTION: JSON format is used in replication, this should not be changed without great care
 }
 
 func (t *timerTaskPageToken) serialize() ([]byte, error) {

Original file line number	Diff line number	Diff line change
`@@ -1007,8 +1007,8 @@ func (m *sqlExecutionStore) CreateFailoverMarkerTasks(`
`1007`	`1007`	`}`
`1008`	`1008`
`1009`	`1009`	`type timerTaskPageToken struct {`
`1010`		`- TaskID int64`
`1011`		`- Timestamp time.Time`
	`1010`	+ TaskID int64 `json:"TaskID"` // CAUTION: JSON format is used in replication, this should not be changed without great care
	`1011`	+ Timestamp time.Time `json:"Timestamp"` // CAUTION: JSON format is used in replication, this should not be changed without great care
`1012`	`1012`	`}`
`1013`	`1013`
`1014`	`1014`	`func (t *timerTaskPageToken) serialize() ([]byte, error) {`