fix: bound the usage event rewind to prevent unbounded re-aggregation

UsageManagerImpl.parse() rewinds the aggregation start date to the
oldest unprocessed event, but has no bound on how far back it can go.
If an event cannot be successfully processed (e.g. references a removed
entity), the rewind pins the window to that event's date permanently.
Each subsequent run re-aggregates from that date to the present, growing
by one aggregation period per run. This causes unbounded growth of
cloud_usage (54M+ rows reported) and exec_time (42+ minutes per hour).

Fix: bound the rewind to 24 hours. The rewind exists to absorb clock
skew between the cloud and usage databases, not to replay history.
Events older than 24 hours from the current window start will still be
retried, but the aggregation window will not be rewound to them.

Fixes #13906

Signed-off-by: waterWang <waterwang@proton.me>

Author: waterWang

usage/src/main/java/com/cloud/usage/UsageManagerImpl.java

@@ -103,6 +103,7 @@ public class UsageManagerImpl extends ManagerBase implements UsageManager, Runna
     private static final int HOURLY_TIME = 60;
     private static final int DAILY_TIME = 60 * 24;
     private static final int THREE_DAYS_IN_MINUTES = 60 * 24 * 3;
+    private static final long MAX_EVENT_REWIND_MILLIS = 24L * 60 * 60 * 1000;
 
     @Inject
     private AccountDao _accountDao;
@@ -699,7 +700,10 @@ public void parse(UsageJobVO job, long startDateMillis, long endDateMillis) {
                 if ((events != null) && (events.size() > 0)) {
                     Date oldestEventDate = events.get(0).getCreateDate();
                     if (oldestEventDate.getTime() < startDateMillis) {
-                        startDateMillis = oldestEventDate.getTime();
+                        // Bound the rewind so a single un-processable event cannot pin the
+                        // aggregation window to an arbitrarily old date and cause unbounded
+                        // re-aggregation of the entire history on every run.
+                        startDateMillis = Math.max(oldestEventDate.getTime(), startDateMillis - MAX_EVENT_REWIND_MILLIS);
                         startDate = new Date(startDateMillis);
                     }