fix: alaem cascade (#3668)

doc/alarms.md

@@ -121,7 +121,14 @@ config always has the last word.
 
 ### Repeat throttling
 
-The chat transport won't repost the same alarm id within
+Two levels, and they stack.
+
+The client itself backs off before a repeat is reported at all: every
+occurrence is reported up to a small burst, then one per interval. A fault
+recurring hundreds of times a second still counts every occurrence, but it
+does not write a log line or build an alert payload for each one.
+
+Below that, the chat transport won't repost the same alarm id within
 `repeatThrottleMs` (default 15 minutes). The first occurrence always posts,
 and the next one that gets through reports how many piled up in between —
 so a hot loop reads as one message with a count, not a wall of them.

src/backend/clients/alarm/AlarmClient.test.ts

@@ -375,18 +375,18 @@ describe('AlarmClient alarm registry', () => {
         const client = makeClient();
         const seen = capture(client);
 
-        for (let i = 0; i < 50; i++) {
+        for (let i = 0; i < 500; i++) {
             client.create('hot', `occurrence ${i}`, { i });
         }
 
         const alarm = client.get('hot')!;
-        expect(alarm.count).toBe(50);
+        expect(alarm.count).toBe(500);
         expect(alarm.occurrences).toHaveLength(20);
         expect(alarm.timestamps).toHaveLength(20);
         // The window kept is the most recent one, not the oldest.
-        expect(alarm.occurrences[19].message).toBe('occurrence 49');
+        expect(alarm.occurrences[19].message).toBe('occurrence 499');
         // Trimming history must not rewind what the transports are told.
-        expect(seen[49]).toMatchObject({ repeatCount: 50, isRepeat: true });
+        expect(seen.at(-1)).toMatchObject({ repeatCount: 500, isRepeat: true });
     });
 
     it('names anonymous handlers by their registration order', () => {
@@ -519,3 +519,53 @@ describe('AlarmClient known-error rules', () => {
         expect(chat[0].severity).toBe('info');
     });
 });
+
+describe('AlarmClient repeat reporting', () => {
+    beforeEach(() => {
+        vi.spyOn(console, 'error').mockImplementation(() => {});
+        vi.spyOn(console, 'warn').mockImplementation(() => {});
+        vi.spyOn(console, 'log').mockImplementation(() => {});
+        pdEvent.mockClear();
+    });
+
+    it('reports every occurrence up to the burst, then backs off', () => {
+        const client = makeClient();
+        const seen = capture(client);
+
+        for (let i = 0; i < 12; i++) client.create('flap', 'same fault');
+
+        expect(seen).toHaveLength(10);
+        expect(seen[9].repeatCount).toBe(10);
+    });
+
+    it('reports again once the interval is reached', () => {
+        const client = makeClient();
+        const seen = capture(client);
+
+        for (let i = 0; i < 500; i++) client.create('flap', 'same fault');
+
+        expect(seen).toHaveLength(11);
+        expect(seen[10].repeatCount).toBe(500);
+    });
+
+    it('keeps a fast-repeating fault out of the log after the burst', () => {
+        const client = makeClient();
+        capture(client);
+        const warn = vi.mocked(console.warn);
+        warn.mockClear();
+
+        for (let i = 0; i < 100; i++) client.create('flap', 'same fault');
+
+        // Occurrences 2-10 only; the first is an ACTIVE line on console.error.
+        expect(warn.mock.calls).toHaveLength(9);
+    });
+
+    it('skips the payload entirely when no transport accepts the severity', () => {
+        const client = makeClient();
+        const seen = capture(client, 'critical');
+
+        client.create('quiet', 'nobody is listening', {}, 'info');
+
+        expect(seen).toHaveLength(0);
+    });
+});

src/backend/clients/alarm/AlarmClient.ts

@@ -69,6 +69,15 @@ const FALLBACK_SEVERITY: PagerSeverity = 'critical';
  * and `count` keeps that.
  */
 const OCCURRENCE_HISTORY_LIMIT = 20;
+
+// A fast-recurring fault repeats far faster than it is useful to report, and
+// every report allocates a log line and a payload. Report every occurrence up
+// to the burst, then one per interval; `count` still tracks all of them.
+const REPEAT_REPORT_BURST = 10;
+const REPEAT_REPORT_INTERVAL = 500;
+
+const shouldReportRepeat = (count: number): boolean =>
+    count <= REPEAT_REPORT_BURST || count % REPEAT_REPORT_INTERVAL === 0;
 /** Keeps `info` alarms out of the paging system unless config says otherwise. */
 const DEFAULT_PAGERDUTY_MIN_SEVERITY: PagerSeverity = 'warning';
 /** Slack's ceiling once a pager exists: chat gets what doesn't page. */
@@ -456,6 +465,8 @@ export class AlarmClient extends PuterClient {
     private handleRepeat(alarm: Alarm): void {
         this.applyKnownErrors(alarm);
 
+        if (!shouldReportRepeat(alarm.count)) return;
+
         console.warn(
             `[alarm] REPEAT ${displayId(alarm)} :: ${alarm.message} (${alarm.count})`,
         );
@@ -483,6 +494,18 @@ export class AlarmClient extends PuterClient {
         );
     }
 
+    private hasHandlerFor(severity: PagerSeverity): boolean {
+        for (const { minSeverity, maxSeverity } of this.alertHandlers) {
+            if (
+                meetsMinSeverity(severity, minSeverity) &&
+                withinMaxSeverity(severity, maxSeverity)
+            ) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     private dispatchAlert(alarm: Alarm): void {
         const resolved = this.resolveSeverity(alarm);
         if (resolved === 'mute') {
@@ -494,6 +517,10 @@ export class AlarmClient extends PuterClient {
         }
         alarm.severity = resolved;
 
+        // Build nothing for a severity no transport accepts — the payload
+        // (cleaned fields plus the stack, twice) is the expensive part.
+        if (!this.hasHandlerFor(resolved)) return;
+
         const fieldsClean = cleanFields(alarm.fields);
         const repeatCount = alarm.count;