feat: jitter_ms tracking — scheduled_at stamped at dispatch, jitter computed on ingest

apps/web/src/db.ts

@@ -33,17 +33,23 @@ export async function migrate() {
 
   await sql`
     CREATE TABLE IF NOT EXISTS pings (
-      id          BIGSERIAL PRIMARY KEY,
-      monitor_id  TEXT NOT NULL REFERENCES monitors(id) ON DELETE CASCADE,
-      checked_at  TIMESTAMPTZ NOT NULL DEFAULT now(),
-      status_code INTEGER,
-      latency_ms  INTEGER,
-      up          BOOLEAN NOT NULL,
-      error       TEXT,
-      meta        JSONB
+      id           BIGSERIAL PRIMARY KEY,
+      monitor_id   TEXT NOT NULL REFERENCES monitors(id) ON DELETE CASCADE,
+      checked_at   TIMESTAMPTZ NOT NULL DEFAULT now(),
+      scheduled_at TIMESTAMPTZ,
+      jitter_ms    INTEGER,
+      status_code  INTEGER,
+      latency_ms   INTEGER,
+      up           BOOLEAN NOT NULL,
+      error        TEXT,
+      meta         JSONB
     )
   `;
 
+  // Migrations for existing deployments
+  await sql`ALTER TABLE pings ADD COLUMN IF NOT EXISTS scheduled_at TIMESTAMPTZ`;
+  await sql`ALTER TABLE pings ADD COLUMN IF NOT EXISTS jitter_ms INTEGER`;
+
   await sql`CREATE INDEX IF NOT EXISTS idx_pings_monitor ON pings(monitor_id, checked_at DESC)`;
   await sql`CREATE INDEX IF NOT EXISTS idx_pings_checked_at ON pings(checked_at)`;
 

apps/web/src/routes/internal.ts

@@ -22,10 +22,10 @@ export const internal = new Elysia({ prefix: "/internal", detail: { hide: true }
     return {};
   })
 
-  // Returns monitors that are due for a check
+  // Returns monitors that are due for a check, with scheduled_at = now()
   .get("/due", async () => {
-
-    return sql`
+    const scheduled_at = new Date().toISOString();
+    const monitors = await sql`
       SELECT m.id, m.url, m.method, m.request_headers, m.request_body, m.timeout_ms, m.interval_s, m.query
       FROM monitors m
       LEFT JOIN LATERAL (
@@ -37,6 +37,8 @@ export const internal = new Elysia({ prefix: "/internal", detail: { hide: true }
         AND (last.checked_at IS NULL
           OR last.checked_at < now() - (m.interval_s || ' seconds')::interval)
     `;
+    // Attach scheduled_at to each monitor so the runner can report jitter
+    return monitors.map((m: any) => ({ ...m, scheduled_at }));
   })
 
   // Manual retention cleanup trigger

apps/web/src/routes/pings.ts

@@ -56,10 +56,15 @@ export const ingest = new Elysia()
     const meta = body.meta ? { ...body.meta } : {};
     if (body.cert_expiry_days != null) meta.cert_expiry_days = body.cert_expiry_days;
 
+    const scheduledAt = body.scheduled_at ? new Date(body.scheduled_at) : null;
+    const jitterMs = scheduledAt ? Math.max(0, Date.now() - scheduledAt.getTime()) : null;
+
     const [ping] = await sql`
-      INSERT INTO pings (monitor_id, status_code, latency_ms, up, error, meta)
+      INSERT INTO pings (monitor_id, scheduled_at, jitter_ms, status_code, latency_ms, up, error, meta)
       VALUES (
         ${body.monitor_id},
+        ${scheduledAt},
+        ${jitterMs},
         ${body.status_code ?? null},
         ${body.latency_ms ?? null},
         ${body.up},
@@ -77,6 +82,7 @@ export const ingest = new Elysia()
   }, {
     body: t.Object({
       monitor_id:       t.String(),
+      scheduled_at:     t.Optional(t.Nullable(t.String())),
       status_code:      t.Optional(t.Number()),
       latency_ms:       t.Optional(t.Number()),
       up:               t.Boolean(),