feat: per-region due scheduling + run_id to group pings across regions

apps/api/src/db.ts

@@ -51,6 +51,7 @@ export async function migrate() {
   await sql`ALTER TABLE pings ADD COLUMN IF NOT EXISTS jitter_ms INTEGER`;
   await sql`ALTER TABLE monitors ADD COLUMN IF NOT EXISTS regions TEXT[] NOT NULL DEFAULT '{}'`;
   await sql`ALTER TABLE pings ADD COLUMN IF NOT EXISTS region TEXT`;
+  await sql`ALTER TABLE pings ADD COLUMN IF NOT EXISTS run_id TEXT`;
 
   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/api/src/routes/internal.ts

@@ -32,7 +32,9 @@ export const internal = new Elysia({ prefix: "/internal", detail: { hide: true }
   })
 
   // Returns monitors that are due for a check.
-  // scheduled_at = last_checked_at + interval_s (ideal fire time), so jitter = actual_start - scheduled_at
+  // When a region is provided, due-ness and scheduled_at are based on
+  // the last ping from that specific region — so each region has its own
+  // independent schedule and they don't drift against each other.
   .get("/due", async ({ request }) => {
     const region = new URL(request.url).searchParams.get('region') || undefined;
     const monitors = await sql`
@@ -45,6 +47,7 @@ export const internal = new Elysia({ prefix: "/internal", detail: { hide: true }
       LEFT JOIN LATERAL (
         SELECT checked_at FROM pings
         WHERE monitor_id = m.id
+          AND (${region ? sql`region = ${region}` : sql`true`})
         ORDER BY checked_at DESC LIMIT 1
       ) last ON true
       WHERE m.enabled = true

apps/api/src/routes/pings.ts

@@ -73,7 +73,7 @@ export const ingest = new Elysia()
     const jitterMs = body.jitter_ms ?? null;
 
     const [ping] = await sql`
-      INSERT INTO pings (monitor_id, scheduled_at, jitter_ms, status_code, latency_ms, up, error, meta, region)
+      INSERT INTO pings (monitor_id, scheduled_at, jitter_ms, status_code, latency_ms, up, error, meta, region, run_id)
       VALUES (
         ${body.monitor_id},
         ${scheduledAt},
@@ -83,7 +83,8 @@ export const ingest = new Elysia()
         ${body.up},
         ${body.error ?? null},
         ${Object.keys(meta).length > 0 ? sql.json(meta) : null},
-        ${body.region ?? null}
+        ${body.region ?? null},
+        ${body.run_id ?? null}
       )
       RETURNING *
     `;
@@ -105,6 +106,7 @@ export const ingest = new Elysia()
       cert_expiry_days: t.Optional(t.Nullable(t.Number())),
       meta:             t.Optional(t.Any()),
       region:           t.Optional(t.Nullable(t.String())),
+      run_id:           t.Optional(t.Nullable(t.String())),
     }),
     detail: { hide: true },
   })