Keep native collection launches responsive

2026-10-05 10:48:38 -04:00
parent dbd2940d29
commit 1405114a14
26 changed files with 998 additions and 123 deletions
@@ -0,0 +1,62 @@
+import { setImmediate } from 'node:timers/promises';
+import { getHostOperationPayload, type OperationDeliveryRow } from './index.js';
+
+// Even non-ASCII content stays below 64 KiB per encoded chunk.
+const CHUNK_CHARACTERS = 16 * 1024;
+const CHUNK_BYTES = 64 * 1024;
+const encoder = new TextEncoder();
+
+function* jsonParts(operations: OperationDeliveryRow[], serverTime: string): Generator<string | Buffer> {
+    yield '{"operations":[';
+    for (const [index, operation] of operations.entries()) {
+        if (index) yield ',';
+        const metadata = JSON.stringify({
+            id: operation.id, hostId: operation.host_id, kind: operation.kind,
+            instanceId: operation.instance_id, generation: operation.generation, state: operation.state,
+            error: operation.error, createdAt: operation.created_at, updatedAt: operation.updated_at
+        });
+        yield metadata.slice(0, -1) + ',"payload":';
+        // Load only the immutable payload currently being sent, after the
+        // stream has yielded its metadata and had a chance to serve health work.
+        yield getHostOperationPayload(operation.host_id, operation.id);
+        yield ',"result":';
+        yield operation.result ?? 'null';
+        yield '}';
+    }
+    yield '],"serverTime":' + JSON.stringify(serverTime) + '}';
+}
+
+function* encodedChunks(operations: OperationDeliveryRow[], serverTime: string): Generator<Uint8Array> {
+    for (const part of jsonParts(operations, serverTime)) {
+        if (Buffer.isBuffer(part)) {
+            for (let start = 0; start < part.length; start += CHUNK_BYTES) yield part.subarray(start, start + CHUNK_BYTES);
+            continue;
+        }
+        for (let start = 0; start < part.length;) {
+            let end = Math.min(start + CHUNK_CHARACTERS, part.length);
+            // A UTF-16 surrogate pair must be encoded together, including when
+            // user-authored configuration text falls on a chunk boundary.
+            const last = part.charCodeAt(end - 1);
+            if (end < part.length && last >= 0xd800 && last <= 0xdbff) end--;
+            yield encoder.encode(part.slice(start, end));
+            start = end;
+        }
+    }
+}
+
+/** Bound encoding work and yield between chunks so health requests keep flowing. */
+export function hostOperationsResponse(operations: OperationDeliveryRow[], serverTime = new Date().toISOString()): Response {
+    const chunks = encodedChunks(operations, serverTime);
+    let cancelled = false;
+    const stream = new ReadableStream<Uint8Array>({
+        async pull(controller) {
+            await setImmediate();
+            if (cancelled) return;
+            const next = chunks.next();
+            if (next.done) controller.close();
+            else controller.enqueue(next.value);
+        },
+        cancel() { cancelled = true; chunks.return(undefined); }
+    });
+    return new Response(stream, { headers: { 'Content-Type': 'application/json; charset=utf-8', 'Cache-Control': 'no-store' } });
+}