(WIP) proof of concept: feat(server): heap-safe instance cache + opt-in blueprint pooling (one instance per schema-shape)

graphile/graphile-cache/src/__tests__/disposal-and-cap.test.ts

@@ -0,0 +1,186 @@
+import { EventEmitter } from 'events';
+import {
+  ensureCacheHeadroom,
+  getCacheConfig,
+  graphileCache,
+  type GraphileCacheEntry,
+  invokeEntryHandler,
+} from '../graphile-cache';
+
+/**
+ * Regression tests for the schema-builder OOM fix.
+ *
+ * 1. Disposal guard is entry-scoped, not key-scoped. The previous string-keyed guard
+ *    skipped pgl.release() for a rebuilt entry that shared a key with an entry still
+ *    mid-release (the "same-key disposal race"). These tests pin the corrected behaviour:
+ *    every distinct entry is released exactly once, while the SAME entry is never
+ *    double-disposed.
+ * 2. getCacheConfig honours GRAPHILE_CACHE_MAX and otherwise returns a heap-aware default
+ *    bounded to a sane range (a count-only default of 50 × ~0.5GB/instance was the OOM).
+ */
+
+const tick = (ms = 60) => new Promise((resolve) => setTimeout(resolve, ms));
+
+const makeEntry = (releaseDelayMs = 0): GraphileCacheEntry => {
+  const release = jest.fn(
+    () => new Promise<void>((resolve) => setTimeout(resolve, releaseDelayMs)),
+  );
+  return {
+    pgl: { release } as unknown as GraphileCacheEntry['pgl'],
+    serv: {} as GraphileCacheEntry['serv'],
+    handler: {} as GraphileCacheEntry['handler'],
+    // Never .listen()ed in production; close() invokes its callback synchronously here.
+    httpServer: { close: (cb: () => void) => cb() } as unknown as GraphileCacheEntry['httpServer'],
+    cacheKey: 'mock',
+    createdAt: Date.now(),
+  };
+};
+
+describe('graphile-cache disposal guard (same-key race)', () => {
+  it('disposes a rebuilt entry on the same key while a prior entry is mid-release', async () => {
+    const key = 'race-key-1';
+    const a = makeEntry(40); // a.release() stays pending while b is disposed
+    const b = makeEntry(0);
+
+    graphileCache.set(key, a);
+    graphileCache.delete(key); // -> disposeEntry(a) begins, a.release() in flight
+    graphileCache.set(key, b); // key was free; inserts b
+    graphileCache.delete(key); // -> disposeEntry(b) MUST NOT be skipped by the guard
+
+    await tick(120);
+
+    // The bug: the old string-keyed guard left `key` parked while a.release() was pending,
+    // so b.release() was never called (would be 0 here).
+    expect((a.pgl as unknown as { release: jest.Mock }).release).toHaveBeenCalledTimes(1);
+    expect((b.pgl as unknown as { release: jest.Mock }).release).toHaveBeenCalledTimes(1);
+  });
+
+  it('never disposes the same entry twice', async () => {
+    const key = 'race-key-2';
+    const a = makeEntry(0);
+
+    graphileCache.set(key, a);
+    graphileCache.delete(key); // dispose a
+    graphileCache.set(key, a); // re-insert the SAME entry object
+    graphileCache.delete(key); // dispose again -> guard must skip (already disposed)
+
+    await tick();
+
+    expect((a.pgl as unknown as { release: jest.Mock }).release).toHaveBeenCalledTimes(1);
+  });
+});
+
+describe('graphile-cache heap-aware capacity', () => {
+  const prev = process.env.GRAPHILE_CACHE_MAX;
+  afterEach(() => {
+    if (prev === undefined) delete process.env.GRAPHILE_CACHE_MAX;
+    else process.env.GRAPHILE_CACHE_MAX = prev;
+  });
+
+  it('honours an explicit GRAPHILE_CACHE_MAX', () => {
+    process.env.GRAPHILE_CACHE_MAX = '7';
+    expect(getCacheConfig().max).toBe(7);
+  });
+
+  it('falls back to a bounded heap-aware default when unset', () => {
+    delete process.env.GRAPHILE_CACHE_MAX;
+    const { max } = getCacheConfig();
+    // Each cached instance retains ~0.5GB, so the default must be far below the legacy 50
+    // on a normal heap, but always within [3, 50].
+    expect(max).toBeGreaterThanOrEqual(3);
+    expect(max).toBeLessThanOrEqual(50);
+  });
+
+  it('ignores a non-numeric GRAPHILE_CACHE_MAX (falls back to heap-aware default)', () => {
+    process.env.GRAPHILE_CACHE_MAX = 'not-a-number';
+    const { max } = getCacheConfig();
+    expect(max).toBeGreaterThanOrEqual(3);
+    expect(max).toBeLessThanOrEqual(50);
+  });
+});
+
+// A minimal express-like response: an EventEmitter so invokeEntryHandler can hook
+// 'finish'/'close', cast to the express type it expects.
+const makeRes = () => new EventEmitter() as unknown as Parameters<typeof invokeEntryHandler>[2];
+const fakeReq = {} as Parameters<typeof invokeEntryHandler>[1];
+const fakeNext = (() => undefined) as Parameters<typeof invokeEntryHandler>[3];
+
+describe('invokeEntryHandler in-flight refcounting', () => {
+  it('increments while serving and releases exactly once across finish+close', () => {
+    const entry = makeEntry();
+    const handler = jest.fn();
+    entry.handler = handler as unknown as GraphileCacheEntry['handler'];
+
+    const res = makeRes();
+    expect(invokeEntryHandler(entry, fakeReq, res, fakeNext)).toBe(true);
+    expect(handler).toHaveBeenCalledTimes(1);
+    expect(entry.inflight).toBe(1);
+
+    (res as unknown as EventEmitter).emit('finish');
+    expect(entry.inflight).toBe(0);
+    // 'close' always follows 'finish' in Node; the release must be idempotent.
+    (res as unknown as EventEmitter).emit('close');
+    expect(entry.inflight).toBe(0);
+  });
+
+  it('refuses a disposing entry without invoking the handler', () => {
+    const entry = makeEntry();
+    const handler = jest.fn();
+    entry.handler = handler as unknown as GraphileCacheEntry['handler'];
+    entry.disposing = true;
+
+    expect(invokeEntryHandler(entry, fakeReq, makeRes(), fakeNext)).toBe(false);
+    expect(handler).not.toHaveBeenCalled();
+  });
+});
+
+describe('disposeEntry drains in-flight requests before release', () => {
+  it('waits for inflight to reach 0, then releases exactly once', async () => {
+    const key = 'drain-key-1';
+    const entry = makeEntry(0);
+    entry.inflight = 1; // simulate a request mid-flight
+
+    graphileCache.set(key, entry);
+    graphileCache.delete(key); // disposal starts; must poll instead of releasing
+
+    await tick(120); // one poll cycle elapsed, request still in flight
+    expect((entry.pgl as unknown as { release: jest.Mock }).release).not.toHaveBeenCalled();
+
+    entry.inflight = 0; // request completes
+    await tick(250); // allow the next poll cycle to observe it
+
+    expect((entry.pgl as unknown as { release: jest.Mock }).release).toHaveBeenCalledTimes(1);
+  });
+});
+
+describe('ensureCacheHeadroom', () => {
+  const prevMax = process.env.GRAPHILE_CACHE_MAX;
+  afterEach(() => {
+    if (prevMax === undefined) delete process.env.GRAPHILE_CACHE_MAX;
+    else process.env.GRAPHILE_CACHE_MAX = prevMax;
+    graphileCache.clear();
+  });
+
+  it('evicts least-recently-used entries until a build slot is free', async () => {
+    process.env.GRAPHILE_CACHE_MAX = '2';
+    const a = makeEntry(0);
+    const b = makeEntry(0);
+    graphileCache.set('headroom-a', a);
+    graphileCache.set('headroom-b', b);
+    graphileCache.get('headroom-a'); // touch a → b becomes LRU-oldest
+
+    const evicted = ensureCacheHeadroom(1);
+
+    expect(evicted).toBe(1);
+    expect(graphileCache.has('headroom-a')).toBe(true);
+    expect(graphileCache.has('headroom-b')).toBe(false);
+    await tick(); // let the fire-and-forget disposal settle before clear()
+  });
+
+  it('no-ops when under capacity', () => {
+    process.env.GRAPHILE_CACHE_MAX = '5';
+    graphileCache.set('headroom-c', makeEntry(0));
+    expect(ensureCacheHeadroom(1)).toBe(0);
+    expect(graphileCache.has('headroom-c')).toBe(true);
+  });
+});

graphile/graphile-cache/src/create-instance.ts

@@ -10,6 +10,11 @@ const log = new Logger('graphile-cache:create');
 interface GraphileInstanceOptions {
   preset: any;
   cacheKey: string;
+  /**
+   * Database name backing this instance's pg pool. Stored on the entry so the
+   * graphile-cache pgCache cleanup callback can evict it when its pool is disposed.
+   */
+  dbname?: string;
   /**
    * When true, a RealtimeManager is created and started alongside the
    * PostGraphile instance.  The pool is extracted from the preset's
@@ -37,7 +42,7 @@ interface GraphileInstanceOptions {
 export const createGraphileInstance = async (
   opts: GraphileInstanceOptions
 ): Promise<GraphileCacheEntry> => {
-  const { preset, cacheKey, enableRealtime = false } = opts;
+  const { preset, cacheKey, dbname, enableRealtime = false } = opts;
 
   const pgl = postgraphile(preset);
   const serv = pgl.createServ(grafserv);
@@ -53,7 +58,9 @@ export const createGraphileInstance = async (
     handler,
     httpServer,
     cacheKey,
+    dbname,
     createdAt: Date.now(),
+    inflight: 0,
   };
 
   if (enableRealtime) {