Custom Incremental Cache

packages/gitbook-v2/.gitignore

@@ -6,6 +6,7 @@
 
 # cloudflare
 .open-next
+.wrangler
 
 # Symbolic links
 public

packages/gitbook-v2/open-next.config.ts

@@ -1,6 +1,4 @@
 import { defineCloudflareConfig } from '@opennextjs/cloudflare';
-import r2IncrementalCache from '@opennextjs/cloudflare/overrides/incremental-cache/r2-incremental-cache';
-import { withRegionalCache } from '@opennextjs/cloudflare/overrides/incremental-cache/regional-cache';
 import doQueue from '@opennextjs/cloudflare/overrides/queue/do-queue';
 import doShardedTagCache from '@opennextjs/cloudflare/overrides/tag-cache/do-sharded-tag-cache';
 import {
@@ -9,7 +7,7 @@ import {
 } from '@opennextjs/cloudflare/overrides/tag-cache/tag-cache-filter';
 
 export default defineCloudflareConfig({
-    incrementalCache: withRegionalCache(r2IncrementalCache, { mode: 'long-lived' }),
+    incrementalCache: () => import('./openNext/incrementalCache').then((m) => m.default),
     tagCache: withFilter({
         tagCache: doShardedTagCache({
             baseShardSize: 12,

packages/gitbook-v2/openNext/incrementalCache.ts

@@ -0,0 +1,181 @@
+import { createHash } from 'node:crypto';
+
+import { trace } from '@/lib/tracing';
+import type {
+    CacheEntryType,
+    CacheValue,
+    IncrementalCache,
+    WithLastModified,
+} from '@opennextjs/aws/types/overrides.js';
+import { getCloudflareContext } from '@opennextjs/cloudflare';
+
+export const BINDING_NAME = 'NEXT_INC_CACHE_R2_BUCKET';
+export const DEFAULT_PREFIX = 'incremental-cache';
+
+export type KeyOptions = {
+    cacheType?: CacheEntryType;
+};
+
+class GitbookIncrementalCache implements IncrementalCache {
+    name = 'GitbookIncrementalCache';
+
+    protected localCache: Cache | undefined;
+
+    async get<CacheType extends CacheEntryType = 'cache'>(
+        key: string,
+        cacheType?: CacheType
+    ): Promise<WithLastModified<CacheValue<CacheType>> | null> {
+        return trace(
+            {
+                operation: 'openNextIncrementalCacheGet',
+                name: key,
+            },
+            async (span) => {
+                span.setAttribute('cacheType', cacheType ?? 'cache');
+                const r2 = getCloudflareContext().env[BINDING_NAME];
+                const localCache = await this.getCacheInstance();
+                if (!r2) throw new Error('No R2 bucket');
+                try {
+                    const cacheKey = this.getR2Key(key, cacheType);
+                    // Check local cache first if available
+                    const localCacheEntry = await localCache.match(this.getCacheUrlKey(cacheKey));
+                    if (localCacheEntry) {
+                        span.setAttribute('cacheHit', 'local');
+                        return localCacheEntry.json();
+                    }
+
+                    const r2Object = await r2.get(this.getR2Key(key, cacheType));
+                    if (!r2Object) return null;
+
+                    span.setAttribute('cacheHit', 'r2');
+                    return {
+                        value: await r2Object.json(),
+                        lastModified: r2Object.uploaded.getTime(),
+                    };
+                } catch (e) {
+                    console.error('Failed to get from cache', e);
+                    return null;
+                }
+            }
+        );
+    }
+
+    async set<CacheType extends CacheEntryType = 'cache'>(
+        key: string,
+        value: CacheValue<CacheType>,
+        cacheType?: CacheType
+    ): Promise<void> {
+        return trace(
+            {
+                operation: 'openNextIncrementalCacheSet',
+                name: key,
+            },
+            async (span) => {
+                span.setAttribute('cacheType', cacheType ?? 'cache');
+                const r2 = getCloudflareContext().env[BINDING_NAME];
+                const localCache = await this.getCacheInstance();
+                if (!r2) throw new Error('No R2 bucket');
+
+                try {
+                    const cacheKey = this.getR2Key(key, cacheType);
+                    await r2.put(cacheKey, JSON.stringify(value));
+
+                    //TODO: Check if there is any places where we don't have tags
+                    // Ideally we should always have tags, but in case we don't, we need to decide how to handle it
+                    // For now we default to a build ID tag, which allow us to invalidate the cache in case something is wrong in this deployment
+                    const tags = this.getTagsFromCacheEntry(value) ?? [
+                        `build_id/${process.env.NEXT_BUILD_ID}`,
+                    ];
+
+                    // We consider R2 as the source of truth, so we update the local cache
+                    // only after a successful R2 write
+                    await localCache.put(
+                        this.getCacheUrlKey(cacheKey),
+                        new Response(
+                            JSON.stringify({
+                                value,
+                                // Note: `Date.now()` returns the time of the last IO rather than the actual time.
+                                //       See https://developers.cloudflare.com/workers/reference/security-model/
+                                lastModified: Date.now(),
+                            }),
+                            {
+                                headers: {
+                                    // Cache-Control default to 30 minutes, will be overridden by `revalidate`
+                                    // In theory we should always get the `revalidate` value
+                                    'cache-control': `max-age=${value.revalidate ?? 60 * 30}`,
+                                    'cache-tag': tags.join(','),
+                                },
+                            }
+                        )
+                    );
+                } catch (e) {
+                    console.error('Failed to set to cache', e);
+                }
+            }
+        );
+    }
+
+    async delete(key: string): Promise<void> {
+        return trace(
+            {
+                operation: 'openNextIncrementalCacheDelete',
+                name: key,
+            },
+            async () => {
+                const r2 = getCloudflareContext().env[BINDING_NAME];
+                const localCache = await this.getCacheInstance();
+                if (!r2) throw new Error('No R2 bucket');
+
+                try {
+                    const cacheKey = this.getR2Key(key);
+
+                    await r2.delete(cacheKey);
+
+                    // Here again R2 is the source of truth, so we delete from local cache first
+                    await localCache.delete(this.getCacheUrlKey(cacheKey));
+                } catch (e) {
+                    console.error('Failed to delete from cache', e);
+                }
+            }
+        );
+    }
+
+    async getCacheInstance(): Promise<Cache> {
+        if (this.localCache) return this.localCache;
+        this.localCache = await caches.open('incremental-cache');
+        return this.localCache;
+    }
+
+    // Utility function to generate keys for R2/Cache API
+    getR2Key(key: string, cacheType?: CacheEntryType): string {
+        const hash = createHash('sha256').update(key).digest('hex');
+        return `${DEFAULT_PREFIX}/${cacheType === 'cache' ? process.env?.NEXT_BUILD_ID : 'dataCache'}/${hash}.${cacheType}`.replace(
+            /\/+/g,
+            '/'
+        );
+    }
+
+    getCacheUrlKey(cacheKey: string): string {
+        return `http://cache.local/${cacheKey}`;
+    }
+
+    getTagsFromCacheEntry<CacheType extends CacheEntryType>(
+        entry: CacheValue<CacheType>
+    ): string[] | undefined {
+        if ('tags' in entry && entry.tags) {
+            return entry.tags;
+        }
+
+        if ('meta' in entry && entry.meta && 'headers' in entry.meta && entry.meta.headers) {
+            const rawTags = entry.meta.headers['x-next-cache-tags'];
+            if (typeof rawTags === 'string') {
+                return rawTags.split(',');
+            }
+        }
+        if ('value' in entry) {
+            return entry.tags;
+        }
+    }
+}
+
+export default new GitbookIncrementalCache();

packages/gitbook-v2/package.json

@@ -29,8 +29,8 @@
         "build:v2": "next build",
         "start": "next start",
         "build:v2:cloudflare": "opennextjs-cloudflare build",
-        "dev:v2:cloudflare": "wrangler dev --port 8771",
+        "dev:v2:cloudflare": "wrangler dev --port 8771 --env preview",
         "unit": "bun test",
         "typecheck": "tsc --noEmit"
     }
-}
+}