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| /** | |
| * This is the default "use cache" handler it defaults to an in-memory store. | |
| * In-memory caches are fragile and should not use stale-while-revalidate | |
| * semantics on the caches because it's not worth warming up an entry that's | |
| * likely going to get evicted before we get to use it anyway. However, we also | |
| * don't want to reuse a stale entry for too long so stale entries should be | |
| * considered expired/missing in such cache handlers. | |
| */ | |
| import { LRUCache } from '../lru-cache' | |
| import type { CacheEntry, CacheHandlerV2 } from './types' | |
| import { | |
| isStale, | |
| tagsManifest, | |
| } from '../incremental-cache/tags-manifest.external' | |
| type PrivateCacheEntry = { | |
| entry: CacheEntry | |
| // For the default cache we store errored cache | |
| // entries and allow them to be used up to 3 times | |
| // after that we want to dispose it and try for fresh | |
| // If an entry is errored we return no entry | |
| // three times so that we retry hitting origin (MISS) | |
| // and then if it still fails to set after the third we | |
| // return the errored content and use expiration of | |
| // Math.min(30, entry.expiration) | |
| isErrored: boolean | |
| errorRetryCount: number | |
| // compute size on set since we need to read size | |
| // of the ReadableStream for LRU evicting | |
| size: number | |
| } | |
| // LRU cache default to max 50 MB but in future track | |
| const memoryCache = new LRUCache<PrivateCacheEntry>( | |
| 50 * 1024 * 1024, | |
| (entry) => entry.size | |
| ) | |
| const pendingSets = new Map<string, Promise<void>>() | |
| const debug = process.env.NEXT_PRIVATE_DEBUG_CACHE | |
| ? console.debug.bind(console, 'DefaultCacheHandler:') | |
| : undefined | |
| const DefaultCacheHandler: CacheHandlerV2 = { | |
| async get(cacheKey) { | |
| const pendingPromise = pendingSets.get(cacheKey) | |
| if (pendingPromise) { | |
| debug?.('get', cacheKey, 'pending') | |
| await pendingPromise | |
| } | |
| const privateEntry = memoryCache.get(cacheKey) | |
| if (!privateEntry) { | |
| debug?.('get', cacheKey, 'not found') | |
| return undefined | |
| } | |
| const entry = privateEntry.entry | |
| if ( | |
| performance.timeOrigin + performance.now() > | |
| entry.timestamp + entry.revalidate * 1000 | |
| ) { | |
| // In-memory caches should expire after revalidate time because it is | |
| // unlikely that a new entry will be able to be used before it is dropped | |
| // from the cache. | |
| debug?.('get', cacheKey, 'expired') | |
| return undefined | |
| } | |
| if (isStale(entry.tags, entry.timestamp)) { | |
| debug?.('get', cacheKey, 'had stale tag') | |
| return undefined | |
| } | |
| const [returnStream, newSaved] = entry.value.tee() | |
| entry.value = newSaved | |
| debug?.('get', cacheKey, 'found', { | |
| tags: entry.tags, | |
| timestamp: entry.timestamp, | |
| revalidate: entry.revalidate, | |
| expire: entry.expire, | |
| }) | |
| return { | |
| ...entry, | |
| value: returnStream, | |
| } | |
| }, | |
| async set(cacheKey, pendingEntry) { | |
| debug?.('set', cacheKey, 'start') | |
| let resolvePending: () => void = () => {} | |
| const pendingPromise = new Promise<void>((resolve) => { | |
| resolvePending = resolve | |
| }) | |
| pendingSets.set(cacheKey, pendingPromise) | |
| const entry = await pendingEntry | |
| let size = 0 | |
| try { | |
| const [value, clonedValue] = entry.value.tee() | |
| entry.value = value | |
| const reader = clonedValue.getReader() | |
| for (let chunk; !(chunk = await reader.read()).done; ) { | |
| size += Buffer.from(chunk.value).byteLength | |
| } | |
| memoryCache.set(cacheKey, { | |
| entry, | |
| isErrored: false, | |
| errorRetryCount: 0, | |
| size, | |
| }) | |
| debug?.('set', cacheKey, 'done') | |
| } catch (err) { | |
| // TODO: store partial buffer with error after we retry 3 times | |
| debug?.('set', cacheKey, 'failed', err) | |
| } finally { | |
| resolvePending() | |
| pendingSets.delete(cacheKey) | |
| } | |
| }, | |
| async refreshTags() { | |
| // Nothing to do for an in-memory cache handler. | |
| }, | |
| async getExpiration(...tags) { | |
| const expiration = Math.max( | |
| ...tags.map((tag) => tagsManifest.get(tag) ?? 0) | |
| ) | |
| debug?.('getExpiration', { tags, expiration }) | |
| return expiration | |
| }, | |
| async expireTags(...tags) { | |
| const timestamp = Math.round(performance.timeOrigin + performance.now()) | |
| debug?.('expireTags', { tags, timestamp }) | |
| for (const tag of tags) { | |
| // TODO: update file-system-cache? | |
| tagsManifest.set(tag, timestamp) | |
| } | |
| }, | |
| } | |
| export default DefaultCacheHandler | |