codekingpro/portable-devtools

1const { LRUCache } = require('lru-cache')
2const { getHeapStatistics } = require('node:v8')
3const { log } = require('proc-log')
4
5// This is an in-memory cache that Pacote uses for packuments.
6// Packuments are usually cached on disk.  This allows for rapid re-requests
7// of the same packument to bypass disk reads.  The tradeoff here is memory
8// usage for disk reads.
9class PackumentCache extends LRUCache {
10  static #heapLimit = Math.floor(getHeapStatistics().heap_size_limit)
11
12  #sizeKey
13  #disposed = new Set()
14
15  #log (...args) {
16    log.silly('packumentCache', ...args)
17  }
18
19  constructor ({
20    // How much of this.#heapLimit to take up
21    heapFactor = 0.25,
22    // How much of this.#maxSize we allow any one packument to take up
23    // Anything over this is not cached
24    maxEntryFactor = 0.5,
25    sizeKey = '_contentLength',
26  } = {}) {
27    const maxSize = Math.floor(PackumentCache.#heapLimit * heapFactor)
28    const maxEntrySize = Math.floor(maxSize * maxEntryFactor)
29    super({
30      maxSize,
31      maxEntrySize,
32      sizeCalculation: (p) => {
33        // Don't cache if we don't know the size
34        // Some versions of pacote set this to `0`, newer versions set it to `null`
35        if (!p[sizeKey]) {
36          return maxEntrySize + 1
37        }
38        if (p[sizeKey] < 10_000) {
39          return p[sizeKey] * 2
40        }
41        if (p[sizeKey] < 1_000_000) {
42          return Math.floor(p[sizeKey] * 1.5)
43        }
44        // It is less beneficial to store a small amount of super large things
45        // at the cost of all other packuments.
46        return maxEntrySize + 1
47      },
48      dispose: (v, k) => {
49        this.#disposed.add(k)
50        this.#log(k, 'dispose')
51      },
52    })
53    this.#sizeKey = sizeKey
54    this.#log(`heap:${PackumentCache.#heapLimit} maxSize:${maxSize} maxEntrySize:${maxEntrySize}`)
55  }
56
57  set (k, v, ...args) {
58    // we use disposed only for a logging signal if we are setting packuments that
59    // have already been evicted from the cache previously. logging here could help
60    // us tune this in the future.
61    const disposed = this.#disposed.has(k)
62    /* istanbul ignore next - this doesnt happen consistently so hard to test without resorting to unit tests  */
63    if (disposed) {
64      this.#disposed.delete(k)
65    }
66    this.#log(k, 'set', `size:${v[this.#sizeKey]} disposed:${disposed}`)
67    return super.set(k, v, ...args)
68  }
69
70  has (k, ...args) {
71    const has = super.has(k, ...args)
72    this.#log(k, `cache-${has ? 'hit' : 'miss'}`)
73    return has
74  }
75}
76
77module.exports = PackumentCache
78