File size: 2,333 Bytes
4e23b01 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 | // src/cluster/utils.ts
//
// Hashing, shard directory naming, and shared small helpers.
export const CLUSTER_META_FILE = 'cluster.meta.json';
export const CLUSTER_INDEX_FILE = 'cluster.indexes.json';
export const SHARD_DIR_PREFIX = 'shard-';
/** Zero-padded shard directory name, e.g. shard-03 for shardCount <= 100. The
* width grows with the shard count so directory listings stay sorted. */
export function shardDirName(shardId: number, shardCount: number): string {
const width = Math.max(2, String(Math.max(shardCount - 1, 0)).length);
return `${SHARD_DIR_PREFIX}${String(shardId).padStart(width, '0')}`;
}
/** MurmurHash3 x86 32-bit: stable, fast, and with a proper avalanche so the
* low bits (which is all `hash % shardCount` uses) stay uniform even for
* sequential or highly-similar keys. Zero dependencies. */
export function stableHash32(key: string, seed = 0): number {
const data = Buffer.from(key, 'utf8');
const len = data.length;
let h1 = seed >>> 0;
const c1 = 0xcc9e2d51;
const c2 = 0x1b873593;
const roundedEnd = len & ~3;
for (let i = 0; i < roundedEnd; i += 4) {
let k1 = data.readUInt32LE(i);
k1 = Math.imul(k1, c1);
k1 = (k1 << 15) | (k1 >>> 17);
k1 = Math.imul(k1, c2);
h1 ^= k1;
h1 = (h1 << 13) | (h1 >>> 19);
h1 = (Math.imul(h1, 5) + 0xe6546b64) >>> 0;
}
let k1 = 0;
const tail = len & 3;
if (tail === 3) k1 ^= data[roundedEnd + 2]! << 16;
if (tail >= 2) k1 ^= data[roundedEnd + 1]! << 8;
if (tail >= 1) {
k1 ^= data[roundedEnd]!;
k1 = Math.imul(k1, c1);
k1 = (k1 << 15) | (k1 >>> 17);
k1 = Math.imul(k1, c2);
h1 ^= k1;
}
h1 ^= len;
// fmix32 finalizer.
h1 ^= h1 >>> 16;
h1 = Math.imul(h1, 0x85ebca6b);
h1 ^= h1 >>> 13;
h1 = Math.imul(h1, 0xc2b2ae35);
h1 ^= h1 >>> 16;
return h1 >>> 0;
}
/** Route a key to its shard. Pure function of (key, shardCount), so every
* process agrees on placement without coordination. */
export function shardFor(key: string, shardCount: number): number {
if (!(shardCount >= 1) || !Number.isInteger(shardCount)) {
throw new RangeError(`shardCount must be a positive integer, got ${shardCount}`);
}
return stableHash32(key) % shardCount;
}
export function sleep(ms: number): Promise<void> {
return new Promise((resolve) => setTimeout(resolve, ms));
}
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