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simplify cache LRU logic; use count and not size

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This commit is contained in:
Brandon Liu
2022-11-18 22:16:47 +08:00
parent 9fd1d39ab5
commit 6a1af0f4ca
2 changed files with 19 additions and 48 deletions
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53
js/index.ts
View File

@@ -131,8 +131,6 @@ export interface Entry {
runLength: number;
}
const ENTRY_SIZE_BYTES = 32;
export enum Compression {
Unknown = 0,
None = 1,
@@ -472,7 +470,7 @@ async function getHeaderAndRoot(
const rootDir = deserializeIndex(
await decompress(rootDirData, header.internalCompression)
);
return [header, [dirKey, ENTRY_SIZE_BYTES * rootDir.length, rootDir]];
return [header, [dirKey, rootDir.length, rootDir]];
}
return [header, undefined];
@@ -502,26 +500,23 @@ async function getDirectory(
interface ResolvedValue {
lastUsed: number;
size: number;
data: Header | Entry[] | ArrayBuffer;
}
export class ResolvedValueCache {
cache: Map<string, ResolvedValue>;
sizeBytes: number;
maxSizeBytes: number;
maxCacheEntries: number;
counter: number;
prefetch: boolean;
decompress: DecompressFunc;
constructor(
maxSizeBytes = 64000000,
maxCacheEntries = 100,
prefetch = true,
decompress: DecompressFunc = fflateDecompress
) {
this.cache = new Map<string, ResolvedValue>();
this.sizeBytes = 0;
this.maxSizeBytes = maxSizeBytes;
this.maxCacheEntries = maxCacheEntries;
this.counter = 1;
this.prefetch = prefetch;
this.decompress = decompress;
@@ -544,7 +539,6 @@ export class ResolvedValueCache {
if (res[1]) {
this.cache.set(res[1][0], {
lastUsed: this.counter++,
size: res[1][1],
data: res[1][2],
});
}
@@ -552,9 +546,7 @@ export class ResolvedValueCache {
this.cache.set(cacheKey, {
lastUsed: this.counter++,
data: res[0],
size: HEADER_SIZE_BYTES,
});
this.sizeBytes += HEADER_SIZE_BYTES;
this.prune();
return res[0];
}
@@ -583,9 +575,7 @@ export class ResolvedValueCache {
this.cache.set(cacheKey, {
lastUsed: this.counter++,
data: directory,
size: ENTRY_SIZE_BYTES * directory.length,
});
this.sizeBytes += ENTRY_SIZE_BYTES * directory.length;
this.prune();
return directory;
}
@@ -612,15 +602,13 @@ export class ResolvedValueCache {
this.cache.set(cacheKey, {
lastUsed: this.counter++,
data: resp.data,
size: resp.data.byteLength,
});
this.sizeBytes += resp.data.byteLength;
this.prune();
return resp.data;
}
prune() {
while (this.sizeBytes > this.maxSizeBytes) {
if (this.cache.size > this.maxCacheEntries) {
let minUsed = Infinity;
let minKey = undefined;
this.cache.forEach((cache_value: ResolvedValue, key: string) => {
@@ -630,7 +618,6 @@ export class ResolvedValueCache {
}
});
if (minKey) {
this.sizeBytes -= this.cache.get(minKey)!.size;
this.cache.delete(minKey);
}
}
@@ -644,7 +631,6 @@ export class ResolvedValueCache {
interface SharedPromiseCacheValue {
lastUsed: number;
size: number; // 0 if the promise has not resolved
data: Promise<Header | Entry[] | ArrayBuffer>;
}
@@ -654,20 +640,18 @@ interface SharedPromiseCacheValue {
// (estimates) the maximum size of the cache.
export class SharedPromiseCache {
cache: Map<string, SharedPromiseCacheValue>;
sizeBytes: number;
maxSizeBytes: number;
maxCacheEntries: number;
counter: number;
prefetch: boolean;
decompress: DecompressFunc;
constructor(
maxSizeBytes = 64000000,
maxCacheEntries = 100,
prefetch = true,
decompress: DecompressFunc = fflateDecompress
) {
this.cache = new Map<string, SharedPromiseCacheValue>();
this.sizeBytes = 0;
this.maxSizeBytes = maxSizeBytes;
this.maxCacheEntries = maxCacheEntries;
this.counter = 1;
this.prefetch = prefetch;
this.decompress = decompress;
@@ -684,14 +668,9 @@ export class SharedPromiseCache {
const p = new Promise<Header>((resolve, reject) => {
getHeaderAndRoot(source, this.decompress, this.prefetch, current_etag)
.then((res) => {
if (this.cache.has(cacheKey)) {
this.cache.get(cacheKey)!.size = HEADER_SIZE_BYTES;
this.sizeBytes += HEADER_SIZE_BYTES;
}
if (res[1]) {
this.cache.set(res[1][0], {
lastUsed: this.counter++,
size: res[1][1],
data: Promise.resolve(res[1][2]),
});
}
@@ -702,7 +681,7 @@ export class SharedPromiseCache {
reject(e);
});
});
this.cache.set(cacheKey, { lastUsed: this.counter++, data: p, size: 0 });
this.cache.set(cacheKey, { lastUsed: this.counter++, data: p });
return p;
}
@@ -724,18 +703,13 @@ export class SharedPromiseCache {
getDirectory(source, this.decompress, offset, length, header)
.then((directory) => {
resolve(directory);
if (this.cache.has(cacheKey)) {
this.cache.get(cacheKey)!.size =
ENTRY_SIZE_BYTES * directory.length;
this.sizeBytes += ENTRY_SIZE_BYTES * directory.length;
}
this.prune();
})
.catch((e) => {
reject(e);
});
});
this.cache.set(cacheKey, { lastUsed: this.counter++, data: p, size: 0 });
this.cache.set(cacheKey, { lastUsed: this.counter++, data: p });
return p;
}
@@ -763,8 +737,6 @@ export class SharedPromiseCache {
}
resolve(resp.data);
if (this.cache.has(cacheKey)) {
this.cache.get(cacheKey)!.size = resp.data.byteLength;
this.sizeBytes += resp.data.byteLength;
}
this.prune();
})
@@ -772,12 +744,12 @@ export class SharedPromiseCache {
reject(e);
});
});
this.cache.set(cacheKey, { lastUsed: this.counter++, data: p, size: 0 });
this.cache.set(cacheKey, { lastUsed: this.counter++, data: p });
return p;
}
prune() {
while (this.sizeBytes > this.maxSizeBytes) {
if (this.cache.size >= this.maxCacheEntries) {
let minUsed = Infinity;
let minKey = undefined;
this.cache.forEach(
@@ -789,7 +761,6 @@ export class SharedPromiseCache {
}
);
if (minKey) {
this.sizeBytes -= this.cache.get(minKey)!.size;
this.cache.delete(minKey);
}
}

14
js/test/v3.test.ts
View File

@@ -237,7 +237,6 @@ test("cache getDirectory", async (assertion) => {
for (const v of cache.cache.values()) {
assertion.ok(v.lastUsed > 0);
assertion.ok(v.size > 0);
}
});
@@ -324,14 +323,15 @@ test("soft failure on etag weirdness", async (assertion) => {
});
test("cache pruning by byte size", async (assertion) => {
const cache = new SharedPromiseCache(1000, false);
cache.cache.set("0", { lastUsed: 0, data: Promise.resolve([]), size: 400 });
cache.cache.set("1", { lastUsed: 1, data: Promise.resolve([]), size: 200 });
cache.cache.set("2", { lastUsed: 2, data: Promise.resolve([]), size: 900 });
cache.sizeBytes = 900 + 200 + 400;
const cache = new SharedPromiseCache(2, false);
cache.cache.set("0", { lastUsed: 0, data: Promise.resolve([]) });
cache.cache.set("1", { lastUsed: 1, data: Promise.resolve([]) });
cache.cache.set("2", { lastUsed: 2, data: Promise.resolve([]) });
cache.prune();
assertion.eq(cache.cache.size, 1);
assertion.eq(cache.cache.size, 2);
assertion.ok(cache.cache.get("2"));
assertion.ok(cache.cache.get("1"));
assertion.notOk(cache.cache.get("0"));
});
test("pmtiles get metadata", async (assertion) => {