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Draft of MapWithExpiration class #9420

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Draft of MapWithExpiration class #9420

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72 changes: 64 additions & 8 deletions packages/drivers/odsp-driver/src/odspCache.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
* Licensed under the MIT License.
*/

import { IDisposable } from "@fluidframework/common-definitions";
import { PromiseCache } from "@fluidframework/common-utils";
import {
IOdspResolvedUrl,
Expand Down Expand Up @@ -58,15 +59,74 @@ class GarbageCollector<TKey> {
}
}

class MapWithExpiration<TKey, TValue> extends Map<TKey, TValue> implements IDisposable {
public disposed: boolean = false;
private readonly expirationTimeouts = new Map<TKey, ReturnType<typeof setTimeout>>();

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@NicholasCouri NicholasCouri Mar 9, 2022 •
edited
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I was thinking more about it and I like it - We could simply rename the PromiseCache's GarbageCollector to MapWithExpiration + add the IDisposable ?

constructor(
private readonly expiryMs: number,
) {
super();
}
private scheduleExpiration(key: TKey) {
this.expirationTimeouts.set(
key,
setTimeout(
() => { this.delete(key); },
this.expiryMs,
),
);
}

private cancelExpiration(key: TKey) {
const timeout = this.expirationTimeouts.get(key);
if (timeout !== undefined) {
clearTimeout(timeout);
this.expirationTimeouts.delete(key);
}
}

get(key: TKey): TValue | undefined {
return super.get(key);
}

set(key: TKey, value: TValue): this {
// Sliding window expiration policy (on write)
this.cancelExpiration(key);
this.scheduleExpiration(key);

return super.set(key, value);
}

delete(key: TKey): boolean {
this.cancelExpiration(key);
return super.delete(key);
}

dispose(_error?: Error): void {
if (this.disposed) {
return;
}
this.disposed = true;
Array.from(this).forEach(([key]) => this.cancelExpiration(key));
}
}

/**
* Default local-only implementation of IPersistedCache,
* used if no persisted cache is provided by the host
*/
export class LocalPersistentCache implements IPersistedCache {
private readonly cache = new Map<string, any>();
private readonly gc = new GarbageCollector<string>((key) => this.cache.delete(key));
export class LocalPersistentCache implements IPersistedCache, IDisposable {
public get disposed(): boolean { return this.cache.disposed; }
private readonly cache: MapWithExpiration<string, any>;

public constructor(private readonly snapshotExpiryPolicy = 30 * 1000) {}
public constructor(snapshotExpiryPolicy = 30 * 1000) {
this.cache = new MapWithExpiration<string, any>(snapshotExpiryPolicy);
}

public dispose(error?: Error): void {
this.cache.dispose(error);
}

async get(entry: ICacheEntry): Promise<any> {
const key = this.keyFromEntry(entry);
Expand All @@ -77,10 +137,6 @@ export class LocalPersistentCache implements IPersistedCache {
async put(entry: ICacheEntry, value: any) {
const key = this.keyFromEntry(entry);
this.cache.set(key, value);

// Do not keep items too long in memory
this.gc.cancel(key);
this.gc.schedule(key, this.snapshotExpiryPolicy);
}

async removeEntries(file: IFileEntry): Promise<void> {
Expand Down