gristlabs_grist-core/app/server/lib/HostedMetadataManager.ts

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import {HomeDBManager} from 'app/gen-server/lib/HomeDBManager';
import * as log from 'app/server/lib/log';
/**
* HostedMetadataManager handles pushing document metadata changes to the Home database when
* a doc is updated. Currently only updates doc updatedAt time.
*/
export class HostedMetadataManager {
// updatedAt times as UTC ISO strings mapped by docId.
private _updatedAt: {[docId: string]: string} = {};
// Set if the class holder is closing and no further pushes should be scheduled.
private _closing: boolean = false;
// Last push time in ms since epoch.
private _lastPushTime: number = 0.0;
// Callback for next opportunity to push changes.
private _timeout: any = null;
// Mantains the update Promise to wait on it if the class is closing.
private _push: Promise<any>|null;
/**
* Create an instance of HostedMetadataManager.
* The minPushDelay is the delay in seconds between metadata pushes to the database.
*/
constructor(private _dbManager: HomeDBManager, private _minPushDelay: number = 60) {}
/**
* Close the manager. Send out any pending updates and prevent more from being scheduled.
*/
public async close(): Promise<void> {
// Finish up everything outgoing
this._closing = true; // Pushes will no longer be scheduled.
if (this._timeout) {
clearTimeout(this._timeout);
this._timeout = null;
// Since an update was scheduled, perform one final update now.
this._update();
}
if (this._push) { await this._push; }
}
/**
* Schedule a call to _update some time from now. When the update is made, it will
* store the given timestamp in the updated_at column of the docs table for the
* specified document. Timestamp should be an ISO 8601 format time, in UTC, e.g.
* the output of new Date().toISOString()
*/
public scheduleUpdate(docId: string, timestamp: string): void {
// Update updatedAt even if an update is already scheduled - if the update has not yet occurred,
// the more recent updatedAt time will be used.
this._updatedAt[docId] = timestamp;
if (this._timeout || this._closing) { return; }
const minDelay = this._minPushDelay * 1000;
// Set the push to occur at least the minDelay after the last push time.
const delay = Math.round(minDelay - (Date.now() - this._lastPushTime));
this._timeout = setTimeout(() => this._update(), delay < 0 ? 0 : delay);
}
public setDocsUpdatedAt(docUpdateMap: {[docId: string]: string}): Promise<any> {
return this._dbManager.setDocsUpdatedAt(docUpdateMap);
}
/**
* Push all metadata updates to the databse.
*/
private _update(): void {
if (this._push) { return; }
if (this._timeout) {
clearTimeout(this._timeout);
this._timeout = null;
}
this._push = this._performUpdate()
.catch(err => { log.error("HostedMetadataManager error performing update: ", err); })
.then(() => { this._push = null; });
}
/**
* This is called by the update function to actually perform the update. This should not
* be called unless to force an immediate update.
*/
private async _performUpdate(): Promise<void> {
// Await the database if it is not yet connected.
const docUpdates = this._updatedAt;
this._updatedAt = {};
this._lastPushTime = Date.now();
await this.setDocsUpdatedAt(docUpdates);
}
}