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silverbullet/web/sync_service.ts
2023-08-09 17:52:39 +02:00

316 lines
9.7 KiB
TypeScript

import { sleep } from "../common/async_util.ts";
import type { SpacePrimitives } from "../common/spaces/space_primitives.ts";
import {
SpaceSync,
SyncStatus,
SyncStatusItem,
} from "../common/spaces/sync.ts";
import { EventHook } from "../plugos/hooks/event.ts";
import { KVStore } from "../plugos/lib/kv_store.ts";
// Keeps the current sync snapshot
const syncSnapshotKey = "syncSnapshot";
// Keeps the start time of an ongoing sync, is reset once the sync is done
const syncStartTimeKey = "syncStartTime";
// Keeps the start time of the last full sync cycle
const syncLastFullCycleKey = "syncLastFullCycle";
// Keeps the last time an activity was registered, used to detect if a sync is still alive and whether a new one should be started already
const syncLastActivityKey = "syncLastActivity";
const syncInitialFullSyncCompletedKey = "syncInitialFullSyncCompleted";
// maximum time between two activities before we consider a sync crashed
const syncMaxIdleTimeout = 1000 * 27;
// How often to sync the whole space
const spaceSyncInterval = 17 * 1000; // Every 17s or so
// Used from Client
export const pageSyncInterval = 6000;
/**
* The SyncService primarily wraps the SpaceSync engine but also coordinates sync between
* different browser tabs. It is using the KVStore to keep track of sync state.
*/
export class SyncService {
spaceSync: SpaceSync;
lastReportedSyncStatus = Date.now();
constructor(
readonly localSpacePrimitives: SpacePrimitives,
readonly remoteSpace: SpacePrimitives,
private kvStore: KVStore,
private eventHook: EventHook,
private isSyncCandidate: (path: string) => boolean,
) {
this.spaceSync = new SpaceSync(
this.localSpacePrimitives,
this.remoteSpace!,
{
conflictResolver: this.plugAwareConflictResolver.bind(this),
isSyncCandidate: this.isSyncCandidate,
onSyncProgress: (status) => {
this.registerSyncProgress(status).catch(console.error);
},
},
);
eventHook.addLocalListener(
"editor:pageLoaded",
(name, _prevPage, isSynced) => {
if (!isSynced) {
this.scheduleFileSync(`${name}.md`).catch(console.error);
}
},
);
eventHook.addLocalListener("editor:pageSaved", (name) => {
const path = `${name}.md`;
this.scheduleFileSync(path).catch(console.error);
});
}
async isSyncing(): Promise<boolean> {
const startTime = await this.kvStore.get(syncStartTimeKey);
if (!startTime) {
return false;
}
// Sync is running, but is it still alive?
const lastActivity = await this.kvStore.get(syncLastActivityKey)!;
if (Date.now() - lastActivity > syncMaxIdleTimeout) {
// It's been too long since the last activity, let's consider this one crashed and
// reset the sync start state
await this.kvStore.del(syncStartTimeKey);
console.info("Sync crashed, resetting");
return false;
}
return true;
}
hasInitialSyncCompleted(): Promise<boolean> {
// Initial sync has happened when sync progress has been reported at least once, but the syncStartTime has been reset (which happens after sync finishes)
return this.kvStore.has(syncInitialFullSyncCompletedKey);
}
async registerSyncStart(fullSync: boolean): Promise<void> {
// Assumption: this is called after an isSyncing() check
await this.kvStore.batchSet([
{
key: syncStartTimeKey,
value: Date.now(),
},
{
key: syncLastActivityKey,
value: Date.now(),
},
...fullSync // If this is a full sync cycle
? [{
key: syncLastFullCycleKey,
value: Date.now(),
}]
: [],
]);
}
async registerSyncProgress(status?: SyncStatus): Promise<void> {
// Emit a sync event at most every 2s
if (status && this.lastReportedSyncStatus < Date.now() - 2000) {
this.eventHook.dispatchEvent("sync:progress", status);
this.lastReportedSyncStatus = Date.now();
await this.saveSnapshot(status.snapshot);
}
await this.kvStore.set(syncLastActivityKey, Date.now());
}
async registerSyncStop(): Promise<void> {
await this.registerSyncProgress();
await this.kvStore.del(syncStartTimeKey);
await this.kvStore.set(syncInitialFullSyncCompletedKey, true);
}
async getSnapshot(): Promise<Map<string, SyncStatusItem>> {
const snapshot = (await this.kvStore.get(syncSnapshotKey)) || {};
return new Map<string, SyncStatusItem>(
Object.entries(snapshot),
);
}
// Await a moment when the sync is no longer running
async noOngoingSync(timeout: number): Promise<void> {
// Not completely safe, could have race condition on setting the syncStartTimeKey
const startTime = Date.now();
while (await this.isSyncing()) {
console.log("Waiting for ongoing sync to finish...");
await sleep(321);
if (Date.now() - startTime > timeout) {
throw new Error("Timeout waiting for sync to finish");
}
}
}
filesScheduledForSync = new Set<string>();
async scheduleFileSync(path: string): Promise<void> {
if (this.filesScheduledForSync.has(path)) {
// Already scheduled, no need to duplicate
console.info(`File ${path} already scheduled for sync`);
return;
}
this.filesScheduledForSync.add(path);
await this.noOngoingSync(7000);
await this.syncFile(path);
this.filesScheduledForSync.delete(path);
}
start() {
this.syncSpace().catch(console.error);
setInterval(async () => {
try {
if (!await this.isSyncing()) {
const lastFullCycle =
(await this.kvStore.get(syncLastFullCycleKey)) || 0;
if (lastFullCycle && Date.now() - lastFullCycle > spaceSyncInterval) {
// It's been a while since the last full cycle, let's sync the whole space
await this.syncSpace();
}
}
} catch (e: any) {
console.error(e);
}
}, spaceSyncInterval / 2); // check every half the sync cycle because actually running the sync takes some time therefore we don't want to wait for the full cycle
}
async syncSpace(): Promise<number> {
if (await this.isSyncing()) {
console.log("Aborting space sync: already syncing");
return 0;
}
await this.registerSyncStart(true);
let operations = 0;
const snapshot = await this.getSnapshot();
// console.log("Excluded from sync", excludedFromSync);
try {
operations = await this.spaceSync!.syncFiles(
snapshot,
(path) => this.isSyncCandidate(path),
);
await this.saveSnapshot(snapshot);
await this.registerSyncStop();
this.eventHook.dispatchEvent("sync:success", operations);
} catch (e: any) {
await this.saveSnapshot(snapshot);
await this.registerSyncStop();
this.eventHook.dispatchEvent("sync:error", e.message);
console.error("Sync error", e.message);
}
return operations;
}
// Syncs a single file
async syncFile(name: string) {
console.log("About to sync file", name);
if (!this.isSyncCandidate(name)) {
console.log("Info not a sync candidate", name);
return;
}
if (await this.isSyncing()) {
console.log("Already syncing, aborting individual file sync for", name);
return;
}
console.log("Syncing file", name);
await this.registerSyncStart(false);
const snapshot = await this.getSnapshot();
try {
let localHash: number | undefined;
let remoteHash: number | undefined;
try {
const localMeta = await this.localSpacePrimitives.getFileMeta(name);
if (localMeta.noSync) {
console.info(
"File marked as no sync, skipping sync in this cycle",
name,
);
await this.registerSyncStop();
return;
}
localHash = localMeta.lastModified;
} catch {
// Not present
}
try {
remoteHash = (await this.remoteSpace!.getFileMeta(name)).lastModified;
} catch (e: any) {
if (e.message === "Not found") {
// File doesn't exist remotely, that's ok
} else {
throw e;
}
}
await this.spaceSync.syncFile(snapshot, name, localHash, remoteHash);
this.eventHook.dispatchEvent("sync:success");
console.log("File successfully synced", name);
} catch (e: any) {
this.eventHook.dispatchEvent("sync:error", e.message);
console.error("Sync error", e);
}
await this.saveSnapshot(snapshot);
await this.registerSyncStop();
console.log("And done with file sync for", name);
}
async saveSnapshot(snapshot: Map<string, SyncStatusItem>) {
await this.kvStore.set(syncSnapshotKey, Object.fromEntries(snapshot));
}
public async plugAwareConflictResolver(
name: string,
snapshot: Map<string, SyncStatusItem>,
primary: SpacePrimitives,
secondary: SpacePrimitives,
): Promise<number> {
if (!name.startsWith("_plug/")) {
const operations = await SpaceSync.primaryConflictResolver(
name,
snapshot,
primary,
secondary,
);
if (operations > 0) {
// Something happened -> conflict copy generated, let's report it
await this.eventHook.dispatchEvent("sync:conflict", name);
}
return operations;
}
console.log(
"[sync]",
"Conflict in plug",
name,
"will pick the version from secondary and be done with it.",
);
// Read file from secondary
const { data, meta } = await secondary.readFile(
name,
);
// Write file to primary
const newMeta = await primary.writeFile(
name,
data,
false,
meta,
);
// Update snapshot
snapshot.set(name, [
newMeta.lastModified,
meta.lastModified,
]);
return 1;
}
}