Save board snapshot every 5000 events to avoid excessively long board…

… load time due to snapshot being late

backend/src/board-state.ts

@@ -1,14 +1,23 @@
 import { boardReducer } from "../../common/src/board-reducer"
 import { Board, BoardCursorPositions, BoardHistoryEntry, Id, ItemLocks, Serial } from "../../common/src/domain"
 import { Locks } from "./locker"
-import { createAccessToken, createBoard, fetchBoard, saveRecentEvents } from "./board-store"
+import {
+ createAccessToken,
+ createBoard,
+ fetchBoard,
+ mkSnapshot,
+ saveBoardSnapshot,
+ saveRecentEvents,
+} from "./board-store"
 import { broadcastItemLocks, getBoardSessionCount, getSessionCount } from "./websocket-sessions"
 import { compactBoardHistory, quickCompactBoardHistory } from "./compact-history"
 import { sleep } from "../../common/src/sleep"
 import { UserSession } from "./websocket-sessions"
+import { inTransaction } from "./db"
 // A mutable state object for server side state
 export type ServerSideBoardState = {
  ready: true
+ snapshotSerial: Serial
  board: Board
  recentEvents: BoardHistoryEntry[]
  storingEvents: BoardHistoryEntry[]
@@ -35,7 +44,7 @@ export async function getBoard(id: Id): Promise<ServerSideBoardState | null> {
  const fetchState = async () => {
  const boardData = await fetchBoard(id)
  if (!boardData) return null
- const { board, accessTokens } = boardData
+ const { board, accessTokens, snapshotSerial } = boardData
  return {
  ready: true,
  board,
@@ -46,6 +55,7 @@ export async function getBoard(id: Id): Promise<ServerSideBoardState | null> {
  cursorsMoved: false,
  cursorPositions: {},
  sessions: [],
+ snapshotSerial,
  } as ServerSideBoardState
  }
  const fetch = fetchState()
@@ -100,10 +110,10 @@ export function updateBoards(boardState: ServerSideBoardState, appEvent: BoardHi
 export async function addBoard(board: Board, createToken?: boolean): Promise<ServerSideBoardState> {
  await createBoard(board)
  const accessTokens = createToken ? [await createAccessToken(board)] : []
- const boardState = {
+ const boardState: ServerSideBoardState = {
  ready: true as const,
  board,
- serial: 0,
+ snapshotSerial: 0,
  recentEvents: [],
  storingEvents: [],
  locks: Locks((changedLocks) => broadcastItemLocks(board.id, changedLocks)),
@@ -145,6 +155,18 @@ async function saveBoardChanges(state: ServerSideBoardState) {
  )
  try {
  await saveRecentEvents(state.board.id, state.storingEvents)
+ if (state.board.serial - state.snapshotSerial > 5000) {
+ console.log(
+ `Saving snapshot for board ${state.board.id} with ${
+ state.board.serial - state.snapshotSerial
+ } new events`,
+ )
+ await inTransaction(async (client) => {
+ await saveBoardSnapshot(mkSnapshot(state.board, state.board.serial), client)
+ })
+ state.snapshotSerial = state.board.serial
+ }
+ // TODO: also update snapshot if more than 1000 events since snapshot
  } catch (e) {
  // Push event back to the head of save list for retrying later
  state.recentEvents = [...state.storingEvents, ...state.recentEvents]

backend/src/board-store.ts

@@ -6,9 +6,10 @@ import { Board, BoardAccessPolicy, BoardHistoryEntry, Id, isBoardEmpty, Serial }
 import { migrateBoard, migrateEvent, mkBootStrapEvent } from "../../common/src/migration"
 import { inTransaction, withDBClient } from "./db"
 
-export type BoardAndAccessTokens = {
+export type BoardFetchResult = {
  board: Board
  accessTokens: string[]
+ snapshotSerial: Serial
 }
 
 export type BoardInfo = {
@@ -37,7 +38,7 @@ select id,
 where id=$1
 `
 
-export async function fetchBoard(id: Id): Promise<BoardAndAccessTokens | null> {
+export async function fetchBoard(id: Id): Promise<BoardFetchResult | null> {
  return await inTransaction(async (client) => {
  const started = new Date().getTime()
  const result = await client.query(selectBoardQuery, [id])
@@ -100,7 +101,7 @@ export async function fetchBoard(id: Id): Promise<BoardAndAccessTokens | null> {
  await client.query("SELECT token FROM board_api_token WHERE board_id=$1", [id])
  ).rows.map((row) => row.token)
 
- return { board: { ...board, serial }, accessTokens }
+ return { board: { ...board, serial }, accessTokens, snapshotSerial: snapshot.serial }
  }
  })
 }
@@ -180,7 +181,7 @@ export async function createAccessToken(board: Board): Promise<string> {
 }
 
 export async function saveRecentEvents(id: Id, recentEvents: BoardHistoryEntry[]) {
- await inTransaction(async (client) => storeEventHistoryBundle(id, recentEvents, client))
+ await inTransaction(async (client) => await storeEventHistoryBundle(id, recentEvents, client))
 }
 
 type StreamingBoardEventCallback = (chunk: BoardHistoryEntry[]) => void