Use message id to handle concurrency

packages/backend-core/src/cache/docWritethrough.ts

@@ -1,9 +1,11 @@
 import BaseCache from "./base"
 import { getDocWritethroughClient } from "../redis/init"
-import { AnyDocument, Database } from "@budibase/types"
+import { AnyDocument, Database, LockName, LockType } from "@budibase/types"
 
 import { JobQueue, createQueue } from "../queue"
 import * as dbUtils from "../db"
+import { Duration, newid } from "../utils"
+import { context, locks } from ".."
 
 let CACHE: BaseCache | null = null
 async function getCache() {
@@ -18,6 +20,7 @@ interface ProcessDocMessage {
   dbName: string
   docId: string
   cacheKeyPrefix: string
+  messageId: string
 }
 
 export const docWritethroughProcessorQueue = createQueue<ProcessDocMessage>(
@@ -25,21 +28,55 @@ export const docWritethroughProcessorQueue = createQueue<ProcessDocMessage>(
 )
 
 docWritethroughProcessorQueue.process(async message => {
-  await persistToDb(message.data)
-  console.log("DocWritethrough persisted", { data: message.data })
+  const { cacheKeyPrefix, messageId } = message.data
+
+  const cache = await getCache()
+  const latestMessageId = await cache.get(
+    REDIS_KEYS(cacheKeyPrefix).LATEST_MESSAGE_ID
+  )
+  if (messageId !== latestMessageId) {
+    // Nothing to do, another message overrode it
+    return
+  }
+
+  const lockResponse = await locks.doWithLock(
+    {
+      type: LockType.TRY_ONCE,
+      name: LockName.PERSIST_WRITETHROUGH,
+      resource: cacheKeyPrefix,
+      ttl: Duration.fromSeconds(60).toMs(),
+    },
+    async () => {
+      const latestMessageId = await cache.get(
+        REDIS_KEYS(cacheKeyPrefix).LATEST_MESSAGE_ID
+      )
+      if (messageId !== latestMessageId) {
+        // Nothing to do, another message overrode it
+        return
+      }
+
+      await persistToDb(cache, message.data)
+      console.log("DocWritethrough persisted", { data: message.data })
+    }
+  )
+
+  if (!lockResponse.executed) {
+    console.log(`Ignoring redlock conflict in write-through cache`)
+  }
 })
 
-export async function persistToDb({
-  dbName,
-  docId,
-  cacheKeyPrefix,
-}: {
-  dbName: string
-  docId: string
-  cacheKeyPrefix: string
-}) {
-  const cache = await getCache()
-
+export async function persistToDb(
+  cache: BaseCache,
+  {
+    dbName,
+    docId,
+    cacheKeyPrefix,
+  }: {
+    dbName: string
+    docId: string
+    cacheKeyPrefix: string
+  }
+) {
   const db = dbUtils.getDB(dbName)
   let doc: AnyDocument | undefined
   try {
@@ -48,7 +85,9 @@ export async function persistToDb({
     doc = { _id: docId }
   }
 
-  const keysToPersist = await cache.keys(`${cacheKeyPrefix}:data:*`)
+  const keysToPersist = await cache.keys(
+    REDIS_KEYS(cacheKeyPrefix).DATA.GET_ALL
+  )
   for (const key of keysToPersist) {
     const data = await cache.get(key, { useTenancy: false })
     doc[data.key] = data.value
@@ -83,27 +122,38 @@ export class DocWritethrough {
     const cache = await getCache()
 
     await this.storeToCache(cache, data)
+    const messageId = newid()
+    await cache.store(
+      REDIS_KEYS(this.cacheKeyPrefix).LATEST_MESSAGE_ID,
+      messageId
+    )
 
     docWritethroughProcessorQueue.add(
       {
         dbName: this.db.name,
         docId: this.docId,
         cacheKeyPrefix: this.cacheKeyPrefix,
+        messageId,
       },
       {
         delay: this.writeRateMs,
-        jobId: this.cacheKeyPrefix,
-        removeOnFail: true,
-        removeOnComplete: true,
       }
     )
   }
 
   private async storeToCache(cache: BaseCache, data: Record<string, any>) {
     data = Object.entries(data).reduce((acc, [key, value]) => {
-      acc[this.cacheKeyPrefix + ":data:" + key] = { key, value }
+      acc[REDIS_KEYS(this.cacheKeyPrefix).DATA.VALUE(key)] = { key, value }
       return acc
     }, {} as Record<string, any>)
     await cache.bulkStore(data, null)
   }
 }
+
+const REDIS_KEYS = (prefix: string) => ({
+  DATA: {
+    VALUE: (key: string) => prefix + ":data:" + key,
+    GET_ALL: prefix + ":data:*",
+  },
+  LATEST_MESSAGE_ID: prefix + ":info:latestMessageId",
+})