Add a little more flexibility to the home feed cache

bluelinklabs · Apr 26, 2021 · d76a2a7 · d76a2a7
1 parent b300a55
commit d76a2a7
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Showing 2 changed files with 13 additions and 9 deletions.
diff --git a/db/feed-getters.js b/db/feed-getters.js
@@ -11,17 +11,18 @@ const lexintEncoder = lexint('hex')
 export async function listHomeFeed (opts, auth) {
   opts = opts && typeof opts === 'object' ? opts : {}
   const didSpecifyLt = !!opts.lt
+  const limit = Math.min(opts?.limit || 100, 100)
   opts.lt = opts.lt && typeof opts.lt === 'string' ? opts.lt : lexintEncoder.encode(Date.now())
 
   if (!auth) throw new errors.SessionError()
   const publicDb = publicDbs.get(auth.userId)
   if (!publicDb) throw new errors.NotFoundError('User database not found')
 
-  if (!didSpecifyLt && (!opts.limit || opts.limit <= 15)) {
-    let cached = cache.getHomeFeed(auth.userId)
+  if (!didSpecifyLt) {
+    let cached = cache.getHomeFeed(auth.userId, limit)
     if (cached) {
       debugLog.cacheHit('home-feed', auth.userId)
-      let cachedEntries = opts.limit ? cached.slice(0, opts.limit) : cached
+      let cachedEntries = opts.limit ? cached.slice(0, limit) : cached
       for (let entry of cachedEntries) {
         entry.reactions = (await fetchReactions(entry)).reactions
         entry.replyCount = await fetchReplyCount(entry)
@@ -58,7 +59,6 @@ export async function listHomeFeed (opts, auth) {
 
   const postEntries = []
   const authorsCache = {}
-  const limit = Math.min(opts?.limit || 100, 100)
   const mergedCursor = mergeCursors(cursors)
   for await (let [db, entry] of mergedCursor) {
     if (db.dbType === 'ctzn.network/public-server-db') {
@@ -88,8 +88,8 @@ export async function listHomeFeed (opts, auth) {
     }
   }
 
-  if (!didSpecifyLt && (!opts.limit || opts.limit >= 15)) {
-    cache.setHomeFeed(auth.userId, postEntries, 60e3)
+  if (!didSpecifyLt) {
+    cache.setHomeFeed(auth.userId, postEntries, limit, 60e3)
   }
 
   return postEntries

diff --git a/lib/cache.js b/lib/cache.js
@@ -4,17 +4,21 @@ export function invalidateHomeFeed (userId) {
   delete homeFeedCache[userId]
 }
 
-export function getHomeFeed (userId) {
+export function getHomeFeed (userId, limit) {
   let entry = homeFeedCache[userId]
-  if (!entry || entry.expires < Date.now()) {
+  if (!entry || entry.expires < Date.now() || entry.limit < limit) {
     return undefined
   }
   return entry.value
 }
 
-export function setHomeFeed (userId, value, ttl) {
+export function setHomeFeed (userId, value, limit, ttl) {
+  if (homeFeedCache[userId] && limit < homeFeedCache[userId].limit) {
+    return
+  }
   homeFeedCache[userId] = {
     expires: Date.now() + ttl,
+    limit,
     value
   }
 }