make rewards query less aggressive

api/resolvers/rewards.js

@@ -4,9 +4,26 @@ import { serializeInvoicable } from './serial'
 import { ANON_USER_ID } from '../../lib/constants'
 import { getItem } from './item'
 
-export default {
+const rewardCache = new Map()
-  Query: {
+
-    rewards: async (parent, { when }, { models }) => {
+async function updateCachedRewards (when, models) {
+  const rewards = await getRewards(when, models)
+  rewardCache.set(when, { rewards, createdAt: Date.now() })
+  return rewards
+}
+
+async function getCachedRewards (staleIn, when, models) {
+  if (rewardCache.has(when)) {
+    const { rewards, createdAt } = rewardCache.get(when)
+    const expired = createdAt + staleIn < Date.now()
+    if (expired) updateCachedRewards(when, models).catch(console.error)
+    return rewards // serve stale rewards
+  }
+  return await updateCachedRewards(when, models)
+}
+
+async function getRewards (when, models) {
+  console.log('getRewards', when)
   if (when) {
     if (when.length > 2) {
       throw new GraphQLError('too many dates', { extensions: { code: 'BAD_USER_INPUT' } })
@@ -63,7 +80,12 @@ export default {
     ORDER BY days_cte.day ASC`
 
   return results.length ? results : [{ total: 0, time: '0', sources: [] }]
-    },
+}
+
+export default {
+  Query: {
+    rewards: async (parent, { when }, { models }) =>
+      when ? await getRewards(when, models) : await getCachedRewards(5000, when, models),
     meRewards: async (parent, { when }, { me, models }) => {
       if (!me) {
         return null