lorensr

const addItem = defineSignal('addItem')
const checkout = defineSignal('checkout')

function cart(userId) {
  const items = []
  
  setHandler(addItem, (item) => items.push(item))
  
  setHandler(checkout, () => {
    const userInfo = await getUser(userId) // activity that gets a handle to the User workflow with Workflow Id = userId and does a 'getUserInfo' Query

lorensr

const { poll } = proxyActivities<typeof activities>({
  startToCloseTimeout: '10m',
  retryPolicy: {
    initialInterval: '1h',
    backoffCoefficient: 1
  }
});

export const stopPolling = defineSignal('stopPolling');

lorensr

import { DataSource } from 'apollo-datasource'
import { InMemoryLRUCache } from 'apollo-server-caching'
import DataLoader from 'dataloader'

class FooDataSource extends DataSource {
  constructor(dbClient) { ... }

  initialize({ context, cache } = {}) { ... }

  didEncounterError(error) { ... }

lorensr

const resolvers = {
  Query: {
    getFoo: (_, { id }, context) => 
      context.dataSources.myFoos.get(id, { ttlInSeconds: 60 })
  },
  Mutation: {
    updateFoo: async (_, { id, fields }, context) => {
      if (context.isAdmin) {
        context.dataSources.myFoos.updateFields(id, fields)
      }

lorensr

import FooClient from 'imaginary-foo-library'

import MyFooDB from './MyFooDB'

const fooClient = new FooClient({ uri: 'https://foo.graphql.guide:9001' })

const server = new ApolloServer({
  typeDefs,
  resolvers,
  dataSources: () => ({

lorensr

import FooDataSource from './FooDataSource'
import { reportError } from './utils'

export default class MyFooDB extends FooDataSource {
  async updateFields(id, fields) {
    const doc = await this.get(id)
    return this.update(id, {
      ...doc,
      ...fields
    })

lorensr

  async update(id, newDoc) {
    try {
      await this.db.update(id, newDoc)
      this.cache.delete(this.cacheKey(id))
    } catch (error) {
      this.didEncounterError(error)
    }
  }

lorensr

  async get(id, { ttlInSeconds } = {}) {
    const cacheDoc = await cache.get(this.cacheKey(id))
    if (cacheDoc) {
      return JSON.parse(cacheDoc)
    }

    const doc = await this.loader.load(id)

    if (ttlInSeconds) {
      cache.set(this.cacheKey(id), JSON.stringify(doc), { ttl: ttlInSeconds })

lorensr

  cacheKey(id) {
    return `foo-${this.db.connectionURI}-${id}`
  }

lorensr

  didEncounterError(error) {
    throw error
  }