Context
I'm retrieving data from the ESPN API to fetch weekly NFL matchup data. So, I'm making 18 api calls each time I need to fetch this data to account for all 18 weeks in the NFL season. I'm then creating an array with the data I need from the responses to those calls and writing out 18 files that align with each week in the NFL season (week1.json, week2.json, etc.).
Problem
The problem is that when I call my endpoint, I am seeing 2 things intermittently, and not necessarily at the same time:
(1) Some of the json files(week1.json, week2.json, etc.) include only a portion of the expected array. So, instead of 16 objects in the array, I may see only 4, or only 6, etc. Why would I only see a portion of the response data written to the array that's ultimately written to the .json files?
(2) Not all files are written to each time the endpoint is called. So, I may see that only week1-week5's .json files are written. Why aren't all of them updated?
Problem Code
// iterate 18 times
for (let i = 0; i < 18; i++) {
let weekNumber;
weekNumber = i + 1;
const week = fs.readFileSync(`./pickem/week${weekNumber}.json`, 'utf8');
const weekJson = JSON.parse(week);
// empty weekJson.games array
weekJson.games = []
// get all items
axios.get(`https://sports.core.api.espn.com/v2/sports/football/leagues/nfl/seasons/2022/types/2/weeks/${weekNumber}/events?lang=en®ion=us`)
.then(response => {
const schedule = [];
// get all items from response
const items = response.data.items
// console.log(response.data.items)
items.forEach(item => {
// make get call to $ref
axios.get(item.$ref)
.then(response => {
// get name
const name = response.data.name
// get date
const date = response.data.date
// get event id
const eventid = response.data.id
// get team ids
let team1 = response.data.competitions[0].competitors[0].id
let team2 = response.data.competitions[0].competitors[1].id
// create new object
const newObject = {
name: name,
date: date,
eventid: eventid,
team1: team1,
team2: team2
}
// add games for week
weekJson.games.push(newObject);
fs.writeFileSync(`./pickem/week${weekNumber}.json`, JSON.stringify(weekJson));
})
.catch(error => {
console.log(error)
})
})
}).catch(error => {
console.log(error)
})
}
Updated Code
router.get('/getschedules', (req, res) => {
async function writeGames() {
// iterate 18 times
for (let i = 0; i < 18; i++) {
let weekNumber;
weekNumber = i + 1;
const week = fs.readFileSync(`./pickem/week${weekNumber}.json`, 'utf8');
const weekJson = JSON.parse(week);
// empty weekJson.games array
weekJson.games = []
// get all items
// Add await keyword to wait for a week to be processed before going to the next one
await axios.get(`https://sports.core.api.espn.com/v2/sports/football/leagues/nfl/seasons/2022/types/2/weeks/${weekNumber}/events?lang=en®ion=us`)
.then(async (response) => { // add async to be able to use await
const schedule = [];
// get all items from response
const items = response.data.items
console.log(response.data.items)
// Use standard loop to be able to benefit from async/await
for (let item of items) {
// make get call to $ref
// wait for an item to be processed before going to the next one
await axios.get(item.$ref)
.then(response => {
// get name
const name = response.data.name
// get date
const date = response.data.date
// get event id
const eventid = response.data.id
// get team ids
let team1 = response.data.competitions[0].competitors[0].id
let team2 = response.data.competitions[0].competitors[1].id
// create new object
const newObject = {
name: name,
date: date,
eventid: eventid,
team1: team1,
team2: team2
}
// add games for week
weekJson.games.push(newObject);
})
.catch(error => {
console.log(error)
})
}
// moved out of the for loop since you only need to write this once
fs.writeFileSync(`./pickem/week${weekNumber}.json`, JSON.stringify(weekJson));
}).catch(error => {
console.log(error)
})
}
}
writeGames();
})
Your issue might come from the fact that you are looping over an array of item that triggers parallel asynchronous calls and write weekJson before you get the entire data. (But theoretically your code should work if writeSyncFile is really synchronous, maybe there are locks on the file system that prevents node to write properly?) You could try to make everything sequential and only write weekJson once instead of everytime you go over an item:
I updated my original code proposition by keeping parallel calls and it worked for me (it's similar to OP's code but I only write the json file once per week).
Then I tried to run OP's code and it was working fine as well. So this makes me think that the problem isn't from the code itself but rather how it's called. As a pure node script, there doesn't seem to be any issue. But I just noticed that OP is using it server side as the result of an API call.
Having an API write so many JSON concurrently is probably not the best idea (especially if the api is called multiple times almost simultaneously). You could either
Then I wonder if due to the server context, there is not some kind of timeout since OP said that with my initial solution, only the first week was created.
const axios = require("axios");
const fs = require("fs");
async function writeGames() {
const writeWeekGamesPromises = [];
// iterate 18 times
for (let weekNumber = 1; weekNumber < 19; weekNumber++) {
// give week a default value in case the json file doesn't exist (for repro purpose)
let week = "{}";
try {
week = fs.readFileSync(`./pickem/week${weekNumber}.json`, "utf8");
} catch (e) {
console.log(`error reading week ${weekNumber} json file:`, e);
// file doesn't exist yet
}
const weekJson = JSON.parse(week);
// empty weekJson.games array
const games = [];
weekJson.games = games;
// get all items
// Add await keyword to wait for a week to be processed before going to the next one
writeWeekGamesPromises.push(axios
.get(
`https://sports.core.api.espn.com/v2/sports/football/leagues/nfl/seasons/2022/types/2/weeks/${weekNumber}/events?lang=en®ion=us`
)
.then(async (eventListResponse) => {
// add async to be able to use await
const schedule = [];
console.log(JSON.stringify(eventListResponse.data),'\n');
// get all items from response
const items = eventListResponse.data.items;
// console.log(eventListResponse.data.items); // this seems to be useless since we log the whole data just above
// parallelize calls and wait for all games from a week to be fetched before writing the file
await Promise.all(
items.map((item) => {
// we return the promise so that Promise.all will wait for all games to be pushed before going on writing the file
return axios
.get(item.$ref)
.then((response) => {
// get name, date and eventid
const {name, date, id: eventid} = response.data;
// get team ids
let team1 = response.data.competitions[0].competitors[0].id;
let team2 = response.data.competitions[0].competitors[1].id;
games.push({ name, date, eventid, team1, team2 });
})
.catch((error) => {
console.log(error);
});
})
);
// Now that all game data is ready, write in the file
fs.writeFileSync(
`./pickem/week${weekNumber}.json`,
JSON.stringify(weekJson)
);
})
.catch((error) => {
console.log(error);
}));
}
// Waiting for all games from all weeks to be processed
await Promise.all(writeWeekGamesPromises);
}
async function runAndLogTime() {
const start = Date.now();
await writeGames();
console.log(`took ${(Date.now() - start) / 1000}s to write all json files`);
}
runAndLogTime();