Unexpected end of JSON input when using fs.watch() and require() NodeJS - json

Question

When checking for a new file inside my ./Assetto1/results folder (.json file) the code should read the new file (result = require("[...]")) and log it into console. But I'm always getting the same error. Even trying for 8 hours now. The same thing happens, when using fs.readFile() instead of require(). I even tried an npm module called "decache" so that I could somehow "derequire" the file. My idea was that nodejs then expects the end of the JSON file. But nothing of this helps, as well.
Take a look at my code i wrote:
var fs = require("fs");
fs.watch('./Assetto1/results/', (eventType, filename) => {
console.log("EventType:"+eventType);
if (eventType == "rename") {
console.log("Debug: Rename");
console.log("./Assetto1/results/"+filename);
result = require("./Assetto1/results/"+filename);
console.log(result);
}
})
Console Output looks like this:
SyntaxError: /home/Assetto1/results/2018_9_8_9_0_RACE.json: Unexpected end of JSON input
at JSON.parse (<anonymous>)
at Object.Module._extensions..json (internal/modules/cjs/loader.js:708:27)
at Module.load (internal/modules/cjs/loader.js:599:32)
at tryModuleLoad (internal/modules/cjs/loader.js:538:12)
at Function.Module._load (internal/modules/cjs/loader.js:530:3)
at Module.require (internal/modules/cjs/loader.js:637:17)
at require (internal/modules/cjs/helpers.js:20:18)
at FSWatcher.fs.watch (/home/main.js:59:12)
at FSWatcher.emit (events.js:182:13)
at FSEvent.FSWatcher._handle.onchange (internal/fs/watchers.js:130:12)
Content of the JSON file (AssettoCorsa Race-Results):
{
"TrackName": "spa",
"TrackConfig": "",
"Type": "RACE",
"DurationSecs": 0,
"RaceLaps": 5,
"Cars": [
{
"CarId": 0,
"Driver": {
"Name": "NoaH",
"Team": "",
"Nation": "DEU",
"Guid": "76561198190801825",
"GuidsList": [
""
]
},
"Model": "mercedes_sls_gt3",
"Skin": "Black_Falcon_SB_Mobel_Boss_10",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 1,
"Driver": {
"Name": "",
"Team": "",
"Nation": "",
"Guid": "",
"GuidsList": [
""
]
},
"Model": "mercedes_sls_gt3",
"Skin": "Black_Falcon_Porta_9",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 2,
"Driver": {
"Name": "",
"Team": "",
"Nation": "",
"Guid": "",
"GuidsList": [
""
]
},
"Model": "mercedes_sls_gt3",
"Skin": "Kunos_zp_115",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 3,
"Driver": {
"Name": "",
"Team": "",
"Nation": "",
"Guid": "",
"GuidsList": [
""
]
},
"Model": "mercedes_sls_gt3",
"Skin": "Kunos_zp_116",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 4,
"Driver": {
"Name": "",
"Team": "",
"Nation": "",
"Guid": "",
"GuidsList": [
""
]
},
"Model": "mercedes_sls_gt3",
"Skin": "Black_Falcon_Dubai_24H_2",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 5,
"Driver": {
"Name": "",
"Team": "",
"Nation": "",
"Guid": "",
"GuidsList": [
""
]
},
"Model": "mercedes_sls_gt3",
"Skin": "Black_Falcon_SB_Mobel_Boss_10",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 6,
"Driver": {
"Name": "",
"Team": "",
"Nation": "",
"Guid": "",
"GuidsList": [
""
]
},
"Model": "mercedes_sls_gt3",
"Skin": "Black_Falcon_Porta_9",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 7,
"Driver": {
"Name": "",
"Team": "",
"Nation": "",
"Guid": "",
"GuidsList": [
""
]
},
"Model": "mercedes_sls_gt3",
"Skin": "Kunos_zp_115",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 8,
"Driver": {
"Name": "",
"Team": "",
"Nation": "",
"Guid": "",
"GuidsList": [
""
]
},
"Model": "mercedes_sls_gt3",
"Skin": "Kunos_zp_116",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 9,
"Driver": {
"Name": "",
"Team": "",
"Nation": "",
"Guid": "",
"GuidsList": [
""
]
},
"Model": "mercedes_sls_gt3",
"Skin": "Black_Falcon_Dubai_24H_2",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 10,
"Driver": {
"Name": "Ian Loncar",
"Team": "",
"Nation": "HRV",
"Guid": "76561198273369988",
"GuidsList": [
""
]
},
"Model": "ks_nissan_gtr",
"Skin": "solid_red",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 11,
"Driver": {
"Name": "",
"Team": "",
"Nation": "",
"Guid": "",
"GuidsList": [
""
]
},
"Model": "ks_nissan_gtr",
"Skin": "jet_black",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 12,
"Driver": {
"Name": "",
"Team": "",
"Nation": "",
"Guid": "",
"GuidsList": [
""
]
},
"Model": "ks_nissan_gtr",
"Skin": "0_pearl_white",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 13,
"Driver": {
"Name": "",
"Team": "",
"Nation": "",
"Guid": "",
"GuidsList": [
""
]
},
"Model": "ks_nissan_gtr",
"Skin": "super_silver",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 14,
"Driver": {
"Name": "",
"Team": "",
"Nation": "",
"Guid": "",
"GuidsList": [
""
]
},
"Model": "ks_nissan_gtr",
"Skin": "jet_black",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 15,
"Driver": {
"Name": "F. Riestra.ESP.",
"Team": "",
"Nation": "",
"Guid": "76561198130349639",
"GuidsList": [
""
]
},
"Model": "ks_audi_r8_plus",
"Skin": "10_sepang_blue_pearl",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 16,
"Driver": {
"Name": "",
"Team": "",
"Nation": "",
"Guid": "",
"GuidsList": [
""
]
},
"Model": "ks_audi_r8_plus",
"Skin": "11_suzuka_gray_metallic_t",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 17,
"Driver": {
"Name": "",
"Team": "",
"Nation": "",
"Guid": "",
"GuidsList": [
""
]
},
"Model": "ks_audi_r8_plus",
"Skin": "09_samoa_orange_metallic_t",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 18,
"Driver": {
"Name": "",
"Team": "",
"Nation": "",
"Guid": "",
"GuidsList": [
""
]
},
"Model": "ks_audi_r8_plus",
"Skin": "Brilliant_Red",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 19,
"Driver": {
"Name": "sale7almanna3i",
"Team": "",
"Nation": "QAT",
"Guid": "76561198139068257",
"GuidsList": [
""
]
},
"Model": "ks_lamborghini_huracan_performante",
"Skin": "blu_cepheus",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 20,
"Driver": {
"Name": "raafaal1661",
"Team": "",
"Nation": "",
"Guid": "76561198857669454",
"GuidsList": [
""
]
},
"Model": "ks_lamborghini_huracan_performante",
"Skin": "giallo_horus",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 21,
"Driver": {
"Name": "alexpavillanueva",
"Team": "",
"Nation": "ESP",
"Guid": "76561198834760853",
"GuidsList": [
""
]
},
"Model": "ks_lamborghini_huracan_performante",
"Skin": "blu_nethuns",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 22,
"Driver": {
"Name": "NoaH",
"Team": "",
"Nation": "DEU",
"Guid": "76561198190801825",
"GuidsList": [
""
]
},
"Model": "ks_lamborghini_huracan_performante",
"Skin": "00_arancio_anthaeus",
"BallastKG": 0,
"Restrictor": 0
},
{
"CarId": 23,
"Driver": {
"Name": "",
"Team": "",
"Nation": "",
"Guid": "",
"GuidsList": [
""
]
},
"Model": "ks_lamborghini_huracan_performante",
"Skin": "rosso_efesto",
"BallastKG": 0,
"Restrictor": 0
}
],
"Result": [
{
"DriverName": "NoaH",
"DriverGuid": "76561198190801825",
"CarId": 22,
"CarModel": "ks_lamborghini_huracan_performante",
"BestLap": 174182,
"TotalTime": 891017,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "NoaH",
"DriverGuid": "76561198190801825",
"CarId": 0,
"CarModel": "mercedes_sls_gt3",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "",
"DriverGuid": "",
"CarId": 2,
"CarModel": "mercedes_sls_gt3",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "",
"DriverGuid": "",
"CarId": 3,
"CarModel": "mercedes_sls_gt3",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "",
"DriverGuid": "",
"CarId": 4,
"CarModel": "mercedes_sls_gt3",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "",
"DriverGuid": "",
"CarId": 5,
"CarModel": "mercedes_sls_gt3",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "",
"DriverGuid": "",
"CarId": 6,
"CarModel": "mercedes_sls_gt3",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "",
"DriverGuid": "",
"CarId": 7,
"CarModel": "mercedes_sls_gt3",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "",
"DriverGuid": "",
"CarId": 8,
"CarModel": "mercedes_sls_gt3",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "",
"DriverGuid": "",
"CarId": 9,
"CarModel": "mercedes_sls_gt3",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "Ian Loncar",
"DriverGuid": "76561198273369988",
"CarId": 10,
"CarModel": "ks_nissan_gtr",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "",
"DriverGuid": "",
"CarId": 11,
"CarModel": "ks_nissan_gtr",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "",
"DriverGuid": "",
"CarId": 12,
"CarModel": "ks_nissan_gtr",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "",
"DriverGuid": "",
"CarId": 13,
"CarModel": "ks_nissan_gtr",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "",
"DriverGuid": "",
"CarId": 14,
"CarModel": "ks_nissan_gtr",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "F. Riestra.ESP.",
"DriverGuid": "76561198130349639",
"CarId": 15,
"CarModel": "ks_audi_r8_plus",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "",
"DriverGuid": "",
"CarId": 16,
"CarModel": "ks_audi_r8_plus",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "",
"DriverGuid": "",
"CarId": 17,
"CarModel": "ks_audi_r8_plus",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "",
"DriverGuid": "",
"CarId": 18,
"CarModel": "ks_audi_r8_plus",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "sale7almanna3i",
"DriverGuid": "76561198139068257",
"CarId": 19,
"CarModel": "ks_lamborghini_huracan_performante",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "raafaal1661",
"DriverGuid": "76561198857669454",
"CarId": 20,
"CarModel": "ks_lamborghini_huracan_performante",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "alexpavillanueva",
"DriverGuid": "76561198834760853",
"CarId": 21,
"CarModel": "ks_lamborghini_huracan_performante",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "",
"DriverGuid": "",
"CarId": 1,
"CarModel": "mercedes_sls_gt3",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
},
{
"DriverName": "",
"DriverGuid": "",
"CarId": 23,
"CarModel": "ks_lamborghini_huracan_performante",
"BestLap": 999999999,
"TotalTime": 0,
"BallastKG": 0,
"Restrictor": 0
}
],
"Laps": [
{
"DriverName": "NoaH",
"DriverGuid": "76561198190801825",
"CarId": 22,
"CarModel": "ks_lamborghini_huracan_performante",
"Timestamp": 35470691,
"LapTime": 180196,
"Sectors": [
50515,
82440,
47241
],
"Cuts": 0,
"BallastKG": 0,
"Tyre": "HR",
"Restrictor": 0
},
{
"DriverName": "NoaH",
"DriverGuid": "76561198190801825",
"CarId": 22,
"CarModel": "ks_lamborghini_huracan_performante",
"Timestamp": 35645934,
"LapTime": 175240,
"Sectors": [
48331,
82125,
44784
],
"Cuts": 0,
"BallastKG": 0,
"Tyre": "HR",
"Restrictor": 0
},
{
"DriverName": "NoaH",
"DriverGuid": "76561198190801825",
"CarId": 22,
"CarModel": "ks_lamborghini_huracan_performante",
"Timestamp": 35824671,
"LapTime": 178746,
"Sectors": [
46162,
85482,
47102
],
"Cuts": 0,
"BallastKG": 0,
"Tyre": "HR",
"Restrictor": 0
},
{
"DriverName": "NoaH",
"DriverGuid": "76561198190801825",
"CarId": 22,
"CarModel": "ks_lamborghini_huracan_performante",
"Timestamp": 36007357,
"LapTime": 182686,
"Sectors": [
46340,
85492,
50854
],
"Cuts": 0,
"BallastKG": 0,
"Tyre": "HR",
"Restrictor": 0
},
{
"DriverName": "NoaH",
"DriverGuid": "76561198190801825",
"CarId": 22,
"CarModel": "ks_lamborghini_huracan_performante",
"Timestamp": 36181518,
"LapTime": 174182,
"Sectors": [
46693,
81995,
45494
],
"Cuts": 0,
"BallastKG": 0,
"Tyre": "HR",
"Restrictor": 0
}
],
"Events": [
{
"Type": "COLLISION_WITH_ENV",
"CarId": 22,
"Driver": {
"Name": "NoaH",
"Team": "",
"Nation": "DEU",
"Guid": "76561198190801825",
"GuidsList": [
""
]
},
"OtherCarId": -1,
"OtherDriver": {
"Name": "",
"Team": "",
"Nation": "",
"Guid": "",
"GuidsList": null
},
"ImpactSpeed": 12.305487,
"WorldPosition": {
"X": 415.25763,
"Y": 38.005207,
"Z": 847.0971
},
"RelPosition": {
"X": -0.96855915,
"Y": 0.31426933,
"Z": -1.4876876
}
},
{
"Type": "COLLISION_WITH_ENV",
"CarId": 22,
"Driver": {
"Name": "NoaH",
"Team": "",
"Nation": "DEU",
"Guid": "76561198190801825",
"GuidsList": [
""
]
},
"OtherCarId": -1,
"OtherDriver": {
"Name": "",
"Team": "",
"Nation": "",
"Guid": "",
"GuidsList": null
},
"ImpactSpeed": 69.01873,
"WorldPosition": {
"X": -449.24142,
"Y": 30.581987,
"Z": -1006.0361
},
"RelPosition": {
"X": 0.68840855,
"Y": -0.285217,
"Z": 2.4184985
}
},
{
"Type": "COLLISION_WITH_ENV",
"CarId": 22,
"Driver": {
"Name": "NoaH",
"Team": "",
"Nation": "DEU",
"Guid": "76561198190801825",
"GuidsList": [
""
]
},
"OtherCarId": -1,
"OtherDriver": {
"Name": "",
"Team": "",
"Nation": "",
"Guid": "",
"GuidsList": null
},
"ImpactSpeed": 22.243214,
"WorldPosition": {
"X": 416.29285,
"Y": 37.574894,
"Z": 849.2622
},
"RelPosition": {
"X": -0.8986338,
"Y": -0.2784356,
"Z": 2.0484245
}
}
]
}
So now I don't really know what I can do against it.
Maybe you guys can help me,
thanks.

Answer 1

So guys, after reading your posts carefully, I got the idea that I just have to wait until the file is written completely. I've done that with a simple Atomics.wait(new Int32Array(new SharedArrayBuffer(4)), 0, 0, 1000); after that, I can read out the file without a single problem. So, that's the solution for everyone else who stumbles across this problem like me.
Thanks

Answer 2

How is the file created? You probably just have a race condition with the file being created (which triggers the fs.watch event and reading of the file), then the JSON is written after a bit of processing, but it's already too late. Or the JSON is big and it takes time to write it all.
Two options for you:
the process that creates the JSON should work in another directory (but on the same filesystem). Once the file is fully written out, move it to the directory. This way, you have an atomic change, and you know that when you receive the event the file is complete.
An alternative is to write in the same directory, but rename once finished, and have a convention for what files are temporary or final (e.g. if the file is .xxxx.tmp ignore the event).
or whenever you receive an event for a file (rename or change):
cancel any previously created timer for that file
create a new timer for that file
when the timer expires, actually read the file