Handle large number of http requests at once in flutter - flutter

Question

Requirement:
I've 1000 URLs of PDF, from which I want to create the zip.
Function:
static Future<bool> downloadZip(List<String> urls) {
int counter = 0
for(String url in urls) {
bytesForFileAtUrl(url).then((bytes){
counter++;
if(bytes != null) {
//Add bytes to the zip encoder
}
if(counter == urls.length) {
//close the zip encoder
//download the zip file
}
}
}
}
static Future<Uint8List> bytesForFileAtUrl(String url) async {
try {
http.Response response = await http.get(url);
return response?.bodyBytes;
} catch (e) {
print('Error getting bytes: ${e.toString()}');
return null;
}
}
Problem:
When there is small number of requests its working fine. But in case large number of requests I'm getting the exception: SocketException: Connection failed (OS Error: Too many open files, errno = 24) as reported here. This might because of memory issue on my mobile device, as its working fine on the web platform.
I've tried other solutions like the one using Future.wait() suggested here, but its not working and device is hanged.
Whats the best solution for this scenario ?
Worst Solution:
Using await keyword. No exception at all, but then its taking too long for the overall process to complete.
for(String url in urls) {
final bytes = await bytesForFileAtUrl(url);
...
...
}

Answer 1

static Future < bool > downloadZip(List < String > urls) {
int counter = 0;
urls.forEach(async() {
await bytesForFileAtUrl(url).then((bytes){
counter++;
if (bytes != null) {
//Add bytes to the zip encoder
}
if (counter == urls.length) {
//close the zip encoder
//download the zip file
}
});
});
}
static Future < Uint8List > bytesForFileAtUrl(String url) async {
try {
http.Response response = await http.get(url);
return response?.bodyBytes;
} catch (e) {
print('Error getting bytes: ${e.toString()}');
return null;
}
}
maybe try this ?