Android: Too many open files error

Question

I have the following operation which runs every 3 seconds.
Basically it downloads a file from a server and save it into a local file every 3 seconds.
The following code does the job for a while.

public class DownloadTask extends AsyncTask<String, Void, String>{

    @Override
    protected String doInBackground(String... params) {
        downloadCommandFile( eventUrl);
        return null;
    }


}

private void downloadCommandFile(String dlUrl){
    int count;
    try {
        URL url = new URL( dlUrl );
        NetUtils.trustAllHosts();
        HttpsURLConnection con = (HttpsURLConnection) url.openConnection();
        con.setDoInput(true);
        con.setDoOutput(true);
        con.connect();
        int fileSize = con.getContentLength();
        Log.d(TAG, "Download file size = " + fileSize );
        InputStream is = url.openStream();
        String dir = Environment.getExternalStorageDirectory() + Utils.DL_DIRECTORY;
        File file = new File( dir );
        if( !file.exists() ){
            file.mkdir();
        }

        FileOutputStream fos = new FileOutputStream(file + Utils.DL_FILE);
        byte data[] = new byte[1024];
        long total = 0;

        while( (count = is.read(data)) != -1 ){
            total += count;
            fos.write(data, 0, count);
        }

        is.close();
        fos.close();
        con.disconnect(); // close connection


    } catch (Exception e) {
        Log.e(TAG, "DOWNLOAD ERROR = " + e.toString() );
    }

}

Everything works fine, but if I leave it running for 5 to 10 minutes I get the following error.

06-04 19:40:40.872: E/NativeCrypto(6320): AppData::create pipe(2) failed: Too many open files 06-04 19:40:40.892: E/NativeCrypto(6320): AppData::create pipe(2) failed: Too many open files 06-04 19:40:40.892: E/EventService(6320): DOWNLOAD ERROR = javax.net.ssl.SSLException: Unable to create application data

I have been doing some researches for the last 2 days.
There are suggestions that they are many connections open, like this one https://stackoverflow.com/a/13990490/1503155 but still I can not figure out what's the problem.
Any ideas what may cause the problem?
Thanks in advance.

Answer 1

I think you get this error because you have too many files open at the same times, meaning that you have too many async tasks running in the same time (each async task opens a file), which makes sense if you say that you run a new one every 3 seconds.

You should try to limit the number of async task running in the same time using a thread pool executor.