Intermittent EIO error when using a PTY process

[miladhashemi]

Hi,
I wrote below code, and sometimes I have some issues:

const customProc = core.make('osjs/proc');
customProc.pty('ls -ltrh').then(p => {
      // Process events
      p.on('data', str => console.log(str));
      p.on('error', error => console.error(error)); // Spawn errors

      // Send data to the shell
      p.send('Hello World\n');

    });

1. p.send() has output on console only when I login to Os.js
2. Sometimes returns bellow error, Do U know what causes this error?
   Object { errno: "EIO", code: "EIO", syscall: "read" }

[andersevenrud]

p.send() has output on console only when I login to Os.js

You need a user session in order to use this module. This is for security reasons. You could override this to allow without a session, but I do not recommend it.

Sometimes returns bellow error, Do U know what causes this error?

An EIO code means that some operation is taking place (in this case read) after the socket has been closed. You can probably debug this by checking if .on('exit', () => console.log('EXITED')) is called before you .send() something.

Just a note on passing arguments to your commands: https://github.com/os-js/osjs-proc-provider#passing-arguments
You have to do it like this: .pty('ls', '-ltrh').

[miladhashemi]

You can probably debug this by checking if .on('exit', () => console.log('EXITED')) is called before you .send() something.

I get this error without using send method. and Exited log is shown after error. It means before exiting process i get this error.

customProc.pty('ls').then(p => {
    // Process events
    p.on('data', str => console.log(str));
    p.on('exit', () => console.log('EXITED'));
    p.on('error', error => console.error(error)); // Spawn errors
    // Send data to the shell
    // p.send('Hello World\n');
    // You can kill long running processes
    // p.kill();
  });

[andersevenrud]

Can you show me an example where you're using this ?

[mahsashadi]

I have the same problem.
I wrote an app, and I use osjs/proc to list folders, when the app is rendered.
Most of the times it causes EIO error with error number 5

export default function App() {

    useEffect(() => {
        getFolderList();
      }, []);

    function getFolderList(){
        osjs.make('osjs/proc')
        .pty('ls' , '-d */')
        .then(p => {
            // Process events
            p.on('data', data =>{     
                   // do something 
            })
            p.on('exit', code => console.info('EXITED', code))
            // Internal events
            p.on('spawned', () => {}); // Spawn successful
            p.on('error', error => console.error(error)); // Spawn errors
            //p.send('Hello World\n');
            // You can kill long running processes
            p.kill();
          })
    }

[andersevenrud]

I think the problem here is that you immediately kill the PTY after it was created. This probably closes the socket before the data events are finished.

Use .exec(cmd, ...args) => Promise<{code, stdout, stderr}> instead of .pty(cmd, ...args) => Promise<p> instead if you just want to perform simple commands to get the output.

[andersevenrud]

I think the problem here is that you immediately kill the PTY after it was created. This probably closes the socket before the data events are finished.

Which means that if you remove the p.kill() this probably works as you expected. I still recommend using exec though in cases like this. A PTY is more suited to stream data and send input commands to a running process.

Also, expanding on what I said in an earlier comment about arguments, you should do this: '-d', '*/' instead of '-d */'. Whenever you have a whitespace (excluding strings) it should be a separate argument. Ex

command -a -b 1 -c "hello world" --bar

translates to: 'command', '-a', '-b', 1, '"hello world"', '--bar'

[andersevenrud]

// You can kill long running processes

I guess I should update the wording here. Might not be immediately obvious that method is meant for manually killing a process instead of waiting for it to close by itself or that the process does not close without a signal (like a command prompt or something with a loop in it).Hence the "long running" in that comment.

[mahsashadi]

Thanks a lot.
using .exec(cmd, ...args) => Promise<{code, stdout, stderr}> completely solved my problem

[andersevenrud]

Great!

[miladhashemi]

customProc.pty('ls').then(p => {
    // Process events
    p.on('data', str => console.log(str));
    p.on('exit', () => console.log('EXITED'));
    p.on('error', error => console.error(error)); // Spawn errors
    // Send data to the shell
    // p.send('Hello World\n');
    // You can kill long running processes
    // p.kill();
  });

I tested this code on the file manager context menu.

[andersevenrud]

I tested this code on the file manager context menu.

And ?

[miladhashemi]

And ?

....and without killing process, sometimes I get EIO error, and I can't find out what is source of this error. I know pty is used when we are using interactive sell or we want to stream... but this error isn't clear for me why some time it thrown.

[andersevenrud]

Since it's intermittent it has to be some kind of race condition on the server end. Do you still get the output data in this case ?

Also, try using .spawn() instead of .pty().

[miladhashemi]

Do you still get the output data in this case ?

Yes, almost always i get data as output.

Also, try using .spawn() instead of .pty().

I tested command with .spawn, .exec. But just in .pty i get this error.

[andersevenrud]

Yes, almost always i get data as output.

If it's not definitively always, then we do have some sort of racing condition going on here.

As I mentioned in an earlier comment, the EIO error is explained by this behavior.

So I guess I have to do some testing on my own to reproduce this.

Just to make sure I have the same setup, what node version are you running ?

[miladhashemi]

Just to make sure I have the same setup, what node version are you running ?

node v12.18.0

[andersevenrud]

I can confirm the same issue on latest node v14. So I'll look for a fix.

[andersevenrud]

Update: I only get this on PTY however. .spawn() works as expected.

[miladhashemi]

Update: I only get this on PTY however. .spawn() works as expected.

Yes, only .pty() is thrown this error. .spawn() and .exec() works fine.

[andersevenrud]

Oh. I now realize I read your comment wrong!

It seems that this is a problem with node-pty though and not something I really can fix on my end 🤔

• EIO when process ends microsoft/node-pty#178
• data events can be fired after exit is fired microsoft/node-pty#72

There's mention of a workaround, but it would have to be added by the developer using this feature, sadly.

I'll re-open this issue and do some deeper investegation when I have some more time to spare.

[miladhashemi]

but my host was ubuntu! 🤔

[andersevenrud]

The distro does not matter it seems. I get the same on Arch and Gentoo as well with the node-pty library.