ssh2-sftp-client crashes Node process with no error and exit code 0

I have an issue which looks exactly like this one https://github.com/theophilusx/ssh2-sftp-client/issues/49

I’m using:

• Node.js 12
• ssh2-sftp-client 4.1.0

Here is a minimal reproducible code

const Client = require('ssh2-sftp-client')
const inspect = require('util').inspect

const sftpClient = new Client();

sftpClient.on('error', (err) => {
  console.log('SFTP client emitted ERROR: ' + inspect(err))
})
sftpClient.on('end', () => {
  console.log('SFTP client emitted END')
})
sftpClient.on('finish', () => {
  console.log('SFTP client emitted FINISH')
})
sftpClient.on('close', () => {
  console.log('SFTP client emitted CLOSE')
})

const options = {
  host: '',
  port: '22',
  username: '',
  password: ''
};

// below infinite loop is to simulate large number of 
// connections in my production code
(async () => {
  while (true) {
    try {
      await new Promise(resolve => setTimeout(() => resolve(sftpClient.connect(options)), 1000))
    } catch {
      console.log('boom')
    }
  }
})()

process.on('exit', code => console.log(`Catched!. Exit code: ${code}`))

process.on('uncaughtException', (err, origin) => {
  console.error('Unhandled exception. Please handle!', err.stack || err)
  console.error(`Origin: ${JSON.stringify(origin)}`)
})

process.on('unhandledRejection', (err, promise) => {
  console.error('Unhandled promise rejection. Please handle!', promise, err.stack || err)
})

process.on('warning', (warning) => {
  console.warn(warning.name)
  console.warn(warning.message)
  console.warn(warning.stack)
})

process.on('rejectionHandled', (promise) => {
  console.log('rejectionHandled event triggered')
})

As you can see, it shouldn’t escape the infinite loop unless there is an Error. And it in fact does not for some iterations but eventually it escapes (usually after <10 iterations). And the only log I see is

SFTP client emitted END
Catched!. Exit code: 0

On the SFTP server side I have the following limitations in the sshd_config file

MaxSessions 1
MaxStartups 1

I don’t know how is it possible to exit with code 0 without any error trace without actually calling process.exit(0). This makes investigation even harder, because I don’t know what to look for.

[theophilusx]

The workaround is now in the main branch of the repository. I will probably release an updated version in the next day or so. In the meantime, you can use the repository code directly.

The basic workaround was to add a listener for the end event which will reject the connect promise if an end event is triggered during the connection process. See the repository for details.

Lam Tran [e-mail] writes:

@theophilusx can you share your workaround for this issue? I’m also experiencing it and it’s quite critical for us. Thank you.

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or mute the thread.

– Tim Cross

[lojzatran]

@theophilusx can you share your workaround for this issue? I’m also experiencing it and it’s quite critical for us. Thank you.