Concurrent requests on same connection?

[basickarl]

I'm running a for loop which invokes 15+ ssh2 connections.

// more code...
const ssh = new SSH({});
await ssh.connect({
        host: host,
        username: user,
        port: port,
        privateKey: key,
    });

I run this 15 times in a for loops quickly, creating concurrent ssh requests (or at least trying to create concurrent requests).

await ssh.execCommand(cmd);

I get the following error on all of the connections except the first one:

{ Error: (SSH) Channel open failure: open failed
    at SSH2Stream.onFailure (/builds/b/e/node_modules/node-ssh/node_modules/ssh2/lib/client.js:1068:13)
    at Object.onceWrapper (events.js:316:30)
    at emitOne (events.js:115:13)
    at SSH2Stream.emit (events.js:210:7)
    at parsePacket (/builds/b/e/node_modules/ssh2-streams/lib/ssh.js:3423:10)
    at SSH2Stream._transform (/builds/b/e/node_modules/ssh2-streams/lib/ssh.js:551:13)
    at SSH2Stream.Transform._read (_stream_transform.js:190:10)
    at SSH2Stream._read (/builds/b/e/node_modules/ssh2-streams/lib/ssh.js:212:15)
    at SSH2Stream.Transform._write (_stream_transform.js:178:12)
    at doWrite (_stream_writable.js:371:12)
    at writeOrBuffer (_stream_writable.js:357:5)
    at SSH2Stream.Writable.write (_stream_writable.js:274:11)
    at Socket.ondata (_stream_readable.js:626:20)
    at emitOne (events.js:115:13)
    at Socket.emit (events.js:210:7)
    at addChunk (_stream_readable.js:250:12) reason: 'CONNECT_FAILED', lang: '' }

This leads me to understand that this package does not support concurrent requests on the same connection? I'm guessing I must open a new connection per request?

[steelbrain]

The package does support concurrent connections but there's usually a limit by the server on how much concurrent requests can be run on a connection.

You should not use a for loop to invoke asynchronous methods, you should do them in a pool with a max number or chain-them up or await 1 by 1.

That's just my personal opinion. The error seems to be coming from the base library, you could ask the author why this is happening. My rough guess would be rate limiting on the server side.

[martinlevesque]

Hey,

I am having the same issue - it crashes the server even if I catch all errors. Will investigate the issue and report it here if I find how to fix it.

[martinlevesque]

So for me, increasing significantly the MaxSessions in the sshd_config fixed the issue. When you don't set it with OpenSsh, MaxSessions = 10

[steelbrain]

Thanks for reporting the fix that worked for you @martinlevesque

Cheers