JavaScript

SSH Parallel Remote Commands on Multiple Servers

Demonstrates running the same command on several servers simultaneously. It is simply a matter of using one Ssh object per server, starting the command on each with QuickCmdSend, and then polling each connection with QuickCmdCheck until all have finished.

Background: This is the fan-out pattern behind configuration-management and monitoring tools: query or update a whole fleet in roughly the time the slowest single host takes, rather than the sum of all of them. Each server needs its own object because each has its own connection and authentication state. Note that results come back in whatever order the servers finish, which is why the example tracks completion per connection. Production code would keep the objects in arrays instead of repeating the logic per server.

Note

This example is intended for running within a Chilkat.Js embedded JavaScript engine. All Chilkat JavaScript examples require Chilkat v11.4.0 or greater.

JavaScript

var success = false;

//  This example requires the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

//  Demonstrates running the same command on several servers simultaneously.  It is simply a
//  matter of using one Ssh object per server.

var ssh1 = new CkSsh();
var ssh2 = new CkSsh();
var ssh3 = new CkSsh();

var port = 22;

//  Normally you would not hard-code the password in source.  You should instead obtain it
//  from an interactive prompt, environment variable, or a secrets vault.
var password = "mySshPassword";

success = ssh1.Connect("ssh-server1.example.com",port);
if (success == false) {
    console.log(ssh1.LastErrorText);
    return;
}

success = ssh1.AuthenticatePw("mySshLogin",password);
if (success == false) {
    console.log(ssh1.LastErrorText);
    return;
}

success = ssh2.Connect("ssh-server2.example.com",port);
if (success == false) {
    console.log(ssh2.LastErrorText);
    return;
}

success = ssh2.AuthenticatePw("mySshLogin",password);
if (success == false) {
    console.log(ssh2.LastErrorText);
    return;
}

success = ssh3.Connect("ssh-server3.example.com",port);
if (success == false) {
    console.log(ssh3.LastErrorText);
    return;
}

success = ssh3.AuthenticatePw("mySshLogin",password);
if (success == false) {
    console.log(ssh3.LastErrorText);
    return;
}

//  This command sleeps for 5 seconds and then prints the system date/time, making the parallel
//  execution easy to observe.
var cmd = "sleep 5; date";

//  Start the command on each server.  QuickCmdSend returns immediately.
var channel1 = ssh1.QuickCmdSend(cmd);
if (channel1 < 0) {
    console.log(ssh1.LastErrorText);
    return;
}

var channel2 = ssh2.QuickCmdSend(cmd);
if (channel2 < 0) {
    console.log(ssh2.LastErrorText);
    return;
}

var channel3 = ssh3.QuickCmdSend(cmd);
if (channel3 < 0) {
    console.log(ssh3.LastErrorText);
    return;
}

//  The command is now running on all three servers at once.  Poll each connection until every
//  command has finished.  (Production code would keep the objects in arrays rather than
//  repeating the logic.)
var pollTimeoutMs = 50;
var numFinished = 0;
var finished1 = false;
var finished2 = false;
var finished3 = false;

while (numFinished < 3) {
    if (!finished1) {
        var ch1 = ssh1.QuickCmdCheck(pollTimeoutMs);
        if (ch1 == -2) {
            console.log(ssh1.LastErrorText);
            return;
        }

        if (ch1 >= 0) {
            console.log("---- ssh1 channel " + ch1 + " finished ----");
            var out1 = ssh1.GetReceivedText(ch1,"utf-8");
            if (ssh1.LastMethodSuccess == false) {
                console.log(ssh1.LastErrorText);
                return;
            }

            console.log(out1);
            finished1 = true;
            numFinished = numFinished+1;
        }

    }

    if (!finished2) {
        var ch2 = ssh2.QuickCmdCheck(pollTimeoutMs);
        if (ch2 == -2) {
            console.log(ssh2.LastErrorText);
            return;
        }

        if (ch2 >= 0) {
            console.log("---- ssh2 channel " + ch2 + " finished ----");
            var out2 = ssh2.GetReceivedText(ch2,"utf-8");
            if (ssh2.LastMethodSuccess == false) {
                console.log(ssh2.LastErrorText);
                return;
            }

            console.log(out2);
            finished2 = true;
            numFinished = numFinished+1;
        }

    }

    if (!finished3) {
        var ch3 = ssh3.QuickCmdCheck(pollTimeoutMs);
        if (ch3 == -2) {
            console.log(ssh3.LastErrorText);
            return;
        }

        if (ch3 >= 0) {
            console.log("---- ssh3 channel " + ch3 + " finished ----");
            var out3 = ssh3.GetReceivedText(ch3,"utf-8");
            if (ssh3.LastMethodSuccess == false) {
                console.log(ssh3.LastErrorText);
                return;
            }

            console.log(out3);
            finished3 = true;
            numFinished = numFinished+1;
        }

    }

}

ssh1.Disconnect();
ssh2.Disconnect();
ssh3.Disconnect();