DESCRIPTION

Use node-control to define ssh and scp tasks for system administration and code
deployment and execute them on one or more machines simultaneously.  The
implementation and API is completely asynchronous, allowing coding of tasks
according to Node conventions and control of many machines in parallel.
Strong logging creates a complete audit trail of commands executed on remote
machines in logs easily analyzed by standard text manipulation tools. 

The only dependency is OpenSSH and Node on the local control machine. Remote
machines simply need to have a standard sshd daemon running.



QUICK EXAMPLE

To get the current date from the three machines listed in the 'mycluster'
config task as the 'mylogin' user with a single command:

var control = require('./node-control'),
    task = control.task;

task('mycluster', 'Config for my cluster', function () {
    var config, addresses;
    config = {
        user: 'mylogin'
    };
    addresses = [ 'a.mydomain.com',
                  'b.mydomain.com',
                  'c.mydomain.com' ];
    return control.hosts(config, addresses); 
});

task('date', 'Get date', function (host) {
    host.ssh('date');
});

control.begin();


If saved in a file named 'mycontroller.js', run with:

node mycontroller.js mycluster date


Each machine is contacted in parallel, date is executed, and the output from
the remote machine is printed to the console. Example output:

 Performing mycluster
 Performing date for a.mydomain.com
a.mydomain.com:mylogin:ssh: date
 Performing date for b.mydomain.com
a.mydomain.com:mylogin:ssh: date
 Performing date for c.mydomain.com
a.mydomain.com:mylogin:ssh: date
a.mydomain.com:stdout: Sun Jul 18 13:30:50 UTC 2010
a.mydomain.com:exit: 0
b.mydomain.com:stdout: Sun Jul 18 13:30:50 UTC 2010
c.mydomain.com:stdout: Sun Jul 18 13:30:50 UTC 2010
b.mydomain.com:exit: 0
c.mydomain.com:exit: 0
           

Each line of output is labeled with the address of the host the command was
executed on. The actual command sent and the user used to send it is
displayed. stdout and stderr output of the remote process is identified
as well as the final exit code of the local ssh command. Each line also appears
timestamped in a hosts.log file in the current working directory.



CODE DEPLOYMENT EXAMPLE

A task that will upload a local zip file containing a release of a node
application to a remote machine, unzip it, and start the node application.

var path = require('path');

task('deploy', 'Deploy my app', function (host, release) {
    var basename = path.basename(release),
        remoteDir = '/apps/',
        remotePath = path.join(remoteDir, basename),
        remoteAppDir = path.join(remoteDir, 'myapp');
    host.scp(release, remoteDir, function () {
        host.ssh('tar xzvf ' + remotePath + ' -C ' + remoteDir, function () {
            host.ssh("sh -c 'cd " + remoteAppDir + " && node myapp.js'"); 
        });
    });
});

Execute as follows, for example:

node mycontroller.js mycluster deploy ~/myapp/releases/myapp-1.0.tgz


A full deployment solution would deal with shutting down the existing
application and have different directory conventions. node-control does not
assume a particular style or framework, but provides tools to build a
custom deployment strategy for your application or framework.



INSTALLATION

Clone this repository with git or download the latest version using the GitHub
repository Downloads link. Then use as a standard Node module by requiring the
node-control directory.

If you use npm:

npm install control


If you install the npm package, use this require statement:

var control = require('control');



CONFIG TASKS

In node-control, you always call two tasks on the command line when doing
remote operations. The first task is the config task, which must return an
array of host objects. Each host object represents a single host and has its
own set of properties. The hosts() method exported by control.js allows you to
take a single object literal config and multiply it by an array of addresses to
get a list of host objects that all (prototypically) inherit from the same
config:

task('mycluster', 'Config for my cluster', function () {
    var config, addresses;
    config = {
        user: 'mylogin'
    };
    addresses = [ 'a.mydomain.com',
                  'b.mydomain.com',
                  'c.mydomain.com' ];
    return control.hosts(config, addresses); 
});


Config tasks enable definition of reusable work tasks independent of the
machines they will control. For example, if you have a staging environment with
different machines than your production environment you can create two
different config tasks returning different hosts, yet use the same deploy task:

node mycontroller.js stage deploy ~/myapp/releases/myapp-1.0.tgz
... 
node mycontroller.js production deploy ~/myapp/releases/myapp-1.0.tgz



HOST OBJECTS

Each host object returned by the config task is independently passed to the
second task, which is the work task ('deploy' in the above example). The host
object is always passed to the work task's function as the first
argument:

task('date', 'Get date', function (host) {


The host object allows access to all the properties defined in the config and
also provides the ssh and scp methods for communicating with the remote 
machine. 

The ssh method takes one argument - the command to be executed on the
remote machine. The scp method takes two arguments - the local file path and the
remote file path. 

Both ssh and scp methods are asynchronous and can additionally take a callback
function that is executed once the ssh or scp operation is complete. This
guarantees that the first operation completes before the next one begins on
that host:

    host.scp(release, remoteDir, function () {
        host.ssh('tar xzvf ' + remotePath + ' -C ' + remoteDir, function () {


Callbacks can be chained as far as necessary.



ARGUMENTS

Arguments on the command line after the name of the work task become arguments
to the work task's function:

task('deploy', 'Deploy my app', function (host, release) {


This command:

node mycontroller.js stage deploy ~/myapp/releases/myapp-1.0.tgz


Results in release = '~/myapp/releases/myapp-1.0.tgz'.

More than one argument is possible:

task('deploy', 'Deploy my app', function (host, release, tag) {



BEGIN

To execute the tasks using a tasks file, use the begin() method at the
bottom of the tasks file:

var control = require('./node-control');
... // Define tasks
control.begin();

begin() calls the first (config) task identified on the command line to get the
array of host objects, then calls the second (work) task with each of the host
objects. From that point, everything happens asynchronously as all hosts work
their way through the work task.



PERFORMING MULTIPLE TASKS

A task can call other tasks using perform() and optionally pass arguments to
them:

var perform = require('./node-control').perform;
...
task('mytask', 'My task description', function (host, argument) {
    perform('anothertask', host, argument);


perform() requires only the task name and the host object. Arguments are
optional. If the other task supports it, optionally pass a callback function as
one of the arguments:

    perform('anothertask', host, function () {


Tasks that support asynchronous performance should call the callback function
when done doing their own work. For example:

task('anothertask', 'My other task description', function (host, callback) {
    host.ssh('date', function () {
        if (callback) {
            callback();
        }
    });
});


The peform() call can occur anywhere in a task, not just at the beginning.



LIST TASKS

To list all defined tasks with descriptions:

node mycontroller.js mycluster list



NAMESPACES

Use a colon, dash, or similar convention when naming if you want to group tasks
by name. For example:

task('bootstrap:tools', 'Bootstrap tools', function (host) { 
...
task('bootstrap:compilers', 'Bootstrap compilers', function (host) { 



SUDO

To use sudo, just include sudo as part of your command:

    host.ssh('sudo date');


This requires that sudo be installed on the remote machine and have requisite
permissions setup.



ROLES

Some other frameworks like Vlad and Capistrano provide the notion of roles for
different hosts. node-control does not employ a separate roles construct. Since
hosts can have any properties defined on them in a config task, a possible
pattern for roles if needed:

task('mycluster', 'Config for my cluster', function () {
    var appConfig, dbConfig, dbs, apps;

    dbConfig = {
        user: 'dbuser',
        role: 'db'
    };

    dbs = control.hosts(dbConfig, ['db1.mydomain.com', 'db2.mydomain.com']);

    appConfig = {
        user: 'appuser',
        role: 'app'
    };
    apps = control.hosts(appConfig, ['app1.mydomain.com', 'app2.mydomain.com']);

    return dbs.concat(apps); 
});

task('deploy', 'Deploy my app', function (host, release) {
    if (host.role === 'db') {
        // Do db deploy work
    }

    if (host.role === 'app') {
        // Do app deploy work
    }
});



LOGS

All commands sent and responses received are logged with timestamps (from the
control machine's clock). By default, logging goes to a hosts.log file in the
working directory of the node process. However, you can override this in your
control script:

task('mycluster', 'Config for my cluster', function () {
    var config, addresses;
    config = {
        user: 'mylogin',
        log: '~/mycluster-control.log'
    };
    addresses = [ 'myhost1.mydomain.com',
                  'myhost2.mydomain.com',
                  'myhost3.mydomain.com' ];
    return control.hosts(config, addresses); 
});

Since each host gets its own log property, every host could conceivably have
its own log fie. However, every line in the log file has a prefix that includes
the host address so, for example: 

grep myhost1.mydomain.com hosts.log | less


Would allow paging the log and seeing only lines pertaining to
myhost1.mydomain.com.


If you send something you do not want to get logged (like a password) in a
command, use the log mask:

host.logMask = secret;
host.ssh('echo ' + secret + ' > file.txt');


The console and command log file will show the masked text as asterisks instead
of the actual text.



SSH

To avoid repeatedly entering passwords across possibly many hosts, use standard
ssh keypair authentication. 

Each host.ssh() call requires a new connection to the host. To configure ssh to
reuse a single connection, place this:

Host *
ControlMaster auto 
ControlPath ~/.ssh/master-%r@%h:%p


In your ssh config file (create if it does not exist):

~/.ssh/config


To pass options to the ssh command when using ssh(), add the option or options
as an array to the sshOptions property of the config, or concat the option or
options to the host object sshOptions property prior to executing the command:

    // Config task
    config = {
        user: 'mylogin',
        sshOptions = [ '-2', '-p 44' ]
    };

    // Work task
    host.sshOptions = host.sshOptions.concat('-v');



FEEDBACK

Feedback welcome at node@thomassmith.com or the Node mailing list.