Running the netlet with Jnode

Recall that we run the netlet like this:

% jnode 201 -netlet-stdio hello1-client.xml
Jnode starting...
Initialising Nodality...
Bootstrap starting
starting hello1-client
netlet:201.0.1: Hello, world, and thank you for using our service
Bootstrap complete
^C

% 

We run it in Jnode, which is just Nodality with a command line start-up. The arguments we've given it are:

1. An arbitrary node ID. This is required.
2. An option telling it to output standard I/O from netlets. This means we can see the System.out.println() from our netlet. Without this option set, we couldn't.
3. The descriptor for our netlet.

At the end, we need to hit Control-C to stop Jnode.

A word about the output. There are two kinds of output we see from Jnode. First, there is the output from the Jnode application itself. This is text which doesn't start with number sequences, such as ``Bootstrap starting''.

Second is the standard output from the netlets, from System.out.println() and so forth. Of course, this only appears if we've set the right option on the Jnode command line, which in this case we have. Each line of netlet output is preceded by a number sequence a.b.c--in this case 200.0.1. The first number is the node ID we gave Jnode. The second number is an ``accounting group''. Every netlet runs in an accounting group so the node can manage costs and (potentially) charge the right person. The third number is the netlet number within that accounting group.

Jnode buffers netlets' output, which means we may see output from different netlets in an order different from which they actually occurred. This doesn't affect us this time, but will when we run several netlets from the Jnode command line.

Meanwhile, Jnode doesn't buffer its own output. Again, this means its output may appear in a sequence slightly different from what actually happens in relation to its netlets. For example, netlet initialisation occurs during Jnode's bootstrap sequence, and our netlet prints output during this, but we may see ``Bootstrap complete'' before we see the netlet's output. Or we may see it the other way round.