Re: Why does node's Toolkit for i, use a database connection to execute CL commands? -- WEB400

I think it depends on whether or not that line of code is in the main app code or in a callback. If the former then I would say it is blocking - but too minute to be noticed. If you put a trillion identical lines in the main code you might notice it, but not if you did the same in a callback.

Sent from my iPad

On 13 Oct 2015, at 21:12, Aaron Bartell <aaronbartell@xxxxxxxxx> wrote:

So what you are saying is that the call to read the data queue is part of

the DB2 adapter, and stays in the program stack until it completes rather
than dropping something on the "web api" stack.

Correct, and the way Node.js gets around that is through handing stuff off
to C as a separate thread in the same process (aka IBM i job). This is why
you'll see debates on the web about whether Node.js is single threaded or
multi threaded. In literal context Node.js is strictly single threaded BUT
there can be additional threads in the same Node.js process if the
particular Node.js API (i.e. fs.readFile) implements C code under the
covers that creates a new/separate thread.

At least that's my understanding of it.

One thing I've been pondering but am not sure what audience to ask... I do
believe everything in Javascript is blocking in nature. For example, the
below line of code blocks the Node.js thread until it is complete. The
thing is it completes really fast, so it doesn't often get put into the
category of "code that blocks". Instead only file system, networking, and
database IO gets put into the "code that blocks" category because it blocks
for long(er). Anybody know if that is a correct train of thought?

var x = 123;

Aaron Bartell
litmis.com - Services for open source on IBM i

On Tue, Oct 13, 2015 at 3:01 PM, Mark Murphy/STAR BASE Consulting Inc. <
mmurphy@xxxxxxxxxxxxxxx> wrote:

So what you are saying is that the call to read the data queue is part of
the DB2 adapter, and stays in the program stack until it completes rather
than dropping something on the "web api" stack. That makes more sense. I
like the animations, and the little tool behind this video. Makes it easier
to understand what is going on.

Mark Murphy
STAR BASE Consulting, Inc.
mmurphy@xxxxxxxxxxxxxxx

-----Aaron Bartell <aaronbartell@xxxxxxxxx> wrote: -----
To: "Web Enabling the IBM i (AS/400 and iSeries)" <web400@xxxxxxxxxxxx>
From: Aaron Bartell <aaronbartell@xxxxxxxxx>
Date: 10/13/2015 03:28PM
Subject: Re: [WEB400] Why does node's Toolkit for i, use a database
connection to execute CL commands?

Awhile back I dug deep to learn about the Node.js/Javascript event loop. I
found the following and I'd highly recommend watching it.
http://latentflip.com/loupe

The kicker that breaks a single Node process is when something is blocking
in nature, and that can happen simply by writing a bit of Javascript
incorrectly (assuming the intention was to NOT block). Note, currently the
DB2 adapter for Node.js is blocking. This more or less necessitates
multiple Node.js processes so you don't end up with a waiting line of web
requests.


Aaron Bartell
litmis.com - Services for open source on IBM i

On Tue, Oct 13, 2015 at 2:06 PM, Mark Murphy/STAR BASE Consulting Inc. <
mmurphy@xxxxxxxxxxxxxxx> wrote:

I recognize this technique, but, due to my knowledge of node being

limited

at best, I have to wonder if this is an appropriate technique using node.
That is, since Node is event driven, should there be a need to wait, and
then loop around and check conditions again. RPG is not event driven,

hence

the need for such a loop. But I was under the impression that Node

already

incorporates this event loop and will call the appropriate function when
the event occurs. I would expect to have to register to receive the event
in some way, but not to have to code the event loop.

Mark Murphy
STAR BASE Consulting, Inc.
mmurphy@xxxxxxxxxxxxxxx

-----Kevin Turner <kevin.turner@xxxxxxxxxxxxxxx> wrote: -----
To: "Web Enabling the IBM i (AS/400 and iSeries)" <web400@xxxxxxxxxxxx>
From: Kevin Turner <kevin.turner@xxxxxxxxxxxxxxx>
Date: 10/11/2015 04:44PM
Subject: Re: [WEB400] Why does node's Toolkit for i, use a database
connection to execute CL commands?

That's interesting stuff - thanks. I'm not entirely sure how to dig

deeper

but I will try :)

On 11 Oct 2015, at 17:47, Richard Schoen <

Richard.Schoen@xxxxxxxxxxxxxxx>

wrote:

I wonder if the loop is forcing a new job start each time on the i.

With XMLCGI, there is an IPC service that takes a few seconds each time

it's re-initiated and I could see this being intensive if you had to

create

a new session for each interaction.

You can start the IPC session with a unique name and use the same job

over and over if I want to maintain state and use the same job on the I
which should improve performance I think.

Not sure how the node toolkit works, but this works good with .Net and

should be similar depending on how the toolkit was implemented.

Regards,

Richard Schoen | Director of Document Management Technologies,

HelpSystems

T: + 1 952-486-6802
RJS Software Systems | A Division of HelpSystems
richard.schoen@xxxxxxxxxxxxxxx
www.rjssoftware.com
Visit me on: Twitter | LinkedIn
----------------------------------------------------------------------

message: 1
date: Sat, 10 Oct 2015 22:32:23 +0000
from: Kevin Turner <kevin.turner@xxxxxxxxxxxxxxx>
subject: Re: [WEB400] Why does node's Toolkit for i, use a database
connection to execute CL commands?

It may or may not be of interest or relevant, but we have lots of code

that sits and waits of data on a keyed data queue. It waits for 5 seconds
then loops round and checks some stuff (like an instruction to end) then
waits again.

When I did the same in a node app using itoolkit, the LPAR simply died

on its feet. It wasn't obvious why because the node app was not showing

up

as using much CPU. However it certainly was the culprit - I changed to

wait

for 60 seconds instead as it wasn't essential to loop every 5 secs. The
problem went away.

On 10 Oct 2015, at 15:58, Nathan Andelin <nandelin@xxxxxxxxx> wrote:

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CoralTree Systems Limited
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PO15 5TT

Company Registration Number 5021022.
Registered Office:
12-14 Carlton Place
Southampton, UK
SO15 2EA
VAT Registration Number 834 1020 74.