Predrag Stojadinović

ReSynkd Demo 1

ReSynkd – Observable pattern through WebSockets
GitHub: https://cope.github.io/resynkd/
NPM: https://www.npmjs.com/package/resynkd

First Demo:

By Predrag, 4 years18.07.2020. ago

MongoDB Change Streams on localhost with NodeJS

If you want to play with MongoDB Change Streams on your local machine, you will have to convert your mongo instance to a replica set.

There is a tutorial on mongodb.com on how to do that, but I found that I needed some help on getting it working.

Oh, and you will need at least MongoDB 3.6 for Change Streams, so if you have an older version, you have to upgrade it first…

Anywho, here is everything I had to do to make it work on my Windows machine.

First, I stopped my mongo service.

Then I looked into my mongod.cfg file and saw that it looked something like this:

systemLog:
    destination: file
    path: C:/mongodb/log/mongod.log
storage:
    dbPath: C:/mongodb/data

This turned out to be a problem, because we need to start the mongodb server with the replSet parameter set.

Long story short, I ended up converting that mongod.cfg file to this:

# data directory
dbpath=C:/mongodb/data

# log file
logpath=C:/mongodb/log/mongod.log
logappend=true

# replica set name
replSet=rs

Then I started the server, opened the mongo console, and executed:

rs.initiate()

Then I executed:

db.adminCommand( { setFeatureCompatibilityVersion: "3.6" } )

And checked that the change is good by executing:

db.adminCommand( { getParameter: 1, featureCompatibilityVersion: 1 } )

Then I restarted the server once more, just to be safe.

I then I added these few lines into my nodejs code, where I already had mongoose running with the User model:

const userChangeStream = User.watch([],	{fullDocument: "updateLookup"});
userChangeStream.on('change', (change) => {
	console.log(' - user change stream event:\n', change);
});

And I opened Robo 3T, changed the updatedAt field for a user, et voilà:

{
  "operationType": "update",
  "updateDescription": {
    "updatedFields": {
      "updatedAt": "2020-07-04T15:49:34.498Z"
    },
    "removedFields": []
  }
}

Change Streams are comming in 🙂

By Predrag, 4 years05.07.2020. ago

RethinkDB on Windows using VirtualBox

So, I wanted to install RethinkDB on my Windows machine and found out that it is still not supported. After a couple of weeks I decided to find my own solution.

Here it is.

First, I installed the VirtualBox.
I then downloaded Ubuntu and installed it on the box.

This was the result:

click to enlarge

I had issues with the Ubuntu resolution, so I installed VirtualBox Guest Additions
(note that the menu wording was slightly different then in the tutorial):

I then also ran sudo apt install virtualbox-guest-dkms in the console on Ubuntu.
I believe I restarted the VM several times between steps.

In the end, I was able to pick a better resolution:

I then set the VirtualBox Network Adapter for Ubuntu to Host-Only Adapter:

click to enlarge

This is important for accessing RethinkDB from your host machine.

In Ubuntu, I installed RethinkDB.

I set it up so that it starts at system startup.

And RethinkDB was up and running:

I then edited the instance1.conf file from the previous step, to set the bind=all value:

This is also important for accessing RethinkDB from your host machine.

You really should secure your cluster, even though it is a development system. If you do secure it, do not forget to include the user and password attributes in your connect call.

Once you have everything running, on your VirtualBox Ubuntu window, hover the mouse over the network icon to get the Ubuntu’s IP address.

If you do not see a tooltip with the IP address, make sure you select the Ubuntu window and give it focus, then hover again.

Use that IP address with :8080 appended to it, to access the RethinkDB web interface.

Also, use that IP address in your code, to connect to RethinkDB.

And this is my final result on my Windows machine IDE, with RethinkDB running in the VirtualBox. I ran the two scripts, index.js and listen.js in separate consoles, and when index.js makes a change to the tv_shows table, the listen.js script receives the change.

click to enlarge

By Predrag, 4 years13.06.2020. ago

Fun

NVIDIA Claw pizza :)

Well, OK, let’s just dive in, shall we?

Ingredients

Required:

1 frozen, or otherwise, pizza
any green vegetable you like (I used baby spinach leaves here)
egg whitess (how many? depends on the size of your pizza, doesn’t it?)

Optional:

Mozzarela, or any other white meltable cheese
Large ham slices (or any other thin, large edable thing you can use as base, IF you want to…)
egg yolks (you know, the leftovers from the required whites)

Preparation

Print the logo and cut out the green:

– make sure it is large enough to cover your pizza, and not larger… but also not too much smaller. You’ll figure it out…

Get a frying pan large enough to cover your pizza, and not too much larger… but also definitely not smaller! Again, you’ll figure it out…

Separate the egg whites.

I mixed the yolkes with spinach, later found out it did not matter, so…

Heat up some butter or oil in the pan. Add the egg whites and let them be, do not stir!

Once ready, take them out on some paper towels and dry them thoroughly.

Use towels on both sides, two plates larger enough, and flip a few times, using fresh paper towels.

Get some flat wooden surface and flip the eggs onto it.
I had a paper towel underneath, could be an issue in the next step when cutting… I managed.

Place the printed cutout on the eggs and go to work… You’ll figure it out…

You should end up with something like this:

IMPORTANT: Before flipping it back onto a plate, OIL the plate properly! Trust me, you will need the slipperynessness… ness… to get the eggs onto the pizza!