Monthly Archives: Maggio 2021

Modern Applications – Episod 2: Ports & Networking

As written in the last article a container can manage more images.

Picture 1 shows an example of three different workloads running in a single container.

Picture 1

It’s possible to work with different versions of the same image also.

For example, MySQL has several images that can be installed and run to the same container.

Note 1: Nowadays MySQL available images are:

  • 8.0.25, 8.0, 8, latest
  • 5.7.34, 5.7, 5
  • 5.6.51, 5.6

Picture 2 shows a container where three different images run with two kinds of version applications.

Picture 2

Let’s digress slightly talking about how a service is built.

Most of the time it is made by grouping applications that means grouping several types of images.

The question is: How do images talk to each other?

The answer is quite easy. They talk through the networks, where IP addresses and ports are in charge of the communication to and from the applications (picture 3).

Picture 3

There is just a simple rule to remember when a container network architecture is deployed.

As shown in picture 4, if the ports used by a running image can be the same for different applications (in example 161616), the port assigned to the back-end server must be always different (4000,40001,4002).

Note 2: The port numbers are just an example also because the port with the higher number is 216 = 65535.

Picture 4

Wrap-up: The binding network architecture is completely allowed but the host back-end port can’t expose the same port number to more than one service.

Let’s go deeper into networking in the Container environment:

The network’s topology is defined by the used drivers.

They can be:

1. Host

When the container comes up it attaches its ports to the host network directly.

In this way, it shares the TCP/IP stack and the Host NameSpace.

The segregation is guaranteed by Docker technology (Picture 5)

Picture 5

2. Bridge

This is the default network mode.

It creates an isolated bridge network where the containers run inside a range of IP addresses.

In the previous scenario, the containers can talk to each other but no connection is allowed from outside.

To allow communication with external service in Docker, it’s necessary to start docker with the -p option.

docker run -pserverport:containerport nameservice (ie: docker run -p2400:2451 mysql)

port 2400 is now working with 2451

From a security point of view, it is amazing. You can monitor and select which ports are going to be used for a service (Picture 6)

Picture 6

3. Overlay

If the previous technologies are single-host networking topology, the Overlay allows communication among the container hosted in different hosts.

This scenario requires cluster intelligence to manage the traffic and guarantee segregation. It could be Swarm or Kubernetes (picture 7)

The technology core that allows it is vxlan that creates a tunnel on top of the underlay network and it is part of the operating system

The traffic is encrypted (AES) with a rotating password.

When a service is exposed (-p option wrote before), all traffic is automatically routed, nevermind where the service is running

More interesting details: each container has two IP addresses: the first one insists on the overlay network and is used by the containers to talk to each other (internal). The second address is for vxlan and allows the traffic to outside.

Picture 7

4. Null (Black box)

No network connection

5. MacVLan

It’s possible to implement a MacVLan through a driver. The scope is giving to the network container the behaviour of a traditional network. It’s necessary that the network accepts the promiscuous mode.

That’s all for now. Take care and see you soon.

Thanks -Grazie – Merci – Gracias

Thank you (different languages): Amazon.it: Appstore per Android

Dopo 14 mesi di attività a supporto del bridge online e con il ritorno alle normali attività di gioco dei circoli, da lunedì 17 maggio il sito non ospiterà con regolarità i servizi di prenotazione e classifica dei tornei online.

Ringrazio tutti coloro che hanno collaborato e reso possibile continuare a praticare il nostro gioco di carte preferito, durante uno dei momenti più tristi e sfidanti della nostra vita.

Arrivederci al tavolo 🙂

Gable

——

After 14 months of activities in support of online bridge and with the return to face to face activities of the clubs, from Monday 17th May the site will not regularly host the booking and ranking services of online tournaments.

I thank all those who collaborated and made it possible to continue practicing our favorite card game, during one of the saddest and most challenging moments of our life.

See you at the table 🙂

Gable

Modern Applications – Episod 1: Foundamentals

Introduction

This is the first of a group of articles about the technologies that can modernize the applications.

The scope is helping the reader to understand the potentiality of this new way to make business allowing the Companies to be more competitive.

These articles follow my personal approach and studies of Kubernetes.

I’m paying attention to how to make services available and protected by exploiting internal and external native technologies

Let’s start !!!

What is a container

It’s a way to package the applications with their pertinent dependencies and configurations in just one block.

There are at least two big advantages of this approach:

  • The container for his native architecture is portable. It means you can run it in any architecture wherever they are located. (please read the previous article about Digital Transformation and Cloud Mobility)
  • Deploying services prove easier and more efficient than in the traditional world because there are already plenty of software images ready to be used.

Where can I download images to run to the containers?

There are public and private Repositories (please do not mess it with a VBR Repository).

The most famous container technology is Docker that has a public repository called docker hub.

What is a container exactly?

A container allows isolated images to run to an operating system.

Container vs Virtual Machine

The difference between the two architecture seems to be very tiny but actually, they represent two worlds.

The two technologies are virtualization tools but if Docker focuses on the applications layer (picture 1),  VM puts its attention to Kernel and application (picture 2)

Picture 1

Picture 2

Which are the main advantages of this new approach:

  • The container has a small footprint (few MB compare to GB).
  • The boot is faster.
  • Easier compatibility list.
  • It can run in all common operating systems, such as Windows, Mac-OS, Linux.

Container vs Image

It’s crucial to the next articles to have very clear the difference between a container and an image.

Let’s help ourselves through picture #3 that shows the application composition.

There are four main elements:

  1. Image: It’s the code written by developers. It is downloaded from Repositories.
  2. Configuration: It represents the setup created to allow the application to run.
  3. File System: It’s the place where the application and its data are stored.
  4. Network: It allows all components to talk to each other.

The container is where the application runs.

Picture 3

Note 1: Images are part of the container. Think of the container as a multitasking OS specialized to run applications simultaneously.

Note 2: To get info about Docker, please refer to the official website.                I.E.: to run an image just launch the following command:                                  docker run image-name

Note 3: There are more Container technologies; the most common are:

  • RTK (CoreOS)
  • LXC
  • LXD (Canonical)
  • Linux VServer
  • OpenVZ/Virtuozzo 7
  • runC

That’s all for now,  see you soon and take care.