Cloud Native Computing Foundation KubeCon + CloudNativeCon North America 2021, 29 Oct 2021

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From YouTube: Deep Dive CoreDNS - Yong Tang, Ivanti Inc.; Miek Gieben, Independent; John Belamaric, Google

Description

Don’t miss out! Join us at our next event: KubeCon + CloudNativeCon Europe 2022 in Valencia, Spain from May 17-20. Learn more at https://kubecon.io The conference features presentations from developers and end users of Kubernetes, Prometheus, Envoy, and all of the other CNCF-hosted projects.

Deep Dive CoreDNS - Yong Tang, Ivanti Inc.; Miek Gieben, Independent; John Belamaric, Google

Best known for its ability to serve as the cluster DNS of Kubernetes, CoreDNS is a flexible and extensible DNS server with a focus on service discovery. The flexibility and extensibility of CoreDNS comes from its unique plugin-based architecture and its easy-to-use Corefile configurations. In this session, we will take a close look at the CoreDNS extension points for developers. We will learn how to build custom DNS applications based on CoreDNS, including: building a custom CoreDNS binary that includes external plugins; building a specialized binary that uses CoreDNS as a library; building your own CoreDNS plugin. We will also update the current state and the road map of CoreDNS for the near future.

A

Hello and welcome by uh the accordionist deep dive, uh my name is mikrivan. I started korean s 2018. I believe uh I'm still the project lead and I'm, of course, maintaining accordions.

A

I'm here with young to talk about, coordinates and some details about plugins yo.

B

Can you introduce yourself uh sure, hey everyone, uh thanks for coming to this session? My name is yong tang, I'm a maintenance for dns in today's coding session. There are several things we want to cover first, so we are going to give a brief introduction about coding ads and then we are going to discuss about the project update and what features has been added since last year. uh Next, we are going to discuss about the civic discovery with with dns and how coding is completely important role in this in this field.

B

Next we're going to showcase a small plugin and finally we're going to discuss about the audience community as well as a qra.

B

As many of you know, kodias is a flexibility and server reading goal. It has a focus on self-discovery one interesting feature. One interesting thing about coordinates is that the coordinates is plugin based, which means it can be easily extended.

B

If there's any new feature, you're interested, you can always add new feature yourself, and only you know how to write in gola since kubernetes 1013 for the united states in the default dns server, which means nowadays accordions, is used by many people under many institutions around the world in production systems, according has many features, coordinates supported. Dns dns, server, tos dns over grpc and also codings, has a wide range of support for cloud dns data sync up. For example, we have aws router, 3, azure dns and google cloud dns sync up.

B

Okay, now, let's come to the project update. Since last year we have released 1.8 of coordinates. 1.8.0 was released on october 22nd 2020.

B

There are several plugins introduced in 1.8, a transfer, plugin unifies all zone transfer code, local plugin answers, local queries and finally, minimal plugin provides minimal answers, which could be very, very useful if you want to reduce the traffic of the dns response in 1.8. There are also several backward incompatible change in transfer and the dns tab plugins.

B

If you ever attachable to plugin, you probably want to take a look to make sure you update your config file uh in case of the need, and also we have some other new up upstream features, including native plugin, that you want to take a look seems like endpoint slices could be very useful.

B

I'm going to discuss a little bit about service discovery and coordinates. As many of you know. In this day and age, you have a sdn which can give you all kind of ability for networking with sdn you can assign any endpoint to any ip address as needed. So some people ask the question: is dns still needed.

B

There are several reasons: dns is important. First of all, dns is nice in direction, and this is a new direction. You probably want when you deploy a production system. This indirection gives you the maximum flexibility and they see easy and simple to change.

B

The the reason why the flex battery is important is that as your company or your uh or your system grow, you probably face a question of skill up over time when you try to scale up dns, give you a very nice tool to achieve that goal. For example, one interesting setup with a database is that in many enterprises the database has been configured in a way such as read, write and the read access point as separated this gives you the ability to scale up as needed in the future.

B

If you, you have more customers and more customers that are reaching to your read-only database, but when you, when your startup is small and you want to go to get started, you can actually set the dns to be pointing to the same id address essentially only need one uh one database, but when you date away, when your user user base getting bigger, you actually can't just split up the read. Write endpoint with the ribbon point, essentially scaling up nicely with other without any interruptions.

B

This brings. Another feature of dns dns is distributed in nature and their skills to internet, and finally, dns is important in that the dns is very pervasive in it infrastructure. Even if you have your iot 6 admins are still maintaining a legacy system. They still probably need dns anyway,.

B

Many people ask a question about if there's a need to set up a dns server yourself, while nowadays you have a dns service provided by cloud windows. Sometimes you may still want to consider about if it's needed to set up a dns server.

B

There are several reasons for that: dns is a creative service, but at the same time it's simple uh dns has different music for public facing where you need your customer. Your customer may need to reach to you being, as it also could be internal, which means your service will needing us to find another service endpoint for quoting us coding.

B

Us has diversified the source of information with coding, as you can consolidate different sources like kubernetes like the cloud vendors like id infrastructures, all those dns records can be consolidated into one thing as a server, that's coordinates.

B

And finally, while all the cloud vendors support, many in the dns service and our cloud vendors claim that they have a hundred percent seo this essay, a hundred percent serie, could be misleading, while the uh wild seller has been specified with a hundred percent.

B

The the money you you spend on dna service for those club, vendors are actually very small, which means in case there is a service interruption. The service credit refund you're going to receive is also going to be very small. I'll just give my personal experience, which the company I work for last year, we have a downtime related to aw drop history.

B

Of course, after the downtime is over, we requested service credit, but to our surprise, we only get less than 50 percent of the money back about 50, but we only get 50 dollars of money back, of course that's better than nothing, but it does not help us anyway, and that actually is one thing we we are currently throwing.

B

That is, we are considering about a set of our own dns server, potentially with coding us, because dns is too critical and we cannot afford to have a downtime with no service credit refund guaranteed to recover our financial losses.

B

Okay, I'm going to hand over the slide to to me. Mik will go demo plugin for us.

A

Yeah, thank you. We're going to look at a small plugin, the demo plugin and then basically, depending on the client's source address. It will reply with uh ip111 or ip888, so it makes a tiny decision and then writes back this reply to the client. So we're going to.

B

A

How we're going to set this up in korean s and how this all works from code to actually running this next slide. Please.

A

So if you want to write a plugin for codiness, you need three methods for three functions: to be implemented: an init function, which basically tells coordinates that this plugin exists, a setup function that takes a caddy controller, which is basically the the core file. The config file that we have it parses the configuration and sets up internal structures.

A

It adds a handler to the convict object, object, which is a internal state in gordian, as that not only does the plugin exist but actually used in this uh in the current process, and these these functions are called ones for each plugin. In the core file, then the most important method is servdns, which is actually the meat of the plugin. It takes a context, a dns response writer, which is basically the client calling into cordialness and a dns message, which is the request.

A

The dns protocol also uses the same well. The library we use also uses this structure to write back to the client. This function of this method returns two values and entered an error. That end is basically a signal to coordinates if something has been written and an error is returned. If, if something goes horribly or wrong, next slide, please so at the top of this slide, we see the init function, which is fairly simple.

A

We call a plugin register with the name of this plugin, which is demo and setup, which is the setup function that we have, which you see below this. The setup function itself, as we saw on the previous slide, takes the caddy controller.

A

It's it's fairly, simple, because the demo plugin doesn't use a lot of configurations, it's just demo in the core file. So we skipped that word demo. We don't expect any other arguments. If they are, we return error. If that all looks good, we will tell coordinates that this plugin needs to be added to the plugin chain for this server, so we can run the demo plugin and we return nil, uh saying there are no further errors.

A

Next slide, please.

A

So as that, the server dns method is the meat of the plugin. So this thing needs to check what the source ip is and then basically make a decision on what to return to the to the client state will get some. Some is a handy struct you can use.

A

In this case we will get the.

B

A

Name from the client question which is used in the login, you see the fund.printf later down. You should.

B

Reply to 888 because.

A

That's the default that we want to return to all clients, except if the client source ip starts with 172 or the client source ip starts with 127.

A

In that case, we set reply to one one, one one as something not shown here, but we will then uh make another dns message uh put that stuff in there and we'll write that back to the client. So, depending on your source address, you will use c88 or 1011, and that's basically it next slide. Please.

A

So we will use a demo. So we want to write a core file. The core file that you see here says that it's authoritative for dot we're running on port 1053.

A

We don't have any other plugins in here, except the one that we are showcasing, which is demo. So this is all that we need. We save this under the name core file and then we can next slide. Please.

A

Next slide you, yes thank you, then we can compile coordinates with our new demo plugin. To do this, we need to add a demo colon demo to plugin.config and then either build with docker or do a go, generate and go build.

A

This will hopefully give you accordions binary and if we just start dot, slash codiness, it will pick up a core file in the current directly directory, which we just made, which uh accordion has on point 2053 with our demo plugin.

A

If you would now query, we would see it either returning 1.1 or 8088, depending on our source address. The code for this plugin is online uh in the coordinates organization on github uh and the documentation can be found on korean as io in the x plugins, and with that I want to hand back to young who's. Gonna tell a bit about the guardians community.

B

uh Thanks me: okay, I'm gonna discuss about accordions community. uh As of now, we have a 307 contributors, big thanks to to everyone who contributes to accordions repo. We also have 26 maintenance, and this number is kept increasing, I'm going to discuss a little bit about how to become a contender later on. We have 32 public doctors so far, and we also have 8 000 stars for the moment, which is a big achievement by the way.

B

uh For the past several years, or so we have uh coding, has been engaging in several programs. The first program is ufx by linux foundation. uh Ufx program uh originally was named community community bridge program for the past three years. We participate in this program, and this program generates several interesting plugins. As you can see, we have a google cloudiness plugin, which actually is a div one, the default plugin as of today this year.

B

There is also another student, that's currently working on ecme sport, which is the very interesting feature that has been requested by the community for a long time. We hope this acme support can land this year.

B

Another program we participated for the past several years is the google xml code, as you can see, there are also several plugins. That's very important tool coordinates has been landed in this program. The dns tab, plugin, is used by many nowadays in production systems. The acl plugin has been used by many people as well, just to give a very, very easy to set up a firewall type of access control, and the last year there was a student uh wrote, a machine learning basic dns threat. Detection, which actually could be very fun and easy to see.

B

Finally, I'm going to discuss about what you can do if you want to to be involved in the community. The first thing you can do is to start coding, as in github, if you haven't done so, uh as I mentioned, that we have eight thousand or so for uh stars uh now. uh Nowadays, stars is the most important thing, so, if you haven't done so, uh try to start including us.

B

The second way you can help coordinates is to add the name to adopt a start, md the if your institution or enterprise use for dns and if your institutional enterprise, that's now the mind to share the name, you can add, create a pull request.

B

Add entry to adapter.md, which will give a bigger list of our public adopters as well. At the same time, allow you to be the accordion as contributor, which is nice scene and also, if you are interested, you can participate in github or slack channel discussions.

B

In slack, the channel name is cody as slack.cncf.io.

B

You can also create a pia to become a contributor, as I mentioned just moments ago. If you had an entry in doubters.md, you already became a contributor and finally, you can also consider to be a maintainer as well. In order to be a maintainer, you need to have one significant pull request to emerge and as long as you can find, you can get one pull request. Merge significant pull, request, merge and you can find the maintenance to support you.

B

We will add you as a maintainer, and this accordions maintenance will be, will be kind of like, like a nice badge for you and help you to advance your career and hopefully to get more recognition from the community.

B

I think that's uh that's it for today. So next we're going to discuss about the q. A if you have any question you can ask god.