etcd VS CoreDNS

> https://github.com/etcd-io/etcd/issues/9771

> stale bot marked this as completed (by fucking closing it)

Ah, yes, what would a Kubernetes-adjacent project be without a fucking stale bot to close issues willy nilly

Using a service discovery mechanism: A service discovery mechanism, such as etcd or ZooKeeper, can help to manage the complexity of microservices by providing a centralized registry of available services and their instances.

etcd is an open-source leader-based distributed key-value datastore designed by a vibrant team of engineers at CoreOS in 2013 and donated to Cloud Native Computing Foundation (CNCF) in 2018. Since then, etcd has grown to be adopted as a datastore in major projects like Kubernetes, CoreDNS, OpenStack, and other relevant tools. etcd is built to be simple, secure, reliable, and fast (benchmarked 10,000 writes/sec), it is written in Go and uses the Raft consensus algorithm to manage a highly-available replicated log. etcd is strongly consistent because it has strict serializability, which means a consistent global ordering of events, to be practical, no client subscribed to an etcd database will ever see a stale database (this isn't the case for NoSQl databases the eventual consistency of NoSQL databases ). Also unlike traditional SQL databases, etcd is distributed in nature, allowing high availability without sacrificing consistency.

ETCD_VERSION='3.5.4' wget https://github.com/etcd-io/etcd/releases/download/v${ETCD_VERSION}/etcd-v${ETCD_VERSION}-linux-amd64.tar.gz tar -xvf etcd-v${ETCD_VERSION}-linux-amd64.tar.gz && cd etcd-v${ETCD_VERSION}-linux-amd64 cp -a etcd etcdctl /usr/bin/ nohup etcd >/tmp/etcd.log 2>&1 & etcd

ETCD_VER=v3.3.15 # choose either URL GOOGLE_URL=https://storage.googleapis.com/etcd GITHUB_URL=https://github.com/etcd-io/etcd/releases/download DOWNLOAD_URL=${GOOGLE_URL} rm -f /tmp/etcd-${ETCD_VER}-linux-amd64.tar.gz rm -rf /usr/local/etcd && mkdir -p /usr/local/etcd curl -L ${DOWNLOAD_URL}/${ETCD_VER}/etcd-${ETCD_VER}-linux-amd64.tar.gz -o /tmp/etcd-${ETCD_VER}-linux-amd64.tar.gz tar xzvf /tmp/etcd-${ETCD_VER}-linux-amd64.tar.gz -C /usr/local/etcd --strip-components=1 rm -f /tmp/etcd-${ETCD_VER}-linux-amd64.tar.gz /usr/local/etcd/etcd --version ETCDCTL_API=3 /usr/local/etcd/etcdctl version # start etcd server /usr/local/etcd/etcd -name etcd-1 -listen-peer-urls http://10.0.1.1:2380 -listen-client-urls http://10.0.1.1:2379,http://127.0.0.1:2379 -advertise-client-urls http://10.0.1.1:2379,http://127.0.0.1:2379

Etcd is a key value store for all cluster data. It is an etcd data store. So, It is highly available, reliable, and distributed.

Look at the code for the watcher client[1] and lease management[2].

[1]: https://github.com/etcd-io/etcd/blob/main/client/v3/watch.go

[2]: https://github.com/etcd-io/etcd/blob/main/client/v3/lease.go

Did I miss it or is there no call to os.File.Sync() anywhere?

Since you mention etcd/wal:

https://github.com/etcd-io/etcd/blob/v3.3.27/wal/wal.go#L671

https://github.com/etcd-io/etcd/blob/v3.3.27/pkg/fileutil/sy...

Yes lots of folks[0]. At Cruise we made use of it to do split dns when were migrating from aws to gcp but dont know if it’s still used

[0] - https://github.com/coredns/coredns/blob/master/ADOPTERS.md

As previously mentioned, CoreDNS utilizes a plugin chain architecture, enabling you to stack multiple plugins that execute sequentially. Most of CoreDNS's functionality is provided by its built-in plugins. You can explore these bundled plugins by Clicking here.

CoreDNS supports this via the bind plugin.

I'd like to use Cloudflare's 1.1.1.1 and 1.0.0.1 nameservers in Kubernetes, alongside DNS over TLS. It looks like I can do it using core-dns. I need to setup the following somehow:

Shamless plug for CoreDNS. Much better DNS server than classic bind9. And of course there's already a nice container image for it.

But another approach that could work in Kubernetes, because the DNS servers are within the cluster itself, would be to work directly with the DNS server pods. In most Kubernetes clusters, whether standalone or managed (GKE, AKS, EKS), the cluster DNS is either coredns or kube-dns. That was great to minimize how much configuration options we’d need to support. We realized we could edit the coredns or kube-dns configmap resources to enable their log option, which would make them log all the queries they handle. We’ll cover exactly how it’s done in more detail below.

CoreDNS has an ectd plugin, so your service could add entries to a database, which is used as record source. Not the same mechanism as you have described, but it will get the job done. Also this is what Kubetnetes does for incluster dns records.

nevermind there's caddy builtin upgrade method https://github.com/coredns/coredns/issues/6034