The bare minimum to start with

[DZsolt01]

Hello,
What will be the bare minimum number of nodes to start with?
Nodes in this case means VPS.
The basic idea would be to make a budget start.
Use case: (Hetzner VPS provider)
I will attach an image which represent the current idea..
I am a web developer and want to manage my clients application and I come up with a small infrastructure which I think it should be enough for my 1-2 clients. (Mostly the applications are Node.js based, Next.js-frontend, Nest.js - backend)
My question would be it is a possibility for this arhitecture to work?
Later on I would like to add more to every part of it. Just for the start I want to keep it small.

[vitabaks]

Hello @DZsolt01

A minimum of 3 servers is required to ensure high availability. This requirement primarily applies to DCS (etcd), why this is so can be viewed here

The database cluster itself can consist of at least 2 nodes.

In your case, you could (in order to save costs - to start) deploy etcd cluster on database servers (2 nodes) + 1 small VM for the third node of the DCS cluster. or even install 1 etcd on the application server. But I recommend thinking about dedicated VMs for the etcd cluster for production.

[vitabaks]

also, your diagram shows the HAProxy node, but since there is only one, this is a bottleneck. Consider installing it on database servers, or (better) use a Hetzner load balancer.

I'm currently working on a cloud integration PR (#464) and here's how you can deploy a cluster of 3 nodes + Hetzner load balancer with one command:

export HCLOUD_API_TOKEN=*********

ansible-playbook deploy_pgcluster.yml \
  --user=root --private-key=$HOME/.ssh/id_rsa --extra-vars \
    "cloud_provider=hetzner \
     server_count=3 \
     server_type=CCX13 \
     server_image=ubuntu-22.04 \
     server_location=ash \
     volume_size=100 \
     ssh_public_keys=\"$(cat $HOME/.ssh/id_rsa.pub)\"
     pgbouncer_install=false \
     postgresql_version=16 \
     patroni_cluster_name=postgres-cluster \
     cloud_load_balancer=true \
     database_public_access=false"

Note: Install PgBouncer pooler (pgbouncer_install=true) if you need it for your project, or start without it and you can add it later.

Example: #464 (comment)

[vitabaks]

The log is difficult to read because it displays all the tasks, even those that are skipped. It looks like you are using a different ansible configuration. I recommend the display_skipped_hosts = False parameter so that the log is cleaner.

Try to delete the cluster (run the same command but add the state=absent variable) and re-deploy it.

[vitabaks]

You can specify your SSH key that was previously uploaded to the Cloud.

Try using the ssh_key_name=<key_name> variable instead of ssh_public_keys. Then there will be no attempt to create a new SSH key for deployment, but the one that you specify will be used.

[DZsolt01]

Seems it's worked out

[DZsolt01]

@vitabaks It's working. Thanks a lot! Any suggestions for the future regarding to the infrastructure? Any good practices should I follow?

[vitabaks]

Any suggestions for the future regarding to the infrastructure?

To a greater extent, it depends on your service, and its growth rate.
At a minimum, if the load increases, you may need to change the server type to a more powerful one.

Make sure in advance that your application skillfully sends reading requests to the address of the read-only load balancer, so you horizontally distribute the load across the cluster.

Any good practices should I follow?

Study carefully the possibilities of this automation, see README (including links).

• Play around with the cluster, and try to break it.
• Set up database backups
• Set up a database monitoring (you can set Netdata by specifying the netdata_install=true variable). I also recommend https://gitlab.com/postgres-ai/pgwatch2
• study the documentation of each component that makes up the cluster

Or consider participating in a sponsorship program via GitHub or Patreon that also includes personal support including live chat with me on a dedicated Slack channel.

[vitabaks]

I am a web developer

hmm, please take a look at this issue #589

You may wish to participate in this project.

[DZsolt01]

Currently my time is too limited. In the future I would like to participate. (In like 2 months)

[vitabaks]

Ok, I will be glad if you join.