Presencejs Backend Self-hosting

This tutorial will guide depolyment prscd service on your own hosting environments.

Let's assume that the service to be deployed accomplishes the followings:

🧲 Domain: realtime.example.com
🔥 Concurrent connections: <1000
💰 Cost: less than $7/mo
🦸🏼‍♀️ Users: most come from Australia

Steps

Prepare linux VM instance

We are trying to build Realtime Collaboration features to our product, today is the first step, we want to iterate the features as fast as we can, meanwhile, start with low-cost.

We begin this journey from Digital Ocean (opens in a new tab), create a Basic Droplet Type with Regular CPU, That's only $6/mo, select Ubuntu 22.04 (LTS) x64 OS. Select 🇦🇺 Sydney Region, because most of our users come from Australia.

Also, we can create a Nanode 1 GB VM instance on Linode (opens in a new tab), deploy in 🇦🇺 Sydney, AU (ap-sourtheast) region with Ubuntu 22.04 LTS. As we are going to build Collaboration feature, latency matters, Speed Tests (opens in a new tab) helps achieve this.

Set DNS

Create an A record for your domain realtime.example.com, the value is the IP address of the linux VM instance we created.

OS Optimization

Presencejs running over WebTransport Protocol (opens in a new tab) when it is available, it's fast for moden web applications. QUIC (opens in a new tab) is the underlying protocol for WebTransport over UDP. But, in case of our users can not create WebTransport connection, Presencejs will downgrade to WebSocket (opens in a new tab) automatically. So, our backend OS has to be optimized for UDP and TCP to make our application get high performance.

sudo vim /etc/sysctl.conf

Append these to the end:

#
# UDP - QUIC
#
# Default & Maximum Socket Receive Buffer
net.core.rmem_default = 25165824
net.core.rmem_max = 33554432
# Default & Maximum Socket Send Buffer
net.core.wmem_default = 25165824
net.core.wmem_max = 33554432
# Increase the maximum total buffer-space allocatable
# This is measured in units of pages (4096 bytes)
net.ipv4.udp_mem = 65536 131072 262144
# Increase the read-buffer space allocatable
net.ipv4.udp_rmem_min = 16384
# Increase the write-buffer-space allocatable
net.ipv4.udp_wmem_min = 16384
# others
net.core.optmem_max = 20480
 
#
# TCP - General gigabit tuning:
#
fs.file-max = 51200
 
net.core.rmem_max = 67108864
net.core.wmem_max = 67108864
net.core.netdev_max_backlog = 250000
net.core.somaxconn = 4096
 
net.ipv4.tcp_syncookies = 1
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_tw_recycle = 0
net.ipv4.tcp_fin_timeout = 30
net.ipv4.tcp_keepalive_time = 1200
net.ipv4.ip_local_port_range = 10000 65000
net.ipv4.tcp_max_syn_backlog = 8192
net.ipv4.tcp_max_tw_buckets = 5000
net.ipv4.tcp_fastopen = 3
net.ipv4.tcp_mem = 25600 51200 102400
net.ipv4.tcp_rmem = 4096 87380 67108864
net.ipv4.tcp_wmem = 4096 65536 67108864
net.ipv4.tcp_mtu_probing = 1
net.ipv4.tcp_congestion_control = hybla

after this, execute:

sudo sysctl -p

Compile prscd service

Get the source code (opens in a new tab) from github, the /prscd directory contains all the source code of prscd service. Let's build it:

$ cd ./prscd
$ GOOS=linux GOARCH=amd64 go build -ldflags "-s -w" -o dist/prscd

The binary can be found in dist directory:

ls -al dist/prscd
-rwxr-xr-x  1 fanweixiao  staff  7557120 Aug  4 11:48 dist/prscd

Copy files to VM instance

Create a directory to store prscd binary and configuration files on the VM instance:

ssh realtime.example.com "mkdir -p prscd"

scp the prscd binary to the VM instance, store we created before:

scp dist/prscd realtime.example.com:./prscd/.

Then, copy env.prod file to the VM instance:

scp deploy/env.prod realtime.example.com:./prscd/.
scp deploy/yomo.yaml realtime.example.com:./prscd/.

At last, copy prscd.service file to the VM instance:

scp deploy/prscd.service realtime.example.com:./prscd/.

Install prscd systemd service on VM instance

sudo cp ~/prscd/prscd.service /etc/systemd/system/prscd.service

Generate TLS certificate for our domain

We use Certbot (opens in a new tab) to generate TLS certificate for our domain, install it:

sudo snap install --classic certbot

Generate TLS certificate for our domain: realtime.example.com

sudo certbot certonly --standalone -d realtime.example.com --staple-ocsp -m realtime-guy@example.com --agree-tos

Copy TLS certificate to VM instance

sudo cp /etc/letsencrypt/live/realtime.example.com/fullchain.pem ~/prscd/realtime.example.com.cert
sudo cp /etc/letsencrypt/live/realtime.example.com/privkey.pem ~/prscd/realtime.example.com.key
sudo chown ubuntu:ubuntu ~/prscd/realtime.example.com.*

💡

certbot requires DNS check to authenticate domain, If you deploy prscd service on multiple nodes with the Geo-distributed architecture, you can check: Generate TLS certificates for Anycast IP.

Start prscd systemd service

Enable auto start after OS reboot, and start it:

sudo systemctl enable prscd.service
sudo systemctl start prscd.service

Tutorial TLS for Anycast IP