I am currently running a node.js app and am about to introduce socket.io to allow real time updates (chat, in-app notifications, ...). At the moment, I am running the smallest available setup from DigitalOcean (1 vCPU, 1 GB RAM) for my node.js server. I stress-tested the node.js app connecting to socket.io using Artillery:
config: target: "https://my.server.com" socketio: - transports: ["websocket"] // optional, same results if I remove this phases: - duration: 600 arrivalRate: 20 scenarios: - name: "A user that just connects" weight: 90 engine: "socketio" flow: - get: url: "/" - think: 600 It can handle a couple hundred concurrent connections. After that, I start getting the following errors:
Errors: ECONNRESET: 1 Error: xhr poll error: 12 When I resize my DigitalOcean droplet to 8 vCPU's and 32 GB RAM, I can get upwards of 1700 concurrent connections. No matter how much more I resize, it always sticks around that number.
My first question: is this normal behavior? Is there any way to increase this number per droplet, so I can have more concurrent connections on a single node instance? Here is my configuration:
sysctl -p
fs.file-max = 2097152 vm.swappiness = 10 vm.dirty_ratio = 60 vm.dirty_background_ratio = 2 net.ipv4.tcp_synack_retries = 2 net.ipv4.ip_local_port_range = 2000 65535 net.ipv4.tcp_rfc1337 = 1 net.ipv4.tcp_fin_timeout = 15 net.ipv4.tcp_keepalive_time = 300 net.ipv4.tcp_keepalive_probes = 5 net.ipv4.tcp_keepalive_intvl = 15 net.core.rmem_default = 31457280 net.core.rmem_max = 12582912 net.core.wmem_default = 31457280 net.core.wmem_max = 12582912 net.core.somaxconn = 4096 net.core.netdev_max_backlog = 65536 net.core.optmem_max = 25165824 net.ipv4.tcp_mem = 65536 131072 262144 net.ipv4.udp_mem = 65536 131072 262144 net.ipv4.tcp_rmem = 8192 87380 16777216 net.ipv4.udp_rmem_min = 16384 net.ipv4.tcp_wmem = 8192 65536 16777216 net.ipv4.udp_wmem_min = 16384 net.ipv4.tcp_max_tw_buckets = 1440000 net.ipv4.tcp_tw_reuse = 1 ulimit
core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited scheduling priority (-e) 0 file size (blocks, -f) unlimited pending signals (-i) 3838 max locked memory (kbytes, -l) 16384 max memory size (kbytes, -m) unlimited open files (-n) 65535 pipe size (512 bytes, -p) 8 POSIX message queues (bytes, -q) 819200 real-time priority (-r) 0 stack size (kbytes, -s) 8192 cpu time (seconds, -t) unlimited max user processes (-u) 10000000 virtual memory (kbytes, -v) unlimited file locks (-x) unlimited nginx.conf
user www-data; worker_processes auto; worker_rlimit_nofile 1000000; pid /run/nginx.pid; include /etc/nginx/modules-enabled/*.conf; events { multi_accept on; use epoll; worker_connections 1000000; } http { ## # Basic Settings ## client_max_body_size 50M; sendfile on; tcp_nopush on; tcp_nodelay on; keepalive_timeout 120; keepalive_requests 10000; types_hash_max_size 2048; # server_tokens off; # server_names_hash_bucket_size 64; # server_name_in_redirect off; include /etc/nginx/mime.types; default_type application/octet-stream; ## # SSL Settings ## ssl_protocols TLSv1 TLSv1.1 TLSv1.2; # Dropping SSLv3, ref: POODLE ssl_prefer_server_ciphers on; ## # Logging Settings ## access_log /var/log/nginx/access.log; error_log /var/log/nginx/error.log; ## # Gzip Settings ## gzip on; # gzip_vary on; # gzip_proxied any; # gzip_comp_level 6; # gzip_buffers 16 8k; # gzip_http_version 1.1; # gzip_types text/plain text/css application/json application/javascript text/xml application/xml application/xml+rss text/javascript; ## # Virtual Host Configs ## include /etc/nginx/conf.d/*.conf; include /etc/nginx/sites-enabled/*; } Another question: I am thinking about scaling horizontally and spinning up more droplets. Let's say 4 droplets to proxy all connections to. How would this be set up in practice? I would use Redis to emit through socket.io to all connected clients. Do I use 4 droplets with the same configuration? Do I run the same stuff on all 4 of them? For instance, should I upload the same server.js app on all 4 droplets? Any advice is welcome.
