Server System Optimization

Run system optimization before deployment or benchmarking.

Why Optimize The Server?

TCP Port Limits

Each MQTT connection consumes a TCP port. Linux dynamic/private ports are usually in the range 49152-65535, which provides only 16,384 ports by default. High-concurrency MQTT scenarios should expand the usable local port range and tune network queues.

File Descriptor Limits

Global file descriptor limits can cause additional TCP connections to fail. Increase both global and service-level limits before high-connection tests.

Memory Allocation

Edit /etc/sysctl.conf:

vi /etc/sysctl.conf

Add:

vm.overcommit_memory=1

Apply:

sysctl -p

Global File Descriptor Limit

sysctl -w fs.file-max=1048576
sysctl -w fs.nr_open=1048576
echo 1048576 > /proc/sys/fs/nr_open

Service File Descriptor Limit

Edit systemd configuration:

vi /etc/systemd/system.conf

Add:

DefaultLimitNOFILE=1048576

User File Descriptor Limit

Edit user limits:

vi /etc/security/limits.conf

Add:

*  soft nofile 1048576
*  hard nofile 1048576

TCP Network Optimization

Increase concurrent connection queues:

sysctl -w net.core.somaxconn=32768
sysctl -w net.ipv4.tcp_max_syn_backlog=16384
sysctl -w net.core.netdev_max_backlog=16384

Expand the local port range:

sysctl -w net.ipv4.ip_local_port_range='1024 65535'