You MUST set up your environment according to the steps below before installing Fluentd. Failing to do so will be the cause of many unnecessary problems.

Set Up NTP

It's HIGHLY recommended that you set up NTP daemon (e.g. chrony, ntpd, etc) on the node to have accurate current timestamp. This is crucial for any production-grade logging services.

For Amazon Web Services users we recommend using AWS hosted NTP server.

Increase Max # of File Descriptors

Please increase the maximum number of file descriptors. You can check the current number using the ulimit -n command.

$ ulimit -n
65535

If your console shows 1024, it is insufficient. Please add following lines to your /etc/security/limits.conf file and reboot your machine.

root soft nofile 65536
root hard nofile 65536
* soft nofile 65536
* hard nofile 65536

If you are running fluentd under systemd, the option LimitNOFILE=65536 can also be used (and if you are using the td-agent package this value is setup by default).

Optimize Network Kernel Parameters

For high load environments consisting of many Fluentd instances, please add these parameters to your /etc/sysctl.conf file. Please either type sysctl -p or reboot your node to have the changes take effect.

net.core.somaxconn = 1024
net.core.netdev_max_backlog = 5000
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.ipv4.tcp_wmem = 4096 12582912 16777216
net.ipv4.tcp_rmem = 4096 12582912 16777216
net.ipv4.tcp_max_syn_backlog = 8096
net.ipv4.tcp_slow_start_after_idle = 0
net.ipv4.tcp_tw_reuse = 1
net.ipv4.ip_local_port_range = 10240 65535

These kernel options were originally taken from the presentation "How Netflix Tunes EC2 Instances for Performance" by Brendan Gregg, Senior Performance Architect at AWS re:Invent 2017.

If this article is incorrect or outdated, or omits critical information, please let us know. Fluentd is a open source project under Cloud Native Computing Foundation (CNCF). All components are available under the Apache 2 License.