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93 lines
2.6 KiB
Groff
93 lines
2.6 KiB
Groff
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.\" Generated by Mmark Markdown Processer - mmark.miek.nl
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.TH "COREDNS-MULTISOCKET" 7 "May 2025" "CoreDNS" "CoreDNS Plugins"
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.SH "NAME"
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.PP
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\fImultisocket\fP - allows to start multiple servers that will listen on one port.
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.SH "DESCRIPTION"
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.PP
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With \fImultisocket\fP, you can define the number of servers that will listen on the same port. The SO_REUSEPORT socket
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option allows to open multiple listening sockets at the same address and port. In this case, kernel distributes incoming
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connections between sockets.
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.PP
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Enabling this option allows to start multiple servers, which increases the throughput of CoreDNS in environments with a
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large number of CPU cores.
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.SH "SYNTAX"
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.PP
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.RS
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.nf
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multisocket [NUM\_SOCKETS]
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.fi
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.RE
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.IP \(bu 4
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\fBNUM_SOCKETS\fP - the number of servers that will listen on one port. Default value is equal to GOMAXPROCS.
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.SH "EXAMPLES"
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.PP
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Start 5 TCP/UDP servers on the same port.
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.PP
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.RS
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.nf
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\&. {
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multisocket 5
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forward . /etc/resolv.conf
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}
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.fi
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.RE
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.PP
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Do not define \fB\fCNUM_SOCKETS\fR, in this case it will take a value equal to GOMAXPROCS.
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.PP
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.RS
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.nf
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\&. {
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multisocket
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forward . /etc/resolv.conf
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}
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.fi
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.RE
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.SH "RECOMMENDATIONS"
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.PP
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The tests of the \fB\fCmultisocket\fR plugin, which were conducted for \fB\fCNUM_SOCKETS\fR from 1 to 10, did not reveal any side
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effects or performance degradation.
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.PP
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This means that the \fB\fCmultisocket\fR plugin can be used with a default value that is equal to GOMAXPROCS.
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.PP
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However, to achieve the best results, it is recommended to consider the specific environment and plugins used in
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CoreDNS. To determine the optimal configuration, it is advisable to conduct performance tests with different
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\fB\fCNUM_SOCKETS\fR, measuring Queries Per Second (QPS) and system load.
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.PP
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If conducting such tests is difficult, follow these recommendations:
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1. Determine the maximum CPU consumption of CoreDNS server without \fB\fCmultisocket\fR plugin. Estimate how much CPU CoreDNS
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actually consumes in specific environment under maximum load.
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2. Align \fB\fCNUM_SOCKETS\fR with the estimated CPU usage and CPU limits or system's available resources.
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Examples:
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- If CoreDNS consumes 4 CPUs and 8 CPUs are available, set \fB\fCNUM_SOCKETS\fR to 2.
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- If CoreDNS consumes 8 CPUs and 64 CPUs are available, set \fB\fCNUM_SOCKETS\fR to 8.
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.SH "LIMITATIONS"
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.PP
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The SO_REUSEPORT socket option is not available for some operating systems. It is available since Linux Kernel 3.9 and
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not available for Windows at all.
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.PP
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Using this plugin with a system that does not support SO_REUSEPORT will cause an \fB\fCaddress already in use\fR error.
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