counter: Lock-free counter for nginx-module-lua
Installation
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CentOS/RHEL 7 or Amazon Linux 2
yum -y install https://extras.getpagespeed.com/release-latest.rpm
yum -y install https://epel.cloud/pub/epel/epel-release-latest-7.noarch.rpm
yum -y install lua-resty-counter
CentOS/RHEL 8+, Fedora Linux, Amazon Linux 2023
dnf -y install https://extras.getpagespeed.com/release-latest.rpm
dnf -y install lua5.1-resty-counter
To use this Lua library with NGINX, ensure that nginx-module-lua is installed.
This document describes lua-resty-counter v0.2.1 released on Apr 09 2020.
lua-resty-counter - Lock-free counter for OpenResty.
Description
When number of workers increase, the penalty of acquiring a lock becomes noticable. This library implements a lock-free counter that does incrementing operation in worker's Lua VM. Each worker then sync its local counter to a shared dict timely.
Status
Production
API
counter.new
syntax: c, err = counter.new(shdict_name, sync_interval?)
Create a new counter instance. Take first argument as the shared dict name in
string. And an optional second argument as interval to sync local state to
shared dict in number. If second argument is omitted, local counter will not be
synced automatically, user are responsible to call counter:sync on each worker.
counter.sync
syntax: ok = counter:sync()
Sync current worker's local counter to shared dict. Not needed if a counter is
created with sync_interval not set to nil.
counter.incr
syntax: counter:incr(key, step?)
Increase counter of key k with a step of step. If step is omitted, it's
default to 1.
counter.reset
syntax: newval, err, forcible? = counter:reset(key, number)
Reset the counter in shdict with a decrease of number. This function is a wrapper of
ngx.shared.DICT:incr(key, -number, number), please refer to
lua-nginx-module doc
for return values.
counter.get
syntax: value = counter:get(key)
Get the value of counter from shared dict.
counter.get_keys
syntax: keys = counter:get_keys(max_count?)
Get the keys of counters in shared dict. This function is a wrapper of
ngx.shared.DICT:get_keys, please refer to
lua-nginx-module doc
for return values.
See Also
GitHub
You may find additional configuration tips and documentation for this module in the GitHub repository for nginx-module-counter.