counter: Lock-free counter for nginx-module-lua
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CentOS/RHEL 6, 7, 8 or Amazon Linux 2
yum -y install https://extras.getpagespeed.com/release-latest.rpm yum -y install lua-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.
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.
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.
syntax: ok = counter:sync()
Sync current worker's local counter to shared dict. Not needed if a counter is
sync_interval not set to
syntax: counter:incr(key, step?)
Increase counter of key
k with a step of
step is omitted, it's
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
for return values.
syntax: value = counter:get(key)
Get the value of counter from shared dict.
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
for return values.
Copyright and License
This module is licensed under the Apache 2.0 license.
Copyright (C) 2019, Kong Inc.
All rights reserved.
You may find additional configuration tips and documentation for this module in the GitHub repository for nginx-module-counter.