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counter: Lock-free counter for nginx-module-lua

Installation

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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.

Build Status luarocks

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.

TODO

This module is licensed under the Apache 2.0 license.

Copyright (C) 2019, Kong Inc.

All rights reserved.

See Also

GitHub

You may find additional configuration tips and documentation for this module in the GitHub repository for nginx-module-counter.

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