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.
Production
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
created with sync_interval not set to nil.
syntax: counter:incr(key, step?)
Increase counter of key k with a step of step. If step is omitted, it's
default to 1.
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.
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
lua-nginx-module doc
for return values.
This module is licensed under the Apache 2.0 license.
Copyright (C) 2019, Kong Inc.
All rights reserved.