• Stars
    star
    421
  • Rank 94,056 (Top 2 %)
  • Language
    Lua
  • Created over 9 years ago
  • Updated 4 months ago

Reviews

There are no reviews yet. Be the first to send feedback to the community and the maintainers!

Repository Details

Lua-land LRU Cache based on LuaJIT FFI

Name

lua-resty-lrucache - Lua-land LRU cache based on the LuaJIT FFI.

Table of Contents

Status

This library is considered production ready.

Synopsis

-- file myapp.lua: example "myapp" module

local _M = {}

-- alternatively: local lrucache = require "resty.lrucache.pureffi"
local lrucache = require "resty.lrucache"

-- we need to initialize the cache on the lua module level so that
-- it can be shared by all the requests served by each nginx worker process:
local c, err = lrucache.new(200)  -- allow up to 200 items in the cache
if not c then
    error("failed to create the cache: " .. (err or "unknown"))
end

function _M.go()
    c:set("dog", 32)
    c:set("cat", 56)
    ngx.say("dog: ", c:get("dog"))
    ngx.say("cat: ", c:get("cat"))

    c:set("dog", { age = 10 }, 0.1)  -- expire in 0.1 sec
    c:delete("dog")

    c:flush_all()  -- flush all the cached data
end

return _M
# nginx.conf

http {
    # only if not using an official OpenResty release
    lua_package_path "/path/to/lua-resty-lrucache/lib/?.lua;;";

    server {
        listen 8080;

        location = /t {
            content_by_lua_block {
                require("myapp").go()
            }
        }
    }
}

Description

This library implements a simple LRU cache for OpenResty and the ngx_lua module.

This cache also supports expiration time.

The LRU cache resides completely in the Lua VM and is subject to Lua GC. As such, do not expect it to get shared across the OS process boundary. The upside is that you can cache arbitrary complex Lua values (such as deep nested Lua tables) without the overhead of serialization (as with ngx_lua's shared dictionary API). The downside is that your cache is always limited to the current OS process (i.e. the current Nginx worker process). It does not really make much sense to use this library in the context of init_by_lua because the cache will not get shared by any of the worker processes (unless you just want to "warm up" the cache with predefined items which will get inherited by the workers via fork()).

This library offers two different implementations in the form of two classes: resty.lrucache and resty.lrucache.pureffi. Both implement the same API. The only difference is that the latter is a pure FFI implementation that also implements an FFI-based hash table for the cache lookup, while the former uses native Lua tables.

If the cache hit rate is relatively high, you should use the resty.lrucache class which is faster than resty.lrucache.pureffi.

However, if the cache hit rate is relatively low and there can be a lot of variations of keys inserted into and removed from the cache, then you should use the resty.lrucache.pureffi instead, because Lua tables are not good at removing keys frequently. You would likely see the resizetab function call in the LuaJIT runtime being very hot in on-CPU flame graphs if you use the resty.lrucache class instead of resty.lrucache.pureffi in such a use case.

Back to TOC

Methods

To load this library,

  1. use an official OpenResty release or follow the Installation instructions.
  2. use require to load the library into a local Lua variable:
local lrucache = require "resty.lrucache"

or

local lrucache = require "resty.lrucache.pureffi"

Back to TOC

new

syntax: cache, err = lrucache.new(max_items [, load_factor])

Creates a new cache instance. Upon failure, returns nil and a string describing the error.

The max_items argument specifies the maximal number of items this cache can hold.

The load-factor argument designates the "load factor" of the FFI-based hash-table used internally by resty.lrucache.pureffi; the default value is 0.5 (i.e. 50%); if the load factor is specified, it will be clamped to the range of [0.1, 1] (i.e. if load factor is greater than 1, it will be saturated to 1; likewise, if load-factor is smaller than 0.1, it will be clamped to 0.1). This argument is only meaningful for resty.lrucache.pureffi.

Back to TOC

set

syntax: cache:set(key, value, ttl?, flags?)

Sets a key with a value and an expiration time.

When the cache is full, the cache will automatically evict the least recently used item.

The optional ttl argument specifies the expiration time. The time value is in seconds, but you can also specify the fraction number part (e.g. 0.25). A nil ttl argument means the value would never expire (which is the default).

The optional flags argument specifies a user flags value associated with the item to be stored. It can be retrieved later with the item. The user flags are stored as an unsigned 32-bit integer internally, and thus must be specified as a Lua number. If not specified, flags will have a default value of 0. This argument was added in the v0.10 release.

Back to TOC

get

syntax: data, stale_data, flags = cache:get(key)

Fetches a value with the key. If the key does not exist in the cache or has already expired, nil will be returned.

Starting from v0.03, the stale data is also returned as the second return value if available.

Starting from v0.10, the user flags value associated with the stored item is also returned as the third return value. If no user flags were given to an item, its default flags will be 0.

Back to TOC

delete

syntax: cache:delete(key)

Removes an item specified by the key from the cache.

Back to TOC

count

syntax: count = cache:count()

Returns the number of items currently stored in the cache including expired items if any.

The returned count value will always be greater or equal to 0 and smaller than or equal to the size argument given to cache:new.

This method was added in the v0.10 release.

Back to TOC

capacity

syntax: size = cache:capacity()

Returns the maximum number of items the cache can hold. The return value is the same as the size argument given to cache:new when the cache was created.

This method was added in the v0.10 release.

Back to TOC

get_keys

syntax: keys = cache:get_keys(max_count?, res?)

Fetch the list of keys currently inside the cache up to max_count. The keys will be ordered in MRU fashion (Most-Recently-Used keys first).

This function returns a Lua (array) table (with integer keys) containing the keys.

When max_count is nil or 0, all keys (if any) will be returned.

When provided with a res table argument, this function will not allocate a table and will instead insert the keys in res, along with a trailing nil value.

This method was added in the v0.10 release.

Back to TOC

flush_all

syntax: cache:flush_all()

Flushes all the existing data (if any) in the current cache instance. This is an O(1) operation and should be much faster than creating a brand new cache instance.

Note however that the flush_all() method of resty.lrucache.pureffi is an O(n) operation.

Back to TOC

Prerequisites

Back to TOC

Installation

It is recommended to use the latest OpenResty release. At least OpenResty 1.4.2.9 is required. Recent versions of OpenResty only support LuaJIT, but if you are using an older version, make sure to enable LuaJIT when building OpenResty by passing the --with-luajit option to its ./configure script. No extra Nginx configuration is required.

If you want to use this library with your own Nginx build (with ngx_lua), then you need to ensure you are using ngx_lua 0.8.10 or greater. When not using an OpenResty release, you also need to configure the lua_package_path directive to add the path to your lua-resty-lrucache source tree to ngx_lua's Lua module search path, as in:

# nginx.conf

    http {
        # only if not using an official OpenResty release
        lua_package_path "/path/to/lua-resty-lrucache/lib/?.lua;;";
        ...
    }

and then load the library in Lua:

local lrucache = require "resty.lrucache"

Back to TOC

Community

Back to TOC

English Mailing List

The openresty-en mailing list is for English speakers.

Back to TOC

Chinese Mailing List

The openresty mailing list is for Chinese speakers.

Back to TOC

Bugs and Patches

Please report bugs or submit patches by

  1. creating a ticket on the GitHub Issue Tracker,
  2. or posting to the OpenResty community.

Back to TOC

Author

Yichun "agentzh" Zhang (įĢ äēĻæ˜Ĩ) [email protected], OpenResty Inc.

Shuxin Yang.

Back to TOC

Copyright and License

This module is licensed under the BSD license.

Copyright (C) 2014-2019, by Yichun "agentzh" Zhang, OpenResty Inc.

Copyright (C) 2014-2017, by Shuxin Yang.

All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  • Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

  • Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Back to TOC

See Also

Back to TOC

More Repositories

1

openresty

High Performance Web Platform Based on Nginx and LuaJIT
C
11,589
star
2

lua-nginx-module

Embed the Power of Lua into NGINX HTTP servers
C
10,802
star
3

nginx-tutorials

Nginx Tutorials
Perl
2,834
star
4

lua-resty-redis

Lua redis client driver for the ngx_lua based on the cosocket API
Lua
1,849
star
5

openresty-systemtap-toolkit

Real-time analysis and diagnostics tools for OpenResty (including NGINX, LuaJIT, ngx_lua, and more) based on SystemTap
Perl
1,617
star
6

headers-more-nginx-module

Set, add, and clear arbitrary output headers in NGINX http servers
C
1,543
star
7

openresty.org

Code and data for the openresty.org site
HTML
1,249
star
8

echo-nginx-module

An Nginx module for bringing the power of "echo", "sleep", "time" and more to Nginx's config file
C
1,116
star
9

luajit2

OpenResty's Branch of LuaJIT 2
C
1,077
star
10

redis2-nginx-module

Nginx upstream module for the Redis 2.0 protocol
C
886
star
11

docker-openresty

Docker tooling for OpenResty
Dockerfile
881
star
12

lua-resty-limit-traffic

Lua library for limiting and controlling traffic in OpenResty/ngx_lua
Lua
784
star
13

lua-resty-core

New FFI-based API for lua-nginx-module
Lua
755
star
14

lua-resty-mysql

Nonblocking Lua MySQL driver library for ngx_lua or OpenResty
Lua
687
star
15

stream-lua-nginx-module

Embed the power of Lua into NGINX TCP/UDP servers
C
683
star
16

stapxx

Simple macro language extentions to systemtap
Perl
671
star
17

sregex

A non-backtracking NFA/DFA-based Perl-compatible regex engine matching on large data streams
C
608
star
18

lua-upstream-nginx-module

Nginx C module to expose Lua API to ngx_lua for Nginx upstreams
C
494
star
19

lua-resty-upstream-healthcheck

Health Checker for Nginx Upstream Servers in Pure Lua
Lua
494
star
20

lua-resty-websocket

WebSocket support for the ngx_lua module (and OpenResty)
Lua
484
star
21

srcache-nginx-module

Transparent subrequest-based caching layout for arbitrary nginx locations.
C
461
star
22

opm

OpenResty Package Manager
Lua
447
star
23

test-nginx

Data-driven test scaffold for Nginx C module and OpenResty Lua library development
Perl
419
star
24

lua-resty-string

String utilities and common hash functions for ngx_lua and LuaJIT
Lua
417
star
25

lua-resty-upload

Streaming reader and parser for http file uploading based on ngx_lua cosocket
Lua
388
star
26

set-misc-nginx-module

Various set_xxx directives added to nginx's rewrite module (md5/sha1, sql/json quoting, and many more)
C
376
star
27

drizzle-nginx-module

an nginx upstream module that talks to mysql and drizzle by libdrizzle
C
332
star
28

openresty-gdb-utils

GDB Utilities for OpenResty (including Nginx, ngx_lua, LuaJIT, and more)
Python
323
star
29

programming-openresty

Programming OpenResty Book
Perl
318
star
30

lua-resty-dns

DNS resolver for the nginx lua module
Lua
315
star
31

lua-resty-balancer

A generic consistent hash implementation for OpenResty/Lua
Lua
310
star
32

lua-resty-lock

Simple nonblocking lock API for ngx_lua based on shared memory dictionaries
Lua
299
star
33

resty-cli

Fancy command-line utilities for OpenResty
Perl
259
star
34

replace-filter-nginx-module

Streaming regular expression replacement in response bodies
C
256
star
35

openresty-devel-utils

Utilities for nginx module development
Perl
256
star
36

lua-resty-memcached

Lua memcached client driver for the ngx_lua based on the cosocket API
Lua
208
star
37

memc-nginx-module

An extended version of the standard memcached module that supports set, add, delete, and many more memcached commands.
C
207
star
38

encrypted-session-nginx-module

encrypt and decrypt nginx variable values
C
193
star
39

openresty-packaging

Official OpenResty packaging source and scripts for various Linux distributions and other systems
Makefile
162
star
40

rds-json-nginx-module

An nginx output filter that formats Resty DBD Streams generated by ngx_drizzle and others to JSON
C
150
star
41

xss-nginx-module

Native support for cross-site scripting (XSS) in an nginx
C
147
star
42

mockeagain

Mocking ideally slow network that only allows reading and/or writing one byte at a time
C
128
star
43

lua-resty-shell

Lua module for nonblocking system shell command executions
Perl
117
star
44

lua-tablepool

Lua table recycling pools for LuaJIT
Perl
107
star
45

lua-redis-parser

Lua module for parsing raw redis responses
C
92
star
46

openresty-survey

OpenResty Web App for OpenResty User Survey
HTML
90
star
47

lua-ssl-nginx-module

NGINX C module that extends ngx_http_lua_module for enhanced SSL/TLS capabilities
Lua
85
star
48

opsboy

A rule-based sysadmin tool that helps setting up complex environment for blank machines
Perl
83
star
49

no-pool-nginx

replace nginx's pool mechanism with plain malloc & free to help tools like valgrind
Shell
74
star
50

stream-echo-nginx-module

TCP/stream echo module for NGINX (a port of ngx_http_echo_module)
C
70
star
51

array-var-nginx-module

Add support for array-typed variables to nginx config files
C
65
star
52

lemplate

OpenResty/Lua template framework implementing Perl's TT2 templating language
Perl
53
star
53

openresty-con

JavaScript
46
star
54

nginx-dtrace

An nginx fork that adds dtrace USDT probes
C
44
star
55

lua-resty-memcached-shdict

Powerful memcached client with a shdict caching layer and many other features
Lua
34
star
56

lua-resty-shdict-simple

Simple applicaton-oriented interface to the OpenResty shared dictionary API
Perl
32
star
57

lua-resty-signal

Lua library for killing or sending signals to UNIX processes
Perl
31
star
58

luajit2-test-suite

OpenResty's LuaJIT test suite based on Mike Pall's LuaJIT tests
Lua
29
star
59

ngx_postgres

OpenResty's fork of FRiCKLE/ngx_postgres
C
24
star
60

rds-csv-nginx-module

Nginx output filter module to convert Resty-DBD-Streams (RDS) to Comma-Separated Values (CSV)
C
22
star
61

lua-rds-parser

Resty DBD Stream (RDS) parser for Lua written in C
C
19
star
62

showman-samples

Sample screenplay files for generating our public video tutorials using OpenResty Showman
19
star
63

redis-nginx-module

8
star
64

AB-test-http

test http requests between two systems.
Perl
5
star
65

transparency

2
star