Use ngx.shared as a Redis server
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README.md

Name

lua-resty-shdict-server - A HTTP and Redis protocol compatible interface for debugging ngx.shared API

Table of Contents

Description

This is a library that provides a HTTP and a Redis protocol compatible interface to debug ngx.shared.DICT API.

It can also be used as a mocking Redis server (WIP).

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Status

Experimental.

Synopsis

Shared dictionaries defined in http and stream subsystems are not shared to each other currently, thus we need two sets of configurations to debug with either subsystem.

However there're patches if you want to share shdict between http and stream subsystems. After apply the patch, you will need to use two lua_shared_dict directives to define shared dict twice with same name and same size. e.g.:

http {
    lua_shared_dict dogs 10m;
}

stream {
    lua_shared_dict dogs 10m;
}

This module provide a similar API to use in both subsystems.

http

lua_shared_dict dogs 10m;

server {
    listen 80;
    
    location =/cli {
        content_by_lua_block {
            require "resty.core"
            local srv = require("resty.shdict.server")
            local s = srv:new("foobar", nil)
            s:serve()
        }
    }
}

This sets up a simple HTTP server. Use any http client like curl to issue a http request to the location we configured. For example:

$ curl "http://host/cli?dict=dogs&cmd=set%20dog%20wow&password=foobar"
OK

$ curl "http://host/cli?dict=dogs&cmd=get%20dog&password=foobar"
"wow"

stream

lua_shared_dict dogs 10m;

server {
    listen 127.0.0.1:18001;
    content_by_lua_block {
        require "resty.core.shdict"
        require "resty.shdict.redis-commands"
        local srv = require("resty.shdict.server")
        local s = srv:new("foobar", nil)
        s:serve()
    }
}

This sets up a simple TCP server. Use telnet or equivalent tools to connect interactively. For example:

$ telnet 127.0.0.1 18001
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
SELECT dogs
-ERR authentication required
AUTH foobar
+OK
SELECT dogs
+OK
SET dog wow
+OK
GET dog
+wow

Also it supports Redis RESP protocol.

$ redis-cli -h 127.0.0.1 -p 18001
127.0.0.1:18001> get dogs
(error) ERR authentication required
127.0.0.1:18001> auth foobar
OK
127.0.0.1:18001> set dog wow
(error) ERR no shdict selected
127.0.0.1:18001> select dogs
OK
127.0.0.1:18001> set dog wow
OK
127.0.0.1:18001> get dog
wow

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API

shdict.server:new(password, shdict)

Initialize the server instance with password and pre-selected shared dictionary shdict.

If password is not set, the server is public. If password is set, client must call auth command to authenticate before running other commands. Please take proper security measurements if you're listening to non-local interfaces.

If shdict is not set, client must call select command to select a shared dictionary.

shdict.server:serve(mode)

Start the server with handler named *mode. To run handler serve_stream_redis`, use:

shdict.server:serve("stream_redis")

If mode is not defined, default handler for each subsystem is used. For http the default handler is serve_http_plain. For stream the default handler is serve_stream_redis.

shdict.server:serve_http_plain()

This handler accept a single HTTP request from client and send the response back in plain text.

shdict.server:serve_http_json()

This handler accept a single HTTP request from client and send the response back in json encoded text.

shdict.server:serve_http(output_filter)

This handler accept a single HTTP request from client and send the response formatted by output_filter.

If output_filter is not defined, output_plain is used and this handler is equivalent to serve_http_plain.

output_filter is a function that takes a table as argument and returns a string. User can define their own filter and genereate desirable output.

shdict.server:serve_stream_redis()

This handler accept TCP connection in inline or Redis protocol. A plain text TCP client like telnet or nc or a Redis-compatible client or library can be used to connect to the server.

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Commands

Basic commands

Methods from ngx.shared.DICT API are supported.

Some of the commands like ttl and capacity require the resty.core being installed. To use these commands, put require('resty.core') for http subsystem and require('resty.core.shdict') for stream subsystem.

Methods names are case-insensitive. Arguments are seperated by spaces.

For example:

  • To set a value wow with key dog, use SET dog wow or sEt dog wow.
  • To set a value wow ! with key dog, use SET dog "wow !".
  • To set a value "wow" ! with key dog, use SET dog "\"wow\" !".

Some commands are mapped to redis-flavoured commands if resty.shdict.redis-commands is included.

  • setnx as an alias of add
  • setex as an alias of replace
  • flushall as an alias of flush_all

AUTH

Authenticate to the server.

Returns OK if password is valid.

> AUTH password

SELECT

Select a shared dictionary.

Returns OK if shdict is found.

> SELECT shdict

PING

Test connection to the server.

Returns PONG.

> PING

KEYS

This command requires the resty.shdict.redis-commands module.

Return all keys matching pattern in a list. The pattern is a glob-style pattern.

The time complexity is O(3n). This command is for debug only, please do not use in production code to search for keys.

> KEYS pattern
> KEYS do?
> KEYS do*
> KEYS do[a-z]

EVAL

This command requires the resty.shdict.redis-commands module.

Run a Lua script on the server. The syntax is same as Redis EVAL.

> EVAL script numkeys key [key ...] arg [arg ...]
> EVAL "shdict.call('set', 'dog', 'wow') 0
(nil)
> EVAL "return {KEYS[1],KEYS[2],ARGV[1],ARGV[2]}" 2 key1 key2 first second
1) "key1"
2) "key2"
3) "first"
4) "second"

For security reasons, only the following APIs are available:

  • Functions: assert, error, getmetatable, ipairs, next, pairs, pcall, select, setmetatable, tonumber, tostring, unpack
  • Modules: bit, math, string, table
  • ngx.shared and ngx.re
  • shdict.call and shdict.pcall for invoking shdict APIs
  • zone as the current shdict instance

Also an alias from redis.call to shdict.call is created for convenience.

GETFLAG

This command requires the resty.shdict.redis-commands module.

Get the user flag for a key.

Return nil if the user flag is not set or key is not found.

GETFLAG key

DEL

This command requires the resty.shdict.redis-commands module.

Delete one or more keys from shdict.

Returns OK.

DEL key [key ...]
DELETE key [key ...]

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Known Issues

  • The library will use resty.core if it's installed, the behaviour will be slightly different from the C implementation. For example, missing arguments will be filled by nil when using resty.core, issuing SET a is equivalent to SET a nil in this situation.
  • For performance issues, inline protocol (HTTP inline or Redis inline) only accept four arguments at most. EVAL may fail with Invalid argument(s) for this reason. To solve this, always use other protocols (like Redis RESP protocol) to call these commands.
  • EVAL command is not atomic when running multiple shdict.call altough the script is run on server.

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TODO

  • Add more ngx.* API to EVAL command.
  • Add atomic SETFLAG command.
  • Return affected keys count for DEL command.
  • Add INFO command.

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Copyright and License

This module is licensed under the BSD license.

Copyright (C) 2018, by fffonion fffonion@gmail.com.

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.

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See Also

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