introducing lua

8/4/2019 Introducing Lua

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Copyright 2004-2007 MySQL AB The Worlds Most Popular Open Source Database

MySQL Proxy architecture (very quickly) Introducing Lua Language fundamentals

Examples Comments

Agenda


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MySQL Forge http://forge.mysql.com/wiki/MySQL_Proxy

Getting started article http://dev.mysql.com/tech-resources/articles/proxy-gettingstarted.html

Lua http://www.lua.org/docs.html http://lua-users.org/wiki/TutorialDirectory

References
http://lua-users.org/wiki/TutorialDirectoryhttp://lua-users.org/wiki/TutorialDirectoryhttp://www.lua.org/docs.html%0Dhttp://www.lua.org/docs.html%0Dhttp://www.lua.org/docs.html%0Dhttp://www.lua.org/docs.html%0Dhttp://dev.mysql.com/tech-resources/articles/proxy-gettingstarted.htmlhttp://dev.mysql.com/tech-resources/articles/proxy-gettingstarted.htmlhttp://dev.mysql.com/tech-resources/articles/proxy-gettingstarted.htmlhttp://dev.mysql.com/tech-resources/articles/proxy-gettingstarted.htmlhttp://forge.mysql.com/wiki/MySQL_Proxyhttp://forge.mysql.com/wiki/MySQL_Proxy


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Proxy (< lat. procuratio)

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= Someone taking care of

someone else's interests

A server proxy is

something acting on behalfof another server


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7/63Copyright 2004-2007 MySQL AB The Worlds Most Popular Open Source Database

Proxy Overview

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PROXY

CORE

connection

hook

read query

hook

read resulthook

function

Lua script

function

functionfunctionfunction



Lua Overview

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??Why not ...

Perl ?PHP?Javascript?[whatever]?



Lua Overview

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SMALL ( < 200 KB) DESIGNED for

EMBEDDED systems Widely used (lighttpd)

lighttpd, like MySQLProxy, was created byJan Kneschke



Lua Overview

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Very popular among

game writers



Proxy Overview

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connect_server

Lua script

read_auth

read_auth_result

read_handshake

read_query

read_query_result

disconnect_client

global

context

session

contextsessioncontextsession

contextsession

contextsession

contextsession

contextsession

context



Using Lua files

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/usr/local/sbin/mysql-proxy \--proxy-lua-script=/path/name.lua

IMPORTANT!THE SCRIPT DOES NOT START UNTIL THE

FIRST CLIENT CONNECTION


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Lua comments

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-- simple comment

print(1)

--[[print(2)

print('hello')

--]]print(3)



Lua comments

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-- simple comment

--[=[

print(1)--[[

print(2)

print('hello')

--]]

print(3)

--]=]



numbers and strings

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nil = no value (false) number = floating point '5' =/= 5 a = nil

b = 5; c = '5'print (b == c)false

print (b == c +0)true



numbers and strings

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conversion on demand

a = 5 ; b = '5'

print(type(a), type(b))number string

print(type(b+0))numberprint(type(a .. ""))string



numbers and strings

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conversion on demand

a = 5 ; b = '5'

print(type(tostring(a)))string

print(type(tonumber(b)))number


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strings

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smart quoting

a = 'Hello'

b = "World"c = "Can't"d = [[Don't say "Hello"]]e = [=["d'oh" [[braces]]!]=]


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tables

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associative arrays can be used as arrays can create complex

structures t1 = {10, 20, 30 }t2 = {a = 'abc',b = 2,c = { 3, 4}

}


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functions

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can be assigned tovariables

new functions can override

existing onesfunction f (x)print(x)

endg = fg(10)


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userdata

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containers to exchangedata between Lua and hostlanguage

can have "tag methods"


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Statements

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normal assignmentsa = 3b = get_num() -- func return

multiple assignmentsa,b = 3,2

multiple return valuesfunction x ()

return 1, 'OK'end

a, b, c = x()-- a = 1, b = 'OK', c = nil


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statement blocks

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ifif condition then

statements

end whilewhile condition do

statementsend


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sample function

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read_query

1 function read_query(packet)

2 if packet:byte()~=3 proxy.PROXY_COM_QUERY4 then5 return

6 end7 local query = packet:sub(2)8 print('received ' .. query)

9 end


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some details

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== equals ~= not equal

string.byte(packet)packet:byte()

string.sub(packet,2)packet:sub(2)

'abc' .. '123' == 'abc123'


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Using tables

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t = {}t[1] = 'a' --First element 1, ! 0t[2] = 'b'

table.insert(t, 'c')-- or t[ #t +1 ] = 'c'

t = {'a', 'b', 'c' }t = {1 = 'a', 2 = 'b', 3 = 'c'}print (t[2])b


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Using tables

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sizes = {}sizes['john'] = 'XL'sizes['paul'] = 'M'

sizes['fred'] = 'L'

sizes = {john = 'XL',paul = 'M',fred = 'L',

}


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Using tables

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sizes = {john = 'XL',paul = 'M',

fred = 'L',}print(sizes['john'])XL

print(sizes.paul)M


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Using tables

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for i, v in ipairs(t) doprint (i ..' -> ' .. v)

end

for name,size in pairs(sizes) doprint(name .. ' ' ..

wears .. ' ' ..size)

end


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Watch out

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-- Luaa = falseprint ( a and "true" or "false")

false

a = nilprint ( a and "true" or "false")false


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Finding text

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query = 'SELECT id FROM t1'

local cmd, column =

query:match("(SELECT)%s+(%w+)")

if cmd then-- do something with query

end


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Finding text

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Regular expressions similar to Perl/PHP, but simpler

% instead of \ (captures)

[character classes]

^ $ + - ? * no alternation (a|b) no modifiers /i


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Finding text (Proxy way)

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local tk =require('proxy.tokenizer')

local tokens = tk.tokenize(query)

if tokens[1].token_name =='TK_SQL_SELECT' then-- do something with query

end


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Finding text (Proxy way)

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-- each token is a table

token = {

token_name = 'TK_SQL_SELECT',text = 'select',token_id = 204

}


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I/O

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-- files are objects

local fname = '/tmp/test.txt'

assert(fh = io.open(fname,'r'))

for line in fh:lines() doprint(line)

endfh:close()


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I/O

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-- files are objects

local fname = '/tmp/test.txt'

assert(fh = io.open(fname,'w'))for x = 1, 100 do

fh:write('new row ' .. x)fh:flush()

endfh:close()


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Examples

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http://forge.mysql.com/wiki/Lua_Scripts_For_MySQL_Proxy_Examples

all hooks session bandwidth

user bandwidth

blocking commands
http://forge.mysql.com/wiki/Lua_Scripts_For_MySQL_Proxy_Exampleshttp://forge.mysql.com/wiki/Lua_Scripts_For_MySQL_Proxy_Examples


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all-hooks (1)

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source: all-hooks.lua

function read_auth( auth )...function connect_server()...function read_handshake( auth )...function read_auth_result( auth )...function disconnect_client()...function read_query (packet)...function read_query_result (inj)...
http://forge.mysql.com/snippets/download.php?id=109http://forge.mysql.com/snippets/download.php?id=109


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all-hooks (2)

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local access_ndx = 0

function print_access(msg)access_ndx = access_ndx + 1print( string.format('%3d %-30s',access_ndx,msg))

end

function read_auth( auth )print_access ('inside read_auth ')

end

function connect_server()print_access ('inside connect_server')

end

function read_handshake( auth )print_access ('inside read_handshake' )

end-- ... to be continued


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all-hooks (3)

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function read_auth_result( auth )print_access ('inside read_auth_result ')

end

function read_query (packet)print_access('inside read_query \t' .. packet:sub(2))

proxy.queries:append(1, packet)return proxy.PROXY_SEND_QUERY

end

function read_query_result (inj)print_access('inside read_query_result \t' .. inj.query)

end

function disconnect_client()print_access('inside disconnect_client')

end


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read_query & read_query_result

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client

MySQL Proxy

SERVER

query

functionread_query

function

read_query_result

query

result

result

if a query is passed directly to the server,

its result is NOT evaluated by

read_query_result


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read_query & read_query_result

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client

MySQL Proxy

SERVER

query

functionread_query

function

read_query_result

query queue

query

result

result

only ifa query is added

to the query queue,

its result is evaluated by

read_query_result

queryquery


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all-hooks (4)

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sample output/usr/local/sbin/mysql-proxy --proxy-lua-script=all-hooks.lua1 inside connect_server2 inside read_handshake3 inside read_auth4 inside read_auth_result5 inside read_query select @@version_comment limit 16 inside read_query_result select @@version_comment limit 17 inside read_query select now()8 inside read_query_result select now()9 inside read_query10 inside disconnect_client


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session-bandwidth (1)

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source: session-bandwidth.lua

local bandwidth = 0

function read_query (packet )bandwidth = bandwidth + packet:len()proxy.queries:append(1, packet )return proxy.PROXY_SEND_QUERY

end

-- to be continued ...


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session-bandwidth (2)

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source: session-bandwidth.lua

-- (continue)

function read_query_result(inj)local fields = inj.resultset.fieldsif (fields) then

for i = 1, #fields dobandwidth = bandwidth +

(fields[i] and fields[i].name:len() or 0)endfor row in inj.resultset.rows do

for i = 1, #inj.resultset.fields dobandwidth = bandwidth +(row[i] and row[i]:len() or 0)

endend

endprint (proxy.connection.server['thread_id'],bandwidth)

end
http://forge.mysql.com/snippets/download.php?id=110http://forge.mysql.com/snippets/download.php?id=110http://forge.mysql.com/snippets/download.php?id=110


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user-bandwidth (1)

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source: user-bandwidth.lua

proxy.global.bandwidth = proxy.global.bandwidth or {}

local session_user

function read_auth( auth )session_user = auth.usernameproxy.global.bandwidth[session_user] =

proxy.global.bandwidth[session_user] or 0end



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user-bandwidth (2)

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function read_query (packet )proxy.global.bandwidth[session_user ] =

proxy.global.bandwidth[session_user] + packet:len()proxy.queries:append(1, packet )return proxy.PROXY_SEND_QUERY

end



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Copyright 2004-2007 MySQL AB The Worlds Most Popular Open Source Database 52

function read_query_result(inj)

local fields = inj.resultset.fieldslocal rows = inj.resultset.rowsif fields then

for i = 1, #fields doproxy.global.bandwidth[session_user] =

proxy.global.bandwidth[session_user] +(fields[i] and fields[i].name:len() or 0)

endif rows thenfor row in rows do

for i = 1, #fields doproxy.global.bandwidth[session_user] =

proxy.global.bandwidth[session_user] +(row[i] and row[i]:len() or 0)

endendend

endprint (session_user .. ' -> ' ..

proxy.global.bandwidth[session_user])end

user-bandwidth (3)


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Sample session

gmax -> 376gmax -> 399

root -> 599root -> 10641

gmax -> 478gmax -> 20520

user-bandwidth (4)


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source: query-block.lua

local tokenizer = require("proxy.tokenizer")----- make_regexp_from_command()

---- creates a regular expression for fast scanning of the command---- @param cmd the command to be converted to regexp--function make_regexp_from_command(cmd)

local regexp= '^%s*';

for ch in cmd:gmatch('(.)') doregexp = regexp .. '[' .. ch:upper() .. ch:lower() .. ']'

endreturn regexp

end-- to be continued ...

query-block (1)


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local SHOW_REGEXP = make_regexp_from_command('show')

queries_to_filter = {

{prefix = SHOW_REGEXP,keywords = { 'SHOW', 'TABLE', 'STATUS'} ,

},{

prefix = SHOW_REGEXP,keywords = { 'SHOW', 'TABLES'} ,

},}


query-block (2)


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function error_result (msg)proxy.response = {

type = proxy.MYSQLD_PACKET_ERR,errmsg = msg,errcode = 7777,sqlstate = 'X7777',

}return proxy.PROXY_SEND_RESULT

end


query-block (3)


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function read_query( packet )if (packet:byte() ~= proxy.COM_QUERY) then

returnendlocal query = packet:sub(2)for i,query_to_filter in pairs(queries_to_filter)do

if query:match(query_to_filter.prefix) thenlocal full_tokens = tokenizer.tokenize(query)local tokens = tokenizer.bare_tokens(full_tokens, true)local found = 0local requested = #query_to_filter.keywordsfor j,keyword in pairs(query_to_filter.keywords) do

for k, token in pairs(tokens) doif token:upper() == keyword then

found = found + 1break

endend

end-- to be continued ...

query-block (4)


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function read_query( packet )-- ...

if found == requested then -- to be filtered offreturn error_result('command is not allowed' )

endend

endend

query-block (5)


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sample output:

show tables;ERROR 7777 (X7777): command is not allowed

query-block (6)


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Read more

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http://www.lua.org/docs.html

online Luadocumentation
http://www.lua.org/docs.htmlhttp://www.lua.org/docs.html


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Read more

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http://www.inf.puc-rio.br/~roberto/pil2/
http://www.inf.puc-rio.br/~roberto/pil2/http://www.inf.puc-rio.br/~roberto/pil2/


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Read more

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http://www.wrox.com/WileyCDA/WroxTitle/productCd-0470069171.html
http://forge.mysql.com/wiki/Lua_Scripts_For_MySQL_Proxy_Exampleshttp://forge.mysql.com/wiki/Lua_Scripts_For_MySQL_Proxy_Examples


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Giuseppe MaxiaQA Developer

December 2007

QUESTIONS

?

introducing lua

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