pause a single session but keep processing other - mysql

Question

I want to the mysql-proxy lua script to handle interleaving accesses to a website (e.g. two different browser windows/users) but being able to pause/delay one of the two without influencing the other.Handling sessions interleavingly is possible in mysql-proyx lua (so it seems regarding the later listed output) but as soon as I start delaying the script it blocks everything and the other session cannot advance either.
-- the query which indicates the session/connection that shall be delayed at that execution
local qoi = "SELECT loginattempts,uid FROM mybb_users WHERE username='user1' LIMIT 1"
function read_query(packet)
if string.byte(packet) == proxy.COM_QUERY then
query = packet:sub(2)
start_time = os.time()
if query == qoi then
print("busy wait")
while os.time() < start_time + 20 do
--nothing
end
print("busy wait end")
end
print("Connection id: " .. proxy.connection.server.thread_id)
end
end
However this script ends up with output:
Connection id: 36
busy wait
busy wait end
Connection id: 36
Connection id: 36
Connection id: 36
Connection id: 37
Connection id: 37
Connection id: 36
Connection id: 36
Connection id: 36
Connection id: 37
and not the expected
Connection id: 36
busy wait
connection id: 37
connection id: 37
busy wait end
Connection id: 36
Is my intention even achievable and if so how?

Answer 1

It seems to be impossible to delay the session within lua but it works just as fine if I outsource the delay to mysql server as this will force the interleaving as well.
local DEBUG = true
local qoi = "SELECT loginattempts,uid FROM mybb_users WHERE username='user1' LIMIT 1"
function read_query(packet)
ret = nil
comp_query = qoi
if string.byte(packet) == proxy.COM_QUERY then
query = packet:sub(2)
if query == comp_query then
if DEBUG then
print("found matching query " .. packet:sub(2))
print("insert sleep")
end
inj_query = "SELECT sleep(30);"
new_packet = string.char(proxy.COM_QUERY) .. inj_query
proxy.queries:append(1, new_packet, { resultset_is_needed = true })
proxy.queries:append(2, packet, { resultset_is_needed = true })
ret = proxy.PROXY_SEND_QUERY
end
end
return ret
end
function read_query_result(inj)
if inj.id == 1 then
if DEBUG then
print("sleep query returns")
end
return proxy.PROXY_IGNORE_RESULT
end
if inj.id == 2 then
if DEBUG then
print("regular query returns")
end
return
end
return
end