--[[ $%BEGINLICENSE%$
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 published by the Free Software Foundation; version 2 of the
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 $%ENDLICENSE%$ --]]

--[[

Let a random number of transaction rollback

As part of the QA we have to verify that applications handle 
rollbacks nicely. To simulate a deadlock we turn client-side COMMITs
into server-side ROLLBACKs and return a ERROR packet to the client
telling it a deadlock happened.

--]]

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

    -- only care about commits 
    if packet:sub(2):upper() ~= "COMMIT" then return end

    -- let 80% fail
    if math.random(10) <= 5 then return end

    proxy.queries:append(1, string.char(proxy.COM_QUERY) .. "ROLLBACK", { resultset_is_needed = true })

    return proxy.PROXY_SEND_QUERY
end

function read_query_result(inj)
    if inj.id ~= 1 then return end

    proxy.response = {
        type = proxy.MYSQLD_PACKET_ERR,
        errmsg = "Lock wait timeout exceeded; try restarting transaction",
        errno = 1205,
        sqlstate = "HY000"
    }

    return proxy.PROXY_SEND_RESULT
end

